ML14120A041

Attachment 5, Byron Station, Units 1 and 2 - Calculation 19-AN-28, Revision 001B Calc. for Second-Level & Third-Level Undervoltage Relays

ML14120A041
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Site:	Byron
Issue date:	02/14/2014
From:	Kolodziej J Exelon Generation Co
To:	Office of Nuclear Reactor Regulation
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ML14120A038	List: ML14120A039 ML14120A040 ML14120A041
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RS-14-116 19-AN-28, Rev. 001B
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{{#Wiki_filter:ATTACHMENT 5BYRON STATIONUNITS 1 AND 2Docket Nos. 50-454 and 50-455Facility Operating License Nos. NPF-37 and NPF-66Calculation 19-AN-28, Revision 001B"Calc. for Second-Level & Third-Level Undervoltage Relays" CC-AA-309-1001 Revision 8ATTACHMENT 1Design Analysis Cover SheetDesign Analysis Last Page No. 6 Attachment A, Appendix DI Page AD3Analysis No.:' 19-AN-28 Revision: 2 001 B Major El Minor 0Title: I Calc. for Second-Level & Third-Level Undervoltage RelaysEC/ECR No.: EC 389241 & EC 389242 Revision: 1 004 & 002Station(s):' BYR Component(s): Unit No.: " 1 & 2 1AP05E-462-B141X Discipline: ELDC 1AP06E-462-B142X Descrip. Code/Keyword: '° E15 2AP05E-T-462-B241X Safety/QA Class:" SR 2AP06E-T-462-B242X System Code: APStructure: N/ACONTROLLED DOCUMENT REFERENCES Document No.: From/To Document No.: From/ToSee Section 5 of this calculation Is this Design Analysis Safeguards Information? I Yes E] No Z If yes, see SY-AA-101-106 Does this Design Analysis contain Unverified Assumptions? '1 Yes El No [] If yes, ATI/AR#:This Design Analysis SUPERCEDES: "1 Calculation 19-AN-28, Rev. 001A 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 undervoltage protection scheme via new Low Degraded VoltageRelays (LDVRs), with a lower setpoint than the existing DVRs (Second-Level Undervoltage Protection). The existing analysis from Revision 001 is not affected; the new third-level undervoltage relays (LDVRs) are addedto the analysis. The original body of the calculation is unchanged. As such, only Attachment A and the associated appendices are included as part of this minor revision. This calculation supersedes Calculation 19-AN-28, Rev. 001Ain its entirety. Approval from Ed Blondin (SMDE) for a minor revision to 19-AN-28 was given on 11/26/2013. /Jt~nu~Preparer: 20J. Kolodziej DatePrint Name/1Sian Narml /7Method of Review: 21 Detailed Review [ AlternateuCalculation ttched) El Testing ElReviewer: 22 G. Hinshaw Z 1- -(LýPrint Name Sign Name DateReview Notes: 22 Independent review [ Peer revi El(For External Anatyses Onlty)External Approver: -4 J. Matthews u 2,0.Print Name --n NaeDateExelon Reviewer: 2C UnP] NaMe ý p D t (01eoPrint Name JSign Name DateIndependent 3rd Party Review Reqd? Is Yes [] No [DExelon Approver: Z Ltj_-"/Print Naife 4N fDate Page AlACC-AA-1 03-1003Revision 9ATTACHMENT 2Owner's Acceptance Review Checklist for External Design AnalysesPage 1 of 3Design Analysis No.: 19-AN-28Rev:001BNo Question Instructions and Guidance Yes I No / N/A1 Do assumptions have All Assumptions should be stated in clear terms with enough [sufficient documented justification to confirm that the assumption is conservative. rationale? For example,

1) the exact value of a particular parameter maynot be known or that parameter may be known to vary overthe range of conditions covered by the Calculation.

