ML14120A040

Attachment 4, Braidwood Station, Units 1 and 2 - Calculation 19-AN-29, Revision 002B, Second-Level Undervoltage Relay Setpoint

ML14120A040
Person / Time
Site:	Braidwood
Issue date:	02/14/2014
From:	Kolodziej J Exelon Generation Co
To:	Office of Nuclear Reactor Regulation
Shared Package
ML14120A038	List: ML14120A039 ML14120A040 ML14120A041
References
RS 14-116 19-AN-29, Rev. 002B
Download: ML14120A040 (18)

Text

ATTACHMENT 4 BRAIDWOOD STATION UNITS I AND 2 Docket Nos. 50-456 and 50-457 Facility Operating License Nos. NPF-72 and NPF-77 Calculation 19-AN-29, Revision 002B "Second-Level Undervoltage Relay Setpoint"

CC-AA-309-1001 Revision 8 ATTACHMENT I Design Analysis Cover Sheet Page Iof I Design Analysis I Last Page No. - Appendix D, Page CD13 Analysis No.:' 19.AN-29 Revision:' 002B Major [3 Minor 0 TiO:' Second-Level Undervaotage Relay Setpoint EC/ECR No.: 392851 &392216 Revision: 001 &002 Station(s):' Bralewood Componen(s):"

Unit No.: ' 1&2 Discipline:' ELDC Descrip. Code/Keyword:" E07 & E1S Safety/QA Class:" SR system Code:" AP ,__

Structure: ',

CONTROLLED DOCUMENT REFERENCES" Document No.: From/To Document No.: From/To See Section 4.0 of this Calculaton Is this Design Analysis Safeguards Information? " Yes0 No O If yes, see SY-AA.101-106 Does this Design Analysis contain Unverified Assumptons?" Yes 0 No 0 If yes, ATIAR#:

This Design Analysis SUPERCEDES:" Calculation t9.AN-29, Rev. 002A In its entirety.

Description of Revision (list changed pages when all pages of original analysis were not changed):

This revision adds a third level of protection to the degraded voltage protection scheme via a new Low Degraded Voltage Relay (DVR) with a lower setpolnt than the adsti"g DVR (second-level). The eisting analysis from Revision 002 is not affected; the new low degraded voltage relay is added to the analysis. The original body of the calculation is unchanged. As such, only Attachment C and the associated appendices are included as part of this minor revision, which are to be added to base calculation. This calculation supersedes Calctilation 19-AN-29, Rev. 002A in Its entirety. Approval from Phil Raush (SMDE) for a minor revision to 19-AN-29 was given on 12102/2013.

Proparer. 1 J.Kolodzisj -

Pu ---

Method of Review: " Detailed Review 0 Alternate alculatlons (a d) Testing Rvewer:1 G.Hinshaw Review Notes:" Independent review , Peer review 0 External Approw:- I. Maome zilf 14 FMUr"m aR Independent 3d* Party Review Reqd?- 0 NoYes No_

Exeo Aprve.

Fý P-ot,4J

Page CIA CC-AA-103-1003 Revision 9 ATTACHMENT 2 Owner's Acceptance Review Checklist for External Design Analyses Page Iof3 Design Analysis No.: 19-AN-29 A1Rv:02B No Question Instructions and Guidance Yes/.No/A I Do assumptions have All Assumptions should be stated in clear terms with enough [V U U sufficient documented justification to confirm that the assumption is conservative.

rationale?

For example, 1) the exact value of a particular parameter may not be known or that parameter may be known to vary over the range of conditions covered by the Calculation. It is appropriaIs to represent or bound the parameter with an assumed value. 2) The predicted pertormanoe of a specific piece of equipment in lieu of actual test date. It is appropriate to use the documented opinion/position of a recognized expert on that equipment to represent predicted equipment Consideration should also be given as to any qualification testing that may be needed to validate the Assumptions. Ask yourself, would you provide more justification if you were performing this analysis? If yes, the rationale is likely incomplete.

2 Are assumptions Ensure the documentation for source and rationale for the compatible with the assumption supports the way the plant is currently or will be way the plant is operated post change and they are not in conflict with any operated and with the design parameters. If the Analysis purpose is to establish a licensing basis? new licensing basis, this question can be answered yes, if the assumption supports that new basis.

3 Do all unverified If there are unverified assumptions without a tracking 0 3]

assumptions have a mechanism indicated, then create the tracking item either tracking and closure through an ATI or a work order attached to the implementing mechanism in place? WO. Due dates for these actions need to support verification prior to the analysis becoming operational or the resultant plant change being op authorized.

4 Do the design inputs The origin of the input, or the source should be identified and [f 0 r-have sufficient be readily retrievable within Exelon's documentation system.

rationale? If not then the source should be attached to the analysis. Ask yourself, would you provide more justification if you were performing this analysis? If yes, the rationale is likely incomplete.

