ML19225D130

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Response to Request for Additional Information (Follow-Up) Regarding Open Phase Protection Per NRC Bulletin 2012-01 - Proposed License Amendment Request
ML19225D130
Person / Time
Site: North Anna  Dominion icon.png
Issue date: 08/08/2019
From: Gerald Bichof
Virginia Electric & Power Co (VEPCO)
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
19-210A, BL 2012-01
Download: ML19225D130 (45)
v • d • e


Text

-f VIRGINIA ELECTRIC AND POWER COMPANY 23261 RICHMOND, VIRGINIA 10CFR50.90 August 8, 2019 U. S. Nuclear Regulatory Commission Serial No. 19-21 OA Attention: Docu*ment Control Desk NAPS/DPM R1 Washington, DC 20555-0001 Docket Nos. 50-338/339 License Nos. NPF-4/7 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 PROPOSED LICENSE AMENDMENT REQUEST RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (FOLLOW-UP)

REGARDING OPEN PHASE PROTECTION PER NRC BULLETIN 2012-01 By letter dated April 30, 2018 (Serial No.18-072) (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18127A073), Virginia Electric and Power Company (Dominion Energy Virginia) submitted a license amendment request (LAR) to add operability requirements, required actions, and surveillance requirements (SR) to the Technical Specifications (TS) for the 4160V emergency bus negative sequence voltage (open phase) protection function.

In response to an NRC Staff request, additional information was provided on March 24, 2019 (Serial No.19-210) (ADAMS Accession No. ML19156A207).

In a July 10, 2019 e-mail from Mr. Ed Miller (NRC) to Mr. Craig Sly (Dominion Energy Virginia), the NRC staff provided a follow-up request for additional information (RAI).

Dominion's response to the follow-up RAI is provided in Attachment 1.

In addition to Dominion's response to the RAI, the following information is provided in the Attachments to this letter:

- Attachment 2 provides a copy of the marked-up Technical Requirements Manual showing how time delays are incorporated

- Attachment 3 provides copy of the UFSAR with the revised 'Insert A' (changes highlighted) and page 8.3-4, as originally submitted, for context

- Attachment 4 provides a copy of the article, "Typical Expected Values of the Fault Resistance in Power Systems"

- Attachment 5 provides a copy of the Study Cases for RAI No. 4 and Attachment 5 to Calculation EE-0894 The information provided in this letter does not affect the conclusions of the significant hazards consideration or the environmental assessment included in the April 30, 2018 LAR.

Serial No. 19-21 OA Docket Nos. 50-338/339 Page 2 of 3 Should you have any questions or require additional information, please contact Ms. Diane E. Aitken at (804) 273-2694.

Respectfully, Gi~?c~6 Sr. Vice President Nuclear Operations and Fleet Performance COMMONWEALTH OF VIRGINIA )

)

COUNTY OF HENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mr. Gerald T. Bischof, who is Sr. Vice President - Nuclear Operations and Fleet Performance, of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, and that the statements in the document are true to the best of his knowledge and belief.

Ackoowledged befora me this 51-ifi day of A~ , 2019.

My Commission Expires: -:w)~31, 20~

DIANE E. AITKEN

~*f.~ NOTARY PUBUC Notary Public .1 REG. 17763114 .

, ~ONWEALTH OF VlffflltM

"'f ~MISSION EXPIRES MARCH 31, 2022 Commitments contained in this letter: None i*.,,."'"r'- ------~--'

.' /-~*' ., t,'

Attachments:

1. Response to NRC Request for Additional Information (Follow-up) Regarding Open Phase Protection per NRC Bulletin 2012 Proposed License Amendment Request
2. Copy of the marked-up Technical Requirements Manual showing how time delays are incorporated
3. Copy of the UFSAR with the revised 'Insert A' (changes highlighted) and page 8.3-4, as originally submitted, for context
4. Copy of the article, "Typical Expected Values of the Fault Resistance in Power Systems"
5. Study Cases for RAI No. 4 and Attachment 5 to Calculation EE-0894

Serial No. 19-21 DA Docket Nos. 50-338/339 Page 3 of 3 cc: U.S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Avenue, NE Suite 1200 Atlanta, GA 30303-1257 State Health Commissioner Virginia Department of Health James Madison Building - ih floor 109 Governor Street Suite 730 Richmond, VA 23219 Mr. G. E. Miller NRC Project Manager - North Anna U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 B-1A 11555 Rockville Pike Rockville, MD 20852-2738 Ms. K. R. Cotton Gross NRC Project Manager - Surry U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector North Anna Power Station

Serial No. 19-210A Docket Nos. 50-338/339 Attachment 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION (FOLLOW-UP)

REGARDING OPEN PHASE PROTECTION PER NRC BULLETIN 2012 PROPOSED LICENSE AMENDMENT REQUEST Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Serial No. 19-21 OA Docket Nos. 50-338/339 Attachment 1 Page 2 of 6 Response to NRC Request for Additional Information (Follow-up)

Regarding Open Phase Protection per NRC Bulletin 2012 Proposed License Amendment Request By application dated April 30, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18127A073), Virginia Electric and Power Company (Dominion Energy Virginia), the licensee for North Anna Power Station, Units 1 and 2, proposed to revise Technical Specifications (TS) 3.3.5 for Loss of Power (LOP)

Emergency Diesel Generator Start Instrumentation. The license amendment request (LAR) addresses the potential for an open phase condition (OPC) that could exist on one or two phases of a primary off-site power source and that would not currently be detected and mitigated by the existing station electrical protection scheme. In response to the NRG Staff's request, the licensee provided additional information on March 24, 2019 (ML19156A207).

The NRG staff has identified the need for additional information (follow-up) to complete the review of LAR.

Applicable Regulatory Requirements Title 10 of the Code of Federal Regulations (10 CFR) Part 50.36(c)(2) provides the requirement for the establishment of TS limiting conditions for operation (LCO).

Specifically, paragraph 50.36(c)(2)(ii) requires that a TS LCO of a nuclear reactor be established for each item meeting one or more of the criteria listed. For this LAR, Criterion 3 applies which states: "A structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a OBA or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier."

10 CFR 50.36(c)(3), Surveillance requirements, requires surveillance relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met.

Request for Additional Information (RAJ)

RA/# 1 In the letter dated May 24, 2019 (in response to RAI-EEOB-3), the licensee stated that because BE1-47N relay operates with an inverse time characteristic, which would result in a range of time delays for various OPC events, the inclusion of the allowable values for the full range of time delays in TS is not considered practical. The North Anna Technical Requirements Manual is being revised to incorporate the setpoint for the BE1-47N relay, which will include the time dial setting.

Please provide a mark-up of North Anna Technical Requirements Manual showing how the time delays will be incorporated and explain how any future changes in time delay settings will be controlled.

Serial No. 19-21 OA Docket Nos. 50-338/339 Attachment 1 Page 3 of 6 Dominion Energy Response provides a copy of the marked-up North Anna Technical Requirements Manual showing how the time delays will be incorporated. Changes to the Technical Requirements Manual are controlled in accordance with station procedures that require a 50.59/72.48 Applicability Review and a detailed Technical Analysis and Safety Assessment.

RAl#2 The staff noticed the following underlined discrepancies in statements made in the LAR and a statement made in the mark-up of UFSAR provided in response to RAI-EEOB-12:

LAR Attachment 1, Page 8: At a minimum of 4 percent negative sequence, the BE1-47N relay will energize [trip] and send a start signal [to EOG] in approximately 11 seconds.

LAR Attachment 1, Page 14: Analysis results show that for most open phase events in which the BE1-47N relays trip, the tripping time is less than 6 seconds after the open phase event occurs.

Mark-up of UFSAR (Page 8.3-4, Insert A): A time dial setting is used which results in a typical trip time delay of less than 6 seconds for any open phase condition sensed at an emergency bus.

Please address how you will resolve these discrepancies. If UFSAR changes are needed to make the UFSAR consistent with the LAR, provide any corresponding UFSAR revision markups.

Dominion Energy Response To address the discrepancies described above, 'Insert A' for page 8.3-4 of the UFSAR change submitted in Attachment 7 to Virginia Electric and Power Company letter dated May 24, 2019, "Response to Request for Additional Information on Proposed License Amendment Request Open Phase Protection Per NRC Bulletin 2012-01," (ADAMS Accession No. ML19156A207) has been revised. Attachment 3 provides a copy of the revised 'Insert A' (changes highlighted) and page 8.3-4, as originally submitted, for context.

RAl#3 In the LAR, Attachment 1, Page 10, the licensee stated that the following open phase conditions were considered:

  • Single open phase without a ground connections;
  • Single open phase with a 350 ohm grounded connection; and
  • Single open phase with a solid grounded connection.

Serial No. 19-21 OA Docket Nos. 50-338/339 Attachment 1 Page 4 of 6 Regarding the 350 ohms ground connection, in the letter dated May 24, 2019 (in response to RAI-EEOB-5), the licensee stated that the total fault impedance of a high resistance fault was calculated based on an empirical model as discussed in the Surry Open Phase Condition Detection Analysis calculation and IEEE paper, "Typical Expected Values of the Fault Resistance in Power Systems." Using the most conservative method discussed in the IEEE paper, a total fault impedance of 173.4 ohms was calculated. This value was doubled to 346. 8 ohms and rounded to 350 ohms for use in North Anna's calculation.

Please provide the following additional information:

(a) A brief calculation showing how the above fault impedance of 173.4 ohms was obtained.

(b) Confirmation that doubling the fault impedance is considered more conservative.

(c) How the above various types of ground connections were considered in the Table-1 provided on Page 15 of LAR, Attachment 1, and explain the significance of "Time= 8 seconds" provided in Table-1.

Dominion Energy Response Response to RAI #3(a):

By letter dated March 14, 2018, Virginia Electric and Power Company submitted, "Clarification of Request for Additional Information Response and Associated License Amendment Request Revision" (ADAMS Accession No. ML18075A324). Pages 4 and 5 of the March 14, 2018 letter provided a summary of the OPC analysis performed for Surry Power Station which included a brief analysis showing how the fault impedance of 173.4 ohms was obtained. These analyses are applicable for North Anna.

Additionally, Attachment 4 provides a copy of the article, "Typical expected values of the fault resistance in power systems," referenced on page 4 of the March 14, 2018 letter as,

'The most conservative method per the reference ... is based on the empirical model proposed by A. Washington, ... "

Response to RAI #3(b):

Case studies were performed that verified doubling the fault impedance was conservative.

Response to RAI #3(c):

The three types of ground connections described above were considered for Buses 1 H, 1J, 2H and 2J in Table 1 on page 15 of Attachment 1 to the license amendment request (LAR) submitted by Virginia Electric and Power Company on April 30, 2019 (ADAMS Accession No. ML18127A073).

Serial No. 19-21 OA Docket Nos. 50-338/339 Attachment 1 Page 5 of 6 Each row of Table 1 is associated with an OPC location/alignment. The columns are associated with the minimum and maximum V 2 (Negative Sequence Voltage) values for each emergency bus. The minimum and maximum values are associated with all three ground conditions that were evaluated.

"Time = 8 seconds" provided in Table 1 is the post-transient time from the open phase event.

RAl#4 In the letter dated May 24, 2019 (in response to RAI-EEOB-8), the licensee stated that for a voltage unbalance greater than 5%, the BE1-47N relays should isolate the motor loads from the OPC condition prior to the 12 x t value reaching 20 pu. To validate this condition was met for the BE1-47N relays, a model was created in EMTP-RV to calculate the time until the 12 x t value for each monitored motor reached 20 pu. This value was compared to the trip time of the BE1-47N relay for each event modeled.

In the LAR, Attachment 1, Page 13, the licensee also stated: "For a voltage unbalance between 1 % and 5%, the NEMA MG-1 de-rating factor was applied to the motor rating. If the brake horsepower (BHP) of the motor is less than the de-rated horsepower rating, then continuous operation of the motor was determined to be acceptable. In cases where the BHP is greater than the de-rated horsepower rating, the motor must be isolated from the faulted source. The calculation quantifies the time duration for which the motor may be operated on the faulted source before the negative sequence current heating capability is exhausted. The resulting time duration was used to determine if manual action (alarm) is acceptable or if automatic action (trip) is necessary."

Because no alarm is provided in the control room if the voltage unbalance is between 1% and 5%, please provide a tabulation of all study cases in which the voltage unbalance is between 1% and 5%, and justification why all these cases are considered acceptable without any alarm or tripping function.

Dominion Energy Response provides 4 tables of the cases in which the negative sequence voltages were between 1% and 5%, one table for each emergency bus. There are three types of results; "Yes", "No", and "Yes***".

"Yes***" results are for Auxiliary Feedwater and Inside Recirculation Spray cases where the NEMA derating factor was unacceptable. The thermal margin for these cases was evaluated to be acceptable in Attachment 5 of calculation EE-0894 (provided in to this response).

Serial No. 19-21 OA Docket Nos. 50-338/339 Attachment 1 Page 6 of 6 Results specified as "No" indicate cases where sufficient NEMA derating was not available. In these cases, motor damage could result after an extended duration of operation, degrading the expected life of the motor. Therefore, to preclude this from occurring, additional relays have been installed on Transformer 1 and Transformer 2 that provide an alarm function to the Main Control Room when these conditions exist. The alarm will alert the operators of the need to isolate the impacted emergency bus.

Serial No. 19-21 OA Docket Nos. 50-338/339 Attachment 2 COPY OF THE MARKED-UP TECHNICAL REQUIREMENTS MANUAL SHOWING HOW TIME DELAYS ARE INCORPORATED Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

ESFAS Instrumentatiori Res~qnse**rimes 4.5

.

  • Table 4.5-"i (page 5 of 5)-

Engineered Safety Features Response Times INITIAlING SIGNAL AND FUNCTION . *RESPONSE TIME IN SECONDS

13. Loss of Po~ter *
a. 4.16 kv Emergency Bus Undervoltage (Loss of Voltage)
  • b. 4.16 kv Emergency-Bus Undervoltage  :::; 11,5(e)with S.J signal (Degraded Voltage)  :::; 74.o<e)witii no SI signal 14.Automatic Switchover to Containment Sump
a. Automatic Actuation Logjc and Actuation N.A; Relays
b. Refueling Water Storage Tank (RWST) :2: 110 Leve 1-Low Low  :::; 200 (e) T~e response times shown are based on the time from when the signal reaches the trip setting until the diesel generator is supplying the emergency bus.

If1/t ~ II /3.,tt 4/j "' 11

(

. S("iiw,,..(. ~ V \-to.~~

(I NAPS TRM 4.5-6 Rev 79, 07/15/10

EOG loss of Power Start Instrumentation Trip Setpoints 4.9 Table 4.9-1 {page I of 1)

EDG Loss of Power Start Instrumentation Trip Setpoints FUNCTION TRIP SETPOINT loss of Power

a. 4160 Volt Emergency Bus 3080 volts with a time delay of Undervoltage (Loss of Voltage) 2.0 +/- 0.5 seconds
b. 4160 Volt Emergency Bus 3746 volts with a time delay of:

Undervoltage (Degraded Voltage) 1. 7.5 +/- 0.75 seconds with Safety Injection (SI) signal; and

2. 56 +/- 6 seconds, without SI signal C. l(I C...o Vol-t G~~,.~'-'1 PS(I.>

A) e!j ~ ,I. jII e S ei()J.,'AC,. '- Vo I +1"4~

(~) /Jl'&i.+ivt Sqauict VattA~e. is cal,tA.(4+eJ as <\. (Je.<'UM.:!-~.t.

oi V\o~*VI."',\ 1/c,\{~je, NAPS TRM 4.9-2 Rev 28, 08/01/02

Serial No. 19-21 OA Docket Nos. 50-338/339 Attachment 3 COPY OF THE UFSAR WITH THE REVISED 'INSERT A' (CHANGES HIGHLIGHTED)

AND PAGE 8.3-4, AS ORIGINALLY SUBMITTED, FOR CONTEXT Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

FOR INFORMATION ONLY Revision 54.05--Updated online 03/14/19 NAPS UFSAR 8.3-4 jNo changes for this page. Page provided for reference only.