It isappropriate to represent or bound the parameter with anassumed value. 2) The predicted performance of a specificpiece of equipment in lieu of actual test data. It is appropriate to use the documented opinion/position of a recognized expert on that equipment to represent predicted equipment performance. Consideration should also be given as to any qualification testing that may be needed to validate the Assumptions. Askyourself, would you provide more justification if you wereperforming this analysis? If yes, the rationale is likelyincomplete. Are assumptions Ensure the documentation for source and rationale for the 11 El2 compatible with the assumption supports the way the plant is currently or will beway the plant is operated post change and they are not in conflict with anyoperated and with the design parameters. If the Analysis purpose is to establish alicensing basis? new licensing basis, this question can be answered yes, if theassumption supports that new basis.3 Do all unverified If there are unverified assumptions without a tracking 0 Elassumptions have a mechanism indicated, then create the tracking item eithertracking 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 E] 0have sufficient be readily retrievable within Exelon's documentation system.rationale? If not, then the source should be attached to the analysis. Askyourself, would you provide more justification if you wereperforming this analysis? If yes, the rationale is likelyincomplete. 5 Are design inputs The expectation is that an Exelon Engineer should be able tocorrect and reasonable clearly understand which input parameters are critical to thewith critical parameters outcome of the analysis. That is, what is the impact of aidentified, if change in the parameter to the results of the analysis? If theappropriate? impact is large, then that parameter is critical. 6 Are design inputs Ensure the documentation for source and rationale for the El E]compatible with the inputs supports the way the plant is currently or will beway the plant is operated post change and they are not in conflict with anyoperated and with the design parameters. licensing basis? I I Page AIBCC-AA-1 03-1003Revision 9ATTACHMENT 2Owner's Acceptance Review Checklist for External Design AnalysesPage 2 of 3Design Analysis No.: 19-AN-28Rev:001BNo Question Instructions and Guidance Yes / No I N/A7 Are Engineering See Section 2.13 in CC-AA-309 for the attributes that are 0 11 ElJudgments clearly 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 19 ElJudgments compatible supports the way the plant is currently or will be operatedwith the way the plant is post change and is not in conflict with any designoperated and with the parameters. If the Analysis purpose is to establish a newlicensing basis? licensing basis, then this question can be answered yes, ifthe judgment supports that new basis.9 Do the results and Why was the analysis being performed? Does the stated Ej [Iconclusions satisfy the purpose match the expectation from Exelon on the proposedpurpose and objective of application of the results? If yes, then the analysis meetsthe Design Analysis? the needs of the contract. 10 Are the results and Make sure that the results support the UFSAR definedconclusions compatible system design and operating conditions, or they support awith the way the plant is proposed change to those conditions. If the analysisoperated and with the supports a change, are all of the other changing documents licensing basis? included on the cover sheet as impacted documents? 11 Have any limitations on Does the analysis support a temporary condition orthe use of the results procedure change? Make sure that any other documents been identified and needing to be updated are included and clearly delineated intransmitted to the the design analysis. Make sure that the cover sheetappropriate includes the other documents where the results of thisorganizations? analysis provide the input.12 Have margin impacts Make sure that the impacts to margin are clearly shown El [] 5abeen identified and within the body of the analysis. If the analysis results indocumented reduced margins ensure that this has been appropriately appropriately for any dispositioned 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 theAnalysis include the sources of input, and other reference material that is notapplicable design basis readily retrievable in Exelon controlled Documents? documentation? 14 Have all affected design Determine if sufficient searches have been performed to E E] [analyses been identify any related analyses that need to be revised alongdocumented on the with the base analysis. It may be necessary to performAffected 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 Kand analysis design basis and ensure that any differences are reconciled. methodology used meet If the input sources or analysis methodology are based oncommitted technical and an out-of-date methodology or code, additional reconciliation regulatory may be required if the site has since committed to a morerequirements? recent code Page AICCC-AA-1 03-1003Revision 9ATTACHMENT 2Owner's Acceptance Review Checklist for External Design AnalysesPage 3 of 3Design Analysis No.: 19-AN-28Rev:001 BNo Question Instructions and Guidance Yes / No / N/A16 Have vendor supporting Based on the risk assessment performed during the pre-job K Eltechnical documents brief for the analysis (per HU-AA-1212), ensure thatand references sufficient reviews of any supporting documents not provided(including GE DRFs) with the final analysis are performed. been reviewed when_ necessary? 17 Do operational limits Ensure the Tech Specs, Operating Procedures, etc. containsupport assumptions operational limits that support the analysis assumptions andSand inputs? inputs.Create an SFMS entry as required by CC-AA-4008. SFMS Number:-- ! CALCULATION TABLE OF CONTENTS19-AN-28 Rev. 001 BPage A2 of A13SECTION: PAGE NO. SUB-PAGENO.TITLE PAGEOWNER'S ACCEPTANCE REVIEWTABLE OF CONTENTS1.0 PURPOSE2.0 METHODOLOGY 3.0 ACCEPTANCE CRITERIA4.05.06.07.08.0ASSUMPTIONS AND LIMITATIONS DESIGN INPUTREFERENCES IDENTIFICATION OF COMPUTER PROGRAMSCALCULATIONS AlA2A3A3A4A5A5A6A8A8A12A13AA1 -AA129ABI -AB33ACI -AC262ADI -AD3AIA-AIC