5 design inputs Are The expectation is that an Exelon Engineer should be able to L- U U correct and reasonable clearly understand which input parameters are critical to the with critical parameters outcome of the analysis. That is, what is the impact of a identified, if change in the parameter to the results of the analysis? If the approprate? Impact is rge, then that parameter scritical.

6 Are design inputs Ensure the documentation for source and rationale for the f" 0 0 compatible with the inputs supports the way the plant is currently or will be way the plant is operated post change and they are not in conflict with any operated and with the design parameters.

licensing basis? I I

Page CIe CC-AA-103-1003 Revision 9 ATTACHMENT 2 Owner's Acceptance Review Checklist for Extmal Design Analyses Page 2 of 3 Design Analysis No.: 1&&1--29 Rev:002 No Queston Instuctions and Guidance Yes I No I NWA 7 Are Engineering See Section 2.13 in CC-A-309 for the attributes that are U U IT Judgments dearly sufficient to Justify Engineering Judgment. Ask yourself, documented and would you provide more justification if you were performing justified? this analysis? If Yes, the rationale is likely incomplete.

8 Are Engineering Ensure the JustIfication for the engineering judgment 1' 0 [r Judgments compatible supports the way the plant is currently or will be operated with the way the plant is post change and is not in conflict with any design operated and with the parameters. If the Analysis purpose is to establish a new licensing basis? licensing basis, then this question can be answered yes, If the Judgment supports that new basis.

Do the results and Why was the analysis being performed? Does the stated -0 0 conclusions satisfy the purpose match the expectatim from Exelon on the proposed purpose and objective of application of the results? If yes, then the analysis meets the Desion Analysis? the needs of the contract.

10 Are the results and Make sure that the results support the UFSAR defined 1lI 0 ]

conclusions compatible system design and operating conditions, or they support a with the way the plant is proposed change to those conditions. If the analysis operated and with the supports a change, are aU of the other changing documents licensing basis? included on the cover sheet as impacted documents?

I I Have any limitations on Does the analysis support a temporary condition or [a" 0 0 the use of the results procedure change? Make sure that any other documents been identified and needing to be updated are included and dearly delineated In transmitted to the the design analysis. Make sure that the cover sheet appropriate Includes the other documents where the results of this organizations? analvsis provide the input 12 Have margin impacts Make sum that the Impacts to margin are dearly shown been identified and within the body of the analysis. If the analysis results In documented reduced margins ensure that this has been appopriately appropriately for any dispositloned in the EC being used to issue the analysis.

negative impacts (Reference ER-AA-2007)?

13 Does the Design Are there sufficient documents included to support the Er 0 Analysis Include the sources of input, and other reference material that is not applicable design basis readily retrievable in Exelon controlled Documents?

documentation?

14 Have all affected design Determine if sufficient searches have been performed to E OU analyses been identify any related analyses that need to be revised along documented on the with the base analysis. It may be necessary to perform Affected Documents List some basic searches to validate this.

(ADL) for the associated Configuration Change?

15 Do the sources of inputs Compare any referenced codes and standards to the current f U U and analysis design basis and ensure that any differences are reconciled.

methodology used meet If the input sources or analysis methodology are based on committed technical and an out-of-date methodology or code, additional reconciliation regulatory may be required if the site has since committed to a more requirements? recent code ....

PageCIC ICC-AA-103-1003

~Revision9 ATIACHMENT 2 Owner's Acceptance Review Checklist for Extemal Design Analyses Page 3 of 3 Design Analysis No.: 19.AN . _Rev,=

No Question Insiuclons and Guidance Yes INoINIA 18 Hav vendor suppor" Based an th risk assessment perormed during the projob L [] U technical documents brief for ft analysis (per HU-AA.1212), ensure that and references suffiiernt reviews of any supporting documents not provided (Including GE DRFs) with Mu final analysis are performed.

been reviewed when necessary?

17 Do opetonal limits Ensure the Tech Specs, Operating Procedures, etc. contain U support ssumptions operational imits that support the analysis assumptions and and Inputs? Inputs.

Create an SFMS entry as required by CC-AA-4008. SFMS Number '43510

Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C2 of C14 DESIGN ANALYSIS TABLE OF CONTENTS SECTION PAGE NO. SUB-PAGE NO.