The 4160V emergency switchgear is arranged in two separate systems designated H and J.

The H bus is associated with train A, while the J bus is associated with train B. The buses are physically as well as electrically, separated from each other in different missile-protected areas on the bottom floor of the service building as shown in Reference Drawing 18. The 4160V Hand J buses are arranged as shown in Reference Drawing 4. The 4160V buses are rated 1200A serving emergency loads through breakers equipped to protect the loads from overcurrent. The 480V emergency switchgear is also separated and located in missile-protected areas.

The 480V emergency switchgear buses H and J are arranged as shown in Reference Drawing 5. These buses are rated at 2000A with breakers equipped with overcurrent protection for the loads. The 480V motor control centers are shown in Reference Drawings 6 through 11 and 19.

The 480V emergency buses are equipped with normally open back feed breakers and an electrical connection which can be powered by a portable generator during a Beyond Design Basis Event.

The loads on the H and J buses on either the 4160V or the 480V level are typically redundant and are sized based on their required functions or the required functions of their associated components (e.g. a motor on a safety-related pump). The safety-related buses and their loads are shown in Reference Drawings 1 through 11 and 19.

There are other interconnections between buses, buses and loads, and buses and sources on the emergency 4160V system. The interconnection between bus and supply will be described for overcurrent; transfer bus underv tage; both 34.5 kV bre or reserve station service transfo tial, or overcurrent. The breaker from the transfer bus trips due to overc ent; undervoltage on either of the transfer or emergency buses; a trip of the feeder breaker fro the transformer to the transfer bus; or transformer pilot wire, differential , or overcurren . The feeder breaker in the emergency bus will trip due to an injection signal is received, at approximately 74% voltage on the bus for 2 seconds, ff- a 90%

degraded voltage level exists for 56 second . Following the safety injection start signal, the emergency diesel generator will load if a 9 o degraded voltage level exists for 7.5 seconds. The emergency diesel generator breaker close on the isolated bus at 95% generator voltage if certain conditions are met. The load breakers a omatically trip on overcurrent or electrical fault and lock out, which prevents the breaker fro being reclosed manually or automatically. Most of the 4160V load breakers also trip on ndervoltage ith time controlled reclosing when voltage is or phase voltage

, or when an open phase condition is detected. [ADD TEXT FROM INSERT A HERE]

unbalance The information contained in the electronic version of the SAR may be different from the information found in the hardcopy version of the SAR. Such differences are intentional and are the result of approved changes to the SAR that have not yet been submitted to the NRG.

Insert A An open phase condition causes a voltage unbalance on the system which is detected via emergency bus negative sequence voltage relays. The negative sequence voltage relays include an inverse time characteristic which introduces a trip time delay based on the magnitude of the negative sequence voltage above the nominal setting of 4% . A time dial setting is used which results in a trip time delay of less than 11 seconds for open phase cond itions that are detected by the emergency bus negative sequence voltage detection relays.

Serial No. 19-210A Docket Nos. 50-338/339 Attachment 4 COPY OF THE ARTICLE, "TYPICAL EXPECTED VALUES OF THE FAULT RESISTANCE IN POWER SYSTEMS" Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Cale. No. EE-0883 Attachment C Page No. C144 ofC155 Rev. No. 000 References Typical expected values of the fault resistance in power systems Virgilio De Andrade, Elmer Sorrentino ZG are very diverse and, additionally, there could be other Abstract-This article presents a range of possible values for objects interposed in the path of the current.

the fault resistance in transmission power systems, considering six existing models for the arc resistance and a model for the II. APPLIED MODELS grounding impedance of the towers. Resistance by possible additional objects in the path of the fault current was not A. Models for the arc resistance considered. Known the short circuit level (without fault impedance), the fault resistance was calculated with the above A.l. Model 1 mentioned models, for line-to-line and line-to-ground faults. This This model probably is the most well-known, and it was calculation was made for diverse nominal voltages and diverse proposed by A. Warrington in 1931 [ 1,2]:

short circuit levels for solid faults. The obtained range might be R = 28707.35

  • L (I) useful to improve the way of computing the settings for the Al 1.4 corresponding protective devices. 1 RA/ Arc resistance (Q), according to model} (j=l ... 6).

Index Terms- Arc resistance, grounding resistance, fault L: Arc length (m).

resistance, short circuit level. 1: Rms value of the fault current (A).

I. INTRODUCTION A.2. Model 2 HORT circuit current may be limited by a fault This model is based on the analysis of Mason [11] about S impedance, which may be composed by three elements:

electric arc, tower grounding, and the presence of objects in the results of Warrington [I], Strom [6] and other authors:

R _ 1804.46

  • L (2)

A2 - l the fault path. Electric arc is a non-linear phenomenon that depends on diverse factors; however, there is a tradition considering the arc as a resistance, dependent on the arc A.3. Model 3 current, in order to compute the short circuit currents in a This model is based on a article written by Goda et al. [3]:

simple way [1-13]. The effective grounding impedance of R =(950+5000)-L (3) towers is mainly resistive, its inductive part is greater when A3 1 12 there are ground wires [14-20], and its value is assumed to be not dependent on the fault current. Impedance of possible A.4. Models 4 and 5 additional objects interposed in the path of the fault current is These models are based on articles written by Terzija and usually considered mainly resistive, and its value might be Koglin [4-5]:

zero or very high [I]; by this reason, fault impedance may be RM=--

G*L (4) described as an unpredictable quantity [21]. 1 For transmission line protection, fault resistance (RF) is R =(855.30+ 4501.58)-L (5) assumed to be composed by the arc resistance (RA) and the A5 l 12 effective grounding resistance of the towers (RG) [11-14]. A G: Constant (between 1080.38 and 1350.47 V/m).

range of values for RF was computed in this article, by using existing models for RA and for the effective grounding A.5. Model 6 impedance of th~ towers (ZG), and by assuming the short This is in a book written by Blackburn and Domin [12]:

circuit level without fault impedance UscL) as known. The R = 1443.57

  • L (6) obtained range for RF may be considered typical for the A6 l nominal voltages used as examples; however, it was considered necessary to emphasize that the RF values may be A.6. Some details about these models out of the studied range because the factors that affect RA and a) Each model was developed from experiments done with a specific range of currents, but they have been used in a wider range. In this work, the value of the fault resistance was V.D. and E.S. are with Universidad Simon Bolivar, Caracas, Venezuela.

E-mail: virgilioandrade@usb.ve calculated of two ways: Method A, considering that each

Cale. No. EE-0883 Attachment C Page No. C145 ofC155 Rev. No. 000 References 2

model is valid for the whole range of currents, and Method B, towers and grounding wires whose length is the average line considering that each model is only valid for the specific span.

range of currents of the corresponding experimental tests Na: Number oflines arriving to the substation.

(table I). r: Quotient of the fault current that does not return through the grounding wires that arrive to the substation divided by TABLE I* RANGE OF CURRENTS FOR METHOD B the total current of the line-to-ground fault.

Model Range of currents (A) The values of Zp and rare:

I 135 - 960 Zp=0.5*Zw+J(0.5*Zwf+Zw*RT (8) 2 1000 - 20000 Z'

3 5000 - 50000 r = 1-_!!'l,_ (9) 4 2000 - 12000 Z'w 5 2000 - 12000 Z'w: Self impedance per unit length of the grounding wires.

6 70 - 20000 Zw: Self impedance of the grounding wires for an average line span dr(Zw = dr

  • Z'w).

b) In this work, a maximum value and a minimum value Z'wL: Mutual impedance per unit length between the are used for the arc length (L). Therefore, for Method A: grounding wires and the phase conductors of the line.

b. I) Model 2 and model 4 are complementary by using model 2 with maximum length (LMAX), and model 4 Ill. RANGEOFUSEDVALUES with minimum length (LMm) and G=I080.38 V/m. RE was assumed to be between 0.01 and 5 Q [20,22], but b.2) Model 3 and model 5 are complementary by using only its minimal value (0.01 Q) is needed for this article model 3 with LMAX and model 5 with LMIN* because it only influences the value of ZaM!N* Rr was assumed b.3) Model 6 is equivalent to the use of G= 1443 .57 V/m; to be between I and 800 Q [12-13,25-27]; its minimal value therefore, its result is an intermediate value between (IQ) is needed to calculate ZaM!N and its maximum value (800 model 2 and model 4, and its calculation is not Q) is needed to calculate ZaMAX*

strictly necessary. Table II shows the range used for the other parameters.

b.4) Model I must be computed with LMAX and LMIN; this These values were estimated from the analysis of the implies the calculation of two different resistances. constructive characteristics that were reviewed for a wide b.5) By this analysis, only the calculation of a subset of variety of transmission lines [25-34].

models is strictly necessary; however, the results of Arc lengths are different for line-to-line faults (Lu) and for the 6 models are shown in this article in order to see line-to-ground faults (LL-a). LMIN was assumed to be the their differences. minimal distance required for a 50 % of probability of the arc c) The analyzed models, with the exception of model 1, can occurrence at the corresponding nominal voltage (with be considered particular cases of the general model stated by standard atmospheric conditions) [35]. A large arc lengthening might exist by convection, wind action and/or electromagnetic Ayrton in 1901 [7], by using the adequate value of the attraction (the arc might evolve in the time), and this affect constants A, B, C, D:

LMAX* By this reason, a value of LMAX was assumed for the R = A+B*L + C+D*L (7) instantaneous action of the protections and other one for the A I 12 delayed action. LMAX for the instantaneous protections was considered to be equal to the minimal distance of separation B. Mode/for the effective grounding impedance of the towers (between phases or between phase and ground, according to This article only considers the case of transmission lines the case) plus 6 meters of initial lengthening, which was with ground wires. Hence, for a line-to-ground fault at a estimated considering a wind speed of 30m/s during O. ls.

tower, a part of the fault current circulates by the individual LMAX for delayed protections was assumed to be 5 times the tower grounding and other one circulates by the ground wires. minimal separation distance between phases, or between This implies that the effective grounding impedance (Za) is phase and ground, according to the case; such multiple is different from the individual grounding resistance of the tower arbitrary and it is based on a qualitative appreciation of the (Rr). Minimal value of the effective grounding impedance available information (in the literature and in videos). The (ZaMm) is assumed to be for faults at a substation, and its criteria enunciated for LMAX have an exception for line-to-maximum value (ZaMAX) is assumed to be for faults in a line ground faults at 69kV because the value for instantaneous without contribution from the remote end. An analysis of the protections would be greater than the value for delayed recommendations for the model of Za [15-17,22-24] was done protections; by this reason, there was only used the arc length specifically for this article, and by such analysis: ZaM!N is calculated for the delayed protection.

assumed to be equal to r multiplied by the parallel equivalent The minimum values for Z'w and the maximum values for of RE with Zp!Na, and ZaMAX is assumed to be the parallel Z'wL are necessary to compute ZaM!N, and they were estimated equivalent of Rr with Zp.

with two grounding wires (ACSR 240/40 at 20°C) and with a RE: Grounding resistance of the substation.

soil resistivity of 20 nm. The maximum values for Z'w were Zp: Equivalent impedance of a ladder network formed by estimated with a soil resistivity of 10000 nm, with a an infinite number of individual grounding resistances of

Cale. No. EE-0883 Attachment C Page No. C146 ofC155 Rev. No.ODO References 3

grounding wire (extra-high-strength steel, 3/8", at I00°C) for I I= h(R,J = Vml (Zm +RA+ ZG) I (11) instantaneous protections and at its admissible short circuit Thevenin voltage (Vm) is the line-to-line voltage for line-temperature (200 °C) for the delayed protections (except in to-line faults and the line-to-neutral value for line-to-ground case of765 kV, that was estimated by two grounding wires of faults. Thevenin impedance (Zm) is the sum of the this type because all the lines analyzed for this case had two impedances of positive and negative sequence for line-to-line grounding wires). The value used for N 0 is 16. faults, and the average of the three sequence impedances for line-to-ground faults. 2 0 is zero for line-to-line faults. lsCL is TABLE II: RANGE FOR THE VARIABLES THAT DEFINE THE VALUES OF ZoMIN the value of h(R,J far RA = 0 (and with 2 0 = 0, for line-to-(UPPER ROW), AND THE VALVES OF ZoMAX FOR INSTANTANEOUS ground faults).

PROTECTIONS (MIDDLE ROW) AND DELAYED PROTECTIONS (LOWER ROW) This analysis is based on the use of phasors. Therefore, the VN Lu LL-G Z'w Z'wL (Q/km) dT effect of non-sinusoidal waveforms is not considered. The (kV) (m) (m) (Q/km) * (m) value used for the Thevenin voltage is the nominal value.

0.23 0.15 0.120 + j0.577 0.059 + j0.362 94 The iterative method for computing the solution is very 69 7.83 5.80 6.098 + j2.502

- 246 simple: the first value of / for computing RA with equation 9.15 5.80 8.129 + j2.502 (10) is fscL; with such value of RA, then/ is updated by using 0.37 0.23 0.120 + j0.573 0.059 + j0.342 101 6.098 + j2.502 equation (11); and with such value of/, RA is updated by using 115 8.49 7.83

- 322 equation (10). This iterative process is repeated until the 12.5 9.15 8.129 + j2.502 0.70 0.42 0.120 + j0.568 0.059 + j0.320 126 convergence is achieved. The error for the current must be 230 11.0 8.77 6.098 + j2.502 lower than 0.1 % as convergence criterion.

- 451 In a graphic way, the solution for the equations (10) and 25.0 13.9 8.129 + j2.502 1.23 0.70 0.120 + j0.563 0.059 + j0.290 152 (11) is at the intersection of the curves (Fig. 1). Generally 400 13.6 10.3 6.098 + j2.502 there is only one solution; nevertheless, in case of two

- 503 38.2 21.5 8.129 + j2.502 solutions, only the solution with lower value of RA has been 2.06 1.33 0.120 + j0.511 0.059 + j0.236 213 considered in this article (the computing method forces such 765 18.0 13.6 3.078 + j 1.489 solution).

- 512 60.0 38.1 4.094 + j 1.489 In practice, the possibility of no intersection of the curves

  • Only the maximum values of Z'wL are required (they are is negligible. If this happen for the maximum arc lengths, the required to compute the minimum fault impedance). recommendation of this article is to evaluate the biggest arc length that allows an intersection of the curves and to use the For each nominal voltage ( VN), the range for the short results of such intersection. An example of this is shown at the circuit level without fault impedance UscL) is between 0.1 and section V.B.3.