9.0 CONCLUSION

S AND RECOMMENDATIONS 10.0 APPENDICES A) ELMS-AC Plus Load Flow ReportsB) Calculation InputC) ELMS-AC Station File ChangesD) High Impedance Fault Clearing Timei i CALCULATION PAGEICALCULATION NO. 19-AN-28 REVISION NO. 001BB Attachment A PAGE NO. A3 of A131.0 PURPOSEThe normal (non-accident) time delay associated with the 4.16 kV ESF bus degraded voltage relays(DVRs) could allow the voltage at the 4.16 kV level to remain at extremely low levels for an extendedperiod as long as 5 minutes and 40 seconds (Section 3.3.5.2 of Ref 6.16). To ensure that the safety-related motors will be available and undamaged during a degraded grid voltage condition, new definite-time third-level undervoltage relays (i.e., low degraded voltage relays (LDVRs)) are being installed. This revision establishes a voltage setpoint for the new LDVRs that is below the existing second-level undervoltage relays (i.e., DVRs) and above the first-level undervoltage relays (i.e., loss of voltage relays(LVRs)) on the 4.16 kV ESF Buses 141, 142, 241, and 242.The accuracy of the relay, the relay setting tolerance and the accuracy of any associated components areconsidered when establishing the setpoint for the newly installed relay.Analytical limits are developed in this calculation for the voltage and time delay settings. The settingsdeveloped in this calculation will be evaluated against existing limits defined in the Technical Specifications.

2.0 METHODOLOGY

The new LDVRs (3rd level) are harmonically filtered ABB 27N undervoltage relays, same as theexisting DVRs (2"d level) and mounted in the same location (Aux. PT & Relay Compartment of theassociated switchgear), and therefore have the same tolerances calculated in the base revision of thiscalculation used to determine the relay setpoint. The 4.16 kV Switchgear loads are analyzed in Calculations 19-AN-3 & 19-AN-7 (Units I & 2respectively), and the 480V Switchgear loads are analyzed in Calculations 19-AU-4 & 19-AU-5 (UnitsI & 2 respectively). An individual analysis of the overcurrent protection for each low voltage safety-related load, under normal operating conditions at a reduced bus voltage is included in References 6.11& 6.12.2.1 Minimum Allowable ValueThe setpoint for the new LDVRs must be high enough to prevent the stalling and tripping of loads(due to actuation of overcurrent protection devices). 2.1.1 The most limiting ESF motor ratio of breakdown torque to running torque will bedetermined. 2.1.2 Using Equation 2.1.2, the breakdown torque will be determined for lowered systemvoltages. ( Vreduced 2%TED Vmd = 2 X %TBD,, V,,a Equation 2.1.2, Vrated )2.1.3 The lowest voltage at the ESF 4.16 kV Switchgear buses that supports an acceptable breakdown torque will be determined by iteration using ELMS-AC PLUS.2.1.4 In order to preclude ESF motor stalling, the worst case (highest) of the voltagesdetermined using the methodology from Section 2.1.3 is used as the minimum allowable value (analytical limit) when determining the new LDVR setpoint. This calculation will CALCULATION PAGECALCULATION NO. 19-AN-28 REVISION NO. 001B Attachment A PAGE NO. A4 of A13use Conditions 2 and 3 in the station ELMS-AC load-flow models (References 6.8 &6.9) to represent maximum summer and winter loading under normal operating conditions, respectively. Since SX flows and Chiller loads are higher in the summermonths, the summer non-LOCA model (ELMS-AC Condition

2) will be used. TheELMS-AC model will be revised to model the applicable ESF loads that are normallyrunning, as identified in Reference 6.10 (shown in Appendix C).2.2 Maximum Allowable ValueThe function of the LDVR is to ensure that equipment is not damaged by prolonged exposure toextremely low voltages.

The maximum allowable voltage is such that the LDVRs do not operateif the ESF motors block start following an SI signal; this scenario is evaluated in References 6.11& 6.12. The setpoint will be chosen based on the value determined using the methodology ofSection VIII of the base calculation. 2.3 Time Delay SettingSection 8.3 of the Byron UFSAR states that the 4160 V ESF Switchgear are protected from faultsvia relays (Westinghouse CO series overcurrent relays, Table 8.3-6) to disconnect faults withminimum system disturbance. Thus, the initial time delay associated with the LDVRs should allowthe overcurrent relays to clear faults prior to tripping the bus. Appendix D of this calculation determines the maximum fault clearing time for a 4.16 kV circuit breaker based on a highimpedance fault on a 480 V bus fed from a protected 4.16 kV ESF bus. Appendix D is used as astarting point to determine the initial setpoint which ultimately must be long enough to preventspurious trips from system transients and short enough to prevent equipment damage. The LDVRtime delay setpoint is based on engineering judgment. The methodology used in Appendix D is asfollows:2.3.1 Using the ELMS-AC models, the division with the highest impedance was selected todetermine the longest fault clearing time.2.3.2 The three phase, bolted fault current is calculated from the system impedance, converted to a phase-to-phase fault, and reduced to account for an arcing fault via References 6.26& 6.27.2.3.3 The phase-to-phase fault current on the 4.16 kV bus is compared to the trip curve for theCO-9 overcurrent relay to determine the fault clearing time (Reference 6.4).3.0 ACCEPTANCE CRITERIA3.1 Low Degraded Voltage RelayConsistent with industry