I I I DESIGN ANALYSIS COVERSHEET Cl OWNER'S ACCEPTANCE REVIEW CHECKLIST FOR EXTERNAL CIA-ClC DESIGN ANALYSES TABLE OF CONTENTS C2 1.0 Purpose C3 2.0 Inputs C3 3.0 Assumptions C5 4.0 References C5 5.0 Identification of Computer Programs C7 6.0 Method of Analysis C7 7.0 Acceptance Criteria C9 8.0 Calculations and Results C9 9.0 Conclusions C14 10.0 Appendices C14 Appendix A - ELMS-AC Plus Load Flow Reports CAI-CA18 Appendix B - Calculation Input CB1-CB12 Appendix C - ELMS-AC Station File Changes CCI-0CCI18 Appendix D - High Impedance Fault Clearing Time CD1-CD13 i i

Analysis No. 19-AN-29 Revision 002B Attachment C PAGE C3 of C14 1.0 PURPOSE The normal (non-accident) time delay associated with the degraded grid voltage relays (DVR) could allow the voltage at the 4.16kV level to remain at extremely low levels for an extended period as long as 5 minutes and 40 seconds (Section 3.3.5.2 of Ref. 4.16). To ensure that the safety-related motors will be available and undamaged, new low degraded voltage, definite time DVRs are installed. This revision establishes a setpoint for the new low degraded voltage DVRs below the existing second-level DVRs and above the first-level loss of voltage relays on 4.16kV ESF Buses 141,142, 241, and 242.

The accuracy of the relay, the relay setting tolerance, and the accuracy of any associated components are considered when establishing the setpoint for the newly installed relay.

Analytical limits are developed in this calculation for the voltage and time delay settings.

This calculation supersedes Calculation 19-AN-29, Rev. 002A in its entirety.

2.0 INPUTS 2.1 Monitoring Circuit Elements 2.1.1 Potential Transformers (Ref. 4.3)

Type Westinghouse Model 9146D46G02 Voltage Ratio 4200- 120V Accuracy Class 0.3W, X, Y and 1.2 Z The PT error and PT ratio used in the calculations in Section 8 are derived from the input data as follows:

AccuracyClass 0.3 PT -error = I 1---= 0.997 100 100 PT -ratio = 4200 = 35

- 120 2.1.2 4.16kV ESF Motor Breakdown Torques Motor Rated BHP Rated Running Load Rated Full Breakdown BDTI Reference #

Voltage (HP) HP  % (Worst Load Torque Torque FLT (V) (HP) Case) (FLT) LB-ft (BDT) LB-ft Aux. Bldg. Vent 4000 444 500 88.8% 2209 5478 248% 4.4, 4.8, & 4.9 Sys. Exh Fans Component 4000 400 450 88.9% - - 238% 4.4, 4.8, & 4.9 Cooling Pumps Centrifugal 4000 560 600 93.4% 270% 4.4, 4.8, & 4.9 Charging Pumps

I Analysis No. 19-AN-29 I Revision 002B Attachment C PAGE C4 of C14 I Motor Rated BHP Rated Running Rated Full Breakdown BDT/ Reference #

Voltage (HP) HP Load % Load Torque Torque FLT (V) (HP) (Worst (FLT) LB-ft (BDT) LB-ft Case)

Aux. Bldg. Vent 4000 298 350 85.2% 1030 2750 267% 4.4, 4.8, & 4.9 Sys. Sup. Fans Containment 4000 0 600 0% 1760 4360 248% 4.14, 4.8, & 4.9 Spray Pumps Aux. FW Pumps 4000 0 1250 0% 1840 4960 270% 4.13, 4.8, & 4.9 RHR Pumps 4000 0 400 0% - - 266% 4.4, 4.8, & 4.9 SI Pumps 4000 0 400 0% - 262% 4.4, 4.8, & 4.9 ESW Pumps 4000 1265 1250 101.2% 7407 - 250% 4.15, 4.8, & 4.9 Control Room 4000 340 461 73.8% 473 1155 244% 4.4, 4.8, & 4.9 Chillers (Note, BHP and Rated HP values taken from ELMS, see Appendix C, pages CC7-CC8, CC38-CC39, CC69-CC70, and CC97-CC98) 2.1.3 460V ESF Motor Breakdown Torques 2.1.3.1 The 460V ESF motors' breakdown torque to rated torque ratio is 200% and is addressed in Assumption 3.2.2.

2.1.4 ABB ITE-27N Undervoltage Relay From the base calculation (Ref. 4.21), the 27N relay (catalog number 41 1T4375-L-HF-DP) has the following characteristics: the total negative error (TNE) is 1.42%, the total positive error (TPE) is 0.90%, the pickup/dropout ratio is 0.5%, and the relay is equipped with a harmonic filter (Reference 4.21. Pages 5 and 16). The 27N relays added per EC's 392851 and 392216 (Refs. 4.11-4.12) are catalog number 411T6375-L-HF-DP and have an adjustable time delay dropout from 0.1-1 seconds (Ref. 4.6. Page 4). The time delay error is equal to the greater of +/- 10%

or +/- 20 milliseconds. (Ref. 4.6, Page 5) 2.1.5 NTS Series 812 Timing Relay The relays are accurate to 2% of the setpoint over the entire operating range. The Series 812 relays added per EC's 392851 and 392216 (Refs.