50 kA. Such range is greater than the usually required values because the objective is to observe the behavior of the results in the range of currents as wide as possible. The range assumed for the angle of the corresponding current is shown in table III. The lower angle values were used to obtain the maximum arc resistance values and vice versa.

TABLE III: RANGE FOR THE ANGLE OF fsCL,, I VN(kV) Line-to-ground Line-to-line 71.6° ... 87.1° 78.7° ... 87.1° a) Unique solution b) Without crossings 69 y 115 (X/R: 3 ... 20) (X/R: 5 ... 20)

Fig. I. Examples of the relationship between the equations 10 and I I.

71.6° ... 87.7° 78.7° ... 87.7° 230 (X/R: 3 ... 25) (X/R: 5 ... 25) 76.0° ... 88.1 ° 81.9° ... 88.1° 400 V. RESULTS (X/R: 4 ... 30) (X/R: 7 ... 30)

78. 7° ... 88.6° 84.3° ... 88.6° A. Effective grounding impedance of the towers 765 (X/R: 5 .. .40) (X/R: 10 .. .40) Table IV shows the results of the effective grounding impedance of the towers (20 ). The effective grounding resistance of the towers (Ro) is simply the real part of the IV. METHOD FOR COMPUTING THE ARC RESISTANCE impedance value.

For the described models, the arc resistance is a decreasing Minimum value of 2 0 is practically zero and its maximum function of the fault current: value is near to 450 (+/-100). This maximum value is RA = g(J) (10) moderate, in comparison with the average individual Arc resistance allows to calculate the fault current by using grounding resistance of the towers (Rr =800 O); this is due to the Thevenin equivalent circuit. A way for expressing this the presence of the grounding wires. Angle of ZoMAX is small, calculation is: but the value in ohms of its reactive component is not

Cale. No. EE-0883 Attachment C Page No. C147 ofC155 Rev. No.ODO References 4

negligible, and it might influence the apparent reactance seen with model 1 for the lower values of fscL and with model 2 for by the distance protections. the higher values. In Method B, model 1 is assumed to be only valid for fault currents between 0.135 and 0.96 kA, and model TABLE IV* EFFECTIVE GROUNDING IMPEDANCE OF TIIE TOWERS 2 for values between 1 and 20 kA; by this, its maximum Maximum values (!1) for values are obtained with model 6 for very low values of fscL, VN instantaneous protections with model 1 for the moderately low values of lscL, with Minimum value (m!1)

(kV) (upper row) and delayed model 2 for almost all the higher values of fscL, and with protections (lower row) model 3 for line-to-line faults whose fscL is greater than 20kA 35.2 /10.9° = 34.6 + j6.67 69 2.51 /12.40° = 2.45 + j0.54 approximately. The maximum values with model 6 in Method 39.9 /8.34°= 39.5 + j5.79 B have little practical application because they are obtained 40.2 /10.9° = 39.4 + j7.58 115 2.73 /13.12° = 2.66 + j0.62 for negligible values of fscL-45.5 /8.30° = 45.0 + j6.57 Fig. 2 and Fig. 3 show that the low and high limits of the 47.3 /10.8° = 46.5 + j8.88 230 3.07 /13.09° = 2.99 + j0.70 graphs tend to be very similar for Method A and Method B.

53.5 /8.26° = 53.0 + j7.69 Additionally, the variables that define the value of the fault 49.9 /10.8° = 49.0 + j9.35 400 3.51 /13.55° = 3.41 + j0.82 impedance are unpredictable. By these two reasons, the use of 56.4 /8.24° = 55.8 + j8.09 the results of Method A is advisable for the sake of simplicity.

36.6 /12.6° = 35.7 + j7.99 765 4.02 /13.44° = 3.91 + j0.93 41.2 /9.73° = 40.6 + j6.96 B.3. Shape of the curves All the curves of the minimal values of RA, and the curves of the maximum values of RA for line-to-line faults, tend to be B. Arc resistance straight lines in the chosen logarithmic scale. This occurs because RA = g(l) is a hyperbolic function in terms of the fault B.J. General description of the graphs of results current, what means a straight line in the logarithmic scale, Fig. 2 and Fig. 3 show the results of the arc resistance (RA) and in these cases the fault impedance is moderate (and by in function of the short circuit level UscL, without fault this, fscL is similar to the value of the fault current).

impedance). The minimum values of resistance are equal in The curves of the maximum values of RA for line-to-ground both figures. The maximum values of Fig. 2 and Fig. 3 faults tend to be inclined straight lines for low values of fscL correspond to the instantaneous and delayed protections, and to become stable horizontally for high values of fscL* This respectively. Each graph in both figures indicates the results occurs because the values of ZG are very high, and for high of the arc models for the minimal and maximum values of RA.

values of fscL, such ZG value tends to define the value of the For example, Fig. 2 shows that for line-to-ground faults at fault current; therefore, as the fault current has little changes, 230kV whose lscL is 1 kA, the value of RA is between 0.36!1 the arc resistance also has little changes.

and 23!1 for Method A, with minimal values in the range There are two cases without intersection between the between 0.36!1 and 0.76!1, and maxima values between 9.5!1 curves RA = g(!) and I = h(R,4). Both were obtained with and 23!1 (according to the considered arc model). The model 1, for the maximum values of RA for line-to-ground corresponding case in Fig. 3 indicates that the maximum value faults at 69kV, and fscL equals to O.lkA (one case is in Fig. 2 for delayed protections is 42!1 (with values between 16!1 and and the other one is in Fig. 3). As it was indicated in section 42!1, according to the considered arc model). IV, the biggest arc length that allows intersection of the curves was computed for such cases, and the result of this B.2. Comparison between Method A and Method B intersection was applied to the graph for these values of fscL-Fig. 2 and Fig. 3 indicate that the minimum values of RA in the Method A are obtained with model 5. For Method B, B.4. Comparison between different nominal voltages model 5 is assumed to be valid only for fault currents between Except in case of the maximum values of RA for line-to-2 and 12 kA; by this, its minimal values are obtained with ground faults, for each fscL value, the estimated values of RA model 6 for low values of lscL, with model 5 for intermediate tend to be greater while greater is the nominal voltage (VN).

values of lscL, and with model 3 for highest values of lscL- The This occurs because the simulated arc length is greater while fact of obtaining the minimal values with model 3 in Method greater is VN.

B only can be seen easily for line-to-line faults at 765kV In case of the maximum values of RA for line-to-ground because the RA values are very small for these high values of faults, the simulated values of ZG are very big and they do not lscL and such RA values leave the graph by the minimum value differ very much between the different VN values. By this, at used in the scale (0.1!1). In the Method B, the assumed range each fscL specific value, for the lower values of VN there is a for the fault current (table 1) is not equal to the range for lsCL greater reduction in the fault current; such reduction in the by the effect of the fault impedance; this is more evident for fault current influences more in the function RA = g(I),

the maximum values of RA for line-to-ground faults because increasing the value of RA, than the influence by the reduction the fault impedances are greater. of the simulated arc length for the lower values of VN.

The maximum values of RA with Method A are obtained

Cale. No. EE-0883 Attachment C Page No. C148 of C155 Rev. No.ODO References 5

L-L. 765 kV

...J. ... }

. *j l

Method A MethodB Fig. 2. Minimal and maximal arc resistances for instantaneous protections.

Legend for the arc models: Model I,* Model 2, x Model 3, 0 Model 4, + Model 5,

  • Model 6.

Cale. No. EE-0883 Attachment C Page No. C149 ofC155 Rev. No. 000 References 6

L-L. 69 kV 1o"t , .. ,.....*.........*......

10*'

L-L. 400 kV 1 10'

I l

3 RA (Q) 3 RA (Q)

.. _-_~.-.,---------~

  • ----*~" --* -
  • 10 ~ .,-------*-*-*--------, *******-*----- 1 o* .~.-

1

!**~*:~i-0 !:: ****i<i:~~

L-G, 765 kV

,.,,v . . .

i  ; l I 10*' ...

  • 10* *, '10*

1

~,----~---~~-~

1 10*1 10~ 10" fsc1.(kA) 10*' 101! 10 fscL(kA) 10 10° 10 fscL(kA)

Method A Method B Fig. 3. Minimal and maximal arc resistances for delayed protections.

Legend for the arc models: Model I,

  • Model 2, x Model 3, 0 Model 4, + Model 5,
  • Model 6.

Cale. No. EE-0883 Attachment C Page No. C150 ofC155 Rev. No. 000 References 7

B. 5. Summa,y of typical values for fscL greater than 1kA TABLE VI: APPROXIMATE RE SULTS OF RA FOR LINE-TO-GROUND For each lscL and VN, Fig. 2 and Fig. 3 indicate exactly the FAULTS, ANDlscL> I KA (EQUATIONS 13 AND 14).

minimal and maximum estimated values of RA. Nevertheless, Maximum (ins tantaneous Maximum (delayed Min. rotecti on) 1rotection) it is also possible to indicate some approximate relations: VN (kV) K K lscL,ST RA.ST K lscL,ST RA.ST a) Except for 69kV and l 15kV, the minimal values of RA (kV) (kV) (Q) (kV) (kA) (Q)

(kA) are approximately IQ at lkA, O.IQ at IOkA, and tend to be 69 0.13 54 3 18 66 3 22 lower than O.IQ for lscL greater than IOkA. For 69kV and 115 0.20 52 4 13 72 4 18 l 15kV, the minimal values of RA tend to be even lower. 230 0.36 49 6 8.2 75 5 15 b) For line-to-line faults, the maximum values of RA for 400 0.60 47 8 5.9 91 7 13 instantaneous protections are approximately 20Q at lkA and 765 1.1 46 16 2.9 130 13 10 2Q at lOkA if VN is 69kV, l 15kV or 230kV, and they are approximately 40Q at lkA and 4Q at IOkA if VN is 400kV or VI. C ONCLUSION 765kV. The corresponding values for delayed protections are A range of typical expected values for the fault resistance approximately 30Q at lkA and 3Q at IOkA if VN is 69kV or in electrical transmission systems was computed, by using six I 15kV, they are approximately 60Q at lkA and 6Q at lOkA if existing models for the arc resistance and a model for the VN is 230kV, and they are approximately IOOQ at lkA and effective grounding impedance of the towers. The minimal lOQ at IOkA if VN is 400kV or 765kV. and maximum expected values for the fault resistance are c) For line-to-ground faults, the maximum values of RA for dependent of the short circuit level and the nominal voltage of instantaneous protections are approximately 60Q at lkA and the system. The component of the fault resistance associated tend to become stable to 25Q at 3kA if VN is 69kV, they are with the effective grounding resistance of the towers is shown approximately 30Q at .lkA and tend to become stable at lOQ in tables because it is not dependent of the short circuit level, at 3kA if VN is I 15kV or 230kV, and they are approximately while the component associated with the arc resistance is 30Q at lkA and 6Q at lOkA if VN is 400kV or 765kV. The shown in graphs in function of the maximum short circuit corresponding values for delayed protections are similar if VN level (without fault impedance). The achieved information can is 69kV, they are approximately 60Q at lkA and tend to be useful to have a fast estimation of the required range of fault resistances.

become stable to 15Q at 3kA if VN is l lSkV, 230kV or The maximum values of the arc resistances were computed 400kV, and they are approximately lOOQ at lkA and 15Q at considering two different assumptions about the arc I OkA if VN is 765kV.

lengthening. The considered arc length for the instantaneous Another way for doing a summary of these results is protections is lower than for the delayed protections.

making use of the fact that the sloping part of the curves tend For line-to-ground faults, the fault impedance has an to a straight line in the logarithmic scale, whose expression is:

inductive part. The angle of the fault impedance is small, but RA fscL = K (12) the modules of the possible maximum values are so high that K: Constant.

The curve of maximum values of RA for line-to-ground the inductive part of the impedance is not insignificant, and it faults can be approximated as the intersection of an inclined might affect the behavior of some distance protections.

straight line with a horizontal one. The horizontal straight line is described by the values of stabilization UscL,ST and RA.SI); VII. REFERENCES therefore: [I] A Warrington, "Reactance relays negligibly affected by arc impedance",

RA lscL = K, iflscL < lsCL,ST (13) Electrical World, Sept. 1931, pp. 502-505.

[2] A Warrington, Protective Relays. Their theo1y and practice. Volume RA = RA.ST, if lscL 2: lscL,ST (14) one, Chapman & Hall Ltd., London, 1976.

This summary of the results is different to the described [3] Y. Goda, M. Iwata, K. Ikeda, S. Tanaka, "Arc voltage characteristics of one in the previous items (a, b, c) and it has a greater accuracy high current fault arcs in long gaps", IEEE Transactions on Power Delivery, Vol. 15, N° 2, April 2000, pp. 791-795.

and simplicity (Tables V and VI).

[4] V. Terzija, H. Koglin, "On the modeling of long arc in still air and arc resistance calculation", IEEE Transactions on Power Delivery, Vol. 19, TABLE V: APPROXIMATE RESULTS OF RA FOR LINE-TO-LINE N° 3, July 2004, pp. 1012-1017

[5] V. Terzija, H. Koglin, "New dynamic model, laboratory testing and FAULTS ANDlscL> 1 KA(EQUATION 12) features of long arc in free air", Electrical Engineering, Springer-Verlag, Maximum Maximum Vol. 83, N° 4, Aug. 2001, pp. 193-201.

VN Minimum (instantaneous (delayed [6] A P. Strom, "Long 60-Cycle arcs in air", American Institute of (kV) orotection) orotection) Electrical Engineers, Vol. 65, N° 3, March 1946, pp. 113-118.

K(kV) K(kV) K(kV) [7] H. Ayrton, "The mechanism of the electric arc", in Proceedings of the Royal Society of London, Vol. 68, 1901, pp. 410-414.

69 0.20 15 18 [8] V. Terzija, D. Dobrijevic, "Short circuit studies in transmission networks 115 0.32 16 24 using improved fault model", in IEEE Power Tech, Lausanne, July 2007, 230 0.60 20 49 pp. 1752-1757.

[9] V. Terzija, R. Ciric, H. Nouri, "A new iterative method for fault currents 400 I.I 25 72 calculation which models arc resistance at the fault location", Electrical 765 1.6 33 112 Engineering, Springer-Verlag, Vol. 89, Feb. 2006, pp. 157-165.

l Cale. No. EE-0883 Attachment C Page No. C151 ofC155 Rev. No. 000 References 8

[10] D. Jeerings, J. Linders, "Ground resistance - revisited", IEEE Transactions on Power Delivery, Vol. 4, N° 2, April 1989, pp. 949-956.

[11] R. Mason, The art and science of protective relaying, John Wiley &

Sons Inc., 1956.

[12] J. Blackburn, T. Domin, Protective relaying. Principles and applications, third edition, Taylor & Francis Group, LLC, Boca Raton, 2007.

[ 13] IEEE guide for protective relay applications to transmission lines, IEEE Standard C37.l 13-1999(R2004), Dec. 2004.

[14] G. Ziegler, Numerical distance protection. Principles and applications, second edition, Siemens, Erlangen, 2006.

[15] J. Endrenyi, "Analysis of transmission tower potentials during ground faults", IEEE Transactions on Power Apparatus and Systems, Vol. PAS-86, N° 10, Oct. 1967, pp. 1274-1283.

[16] Short-circuit currents in three-phase a.c. systems - Part 3: Currents during two separate simultaneous line-to-earth short circuits and partial short-circuit currents flowing through earth, !EC Standard 60909-3, Sept. 2003.