practice, the ultimate tripping point of the LDVR setpoint should be lowenough to prevent spurious actuation during transients such as those experienced during thestarting of large plant motors. The setpoint must be high enough to prevent the stalling, tripping(due to overcurrent protection devices) or damaging of Class IE motors due to low voltage.

Thetime delay setpoint should allow the overcurrent protective devices to clear faults prior to trippingthe bus on low degraded voltage. CALCULATION PAGEI CALCULATION NO. 19-AN-28 REVISION NO. 001B Attachment A PAGE NO. A5 of A134.0 ASSUMPTIONS AND LIMITATIONS 4.1 Assumptions Requiring Verification None.4.2 Assumptions NOT Requiring Verification 4.2.1 It is assumed that onsite events, such as large motor starts, will cause larger transients inonsite system voltages than events elsewhere in the offsite electrical system. Thestrength and stability of the offsite electrical system is routinely evaluated considering various transients to ensure its adequacy to support the onsite distribution system.4.2.2 At the 480 V level the breakdown torque of each of the Class IE motors, with theexception of the Control Room HVAC Return Fans (See Section 5.1.4.2), is assumed tobe 200% of the rated running torque. This is the minimum required by NEMA StandardMG 1-2011 (Reference 6.2) for Design A and B motors <200hp. This is acceptable forByron Station since the safety-related motors at the 480 V level are less than 200hp.5.0 DESIGN INPUT5.1 Monitoring Circuit Elements5.1.1 Loss of Voltage Relays (Reference 6.22)Type Westinghouse Model CV-7Voltage Tap Settings (Vac) 55, 64, 70, 82, 93, 105, 120, 140Time Lever Settings 1/2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11The LVRs are currently set to time lever setting 2 which corresponds to 1.8 seconds witha 10% setting tolerance (References 6.5 & 6.22).5.1.2 Potential Transformers (Reference 6.3)Type Westinghouse Model 9146D46G02 Voltage Ratio 4200 -120VAccuracy Class 0.3W, X, Y and 1.2 ZThe PT error and PT ratio used in the calculations in Section 8 are derived from the inputdata as follows:0.3PT _error = 1 Accuracy_ Class = I --- = 0.997100 1004200PT _ ratio =1 = 35-120 CALCULATION PAGEI CALCULATION NO. 19-AN-28 REVISION NO. 001B Attachment A PAGE NO. A6 of A135.1.3 4 kV ESF Motor Breakdown TorquesMotor Rated Running Rated Full Breakdown BDT/ Reference

1. Voltage Load % Load Torque Torque FLT(V) (Worst Case) (FLT) LB-ft (BDT) LB-ftAux. Bldg. Vent Sys. Exh Fans 4000 98.8% 2209 5478 248% 6.4, 6.8, & 6.9Component Cooling Pumps 4000 96.7% --238% 6.4, 6.8, & 6.9Centrifugal Charging Pumps 4000 115% --270% 6.4, 6.8, & 6.9Aux. Bldg. Vent Sys. Sup. Fans 4000 108.3% 1030 2750 267% 6.4, 6.8, & 6.9Containment Spray Pumps 4000 0% 1760 4360 248% 6.14. 6.8, & 6.9Aux. FW Pumps 4000 0% 1840 4960 270% 6.13, 6.8, & 6.9RHR Pumps 4000 0% 1075 3000 279% 6.4, 6.8, & 6.9SI Pumps 4000 0% --262% 6.4, 6.8, & 6.9ESW Pumps 4000 109.6% 7407 -250% 6.15, 6.8, & 6.9Control Room Chillers 4000 73.8% 473 1155 244% 6.4, 6.8, & 6.95.1.4 460 V ESF Motor Breakdown Torques5.1.4.1 The 460 V ESF motors breakdown torque to rated torque ratio is 200% and isaddressed in Assumption 4.2.2.5.1.4.2 The 460 V Control Room HVAC Return Fans (OVC02CA