4.11-4.12) are model 812-1-6-02-0 and have an operating range of 0.5 -

5 seconds (Ref. 4.22).

2.1.6 ELMS-AC Plus Files for Braidwood Units 1 and 2 (Refs. 4.7-4.9).

2.1.7 EC 389241 Rev. 004, "Degraded Voltage 5 Minute Timer Resolution -

Unit 1" (Ref. 4.5).

Analysis No. 19-AN-29 Revision 002B Attachment C PAGE C5 of C14-1 3.0 ASSUMPTIONS 3.1 Assumptions Requiring Verification None.

3.2 Assumptions NOT Requiring Verification 3.2.1 It is assumed that onsite events, such as large motor starts, will cause larger transients in onsite system voltages than events elsewhere in the offsite electrical system. The strength and stability of the offsite electrical system is routinely evaluated considering various transients to ensure its adequacy to support the onsite distribution system.

3.2.2 At the 480V level, the breakdown torque of each of the Class 1E motors is assumed to be 200% of the rated running torque. This is the minimum required by NEMA Standard MG 1-1978 (Ref. 4.2) for Design A and B motors < 200HP. This is acceptable for Braidwood Station since the safety-related motors at the 480V level are less than 200HP.

4.0 REFERENCES

4.1 NUREG-0800, Standard Review Plan, Chapter 8, Branch Technical Position PSB-1, Rev. 0, July 1981.

4.2 NEMA MG 1-1978, Part 12 (Appendix B, Page CB2).

4.3 S&L DIT No. BB-EPED-01 78, dated 5-7-1992, Undervoltage Relay Accuracy Calculation Input Data (Appendix B, Page CB3).

4.4 Calculation 19-AN-3, Rev. 16, "Protective Relay Settings for 4.16kV ESF Switchgear."

4.5 EC 389241 Rev. 004, "Degraded Voltage 5 Minute Timer Resolution - Unit 1" 4.6 ABB IB 7.4.1.7-7 Issue E, Instructions Single Phase Voltage Relays.

4.7 Exelon TODI DIT-BRW-2013-0017, Rev. 01, ELMS File Revision Information (Appendix B, Page CB10).

4.8 ELMS-AC PLUS modification files for Braidwood - Unit 1; A1A4141.MA2 and A1A4142.MA2.

4.9 ELMS-AC PLUS modification files for Braidwood - Unit 2; A2A4241 .M77 and A2A4242.M77.

4.10 Station Drawing 20E-1-4001A, Rev Q, "Station One Line Diagram."

4.11 EC 392851 Rev. 001, "Degraded Voltage 5 Minute Timer Resolution - Unit 1."

4.12 EC 392216 Rev. 002, "Degraded Voltage 5 Minute Timer Resolution - Unit 2."

Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C6 of C14 I 4.13 Vendor Drawing 664834, Westinghouse Speed vs. Torque, Load Torque vs.

Speed, Speed vs. Current Curves (Appendix B, Page CB4).

4.14 Vendor Drawing 664832, Westinghouse Speed vs. Torque, Load Torque vs.

Speed, Speed vs. Current Curves (Appendix B, Page CB5).

4.15 Vendor Drawing DHC770322-1, ESW Pump Motors (Appendix B, Page CB6).

4.16 Technical Specification 3.3.5, Amendment 165, Loss of Power (LOP) Diesel Generator (DG) Start Instrumentation.

4.17 Station Drawing 20E-1-4030AP30, Rev. T, Schematic Diagram 4160V ESF Switchgear Bus 141 Undervoltage Relays - PR9A-427-B141 & PR9C-427-B141, PR29A-427-ST1 1 & PR29C-427-ST1 1.

4.18 Station Drawing 20E-1-4030AP39, Rev. S, Schematic Diagram 4160V ESF Switchgear Bus 142 Undervoltage Relays - PR10A-427-B142 & PR10C-427-B142, PR32A-427-ST12 & PR32C-427-ST12.

4.19 Station Drawing 20E-2-4030AP30, Rev. R, Schematic Diagram 4160V ESF Switchgear Bus 241 Undervoltage Relays - PR31A-427-B241 & PR31C-427-B241, PR11A-427-ST21 & PR11C-427-ST21.

4.20 Station Drawing 20E-2-4030AP39, Rev. R, Schematic Diagram 4160 ESF Switchgear Bus 242 Undervoltage Relays - PR29A-427-B242 & PR29C-427-B242, PR5A-427-ST22 & PR5C-427-ST22.

4.21 Calculation 19-AN-29, Rev. 002, CaIc. for Second-Level Undervoltage Relay Setpoint.

4.22 NTS Manual No. 812-01, NTS Series 812 Timing Relay, March 1999 (Appendix B, Pages CB7-CB-8).

4.23 IEEE Std. 141-1993, IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (Appendix B, Page CB9).

4.24 Procedure MA-MW-772-799, Rev. 004, "Acceptance Criteria for Protective Relays."

4.25 Station Drawing 20E-1-4002C, Rev. S, Single Line Diagram 4.16kV Switchgear Bus 141 & 143 Diesel Generator 1A & 480V Switchgear.