[17] A. Meliopoulos, Power system grounding and transients, Marcel Dekker, Inc., New York, 1988.

[ 18] C. Ramirez, Subestaciones de a/ta y extra a/ta tension, second edition, Mejia Villegas S.A., Medellin, 2003.

[ 19] J. Martin, Diseiio de subestaciones e/ectricas, second edition, McGraw-Hill, Mexico D. F., 1987.

[20] H. Langrehr, Va/ores btisicos de ctilculo para sistemas de a/ta tension, second edition, AEG-Telefunken, Berlin, 1970.

[21] J. Barnard, A. Pahwa, "Determination of the impacts of high impedance faults on protection of power distribution systems using a probabilistic model", Electric Power Systems Research, N° 28, 1993, pp. 11-18.

[22] IEEE guide for safety in AC substation grounding, IEEE Standard 80-2000, Aug. 2000.

[23] M. Vintan, "Fault current distribution computation on overhead transmission lines", in Proceedings of the Fifth International World Energy System Conference, Vol. II, Oradea, Rumania, 2004, pp. 273-279.

[24] S. Sebo, "Zero-sequence current distribution along transmission lines",

IEEE Transactions on Power Apparatus and Systems, Vol. PAS-88, N° 6, June 1969, pp. 910-919.

[25] T. White, R. Adler, S. Daniel, C. Helsing, M. Lauby, R. Ludorf, W.

Ruff, "An IEEE survey of transmission line population and design characteristics", IEEE Transactions on Power Delivery, Vol. 6, N° 4, Oct. 1991, pp. 1934-1945.

[26] ABB Electric Systems Technology Institute, Electrical transmission and distribution reference book, fifth edition, Raleigh, 1997.

[27] Electric Power Research Institute, Transmission line reference book, 345 kV and above, second edition, Palo Alto, 1982.

[28] Electrical equipment - Data for short-circuit current calculations in accordance with /EC 909 (/988), !EC Standard 909-2, Aug. 1992.

[29] F. Kiessling, P. Nefzger, J.E Nolasco, U. Kaintzyk, Overhead power lines - Planning, design, construction, Springer, Berlin, 2003.

[30] Areva T&D, Network protection & automation guide, first edition, Paris, 2005.

[31] A. Hileman, Insulation Coordination for Power Systems, Taylor &

Francis Group, LLC, Boca Raton, 1999.

[32] K. Girkmann, E. Kiinigshofer, Die hochspannungs-freileitungen, second edition, Springer-Verlag, Vienna, 1952.

[33] Ch. Lavanchy, Etude et construction des /ignes electriques aeriennes, second edition, J.-B. Bailliere, Paris, 1952.

[34] W. Lewis, The protection of transmission systems against lightning, Dover Publications, Inc., New York, 1965.

[35] Insulation co-ordination - Part 2: Application guide, !EC Standard 71-2, third edition, Dec. 1996.

Serial No. 19-210A Docket Nos. 50-338/339 Attachment 5 STUDY CASES FOR RAI NO. 4 AND ATTACHMENT 5 TO CALCULATION EE-0894 Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

lH Emergency Bus Cases BE1-47N Re lay Case Resul t s (EE-0894 Attachment ll Case# Unit 1 Unit2 Bus Open Phase LOCA Negative Sequence, V2 t = 8s  % V2  % Deratin Derating Acceptable Power Power Loading (L-N rms, at 4200:120 PT secondaries) (SWGR lH Equipment)

%  % Location Ground SWGRlH SWGR lJ SWGR 2H SWGR 2J SWGR lH SWGRl H AFW SW CH LHSI OSRS QS ISRS cc 1 0 0 Norm TXl No No 2.821 0.305 0.309 2.829 4.07 0.81 Yes No Yes N/A N/A N/A N/A Yes 2 0 0 Norm TXl No No 2.8 15 0.307 0.311 2.823 4.06 0.81 Yes No Yes N/A N/A N/A N/A Yes 3 0 0 Norm TXl No No 2.842 0.305 0.309 2.850 4.10 0.81 Yes No Yes N/A N/A N/A N/A Yes 14 0 0 Norm TXl No Yes 2.844 0.301 0 .306 2.853 4.11 0.81 Yes*** No Yes No Yes Yes Yes*** N/A 19 0 0 Norm TXl No No 2.843 0.305 0.308 2.851 4.10 0.81 Yes No Yes N/A N/A N/A N/A Yes 22 0 0 Min TXl No No 2.897 0.3 17 0.304 2.898 4.18 0.80 Yes No Yes N/A N/A N/A N/A Yes 29 0 0 Min TXl No Yes 2.881 0.297 0.300 2.891 4.16 0.80 Yes*** No Yes No Yes Yes Yes*** N/A 32 0 0 Min TXl No No 2.920 0.318 0.303 2.922 4.21 0.80 Yes No Yes N/A N/A N/A N/A Yes 35 100 100 Norm TXl No No 1.965 0.330 0.323 1.969 2.84 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 38 100 100 Norm TXl No Yes 1.980 0.347 0.323 1.985 2.86 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 41 100 100 Norm TXl No No 1.935 0.323 0.323 1.968 2.79 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 44 100 100 Min TXl No No 1.891 0.299 0.343 1.891 2.73 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 47 100 100 Min TXl No Yes 2.002 0.325 0.338 2.009 2.89 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 50 100 100 Min TXl No No 1.871 0.301 0.309 1.872 2.70 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 233 0 O Norm GSU 1 No No 0.937 0.323 0.322 0.306 1.35 0.98 Yes Yes Yes N/A N/A N/ A N/A Yes 236 0 0 Norm GSU 1 No Yes 0.985 0 .342 0.323 0.340 1.42 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/ A 239 0 O Norm GSU 1 No No 0.938 0 .316 0.325 0.360 1.35 0.98 Yes Yes Yes N/A N/A N/ A N/A Yes 242 0 0 Min GSU 1 No No 0.983 0.300 0.322 0.307 1.42 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 245 0 0 Min GSU 1 No Yes 0.976 0.302 0.321 0.307 1.41 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 248 0 0 Min GSU 1 No No 0.983 0 .317 0.325 0.360 1.42 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 252 0 0 Norm GSU 1 350 Ohm No 0.693 0 .734 0.700 7.496 1.00 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 253 0 0 Norm GSU 1 GND No 1.023 1.144 1.079 14.571 1.48 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 255 0 0 Norm GSU 1 350 Ohm Yes 0.694 0.723 0.680 7.462 1.00 0.99 Yes Yes Yes Yes Yes Yes Yes N/ A 256 0 0 Norm GSU 1 GND Yes 1.021 1.123 1.020 14.479 1.47 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 258 0 O Norm GSU 1 350 Ohm No 0.695 0 .735 0.700 7.480 1.00 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 259 0 O Norm GSU 1 GND No 1.024 1.147 1.081 14.544 1.48 0.97 Yes Yes Yes N/A N/A N/ A N/A Yes 261 0 0 Min GSU 1 350 Ohm No 0.695 0 .736 0.694 7.894 1.00 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 262 0 0 Min GSU 1 GND No 1.025 1.148 1.037 15.370 1.48 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 264 0 0 Min GSU 1 350 Ohm Yes 0.694 0 .724 0.688 7.460 1.00 0.99 Yes Yes Yes Yes Yes Yes Yes N/A 265 0 0 Min GSU 1 GND Yes 1.021 1.124 1.020 14.477 1.47 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 267 0 0 Min GSU 1 350 Ohm No 0.697 0 .737 0.395 7.859 1.01 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 268 0 0 Min GSU 1 GND No 1.027 1.151 1.039 15.299 1.48 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 270 0 O Norm GSU 2 350 Ohm No 0.899 6.329 0.970 0.899 1.30 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 271 0 O Norm GSU 2 GND No 1.685 14.177 1.591 1.685 2.43 0.92 Ives Yes Yes N/A N/A N/A N/A Yes 273 0 O Norm GSU 2 350 Ohm Yes 0.804 6.290 0.857 0.804 1.16 0.98 Yes Yes Yes Yes Yes Yes Yes* ** N/A 274 0 0 Norm GSU 2 GND Yes 1.450 13.959 1.583 1.452 2.09 0.94 Yes* .. Yes Yes Yes Yes Yes Yes*** N/A 276 0 O Norm GSU 2 350 Ohm No 0.898 6.331 0.853 0 .899 1.30 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 277 0 O Norm GSU 2 GND No 1.684 14.175 1.580 1.685 2.43 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 279 0 0 Min GSU 2 350 Ohm No 0.887 11.215 0.863 0.887 1.28 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 280 0 0 Min GS U 2 GND No 1.642 25.691 1.615 1.645 2.37 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 282 0 0 M in GSU 2 350 Oh m Yes 0.884 6.288 0.859 0.885 1.28 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 283 0 0 Min GSU 2 GND Yes 1.564 14.062 1.582 1.571 2.26 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 285 0 0 Min GSU 2 350 Ohm No 0.901 6.637 0.857 0.901 1.30 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 286 0 0 Min GSU 2 GND No 1.617 14.940 1.585 1.623 2.33 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 288 0 0 Norm GSU 2 350 Ohm No 0.877 0.792 6.424 0.709 1.27 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 289 0 0 Norm GSU 2 GND No 1.639 1.507 14.270 1.189 2.37 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 291 0 0 Norm GSU 2 350 Ohm Yes 0.867 0.792 6.401 0.696 1.25 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 292 0 o Norm GSU 2 GND Yes 1.612 1.506 14.188 1.130 2.33 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 294 0 0 Norm GSU 2 350 Ohm No 0.852 0.849 6.281 0.657 1.23 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 295 0 O Norm GSU 2 GND No 1.642 1.510 14.240 1.191 2.37 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 297 0 0 Min GSU 2 350 Ohm No 0.879 0.795 6.752 0.691 1.27 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 298 0 0 Min GSU 2 GND No 1.644 1.511 15.030 1.153 2.37 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 300 0 0 Min GSU 2 350 Ohm Yes 0 .867 0 .792 6.401 0.692 1.25 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 301 0 0 Min GSU 2 GND Yes 1.612 1.506 14.188 1.148 2.33 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 303 0 0 Min GSU 2 350 Ohm No 0.854 0.851 6.602 0.615 1.23 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 304 0 0 M in GSU 2 GND No 1.647 1.514 14.974 1.155 2.38 0.93 Yes Yes Yes N/A N/A N/A N/A Yes Switchyard Unbalance Cases (EE-0894 Attachment 2) 2 0 O Norm TXl B No 2.193 1.835 1.674 2.198 3.16 0.88 Yes Yes Yes N/A N/A N/A N/A Yes 3 0 O Norm TXl C No 2.867 1.827 1.667 2. 875 4.14 0 .80 Yes No Yes N/A N/A N/A N/A Yes 9 100 100 Norm TXl A No 3.094 1.873 1.081 3.102 4 .47 0 .77 Yes No Yes N/A N/A N/A N/A Yes 10 100 100 Norm TX1 A Yes 3. 067 1.799 1.801 3.088 4.4 3 0.78 Yes*** No Yes No Yes Yes Yes*** N/A 11 100 100 Norm TX1 A No 3.071 1.837 1.800 3.079 4.43 0.78 Yes No Yes N/A N/A N/A N/A Yes 12 100 100 Min !n<l A No 3.238 1.711 1.689 3.240 4 .67 0.75 Yes No Yes N/A N/A N/A N/A Yes 14 100 100 Min !n<l A No 3.2 15 1.690 1.691 3.216 4.64 0.76 Yes No Yes N/A N/A N/A N/ A Yes 15 0 0 Norm TX2 A No 1.631 1.714 4.143 1.632 2.35 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 16 0 0 Norm TX2 A Yes 1.505 1.714 4.157 1.505 2.17 0.94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 17 0 0 Norm TX2 A No 1.629 1.714 4 .167 1.629 2.35 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 18 0 0 Min TX2 A No 1.560 1.716 4 .270 1.560 2.25 0 .93 Yes Yes Yes N/A N/A N/A N/A Yes 19 0 0 Min TX2 A Yes 1.551 1.715 4 .130 1.552 2.24 0 .93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 20 0 0 Min TX2 A No 1.562 1.716 4 .293 1.562 2.26 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 21 100 100 Norm TX2 A No 1.815 1.686 3.577 1.816 2.62 0.91 Yes Ye s Yes N/A N/A N/A N/A Yes 22 100 100 Norm TX2 A Yes 1.654 1.689 3.598 1.655 2.39 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 23 100 100 No rm TX2 A No 1.882 1.709 3.612 1.816 2.72 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 24 100 100 Min TX2 A No 1.727 1.686 3.666 1.726 2.49 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 25 100 100 Min TX2 A Yes 1.683 1.708 3.578 1.683 2.43 0.92 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 26 100 100 Min TX2 A No 1.704 1.696 3.664 1.703 2.46 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 27 0 0 Norm GSU 1 A No 2.046 1.789 1.662 1.573 2.95 0.89 Yu Yes Yes N/A- - N/A- N/-A N/A -- Yes 28 0 0 Norm GSU 1 A Yes 1.988 1.666 1.636 1.572 2.87 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 29 0 0 Norm GSU 1 A No 2.045 1.592 1.730 1.740 2.95 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 30 0 0 Min GSU 1 A No 2.090 1.655 1.662 1.579 3.02 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 31 0 0 Min GSU 1 A Yes 2.020 1.662 1.636 1.573 2.92 0.89 Yes*** Yes Yes Ye s Yes Yes Yes*** N/A 32 0 0 Min GSU 1 A No 2.045 1.592 1.730 1.741 2.95 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 33 0 O Norm GSU 1 A No 1.574 1.737 1.636 1.966 2.27 0.93 Yes Yes Yes N/ A N/A N/A N/A Yes 34 0 0 Norm GS U 1 A Yes 1.539 1.758 1.569 2.006 2.22 0.94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 35 0 O Norm GSU 1 A No 1.539 1.789 1.662 1.974 2.22 0.94 Yes Yes Yes N/A N/A N/A N/A Yes 36 0 0 Min GSU 1 A No 1.538 1.789 1.531 2.060 2.22 0.94 Yes Yes Yes N/A N/A N/A N/A Yes 37 0 0 Min GSU 1 A Yes 1.539 1.758 1.524 1.973 2.22 0 .94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 38 0 0 Min GSU 1 A No 1.539 1.790 1.531 2.041 2.22 0.94 Yes Yes Yes N/A N/A N/A N/A Yes 39 0 O Norm GSU 2 A No 2.171 1.774 2.058 2.172 3.13 0 .88 Yes Yes Yes N/A N/A N/A N/A Yes 40 0 0 Norm GSU 2 A Yes 1.93 1 1.883 2.109 1.935 2.79 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 41 0 0 Norm GSU 2 A No 2.171 1.782 1.999 2.171 3.13 0.88 Yes Yes Yes N/ A N/A N/ A N/A Yes 42 0 0 Min GSU 2 A No 2.014 2.323 1.998 2.023 2.91 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 43 0 0 Min GSU 2 A Yes 2.004 1.339 2.013 2.009 2.89 0.89 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 44 0 0 Min GSU 2 A No 2.098 1.850 2.004 2.102 3.03 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 45 0 0 Norm GSU 2 A No 2.161 1.971 1.875 1.515 3.12 0.88 Yes Yes Yes N/A N/A N/A N/A Yes 46 0 O Norm GSU 2 A Yes 2.126 1.971 1.814 1.510 3.07 0.88 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 47 0 0 Norm GS U 2 A No 2.161 1.971 1.859 1.516 3.12 0.88 Yes Yes Yes N/A N/A N/A N/A Yes 48 0 0 Min GSU 2 A No 2.161 1.970 1.874 1.481 3.12 0.88 Yes Yes Yes N/A N/A N/A N/A Yes 49 0 0 Min GSU 2 A Yes 2.125 1.973 1.813 1.477 3.07 0.88 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 50 0 0 Min GSU 2 A No 2.161 1.971 1.859 1.483 3.12 0.88 Yes Yes Yes N/A N/A N/A N/A Yes