4.26 Calculation 19-AN-7, Rev. 11, Protective Relay Settings for 4.16kV ESF Switchgear.

4.27 Calculation 19-AQ-63, Rev. 007, "Division Specific Degraded Voltage Analysis".

4.28 EC 393032 Rev. 000, "Affected Relay Setting Orders (RSO) and Thermal Overloads (TOL) for DVR Project U2".

4.29 Calculation 19-AU-4, Rev. 18, "480V Unit Substation Breaker and Relay Settings".

Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C7 of C14 4.30 Calculation 19-AU-5, Rev. 13, "480V Unit Substation Breaker and Relay Settings".

4.31 EC 357385 Rev. 000, "Evaluation of AP System Block Start Capability" (Braidwood).

4.32 EC 365038 Rev. 000, "Evaluation of AP System Block Start Capability" (Byron).

4.33 Calculation 19-AK-4, Rev. 002, "ELMS-AC Plus Project Specific Implementation".

4.34 Calculation 19-AN-3, Rev. 16F, "Protective Relay Settings for 4.16kV ESF Switchgear."

5.0 IDENTIFICATION OF COMPUTER PROGRAMS 5.1 Microsoft Word 2003 (Text only), S&L Computer No. ZD6585, Program No.

03.2.286-1.0.

5.2 Advanced AC Electrical Load Monitoring System (ELMS-AC PLUS) Ver. 1.2, S&L Computer No. 8809, Program No. 03.7.379-1.2.

5.3 Mathcad Version 14.35, S&L Computer No. ZD6585, Program No. 03.7.548-1435.

5.4 ETAP PowerStation Version 7.0.ON S&L Computer No. ZD6585, Program No.

03.7.696-7.00.

6.0 METHOD OF ANALYSIS The new relays (low degraded voltage) are harmonically filtered ABB 27N undervoltage relays, same as the existing DVRs (2 nd level) and mounted in the same location (Aux. PT

& Relay Compartment of the associated switchgear), and therefore have the same tolerances calculated in the base revision of this calculation used to determine the relay setpoint.

The overcurrent protection on the 4.16kV and 480V system motors is set to trip the breakers and thermal overload heaters to protect the Class 1 E motors from being damaged. The motor trip setting coordination is addressed in separate analyses as described in the remainder of this paragraph. The protective relay settings for the 4.16kV ESF Switchgear loads are analyzed in Calculations 19-AN-3 & 19-AN-7 (Units 1 & 2, respectively, Refs. 4.4 and 4.26), and the 480V Switchgear loads are analyzed in Calculations 19-AU-4 & 19-AU-5 (Units 1 & 2, respectively, Refs. 4.29 and 4.30). The thermal overload settings for the low voltage motors, under normal operating conditions at a reduced bus voltage, is addressed in EC 393032 (Ref. 4.28).

6.1 Minimum Allowable Value The setpoint for the new low degraded voltage relays must be high enough to prevent the stalling, damaging, and tripping of loads (due to actuation of overcurrent protection devices).

6.1.1 The most limiting ESF motor ratio of breakdown torque to running torque will be determined.

Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C8 of C14 6.1.2 Using Equation 6.1.2, the breakdown torque will be determined for lowered system voltages.

S,1

%TBD., ,V_- (K(Vreduced Vrated ) x %TED., - v,, Equation 6.1.2 6.1.3 The lowest voltage at each 4.16kV ESF bus that supports an acceptable breakdown torque will be determined by iteration using ELMS-AC PLUS.

6.1.4 In order to preclude ESF motor stalling, the worst case (highest) of the voltages determined using the methodology from Section 6.1.3 is used as the minimum allowable value (analytical limit) when determining the new low degraded voltage relay setpoint. This calculation will use Conditions 2 and 3 in the station ELMS-AC load-flow models (Refs. 4.8, 4.9, and 4.33) to represent maximum summer and winter loading under normal operating conditions, respectively. Both Conditions 2 and 3 with Source 2 (SAT supply) will be analyzed to determine the minimum allowable setpoint value. Loading under Conditions 2 and 3 is greater than Condition 1. The ELMS-AC model will be revised to model the applicable ESF loads that are normally running (See Appendix C for changes made to the base ELMS-AC model).

6.2 Maximum Allowable Value The function of the low degraded voltage relay is to ensure that equipment is not damaged by prolonged exposure to extremely low voltages. The maximum allowable voltage is such that the DVRs do not operate if the ESF motors block start following an SI signal. The chosen setpoint is analyzed to ensure that the relay will not spuriously actuate during a block start.