      • Values have been evaluated as acceptable in EE-0894 Attachment 5

1J Emergency Bus Cases BE1-47N Relay Case Resu lts (EE-0894 Attach ment 1)

Case# Unit 1 Unit 2 Bus Open Ph ase LOCA Negative Sequence, V2 t = 8s %V2  % Deratin g Deratin g Acce ptable Power Power Loading (L-N rms, at 4200:120 PT secondaries) (SWG R lJ Equ ipment)

%  % Location Ground SWGR lH SW GR lJ SWGR 2H SWG R 2J SW GR l J SW GR lJ AFW SW CH LHSI OS RS QS ISRS cc 234 0 0 Norm GSU 1 GN D-R No 7.5 28 0 .716 0.676 0.642 1.03 0.99 Yes Yes Yes N/A N/A N/ A N/A Yes 235 0 0 Norm GSU 1 GND No 14.756 1.143 1.070 1.009 1.65 0.96 Yes Yes Yes N/ A N/ A N/A N/A Yes 238 0 0 Norm GSU 1 GND Yes 14.563 1.064 1.053 1.005 1.54 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 241 0 0 Norm GSU 1 GND No 14.746 1.028 1.106 1.100 1.48 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 244 0 0 Min GSU 1 GND No 15.560 1.072 1.074 1.013 1.55 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 241 0 0 Min GSU 1 GND Yes 14.563 1.065 1.053 1.005 1.54 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/ A 25( 0 0 M in GSU 1 GND No 14.746 1.028 1. 106 1.10( 1.48 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 252 0 O Norm GSU 1 GND-R No 0.693 0. 734 0.700 7.49E 1.06 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 253 0 O Norm GSU 1 GND No 1.023 1.144 1.079 14.5 71 1.65 0.96 Yes Yes Yes N/A N/A N/A N/A Yes 255 0 0 Norm GSU 1 GND-R Yes 0.694 0.723 0.680 7.462 1.04 0.99 Yes Yes Yes Yes Yes Yes Yes N/A 25E 0 0 Norm GSU 1 GND Yes 1.021 1.123 1.020 14.47S 1.62 0.97 Yes *** Ye s Yes Yes Yes Yes Yes*** N/A 258 0 O Norm GSU 1 GND-R No 0.695 0.735 0.700 7.48( 1.06 0.99 Yes Yes Yes N/A N/A N/ A N/A Yes 259 0 O Norm GSU 1 GND No 1.024 1.147 1.081 14.54~ 1.66 0.96 Yes Yes Yes N/A N/A N/A N/A Yes 26 1 0 0 M in GSU 1 GND-R No 0.695 0.736 0.694 7.894 1.06 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 262 0 0 Min GSU 1 GND No 1.025 1.148 1.037 15.37( 1.66 0.96 Yes Yes Yes N/A N/A N/A N/A Yes 264 0 0 Min GSU 1 GND-R Yes 0.694 0.724 0.688 7.46( 1.04 0.99 Yes Yes Yes Yes Yes Yes Yes N/A 265 0 0 M in GSU 1 GND Yes 1.021 1.124 1.020 14.47 1 1.62 0.97 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 26 1 0 0 M in GSU 1 GND-R No 0.697 0.737 0.395 7.859 1.06 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 268 0 0 M in GSU 1 GND No 1.027 1.151 1.039 15.29S 1.66 0.96 Yes Yes Yes N/A N/A N/ A N/A Yes 272 0 0 Norm GSU 2 No Yes 0.328 0.768 0.326 0.33( 1.1 1 0.99 Yes Yes Yes Yes Yes Yes Yes N/A 275 0 0 Norm GSU 2 No No 0.329 0.705 0. 348 0. 329 1.02 0.99 Yes Yes Yes N/A N/A N/ A N/A Yes 278 0 0 Min GSU 2 No No 0.362 0.906 0. 344 0.363 1.31 0 .98 Yes Yes Yes N/A N/A N/ A N/A Yes 284 0 0 Mi n GSU 2 No No 0.352 0 .695 0.346 0.353 1.00 0.99 Yes Yes Yes N/A N/A N/ A N/A Yes 288 0 0 Norm GSU 2 GN D-R No 0.877 0.792 6.424 0 .709 1.14 0.98 Yes Yes Yes N/A N/A N/ A N/A Yes 289 0 0 Norm GSU 2 GND No 1.639 1.507 14 .270 1.189 2. 18 0.94 Yes Yes Yes N/A N/A N/A N/A Yes 291 0 O Norm GSU 2 GND-R Yes 0.867 0 .792 6.401 0.69E 1.14 0 .99 Yes Yes Yes Yes Yes Yes Yes*** N/A 292 0 0 Norm GSU 2 GND Yes 1.612 1.506 14 .188 1.13( 2.17 0 .94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 294 0 0 Norm GSU 2 GND-R No 0 .85 2 0.849 6.281 0.657 1.23 0.98 Yes Yes Ye s N/A N/A N/A N/A Yes 295 0 0 Norm GSU 2 GND No 1.642 1.510 14.240 1.191 2.18 0 .94 Yes Yes Yes N/ A N/A N/A N/A Yes 29 1 0 0 M in GSU 2 GND-R No 0.879 0.795 6. 752 0.691 1.15 0 .98 Yes Yes Yes N/A N/ A N/A N/A Yes 298 0 0 M in GSU 2 GND No 1.644 1.511 15.030 1.153 2.18 0 .94 Yes Yes Yes N/A N/ A N/A N/A Yes 30( 0 0 M in GSU 2 GND-R Yes 0 .867 0.792 6.40 1 0 .692 1.14 0 .99 Yes Yes Yes Yes Yes Yes Yes*** N/ A 301 0 0 Min GSU 2 GND Yes 1.612 1.506 14.188 1.148 2.17 0 .94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 303 0 0 Min GSU 2 GND-R No 0 .854 0.851 6.602 0.6 15 1.23 0.98 Yes Yes Yes N/A N/A N/A N/ A Yes 304 0 0 Min GSU 2 GND No 1.647 1.514 14 .974 1.155 2.19 0 .94 Yes Yes Yes N/A N/A N/A N/A Yes Switchya rd Unbalance Cases (EE-0894 Attach ment 2) 1 0 O Norm TXl A No 3.730 1.807 1.649 3.74( 2.6 1 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 2 0 0 Norm TXl B No 2.193 1.835 1.674 2.198 2.65 0.91 Yes Yes Yes N/A N/ A N/ A N/A Ye s 3 0 0 Norm TXl C No 2.867 1.827 1.667 2.875 2.64 0.91 Yes Yes Yes N/A N/A N/ A N/A Yes 4 0 O Norm TXl A Yes 3.747 1.463 1.623 3.758 2.1 1 0.94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 5 0 0 Norm TXl A No 3.750 1.814 1.649 3.76 1 2.62 0 .91 Yes Yes Yes N/A N/A N/A N/A Yes 6 0 0 M in TXl A No 3.928 1.648 1.602 3.930 2.38 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 7 0 0 Min ITXl A Yes 3.840 1.624 1.601 3.854 2.34 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 8 0 0 Min TXl A No 3.952 1.649 1.602 3.953 2.38 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 9 10( 100 Norm TXl A No 3.094 1.873 1.081 3.102 2.70 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 10 10( 100 Norm TXl A Yes 3.067 1.799 1.801 3.088 2.60 0.91 Yes*** Yes Yes Yes Yes Yes Yes*** N/ A 11 100 100 No rm TXl A No 3.071 1.837 1.800 3.079 2.65 0.91 Yes Yes Yes N/A N/A N/ A N/A Yes 12 100 100 M in TXl A No 3.238 1.711 1.689 3.24( 2.47 0.92 Yes Yes Yes N/ A N/A N/A N/A Yes 13 100 100 M in TXl A Yes 3.825 1.384 1.307 3.827 2 .0( 0.95 Yes*** Yes Ye s Yes Yes Ye s Yes*** N/A 14 100 100 Min TXl A No 3.215 1.690 1.691 3.216 2.44 0 .92 Yes Ye s Yes N/ A N/A N/ A N/A Yes 15 0 0 Norm TX2 A No 1.63 1 1.714 4 .143 1.632 2.47 0 .92 Yes Yes Yes N/ A N/A N/ A N/A Yes 16 0 O Norm TX2 A Yes 1.505 1.714 4. 157 1.505 2.47 0 .92 Yes*** Yes Yes Yes Yes Yes Yes*** N/ A 17 0 O Norm TX2 A No 1.629 1.714 4.167 1.62S 2.47 0 .92 Yes Yes Yes N/A N/A N/A N/A Yes 18 0 0 Mi n TX2 A No 1.5 60 1.716 4.270 1.56( 2.48 0.92 Yes Yes Yes N/A N/ A N/A N/A Yes 19 0 0 Mi n TX2 A Yes 1.551 1.715 4.130 1.552 2.47 0.92 Yes*** Yes Yes Yes Yes Ye s Yes*** N/A 20 0 0 Min TX2 A No 1.562 1.716 4.293 1.562 2.48 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 21 10( 100 Norm TX2 A No 1.8 15 1.686 3.577 1.81E 2.43 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 22 10( 100 Norm TX2 A Yes 1.654 1.689 3.598 1.655 2.44 0.92 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 23 10( 100 Norm TX2 A No 1.882 1.709 3. 612 1.81E 2.47 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 24 10( 100 Min TX2 A No 1.727 1.686 3.666 1.726 2.43 0.92 Yes Yes Yes N/A N/ A N/A N/A Yes 25 10( 100 Min TX2 A Yes 1.683 1.708 3.578 1.683 2.47 0.92 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 26 10( 100 Min TX2 A No 1.704 1.696 3.664 1.703 2.45 0 .92 Yes Yes Yes N/A N/A N/ A N/A Yes 27 0 0 Norm GSU 1 A No 2.046 1.789 1.662 1.573 2.58 0 .91 Yes Yes Yes N/A N/A N/ A N/A Yes 28 0 O Norm GSU 1 A Yes 1.988 1.666 1.636 1.572 2.40 0 .93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 29 0 0 Norm GSU 1 A No 2.045 1.592 1.730 1.74( 2.30 0 .93 Yes Yes Yes N/A N/A N/A N/A Yes 30 0 0 Min GSU 1 A No 2.090 1.655 1.662 1.579 2.39 0 .93 Yes Yes Yes N/ A N/ A N/A N/A Yes 31 0 0 Mi n GSU 1 A Yes 2.020 1.662 1.636 1.573 2.40 0 .93 Yes*"" Yes Yes Yes Yes Yes Yes*** N/A 32 0 0 Min GSU 1 A No 2.045 1.592 1.730 1.741 2.30 0.93 Yes Yes Yes N/A N/ A N/ A N/A Ye s 33 0 0 Norm GSU 1 A No 1.574 1.737 1.636 1.96E 2.51 0.92 Yes Yes Yes N/A N/ A N/A N/A Yes 34 0 0 Norm GSU 1 A Yes 1.5 39 1.758 1.569 2.006 2.54 0.92 Yes*** Yes Yes Yes Yes Yes Yes*** N/ A 35 0 0 Norm GSU 1 A No 1.539 1.789 1.662 1.974 2.58 0.91 Yes Yes Yes N/A N/A N/ A N/A Yes 36 0 0 M in GSU 1 A No 1.538 1.789 1.531 2.06( 2.58 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 37 0 0 Min GSU 1 A Yes 1.539 1.758 1.524 1.973 2 .54 0 .92 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 38 0 0 Min GSU 1 A No 1.539 1.790 1.531 2.041 2.58 0.91 Yes Yes Yes N/A N/A N/ A N/A Yes 39 0 0 Norm GSU 2 A No 2. 171 1.774 2.058 2.172 2.56 0 .92 Yes Yes Yes N/A N/A N/A N/A Yes 40 0 0 Norm GSU 2 A Yes 1.931 1.883 2.109 1.935 2.72 0.91 Yes*** Yes Yes Yes Yes Yes Yes*** N/ A 41 0 O Norm GSU 2 A No 2.171 1.782 1.999 2. 171 2.57 0.92 Yes Yes Yes N/A N/ A N/A N/A Yes 42 0 0 M in GSU 2 A No 2.014 2.323 1.998 2.023 3.35 0.8E Yes Yes Yes N/ A N/A N/A N/A Yes 43 0 0 M in GSU 2 A Yes 2.004 1.339 2.013 2.009 1.93 0.95 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 44 0 0 M in GSU 2 A No 2.098 1.850 2.004 2. 102 2.67 0 .91 Yes Yes Yes N/ A N/A N/A N/A Yes 45 0 0 No rm GSU 2 A No 2.161 1.971 1.875 1.515 2.84 0.9( Yes Yes Yes N/A N/A N/A N/A Yes 46 0 O Norm GSU 2 A Yes 2.126 1.971 1.8 14 1.5 10 2.84 0.9( Yes*** Yes Yes Yes Yes Yes Yes*** N/A 47 0 O Norm GSU 2 A No 2.161 1.971 1.859 1.516 2.85 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 48 0 0 Min GSU 2 A No 2. 161 1.970 1.874 1.481 2.84 0 .90 Yes Yes Yes N/A N/ A N/A N/A Yes 49 0 0 Min GSU 2 A Yes 2.125 1.973 1.813 1.477 2.85 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 50 0 0 Min GSU 2 A No 2.161 1.971 1.859 1.483 2.84 0.90 Yes Yes Yes N/A N/A N/ A N/A Yes

      • Va lues have been evaluated as acce ptable in EE-0894 Attachment 5

2H Emergency Bus Cases BE1-47N Relav Case Results (EE-0894 Attachment 1)

Case# Unit l Unit2 Bus Open Phase LOCA Negative Sequence, V2 t = 8s  % V2  % Deratin aerating Acceptable Power Power Loadin2 (L-N rms, at 4200:120 PT secondaries)

%  % Location Ground SWGR lH SWGR lJ SWGR2H SWGR 2J SWGR 2H SWGR 2H AFW SW CH LHS I OSRS QS ISRS cc 52 100 100 Min ITT<l GND No 19.008 0.422 0.848 19.014 1.22 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 53 0 0 Norm ITT<2 No No 0.313 0.349 3.156 0.313 4.55 0.77 Yes No Yes N/A N/A N/A N/A Yes 56 0 O Norm rrx2 No Yes 0.323 0.323 3.176 0.323 4.58 0.76 Yes*** No Yes No Yes Yes Yes*** N/A 59 0 0 Norm rrx2 No No 0.311 0.322 3.180 0.311 4.59 0.76 Yes No Yes N/A N/A N/A N/A Yes 62 0 0 Min ITT<2 No No 0.309 0.329 3.203 0.309 4.62 0.76 Yes No Yes N/A N/A N/A N/A Yes 65 0 0 Min ITT<2 No Yes 0.297 0.330 3.148 0.297 4.54 0.77 Yes*** No Yes No Yes Yes Yes*** N/A 68 0 0 Min ITT<2 No No 0.308 0.330 3.227 0.308 4.66 0.75 Yes No Yes N/A N/A N/A N/A Yes 71 100 100 Norm ITX2 No No 0.326 0.361 2.445 0.326 3.53 0.85 Yes No Yes N/A N/A N/A N/A Yes 74 100 100 Norm ITX2 No Yes 0.335 0.363 2.457 0.336 3.55 0.85 Yes*** No Yes No Yes Yes Yes*** N/A 77 100 100 Norm 1Tx2 No No 0.325 0.299 2.398 0.325 3.46 0.86 Yes No Yes N/A N/A N/A N/A Yes 80 100 100 Min ITT<2 No No 0.356 0.361 2.418 0.356 3.49 0.85 Yes No Yes N/A N/A N/A N/A Yes 83 100 100 Min rrx2 No Yes 0.337 0.361 2.415 0.336 3.49 0.85 Yes*** No Yes No Yes Yes Yes*** N/A 86 100 100 Min rrx2 No No 0.319 0.344 2.417 0.319 3.49 0.85 Yes No Yes N/A N/A N/A N/A Yes 235 0 0 Norm GSU 1 GND No 14.756 1.143 1.070 1.009 1.54 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 23E 0 0 Norm GSU 1 GND Yes 14.563 1.064 1.053 1.005 1.52 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 24( 0 0 Norm GSU 1 GND-R No 7.521 0.656 0.697 0.727 1.01 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 241 0 0 Norm GSU 1 GND No 14.746 1.028 1.106 1.100 1.60 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 244 0 0 Min GSU 1 GND No 15.560 1.072 1.074 1.013 1.55 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 24i 0 0 Min GSU 1 GND Yes 14.563 1.065 1.053 1.005 1.52 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 249 0 0 Min GSU 1 GND-R No 7.521 0.656 0.697 0.737 1.01 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 25( 0 0 Min GSU 1 GND No 14.746 1.028 1.106 1.100 1.60 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 252 0 0 Norm GSU 1 GND-R No 0.693 0.734 0.700 7.496 1.01 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 253 0 0 Norm GSU 1 GND No 1.023 1.144 1.079 14.571 1.56 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 25E 0 O Norm GSU 1 GND Yes 1.021 1.123 1.020 14.479 1.47 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 25E 0 0 Norm GSU 1 GND-R No 0.695 0.735 0.700 7.480 1.01 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 259 0 0 Norm GSU 1 GND No 1.024 1.147 1.081 14.544 1.56 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 261 0 0 Min GSU 1 GND-R No 0.695 0.736 0.694 7.894 1.00 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 262 0 0 Min GSU 1 GND No 1.025 1.148 1.037 15.37( 1.50 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 265 0 0 Min GSU 1 GND Yes 1.021 1.124 1.020 14.47, 1.47 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 26E 0 0 Min GSU 1 GND No 1.027 1.151 1.039 15.299 1.50 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 27( 0 0 Norm GSU 2 GND-R No 0.899 6.329 0.970 0.899 1.40 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 271 0 0 Norm GSU 2 GND No 1.685 14.177 1.591 1.685 2.30 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 273 0 0 Norm GSU 2 GN D-R Yes 0.804 6.290 0.857 0.804 1.24 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 274 0 0 Norm GSU 2 GND Yes 1.450 13.959 1.583 1.452 2.28 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 276 0 0 Norm GSU 2 GND-R No 0.898 6.331 0.853 0.899 1.23 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 271 0 0 Norm GSU 2 GND No 1.684 14.175 1.580 1.685 2.28 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 279 0 0 Min GSU 2 GND-R No 0.887 11.215 0.863 0.887 1.25 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 28( 0 0 Min GSU 2 GND No 1.642 25.691 1.615 1.645 2.33 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 282 0 0 Min GSU 2 GND-R Yes 0.884 6.288 0.859 0.885 1.24 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 283 0 0 Min GSU 2 GND Yes 1.564 14.062 1.582 1.571 2.28 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 285 0 0 Min GSU 2 GND-R No 0.901 6.637 0.857 0.901 1.24 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 286 0 0 Min GSU 2 GND No 1.617 14.940 1.585 1.623 2.29 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 28, 0 O Norm GSU 2 No No 0.327 0.351 0.711 0.325 1.03 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 29C 0 0 Norm GSU 2 No Yes 0.326 0.357 0.699 0.338 1.01 0.99 Yes Yes Yes Yes Yes Yes Yes N/A 293 0 0 Norm GSU 2 No No 0.327 0.355 0.707 0.327 1.02 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 296 0 0 Min GSU 2 No No 0.327 0.356 0.706 0.322 1.02 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 299 0 0 Min GSU 2 No Yes 0.326 0.358 0.719 0.324 1.04 0.99 Yes Yes Yes Yes Yes Yes Yes N/A 302 0 0 Min GSU 2 No No 0.327 0.356 0.693 0.323 1.00 0.99 Yes Yes Yes N/A N/A N/A N/A Yes Switchyard Unbalance Cases (EE-0894 Attachment 2) 1 0 O Norm rrx1 No No 3.730 1.807 1.649 3.740 2.38 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 2 0 O Norm rm No No 2.193 1.835 1.674 2.198 2.42 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 3 0 0 Norm 1rx1 No No 2.867 1.827 1.667 2.875 2.41 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 4 0 0 Norm ITT<l No Yes 3.747 1.463 1.623 3.758 2.34 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 5 0 O Norm ID<l No No 3.750 1.814 1.649 3.761 2.38 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 6 0 0 Mi n ID<l No No 3.928 1.648 1.602 3.930 2.31 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 7 0 0 M in ITT(l No Yes 3.840 1.624 1.601 3.854 2.31 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 8 0 0 Min rrx1 No No 3.952 1.649 1.602 3.953 2.31 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 9 100 100 Norm rrx1 No No 3.094 1.873 1.081 3.102 1.56 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 10 100 100 Norm ITXl No Yes 3.067 1.799 1.801 3.088 2.60 0.91 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 11 100 100 Norm ITXl No No 3.071 1.837 1.800 3.079 2.60 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 12 100 100 Min ID<l No No 3.238 1.711 1. 689 3.240 2.44 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 13 100 100 Min ID<l No Yes 3.825 1.384 1.307 3.827 1.89 0.95 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 14 100 100 Min ID<l No No 3.2 15 1.690 1.691 3.216 2.44 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 27 0 0 Norm GSU 1 No No 2.046 1.789 1.662 1.573 2.40 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 28 0 0 Norm GSU 1 No Yes 1.988 1.666 1.636 1.572 2.36 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 29 0 0 Norm GSU 1 No No 2.045 1.592 1.730 1.740 2.50 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 30 0 0 Min GSU 1 No No 2.090 1.655 1.662 1.579 2.40 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 31 0 0 Min GSU 1 No Yes 2.020 1.662 1.636 1.573 2.36 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 32 0 0 Min GSU 1 No No 2.045 1.592 1.730 1.741 2.50 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 33 0 0 Norm GSU 1 No No 1.574 1.737 1.636 1.966 2.36 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 34 0 0 Norm GSU 1 No Yes 1.539 1.758 1.569 2.006 2.26 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 35 0 0 Norm GSU 1 No No 1.539 1.789 1.662 1.974 2.40 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 36 0 0 Min GSU 1 No No 1.538 1.789 1.531 2.060 2.21 0.94 Yes Yes Yes N/A N/A N/A N/A Yes 37 0 0 Min GSU 1 No Yes 1.539 1.758 1.524 1.973 2.20 0.94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 38 0 0 Min GSU 1 No No 1.539 1.790 1.531 2.041 2.21 0.94 Yes Yes Yes N/A N/A N/A N/A Yes 39 0 0 Norm GSU 2 No No 2.171 1.774 2.058 2.172 2.97 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 40 0 0 Norm GSU 2 No Yes 1.931 1.883 2.109 1.935 3.04 0.88 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 41 0 0 Norm GSU 2 No No 2.171 1.782 1.999 2.171 2.88 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 42 0 0 M in GSU 2 No No 2.014 2.323 1.998 2.023 2.88 0.90 Yes Yes Yes N/A N/A N/A N/ A Yes 43 0 0 Min GSU 2 No Yes 2.004 1.339 2.013 2.009 2.91 0.89 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 44 0 0 Min GSU 2 No No 2.098 1.850 2.004 2.102 2.89 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 45 0 0 Norm GSU 2 No No 2.161 1.971 1.875 1.515 2.71 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 46 0 0 Norm GSU 2 No Yes 2.126 1.971 1.814 1.510 2.62 0.91 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 47 0 0 Norm GSU 2 No No 2.161 1.971 1.859 1.516 2.68 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 48 0 0 Min GSU 2 No No 2.161 1.970 1.874 1.481 2.71 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 49 0 0 Min GSU 2 No Yes 2.125 1.973 1.813 1.477 2.62 0.91 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 50 0 0 Min GSU 2 No No 2.161 1.971 1.859 1.483 2.68 0.91 Yes Yes Yes N/A N/A N/A N/A Yes

  • ** Values have been evaluated as acceptable in EE-0894 Attachment 5

2JE mergen cv Bus Cases BE1-47N Relay Case Results (EE-0894 Attachment 1)

Case# Unit 1 Unit 2 Bus Open Phase LOCA Negative Sequence, V2 t = 8s  % V2  % Deratin Derating Acceptable Power Power Loading (L-N rms, at 4200 :120 PT secondaries) (SWGR 1J Equipment)