The setpoint will be chosen based on the value determined using the methodology of Section VIII of the base calculation.

6.3 Time Delay Setting Section 8.3 of the Braidwood UFSAR states that the 4.16kV ESF buses are protected from faults via relays (Westinghouse CO series overcurrent relays, Table 8.3-6) to disconnect faults with minimum system disturbance. Thus, the initial time delay associated with the low degraded voltage relays should allow the overcurrent relays to clear faults prior to tripping the bus. The low degraded voltage time delay setpoint is based on the following consideration. The time needed for a 4.16kV circuit breaker to clear a high impedance fault on a 480V bus will be longer than the time needed to clear a faulted 4.16kV bus. Therefore, Appendix D of this calculation determines the maximum fault clearing time for a 4.16kV circuit breaker based on a high impedance fault on a 480V bus fed from a protected 4.16kV ESF bus. This is used as a starting point to determine the initial setpoint, which ultimately must be long enough to prevent spurious trips from system transients and short enough to prevent equipment damage. Additional time delay is added for margin. The methodology used in Appendix D is as follows:

6.3.1 Using the ELMS-AC models, the division (11, 12, 21, or 22) with the

Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C9 of C141 highest impedance is selected to determine the longest fault clearing time.

6.3.2 The phase-to-phase fault current is calculated using a simplified ETAP model (created from the ELMS AC files) and reduced to account for an arcing fault via Ref. 4.23.

6.3.3 The phase-to-phase fault current on the 4.16kV bus is compared to the trip curve for the CO-9 overcurrent relay to determine the fault clearing time (Page H12 of Ref. 4.4).

7.0 ACCEPTANCE CRITERIA 7.1 Low Degraded Voltage Relay Consistent with industry practice, the ultimate tripping point of the low degraded voltage relay setpoint should meet the following requirements:

7.1.1 The setpoint should be high enough to prevent the stalling, damaging, and tripping (due to overcurrent protection devices) of Class 1E motors due to low voltage.

7.1.2 The setpoint should be low enough to prevent spurious actuation during transients such as those experienced during the block starting of ESF motors following a SI initiation.

7.1.3 The time delay setpoint should allow the overcurrent relays to clear faults prior to tripping the bus on low degraded voltage.

8.0 CALCULATIONS AND RESULTS 8.1 The minimum allowable voltage for the new low degraded voltage relay actuation has been selected as follows:

8.1.1 Selection of Limiting Breakdown Torque 8.1.1.1 Motors running at reduced voltages have reduced torque output proportional to the square of the voltage ratio.

Therefore, Equation 6.1.2 is used to determine the breakdown torque at reduced voltage.

2I-Vrted )jX

%TBD@~Vreduced

- *,Vreduced %TBD@ Vrated The minimum allowable voltage to preclude motor stall at the 4.16kV level has been determined as follows:

V~ia1..: = 000%TBDO(*Vreduced Vmin allowed 4000, %TBD @~ Vrated

I Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C10 of C14 I (See Section 2.1.2 for Table Input)

Motor BHP Rated HP TBD@Vrated TBD@Vreduced* Vminallowed (HP) (HP) (%) (%) (V)

Aux. Bldg. Vent Sys. Exh. Fans 444 500 248% 100% 2540.0 Component Cooling Pumps 400 450 238% 100% 2592.8 Centrifugal Charging Pumps 560 600 270% 100% 2434.3 Aux. Bldg. Vent Sys. Sup. Fans 298 350 267% 100% 2448.0

• TBD@reduced is proportional to the motor BHP from References 4.8 & 4.9. For motors below rated HP, 100% torque is used for conservatism.

Motor BHP Rated HP TBD@Vrated TBD@Vreduced* Vminallowed (HP) (HP) (%) (%) (V)

Containment Spray Pumps 0 600 248% 100% 2540.0 Aux. FW Pumps 0 1250 270% 100% 2434.3 RHR Pumps 0 400 266% 100% 2452.6 SI Pumps 0 400 262% 100% 2471.2 ESW Pumps 1265 1250 250% 101.2% 2545.0 Control Room Chillers 340 461 244% 100% 2560.7

• TBD@1.dued is proportional to the motor BHP from References 4.8 & 4.9. For motors below rated HP, 100% torque is used for conservatism.

At a reduced voltage of 2592.8V (64.8% of 4000V), the breakdown torque will equal the running torque for the Component Cooling Pumps. This bounds the 4.16kV system motors.