%  % Location Ground SWGR l H SW GR lJ SW GR 2H SWGR 2J SW GR lJ SW GR l J AFW SW CH LHSI OSRS QS ISRS cc 1 0 0 Norm TXl No No 2.821 0.305 0.309 2.829 4.08 0.81 Yes No Yes N/A N/A N/A N/A Yes 2 0 0 Norm TXl No No 2.815 0.307 0.311 2.823 4.07 0.81 Yes No Yes N/A N/A N/A N/A Yes 3 0 O Norm TXl No No 2.842 0.305 0.309 2.850 4.11 0.81 Yes No Yes N/A N/A N/A N/A Yes 14 0 O Norm TXl No Yes 2.844 0.301 0.306 2.853 4.12 0.80 Yes*** No Yes No Yes Yes Yes*** N/A 19 0 0 Norm TXl No No 2.843 0.305 0.308 2.851 4.11 0.81 Yes No Yes N/A N/A N/A N/A Yes 22 0 0 Min TXl No No 2.897 0.317 0.304 2.898 4.18 0.80 Yes No Yes N/A N/A N/A N/A Yes 29 0 0 Min TXl No Yes 2.881 0.297 0.300 2.891 4.17 0.80 Yes*** No Yes No Yes Yes Yes*** N/A 32 0 0 M in TXl No No 2.920 0.318 0.303 2.922 4.22 0.80 Yes No Yes N/A N/A N/A N/A Yes 35 100 100 Norm TXl No No 1.965 0.330 0.323 1.969 2.84 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 38 100 100 Norm TXl No Yes 1.980 0.347 0.323 1.985 2.86 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 41 100 100 Norm TXl No No 1.935 0.323 0.323 1.968 2.84 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 44 100 100 Min TXl No No 1.891 0.299 0.343 1.891 2.73 0. 91 Yes Yes Yes N/A N/A N/A N/A Yes 47 100 100 Mi n TXl No Yes 2.002 0.325 0.338 2.009 2.90 0.89 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 50 100 100 M in TXl No No 1.87 1 0.301 0.309 1.872 2.70 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 235 0 0 Norm GSU 1 GND No 14.756 1.143 1.070 1.009 1.46 0.97 Yes Yes Yes N/A N/A N/ A N/A Yes 23S 0 0 Norm GSU 1 GND Yes 14.563 1.064 1.053 1.005 1.45 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 24C 0 0 Norm GSU 1 GND-R No 7.521 0.656 0.697 0.727 1.05 0.99 Yes Yes Yes N/A N/A N/ A N/A Yes 241 0 0 Norm GSU 1 GND No 14.746 1.028 1.106 1.100 1.59 0.97 Yes Yes Yes N/A N/A N/A N/ A Yes 244 0 0 Mi n GSU 1 GND No 15.560 1.072 1.074 1.013 1.46 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 247 0 0 Min GSU 1 GND Yes 14.563 1.065 1.053 1.005 1.45 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 249 0 0 Min GSU 1 GND-R No 7.521 0.656 0.697 0.737 1.06 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 25C 0 0 M in GSU 1 GND No 14.746 1.028 1.106 1.100 1.59 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 251 0 0 Norm GSU 1 No No 0.343 0.322 0.322 0.966 1.39 0.98 Yes Ye s Yes N/A N/A N/A N/A Yes 254 0 0 Norm GSU 1 No Yes 0. 343 0.322 0.338 0.981 1.42 0.97 Yes Yes Yes Yes Yes Yes Yes*** N/A 257 0 0 Norm GSU 1 No No 0.344 0.322 0.322 0.969 1.40 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 260 0 0 Min GSU 1 No No 0.344 0.323 0.342 1.002 1.45 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 263 0 0 Min GSU 1 No Yes 0.346 0.322 0.340 0.972 1.40 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 266 0 0 Min GSU 1 No No 0.344 0.323 0.342 0.986 1.42 0.97 Yes Yes Yes N/A N/A N/A N/A Yes 270 0 0 Norm GSU 2 GN D-R No 0.899 6.329 0. 970 0.899 1.30 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 271 0 0 Norm GSU 2 GND No 1.685 14.177 1.591 1.685 2.43 0.92 Yes Yes Yes N/A N/A N/A N/ A Yes 273 0 0 Norm GSU 2 GND-R Yes 0.804 6.290 0.857 0.804 1.16 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 274 0 0 Norm GSU 2 GND Yes 1.450 13.959 1.583 1.452 2. 10 0.94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 276 0 0 Norm GSU 2 GND-R No 0.898 6.331 0.853 0.899 1.30 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 277 0 O Norm GSU 2 GN D No 1.684 14.175 1.580 1.685 2.43 0.92 Yes Yes Yes N/A N/A N/A N/ A Yes 279 0 0 M in GSU 2 GN D-R No 0.887 11.215 0.863 0.887 1.28 0.98 Yes Yes Yes N/A N/A N/A N/ A Yes 280 0 0 M in GSU 2 GND No 1.642 25.691 1.615 1.645 2.37 0.93 Yes Yes Yes N/A N/ A N/A N/A Yes 282 0 0 Min GSU 2 GND-R Yes 0.884 6.288 0.859 0.885 1.28 0.98 Yes Yes Yes Yes Yes Yes Yes*** N/A 283 0 0 Mi n GSU 2 GND Yes 1.564 14.062 1.582 1.571 2.27 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 285 0 0 Min GSU 2 GND-R No 0.901 6.637 0.857 0.901 1.30 0.98 Yes Yes Yes N/A N/A N/A N/A Yes 28E 0 0 Min GSU 2 GND No 1.617 14.940 1.585 1.623 2.34 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 28S 0 0 Norm GSU 2 GN D-R No 0.877 0.792 6.424 0.709 1.02 0.99 Yes Yes Yes N/A N/A N/A N/A Yes 289 0 0 Norm GSU 2 GND No 1.639 1.507 14.270 1.189 1.72 0.96 Yes Yes Yes N/A N/A N/A N/A Yes 29 1 0 0 Norm GSU 2 GND-R Yes 0.867 0.792 6.401 0.696 1.00 0.99 Yes Yes Yes Yes Yes Yes Yes N/A 292 0 0 Norm GSU 2 GN D Yes 1.612 1.506 14.188 1.130 1.63 0.97 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 295 0 0 Norm GSU 2 GND No 1.642 1.510 14.240 1.191 1.72 0.96 Yes Yes Yes N/A N/A N/A N/A Yes 29S 0 0 Min GSU 2 GN D No 1.644 1.511 15.030 1.153 1.66 0.96 Yes Yes Yes N/A N/A N/ A N/A Yes 301 0 0 M in GSU 2 GND Yes 1.612 1.506 14.188 1.148 1.66 0.96 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 304 0 0 Min GSU 2 GND No 1.647 1.514 14.974 1.155 1.67 0.96 Yes Yes Yes N/A N/A N/A N/A Yes Switchyard Unbalance Cases (EE-0894 Attachment 2) 2 0 0 Norm TXl No No 2.193 1.835 1.674 2.198 3.173 0.88 Yes Yes Yes N/A N/A N/A N/ A Yes 3 0 0 Norm TXl No No 2.867 1.827 1.667 2.875 4.149 0.80 Yes No Yes N/A N/A N/A N/ A Yes 9 100 100 Norm TXl No No 3.094 1.873 1.081 3.102 4.477 0.77 Yes No Yes N/A N/A N/A N/A Yes 10 100 100 Norm TXl No Yes 3.067 1.799 1.801 3.088 4.457 0.77 Yes*** No Yes No Yes Yes Yes*** N/A 11 100 100 Norm TXl No No 3.071 1.837 1.800 3.079 4.444 0.78 Yes No Yes N/A N/A N/A N/A Yes 12 100 100 Min TXl No No 3. 238 1.711 1.689 3.240 4.676 0. 75 Yes No Yes N/A N/A N/A N/A Yes 14 100 100 M in TXl No No 3.2 15 1.690 1.691 3.216 4.643 0.76 Yes No Yes N/A N/A N/A N/A Yes 15 0 0 Norm TX2 No No 1.631 1.714 4.143 1.632 2.355 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 16 0 0 Norm TX2 No Yes 1.505 1.714 4.157 1.505 2.172 0.94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 17 0 0 Norm TX2 No No 1.629 1.714 4.167 1.629 2.352 0. 93 Yes Yes Yes N/A N/A N/A N/A Yes 18 0 0 Min TX2 No No 1.560 1.716 4.270 1.560 2.251 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 19 0 0 Min TX2 No Yes 1.551 1.715 4.130 1.552 2.241 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 20 0 0 M in TX2 No No 1.562 1.716 4. 293 1.562 2.255 0.93 Ye s Yes Yes N/A N/ A N/A N/A Yes 21 100 100 Norm TX2 No No 1.815 1.686 3.577 1.816 2.621 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 22 100 100 Norm TX2 No Yes 1.654 1.689 3.598 1.655 2.388 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 23 100 100 Norm TX2 No No 1.882 1.709 3.612 1.816 2.621 0.91 Yes Yes Yes N/A N/A N/A N/A Yes 24 100 100 Min TX2 No No 1.727 1.686 3. 666 1.726 2.492 0.92 Yes Yes Yes N/A N/ A N/ A N/A Yes 25 100 100 Mi n TX2 No Yes 1.683 1.708 3.578 1.683 2.43( 0.92 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 26 100 100 M in TX2 No No 1.704 1.696 3.664 1.703 2.459 0.92 Yes Yes Yes N/A N/ A N/A N/A Yes 27 0 0 Norm GSU 1 No No 2.046 1.789 1.662 1.573 2.271 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 28 0 O Norm GSU 1 No Yes 1.988 1.666 1.636 1.572 2.269 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 29 0 0 Norm GSU 1 No No 2. 045 1.592 1.730 1.740 2.512 0.92 Yes Yes Yes N/A N/A N/A N/A Yes 30 0 0 Min GSU 1 No No 2.090 1.655 1.662 1.579 2.279 0.93 Yes Yes Yes N/A N/A N/A N/A Yes 31 0 0 Min GSU 1 No Yes 2.020 1.662 1.636 1.573 2. 27( 0.93 Yes*** Yes Yes Yes Yes Yes Yes*** N/ A 32 0 0 Min GSU 1 No No 2.045 1.592 1.730 1.741 2.512 0.92 Yes Yes Yes N/A N/A N/ A N/A Yes 33 0 0 Norm GSU 1 No No 1.574 1.737 1.636 1.966 2.837 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 34 0 0 No rm GSU 1 No Yes 1.539 1.758 1.569 2.006 2.896 0.89 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 35 0 0 Norm GSU 1 No No 1.539 1.789 1.662 1.974 2.849 0.90 Yes Yes Yes N/A N/A N/A N/A Yes 36 0 0 M in GSU 1 No No 1.538 1.789 1.531 2.060 2.974 0.89 Yes Yes Yes N/A N/ A N/ A N/A Yes 37 0 0 Min GSU 1 No Yes 1.539 1.758 1.524 1.973 2.848 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 38 0 0 Min GSU 1 No No 1.539 1.790 1.531 2.041 2.947 0.89 Yes Yes Yes N/A N/ A N/A N/A Yes 39 0 0 Norm GSU 2 No No 2.171 1.774 2.058 2.172 3.135 0.88 Yes Yes Yes N/A N/A N/A N/A Yes 40 0 0 Norm GSU 2 No Yes 1.931 1.883 2.109 1.935 2.793 0.90 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 41 0 0 Norm GSU 2 No No 2.171 1.782 1.999 2.171 3.134 0.88 Yes Yes Yes N/ A N/A N/ A N/A Yes 42 0 0 Min GSU 2 No No 2.014 2.323 1.998 2.023 2.919 0.89 Yes Yes Yes N/A N/ A N/A N/A Yes 43 0 0 Min GSU 2 No Yes 2.004 1.339 2.013 2.009 2.900 0.89 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 44 0 0 Min GSU 2 No No 2.098 1.850 2.004 2.102 3.034 0.89 Yes Yes Yes N/A N/A N/A N/A Yes 45 0 0 Norm GSU 2 No No 2.161 1.971 1.875 1.515 2.187 0. 94 Yes Yes Yes N/A N/ A N/A N/A Yes 46 0 0 No rm GSU 2 No Yes 2.126 1.971 1.814 1.510 2.179 0.94 Yes*** Yes Yes Yes Yes Yes Yes*** N/A 47 0 0 Norm GSU 2 No No 2.161 1.971 1.859 1.516 2.188 0.94 Yes Yes Yes N/A N/ A N/A N/A Yes 48 0 0 Min GSU 2 No No 2.161 1.970 1.874 1.481 2.138 0.94 Yes Yes Yes N/A N/A N/ A N/A Yes 0.94 Yes*** Yes***

49 0 0 Min GSU 2 No Yes 2. 125 1.973 1.813 1.477 2.131 Yes Yes Yes Yes Yes N/A 50 0 0 Min . G.S.U 2 No No 2.161 1.971 1.859 1.483 2.141 0.94 Yes Yes Yes N/A N/A N/A N/A Yes

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions mMPR May 24, 2017 1114-0058-LTR-001, Rev. 0 Mr. Joseph DeMarco Dominion Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, Virginia 23060

Subject:

Calculation for AFW and ISRS Motor's Thermal Performance during an Unbalanced Condition

Dear Mr. DeMarco:

Attached, is the final Nuclear QA Calculation for the North Anna Power Station's AFW and ISRS motor's thermal performance during an unbalanced voltage condition. We incorporated the two references provided by Dominion.

The AFW pump motor insulation has reasonable assurance of operating for greater than 30 days during a design basis accident requiring 111 % loading, at end of life, with a concurrent negative sequence voltage of 3.176V (4.6% unbalance) at the secondary of the 4200: 120V potential transformer. Under the same voltage unbalance condition, the ISRS motors will have a service life of greater than 30 days during a design basis event occurring at the 60 year operating point.

Should you have any questions, or require any additional information, please contact us.

Sincerely, fi~b*

John Festa Enclosure(s): Calculation for AFW and ISRS Pump Motors cc: Mike Morris Page 1 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions r+JMPR Thermal Evaluation of AFW and ISRS Pump Motors During an Open Phase Condition RECORD OF REVISIONS Revision Pages /Sections Revision Description Number Revised 0 All Page 2 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions fQMPR Table of Contents

1. 0 Summary of Purpose and Results .................................................................... 1 1.1. Purpose ..................................................................................................................... 1 1.2. Results ...................................................................................................................... }

2.0 Background......................................................................................................... 1 2.1. Scope ........................................................................................................................ 2

3. 0 Methodology ....................................................................................................... 2 3.1. NEMA Derating Factor............................................................................................ 3 3.2. Temperature Rise at Service Factor ........................................................................ .4 3.3. Determining Equivalent Motor Life ....................................................................... .4
4. 0 Auxiliary Feed Water Pump Motor .................................................................... 6 4.1. Verified Assumptions .............................................................................................. 6 4.2. Unverified Assumptions .......................................................................................... 7 4.3. Design Inputs ........................................................................................................... 7 4.4. Acceptance Criteria .................................................................................................. 7 4.5. Calculation ............................................................................................................... 8 5.0 Inside Recirculation Spray Pump Motors ....................................................... 10 5.1. Verified Assumptions ............................................................................................ 10 5.2. Unverified Assumptions ........................................................................................ 10 5.3. Design Inputs ......................................................................................................... 10 5.4. Acceptance Criteria ................................................................................................ 11 5.5. Calculation ............................................................................................................. 11
6. 0 References ........................................................................................................ 12 Page 3 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions

  • MPR 1.0 Summary of Purpose and Results
1. 1. Purpose The purpose of this calculation is to evaluate the thermal performance of the North Anna Power Station Auxiliary Feedwater (AFW) and Inside Recirculation Spray (ISRS) motors during an unbalanced voltage condition concurrent with a design basis accident.

1.2. Results The AFW pump motor insulation has reasonable assurance of operating for greater than 30 days during a design basis accident requiring 111 % loading, at end of life, with a concurrent negative sequence voltage of 3.176V (4.6% unbalance) at the secondary of the 4200:I20V potential transformer. Under the same voltage unbalance condition, the ISRS motors will have a service life of greater than 30 days during a design basis event occurring at the 60 year operating point.

2.0 Background A bus with unbalanced voltages, such as those in an open phase condition, can induce higher than normal currents in operating polyphase motors. Since motor heating occurs as the square of motor current, elevated currents will cause the temperature of the motor components to rise.

With the rotor being more thermally robust, the stator winding insulation is the limiting component to motor life under high thermal stresses (Reference 5). If the insulation degrades to the point that it no longer provides a sufficient barrier between the windings and the stator's iron core, a short to ground, turn to turn short, or an open circuit could occur. Depending on the extent of damage, some or all of these faults will cause motor failure.

The National Electric Manufacturers Association (NEMA) establishes insulation temperature limits to prevent excessive degradation of insulation. Maintaining temperatures below these limits does not stop the chemical degradation of insulation, but ensures that the insulation degradation is slow enough that the motor has a normal life expectancy. Table 2-1 shows the rated temperatures for each insulation class (Reference I 0).

Page 4 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions Table 2-1. NEMA Insulation Class Temperature Ratings for Motors Class Temperature Rating A 105° C B 130° C F 155° C H 180° C North Anna Power Station (NAPS) plans to install relays that sense negative sequence voltage and trip to protect safety related motors during open phase conditions. Due to bus loading, transformer arrangement, and relay setpoint, the negative sequence relays will not trip on every open phase condition. This calculation verifies that the AFW pump and ISRS pump motors will meet design life requirements with an unbalanced voltage condition of 3 .l 76V negative sequence voltage at the secondary of the 4200:120V potential transformer.

2.1. Scope This calculation evaluates that:

  • The AFW pump motors can operate at rated capacity for a minimum of 180 days during a design basis event.
  • ISRS pump motors meet the minimum service life of 30 days during a design basis event that occurs at the end of the motor operating life.

The evaluation examines thermal effects at this negative sequence voltage. Other effects that can occur due to high negative sequence voltage, such as torque reduction, over-current device tripping, and speed changes are not part of this evaluation.

3.0 Methodology The following sections outline the method used to determine estimated motor life while operating under unbalanced voltage conditions.

Page 5 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions 9JMPR

3. 1. NEMA Derating Factor NEMA MG-I (Reference I 0) recommends using a derating factor for operation of polyphase squirrel-cage induction motors and large synchronous machines under voltage unbalance conditions. This derating factor accounts for the added heating, particularly of the rotor bars and stator iron, and the reduction in torque caused by the voltage unbalance.

NAPS specified that the AFW and ISRS pump motors are required to operate with a negative sequence voltage of 3.176V at the secondary of the 4200V:120V, open delta configuration, potential transformer (Reference 0). Transformer primary side line to line voltage is taken to be I 00% and is set to 4160V (Reference 1).

4160V (line to line) on the primary of the potential transformer is taken to be I 00% voltage.

However, sequence voltages use a line to neutral base (Reference 2, Section 2.5). Therefore, 100% sequence voltage on the secondary side corresponds to:

4160V 120V

_../3_3_

  • 4200V = 68.62V The negative sequence voltage as a percentage is:

3.176V 4.6%

68.62V The NEMA voltage unbalance percentage can be approximated by the ratio of negative to positive sequence voltage, provided the ratio is <5% (Reference 5, page 51) Since positive sequence voltage is 100%, the ratio of negative to positive sequence voltage is 4.6%. Thus, the 3.176V negative sequence voltage results in approximately 4.6% NEMA voltage unbalance.

2 3 4 5 PERCENT VOLTAGE UNBALANCE Figure 3-1. NEMA Derating Factor Page 6 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions r+JMPR When an induction motor is operated with 4.6% unbalance, NEMA MG-1-2009 recommends multiplying the rated horsepower by a derating factor of :::::0.78, see Figure 3-1, to reduce the possibility of damage. Equivalently, the NEMA derating curve means that at 4.6% unbalance, 1

the motor's output power should be multiplied by-- = 1.28 to obtain an equivalent motor 0.78 loading. The motor can then be evaluated at this equivalent motor loading.

  • 3.2. Temperature Rise at Service Factor The expected temperature rise while operating at service factor can be calculated using either data from a service test or the rated temperature rise for the insulation. To calculate the expected temperature rise, a ratio can be created using conservation of energy. When the motor is at thermal equilibrium the heat loss is equal to the heat input.

(!zoss = <2input Heat loss equals the heat transfer coefficient times the temperature rise above ambient. Heat input is equal to the I2R heat generation (to a first order). For thermal equilibrium:

Where U = heat transfer coefficient.

At different motor loadings:

Taking U and R to be constant across motor loading, the two equations can be set equal to each other.

tffx% 11Tv%

Ii% 1:%

This ratio is then used to determine the temperature rise while operating at the motor service factor.