8.1.1.2 Per Assumption 3.2.2, the minimum breakdown torque for the Class 1 E motors at the 480V level is 200%.

8.1.1.3 Motors running at reduced voltages have reduced torque output proportional to the square of the voltage ratio.

oVreduced 2

%TBD 4. Vu.d. =/- / X %TBD 0 VWa

- Vrated )

O/oTBD'Vr 1=00 *. inAIo460V 2 X200 (Section 2.1.3.1) 460V

= VM AIIow460V = 325.3V At a reduced voltage of 325.3V (70.72% of 460V), the breakdown torque will equal the running torque for the 460V ESF motors. Because this is higher than the limiting voltage for the 4.16kV ESF buses calculated in Section 8.1.1.1, this is the limiting voltage. Therefore, the station ELMS model has been analyzed to determine the 4.16kV ESF bus voltage required to ensure all 480V system motors are > 70.72% of

I Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE CII of C14 rated terminal voltage. From Appendix A page CA1, the minimum required voltage on each of the four buses, 141,142, 241, & 242, are 3005.4V, 3058.5V, 2984.9V, and 3029.5V, respectively. Therefore, the highest minimum voltage required on all four buses (141, 142, 241, & 242) is determined to be 3058.5V (3058.5V/35 = 87.39V, Section 2.1.1) and is used as the Analytical Limit (AL).

8.1.1.4 Voltage Setpoint 4.16kV Buses 141 (Div. 11), 142 (Div. 12), 241 (Div. 21), and 242 (Div. 22).

Nominal Relay Dropout Setpoint = Minimum Relay Dropout +

Total Negative Error (in percent of nominal relay dropout setpoint, from Section IX.D of the base revision)

= 87.39V/(1-0.0142)

= 88.65 This equates to 88.65V*35 (PT Ratio) = 3102.75V. A 4.16kV ESF bus voltage of 3120V (75% of rated bus voltage) is chosen for additional margin. Therefore, the new low degraded voltage relay setpoint is 3120V/35 = 89.143V rounded up to the nearest hundredth volt yields 89.15V.

8.1.1.5 Time Delay Setting The LDVR time delay setting needs to be long enough to prevent spurious tripping, and short enough to protect the motors from overload tripping and lockout due to prolonged exposure to low bus voltage (low degraded voltage). The LDVR should trip before overload relays for a sustained low bus voltage condition Minimum Setting Criteria Section 8.3 of the Braidwood UFSAR states that the 4.16kV ESF buses are protected from faults via relays (Westinghouse CO series overcurrent relays, Table 8.3-6) to disconnect faults with minimum system disturbance. Thus, the initial time delay associated with the low degraded voltage relays should allow the overcurrent relays to clear faults prior to tripping the bus.

Attachment D of this calculation determines the maximum fault clearing time for a 4.16kV circuit breaker based on a high impedance fault on a 480V bus fed from a protected 4.16kV ESF bus. The longest fault clearing time has been determined to be approximately 1 second, with additional margin of 2 seconds to establish the nominal setpoint (3 seconds) and allow time for the bus voltage to recover. The contacts of the new low degraded voltage relays that are part of the trip circuit

I Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C12 of C14 I are connected in series with a new NTS time delay relay connected to prevent spurious 4.16kV bus trips when repowering a dead bus (Refs. 4.11 and 4.12).

The total time delay setpoint for the LDVR and NTS time delay relay is 3 seconds. The LDVRs will have a time delay of 0.5 second and the NTS time delay relays will have a time delay of 2.5 seconds.

The time delay tolerance is taken from Sections 2.1.4 and 2.1.5 and the total time delay error is calculated below:

TPE = TNE = (LDVR time delay

• tol.) + (NTS time delay

• tol.)

= 0.5s

• 10% + 2.5s

• 2% = U.s Maximum Setting Criteria The 4kV and 480V ESF motors are protected from damage, due to overcurrent, by thermal overload (TOL) relays and phase overcurrent relays. The maximum LDVR time delay is evaluated below to ensure coordination with the motor overcurrent protection.

The WO MCR chillers are the only normally running 4.16kV loads running on Buses 141, 142, 241, and 242 that lockout following a trip. The 480V MCC motor loads have thermal overload relays that lockout following a trip. The remaining 4.16kV loads and 480V switchgear loads will restart if tripped on overcurrent prior to the LDVRs disconnecting the associated bus (Ref. 4.28).

Calculation 19-AN-3, Rev. 16F (Ref. 4.34) established that the WO MCR Chiller motor overcurrent relay would not trip for the LDVR setpoint plus total negative error, which equates to 1/(73.9%) = 135.32%. For a sustained undervoltage at the Loss of Voltage Relay allowable value of 65.6% (Section 3.3.5.2 of Ref. 4.16), full load current for the motors would be 1/(65.6%) = 152.4%. Even at a full load current of 250%, the WO MCR chiller motor CO-5 relay would trip in approximately 5 seconds. The TOL trip curves for the 480V MCC loads show a cold start minimum trip time of approximately 25 seconds for 250% of the trip rating. Therefore, the LDVR setting should not be any higher than 5 seconds.

LDVR Time Delay Setting In order to have margin between the maximum allowable value and the setpoint for the time delay, the maximum allowable value is set at 3.5 seconds. The maximum allowable value of 3.5 seconds is greater than the nominal setpoint (3 seconds) plus the total positive error (0.1 seconds). The LDVR setting of

Analysis No. 19-AN-29 Revision 002B I Attachment C PAGE C13 of C14 3.5 seconds is acceptable because it is above the minimum setting and below the maximum setting, with margin for timing tolerances.

8.1.1.6 Maximum Relay Reset The maximum reset voltage is calculated from the maximum dropout voltage and PU/DO ratio as shown in Section 2.1.4:

Max. Relay Dropout = Nominal Relay Dropout (DO) + TPE (in

% of DO)

= 89.15V * (1.0 + 0.009)

= 89.95V Max. Relay Pickup = Max. Relay Dropout / PU/DO ratio

= 89.95V / 0.995 = 90.40V Max. Reset Bus Voltage = 90.40V

• 35 = 3164V 8.2 Maximum Allowable Setpoint Value The low degraded voltage relay setpoint chosen in Section 8.1 is analyzed to ensure that the relay will not spuriously actuate during a block motor start. A block start analysis has been performed in EC 389241 (Input 2.1.7) for Byron Divisions 11 & 12 based on the loads listed in Table 8.3-5 of the UFSAR as continuously energized during the initial period. Previous block start analyses in EC Eval 357385 for Braidwood (Ref. 4.31) and EC Eval 365038 for Byron (Ref. 4.32) have shown that Unit 1 is the bounding case for both plants. Furthermore, the results of these EC Evaluations show that the voltages at ESF Buses 141 and 142 are higher at Braidwood than at Byron. This is mainly due to the fact that the Braidwood DVR setpoint (95.8%) is higher than the Byron DVR setpoint (92.5%), which affects the analytical limit for the block start evaluation, as described below. Additionally, comparison of the loads listed in Table 8.3-5 of the UFSAR for Byron and Braidwood shows that the ESF Switchgear load for Byron is higher than for Braidwood. Therefore, the block start analysis performed under EC 389241 (Input 2.1.7) is bounding, and can be considered as adequate justification that the new low DVRs installed under this EC will not spuriously actuate during a block start.

In EC 389241 (Input 2.1.7), the block start was run using ELMS Load Condition 4 (LOCA) at the DVR minimum pickup voltage, 0.5% above the analytical limit of bus voltage on the 4.16kV bus (141 and 142) to simulate the lowest possible bus voltage the 4.16 kV bus can recover to post motor start without the DVR transferring the bus to the EDG. The analytical limit voltage at Buses 141 & 142 and the pick up to dropout ratio for the DVR were obtained from the Byron Degraded Voltage Calculation 19-AQ-63 Rev. 7 (Ref. 4.27). This is based on the Byron DVR setpoint, which is lower than the Braidwood DVR setpoint (92.5%

compared to 95.8%).

Block starting of loads places a large voltage transient on the AP system from the

Analysis No. 19-AN-29 I Revision 002B I Attachment C PAGE C14 of C147 large starting currents drawn by the various motors. If the voltage drops below the top of the relay tolerance band the new low DVRs could dropout and trip the 4.16kV ESF bus (141 or 142) spuriously. The new low DVR's maximum relay dropout voltage, as calculated in Section 8.1 of this calculation, is 89.95V x 35 (PT Ratio) = 3148.25V. This is the same relay dropout voltage considered in EC 389241 (Input 2.1.7). The results of the analysis in EC 389241 show that the new low DVR relays will not trip during a block start. Since the conditions for Byron Unit 1 are bounding of Braidwood (both units), this is true for Braidwood as well. This is the largest design transient created as a result of plant operations; the voltage dip from a block start will not spuriously cause the new DVRs to actuate.

8.3 Results With the new low degraded voltage relay set at 89.15V, the low degraded voltage relay will actuate prior to any safety-related motors stalling and will not spuriously actuate during a block start thus satisfying the acceptance criteria. The overcurrent protection on the 4.16kV and 480V system motors is analyzed using the new low degraded voltage relay setpoint in separate analyses as described in the second paragraph of Section 6.0.

9.0 CONCLUSION

S 9.1 Low Degraded Voltage Relay Settings Based on the acceptance criteria of Section 7.0 and the calculations of Section 8.0, the following relay settings are recommended:

Nom. Relay Dropout Setpoint = 89.15 V Nom. Relay Pickup (Reset) Setpoint = 89.15 V/ 0.995 = 89.60 V Time Delay Setpoint = 0.5 second 9.2 Time Delay Relay Setting Based on the acceptance criteria of Section 7.0 and the calculations of Section 8.0, the following relay setting is recommended:

Time Delay Setpoint = 2.5 seconds 10.0 APPENDICES A) ELMS-AC Plus Load Flow Reports B) Calculation Input C) ELMS-AC Station File Changes D) High Impedance Fault Clearing Time