3.3. Determining Equivalent Motor Life A motor's rated insulation life can be determined by using environmental qualification information or calculated manually. Safety grade motors located in an environment with an elevated temperature typically operate under an environmental qualification program which documents the procurement specification requirements, operating conditions, and service life.

Page 7 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions r.JMPR The NEMA insulation class limit is normally based on a 20,000 hour0 days <br />0 hours <br />0 weeks <br />0 months <br /> (2.3 year) operating period (Reference 4). That is, the insulation is expected to operate continuously at its maximum temperature for 2.3 years without failing. A motor operating below the insulation temperature limits will have a life expectancy much greater than 2.3 years.

If a motor violates a NEMA temperature limit because of unbalanced voltages or other reasons, it is possible to calculate the amount of service life remaining. An environmental qualification report will typically contain the qualified life and activation energy of the stator winding insulation. With this information, the motor's temperature and time history can be used to estimate how much the insulation has degraded using the Arrhenius methodology. The Arrhenius equation is as follows:

H = t e (i2 -iJ(f)

Where:

H= Equivalent life hours at rated insulation temperature.

t= time at T1 T 1 = motor temperature in Kelvin T2 = Reference temperature for equivalent life in Kelvin

<p = activation energy K = Boltzmann's constant (8.617E-5 eV/°K, Reference 9)

If the activation energy, <p, for the insulation is unknown, an approximation of the Arrhenius equation can be used to estimate service life. Using a rule of thumb that for every 10° rise above motor insulation rating can reduce motor life by one-half (Reference 5) The Arrhenius equation approximation is as follows:

Page 8 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions laMPR T-Trated H =t *2 10 Where:

H = equivalent life hours Trated = insulation rated temperature (l 30°C for Class B insulation, Reference 10)

T = operating temperature t = operating time The Arrhenius equation or Arrhenius approximation are used to calculate the equivalent life hours remaining at the end of the motor service life. For the worst case thermal aging analysis, a design basis accident is assumed to occur at the end of the motor service life. The motors are assumed to operate with a temperature rise at service factor loading, unless specified otherwise in the EQ report, and a negative sequence voltage of 3.176V (4.6% unbalance). The pump motor satisfies design requirements if there are equivalent life hours remaining upon completion of the design basis accident duty cycle.

4.0 Auxiliary Feed Water Pump Motor

4. 1. Verified Assumptions 4.1.1. AFW Pump Insulation Degradation Estimate To model insulation life degradation, an approximation of the Arrhenius equation is used. An industry accepted rule of thumb states that each 10° rise above the NEMA motor insulation rating will reduce motor life by one half (Reference 5).

4.1.2. Motor Testing Duration The time required to perform the quarterly AFW pump service testing is assumed to be 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, which sums to a total of 16 maintenance run hours per year. Reference 11 shows AFW pump run time during the service test of less than one hour. Four hours of AFW run time per quarter is used for conservatism.

4.1.3. Unit Trip per Calendar Year Condition II events are defined as events of moderate frequency that at worst case result in reactor shutdown without fuel damage or reactor vessel overpressurization (Reference 15, page 67). Per reference 15, a plant trip resulting from a class II event is predicted to occur 2:: 10- 1 Page 9 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions

._MPR times per calendar year. For this calculation, a condition II event is assumed to occur once per calendar year. During this event, the AFW pumps are assumed to run for a duration of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

4.1.4. Ambient Temperature During testing, 20°C is assumed for the ambient temperature. Reference 7 documents that the suction piping temperature was 67°F (19 .4°C) during testing, therefore 20°C is a reasonable assumption for the ambient temperature.

4.2. Unverified Assumptions There are no unverified assumptions in this calculation.

4.3. Design Inputs 4.3.1. Motor Characteristics AFW pump ratings obtained from NAPS calculation EE-0025 Rev 3, Attachment 14.3, Page 1 (Reference 6) and shown in Table 4-1 below.

Table 4-1. Motor Parameters for AFW Pumps Parameter Value Rated Voltage 4000V Horsepower 450 hp Service Factor 1.15 Full Load Amps 57.3 Rated Ambient Temperature 40°c Insulation Class B Temperature Rise at Service Factor Loading 90°C 4.3.2. Voltage Unbalance Per Reference 1, the AFW pump motors are required to operate with a negative sequence voltage of 3.176V at the 4200: 120V potential transformer secondary. This design input is used as the worst-case unbalance voltage condition under which the AFW pump will operate.

4.4. Acceptance Criteria Per Reference 1, the AFW pump motor must be able to run continuously for 30 days during a design basis accident occurring at the end of the motor's 60 year service life.

Page 10 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions r.JMPR 4.5. Calculation Per reference 1 and 11, during the last AFW pump motor performance test, stator temperature stabilized at approximately 57 .2° C (135° F) with a line current of 4 7 A (Reference 7, page 41, Reference 13, plot of AFW pump temperature). As stated in section 4.1.3 ambient temperature during testing assumed to be 20° C. Thus the temperature rise during testing periods is L'lT=37.2°C.

Using these parameters and the relationship between temperature rise and line current, we can estimate the temperature rise of the motor at different motor loadings. Using the relationship between temperature rise and stator current developed in Section 3.3, the temperature rise for the AFW motor operated at the service factor of 115% and Full Load Amps of 57 .3A is calculated below.

37.2°C (47A) 2 (57.3A

  • 1.15) 2 LiT115 % = 73.1 °C The AFW pumps are located in a mild environment and thus do not have an environmental qualification (EQ) report. Since the activation energy of the AFW pump motor insulation is not available, the Arrhenius equation approximation from section 3.3 is used to calculate ins*uJation equivalent life at a given temperature. Additionally, a nominal motor equivalent life of 20,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> will be used.

Based on the system operating conditions described in Section 2.2 of Reference 8, the AFW pumps operate infrequently. An AFW pump is not normally running while the plant is in Mode 1 or during normal shutdown conditions. As described, the AFW pumps only operate for maintenance or because of an infrequent fault, such as a loss of offsite power.

The evaluation analyzes the AFW motor thermal degradation for 60 year plant life. The AFW motor is not continuously run and will be operated infrequently for tests and in the event of a unit trip. At the end of plant life, a design basis accident is assumed to occur concurrent with a negative sequence voltage of 3.176V (4.6% unbalance) at the secondary of the 4200:120V potential transformer. The evaluation will determine how long the motor can operate before qualified insulation life is exhausted.

During plant life, the AFW pumps are assumed to operate for a duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> once per quarter as part of regular service testing - a total of 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> per year. Additionally, a condition II event which causes a plant trip is assumed to occur once per calendar year. This plant trip will cause the AFW pump to run for a duration of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Thus, the AFW pumps will run for a total of 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> per year for normal plant operation. During this time, the pump's temperature rise is Page 11 of 16

EE-0894 Rev. a Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions fQMPR assumed to be 73.1 °C. That is, the pump is operated at its service factor (115%). This is a conservative assumption since maintenance only requires 82% loading (Reference 7).

Additionally, during maintenance, or other infrequent operations, the ambient temperature is assumed to be 20°C, for an insulation temperature of 20°+73 .1 °= 93 .1 °C ..

The total equivalent life of the AFW pump due to testing and plant trips is calculated below:

hours 93.1 °-130° H1 = 28 - -

  • 60years
  • 2 year 10 H1 = 130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br /> When the motor is not operating (plant life minus 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> per year), it will be assumed to be in a standby condition, in a 20°C room.

days hours ) 20°-130° H2 = 60years * ( 365.25-- year

  • 24-d-- -

ay 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />

  • 2 10 H2 = 256 hours0.00296 days <br />0.0711 hours <br />4.232804e-4 weeks <br />9.7408e-5 months <br /> At the end of life, the evaluation postulates a design basis accident occurs with a concurrent open phase condition of 3.176V negative sequence voltage (4.6% voltage unbalance). The AFW pump motor is required to run at 111 % loading (References 1 and 6). Running the motor at 111 % loading while using the NEMA derating factor to account for 3.176V negative sequence voltage will have an equivalent heating effect as running the motor at 111 %
  • 1.28 = 142%

loading.

Using the temperature estimation formula:

37.2°C (47A) 2 (57.3A

  • 1.42) 2 LlT142% = 111.5°C For this condition, the motor is considered to be in a 40°C room. The insulation temperature will be 40°+ 111.5° = l 5 l .5°C. This is about 20°C above the NEMA B rated 130°C for Class B insulation, but will not result in immediate failure since it is not near a temperature that will damage bearings or the motor casing, etc. With these values, the time before insulation rated life is exhausted can be calculated:

151.5°-130° 20,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> - H1 - H2 =t *2 10 Page 12 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions r.JMPR t == 4420 hours0.0512 days <br />1.228 hours <br />0.00731 weeks <br />0.00168 months <br /> ~ 184 days In conclusion the AFW pumps insulation has reasonable assurance of operating for greater than 180 days during a design basis accident requiring 111 % loading, at end of life, with a concurrent negative sequence voltage of 3.176V (4.6% unbalance).

5.0 Inside Recirculation s*pray Pump Motors

5. 1. Verified Assumptions 5.1.1. Positive Sequence Voltage For the calculation of voltage unbalance with a negative sequence voltage of 3.176V (Reference I), the positive sequence voltage is assumed to be 100%.

5.2. Unverified Assumptions There are no unverified assumptions in this calculation.

5.3. Design Inputs 5.3.1. Motor Characteristics ISRS ratings in Table 5-1 were obtained from NAPS Calculation EE-0025 Rev 3, Attachment 14.3, Page 26 (Reference 6) and the EQ report (Reference 9).

Table 5-1. Motor Parameters for ISRS Pumps Parameter Value Rated Voltage 460V Horsepower 300 hp Service Factor 1.00 Full Load Amps 338 Insulation Class H Temperature Rise 80°C 5.3.2. Motor Qualified Life The EQ report calculates the ISRS motors have a qualified life of 2268.54 years at 132°F (55.56°C). However, the EQ specification calculates the motors use 68.73 years of equivalent Page 13 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions aJMPR life (at l 32°F) in 60 years of plant life. At the end of plant life, the ISRS motors have (2268.54 - 68.73) ~ 2200 years of equivalent life (at 132°F) remaining.

5.3.3. Voltage Unbalance Per Reference 1, the ISRS pump motors are required to operate with a negative sequence voltage of 3.176 Vat the 4200: 120V potential transformer secondary. This design input is used as the worst-case unbalance voltage condition under which the ISRS motors will operate.

5.4. Acceptance Criteria Per Reference I, the required service life of the ISRS pump motors is 30 days under conditions and duty cycle occurring during a design basis accident.

5.5. Calculation This evaluation examines a design basis accident at end of a 60 year plant life, with a concurrent open phase condition causing a negative sequence voltage of 3.176V (4.6% unbalance).

Reference 6 lists the loading of the ISRS at 98.33% of full load. For calculation simplicity and conservatism, the ISRS will be considered to be at 100% load. As calculated previously, with a negative sequence voltage of 3. l 76V (4.6% unbalance), the NEMA derating factor multiplier is 1.28. Therefore, during unbalanced conditions the motor has an equivalent loading of I 00%

  • 1.28 = 128%.

Using Full load amps and rated temperature rise from Table 5-1 80°C (338A) 2 (338A

  • 1.28) 2 LIT12B% = 131 °C.

The EQ report (Reference 9) analyzes the worst case ambient temperature profile consisting of the worst case MSLB and LOCA profiles. Per the EQ report, during the first 2000 seconds of an accident, a MSLB causes a bounding temperature of 261 °F = 127.2°C on the surface of the motor. After the first 2000 seconds, the LOCA temperature profile is bounding. The EQ report calculates an equivalent time and temperature for the LOCA temperature profile. The report calculates the LOCA profile is equivalent to 674,478 seconds (=187.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />) at 150°F (65.6°C).

This temperature profile covers the entire 30 day mission time of the ISRS motor (Reference 9).

To calculate the insulation degradation during the design basis accident, two Arrhenius calculations are necessary: 2000 seconds at 127.2°C + 131 °C = 258.2°C or 531 °Kand 187.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> at 65.6°C + 131 °C = 196.6°C or 470°K. The combined equivalent life expended by these Page 14 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions r.JMPR two conditions must be less than 2200 years ofremaining equivalent life of the motor. The ISRS pump motors use NEMA class H insulation with a thermal limit of 180°C.

The EQ report provides enough information for this motor to use the full Arrhenius equation described in section 3.3.

Per reference 9, the following parameters are used.

T2 = 55.56°C or 328.71 °K

<p = 1.077eV K = 8.617E-5 eV/°K Using the full Arrhenius equation:

H1 ~ 124 years And 1 1 )( 1.077eV )

( 328.71 °K 470°K

  • _ eV 8 617 10 5 H2 = 187.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> e * °K H2 ~ 1969 years Combining H1 and H2 results in 2093 years of equivalent life used during a design basis accident with a negative sequence voltage of 3. l 76V (4.6% unbalance). This result is below the 2200 years of equivalent life that remains at the end of 60 years of plant life. Therefore, the ISRS motor is thermally rated for the entire mission time of a design basis accident, with a concurrent open phase causing 3.165V negative sequence voltage (4.6% unbalance) at the end of the 60 year plant life.

6.0 References

1. Email from Joseph Demarco to John Festa on 4/17/2017 at 11 :05AM, Subject, Fwd.:

[External] NAPS Motor Analysis- Document Request (Relevant portion of email is in red text. Red text contains response to questions posed by John Cunningham in a previous email on 4/14/17)

Page 15 of 16

EE-0894 Rev. 0 Evaluation of AFW and ISRS Motor's Thermal Margin during Unbalanced Conditions r+JMPR

2. Blackbum, J. Lewis, Symmetrical Components for Power Systems Engineering, Boca Raton, FL: CRC, 2011
3. Pillay, P. and Manyage, M., Definitions of Voltage Unbalance, IEEE Power Engineering Review, May 2001
4. ASTM D 2307: Standard Test Method for Thermal Endurance of Film-Insulated Round Magnet Wire
5. Pillay, P. and Manyage, M., Loss of Life in Induction Machines Operating with Unbalanced Supplies, IEEE Transactions on Energy Conversion, 21(3), December 2006.
6. NAPS Calculation EE-0025, Revision 3
7. NAPS Procedure No 2-PT-71.2Q, Rev 40, Unit 2, 2-FW-0-3A, A Motor-Driven AFW Pump and Valve Test, Completed 1/4/17.
8. System Design Basis Document for Auxiliary Feedwater Systems, North Anna Power Station, SDBD-NAPS-AFW, Rev 15.
9. Qualification Documentation, QDR-N-4.4/QDR-S-4.4, ISRS Pumps, Rev 11.
10. NEMA MG-1: Motors and Generators, 2009.
11. Plot of AFW pump Test Data form Procedure No 2-PT-71.2Q, Rev 40, Unit 2, 2-FW 3A completed January 4, 2017.
12. NAPS Document ETE-NA-2016-0088, Design Basis for AFW Pump mission time, November, 2016.
13. Email from Joseph Demarco to John Festa on May 18, 2017,

Subject:

FW: [External]

Calculation for the AFW & ISRS Motor Evaluation. Includes attached plot of ASW pump service test.

14. NAPS Updated Final Safety Analysis Report Chapter 15, Rev 51.06.
15. Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants.

American Nuclear Society 51.1, 1983.

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