& OVC02CB) run at49HP and are rated 40HP (Reference 6.8). The fans have a breakdown torqueof 225% of motor rated torque (Reference 6.23).5.1.5 ABB ITE-27N Undervoltage RelayThe total negative error (TNE) is 1.42%, the total positive error (TPE) is 0.90%, apickup/dropout ratio of 0.5%, and harmonic filter 41 IT6375-L-HF-DP (Reference 6.21Pages 5 & 16). The relay has an adjustable time delay from 0.1-I seconds (Reference 6.6Page 4). The time delay error is equal to the greater of +/- 10% or +/- 20 milliseconds. (Reference 6.6 Page 5)5.1.6 NTS Series 812 Timing RelaysThe relays are accurate to 2% of the setpoint over the entire operating range. The 812-1-6-02-0 relay has an operating range of 0.5 -5 seconds (Reference 6.25).

6.0 REFERENCES

6.1 NUREG-0800, Standard Review Plan, Chapter 8, Branch Technical Position PSB- 1, Rev. 0, July1981.6.2 NEMA MG 1-2011, Part 12 (Appendix B Page AB2). CALCULATION PAGECALCULATION NO. 19-AN-28 REVISION NO. 001B Attachment A PAGE NO. A7 of A136.3 S&L DIT No. BB-EPED-0178, dated 5-7-1992, Undervoltage Relay Accuracy Calculation InputData (Appendix B Page AB3).6.4 Calculation 19-AN-3, Rev. 16, Protective Relay Settings for 4.16kV ESF Switchgear (Appendix BPages AB4 -AB 10).6.5 Work Order 00492205, 03/31/04 Bus 242 Tech Spec Undervoltage Relays (Appendix B PageAB 11).6.6 ABB lB 7.4.1.7-7 Issue E, Instructions Single Phase Voltage Relays.6.7 Exelon TODI BYR- 12-002, Rev. 000, ELMS File Revision Information. 6.8 ELMS-AC PLUS modification files for Byron -Unit 1; B IA4141.M97 and B IA4142.M97 (Appendix B Pages ABI2 & ABI3).6.9 ELMS-AC PLUS modification files for Byron -Unit 2; B2A4241.M75 and B2A4242.M75. 6.10 EC 377631 Rev. 000, Evaluation And Technical Basis For The AP System Second LevelUndervoltage (Degraded Voltage) Time Delay Setting, Approved Feb. 3, 2010 (Appendix B PageAB14).6.11 EC 389241 Rev. 004, Degraded Voltage 5 Minute Timer Resolution -Unit I (Appendix B PageABI5).6.12 EC 389242 Rev. 002, Degraded Voltage 5 Minute Timer Resolution -Unit 2 (Appendix B PageABI6).6.13 Vendor Drawing 664834, Westinghouse Thermal Limit and Acceleration Time vs. Current Curve(Appendix B Page AB 17).6.14 Vendor Drawing 664832, Westinghouse Thermal Limit and Acceleration Time vs. Current Curve(Appendix B Page AB 18).6.15 Vendor Drawing DHC770322-I, ESW Pump Motors (Appendix B Page AB 19).6.16 Technical Specification 3.3.5, Loss of Power (LOP) Diesel Generator (DG) Start Instrumentation. 6.17 Station Drawing 6E-1-4030AP30, Rev. U, Schematic Diagram 4160V ESF SWGR Bus 141Undervoltage Relays: PR9A-427-B 14 1, PR9C-427-B 141, PR29A-427-ST 11, & PR29C-427-ST 11.6.18 Station Drawing 6E-1-4030AP39, Rev. U, Schematic Diagram 4160V ESF SWGR Bus 141Undervoltage Relays: PRIOA-427-B 142, PR1OC-427-B 142, PR32A-427-ST12, & PR32C-427-ST126.19 Station Drawing 6E-2-4030AP30, Rev. T, Schematic Diagram 4160V ESF SWGR Bus 241Undervoltage Relays: PR31A-427-B241, PR31C-427-B24 I, PR29A-427-ST21, & PR29C-427-ST2 1.6.20 Station Drawing 6E-2-4030AP39, Rev. Q, Schematic Diagram 4160V ESF SWGR Bus 242Undervoltage Relays PR29A- 427-B242, PR29C-427-B242, PR5A- 427-ST22, & PR5C-427-ST22.6.21 Calculation 19-AN-28, Rev. 001, Calc. For Second-level Undervoltage Relay Setpoint (Appendix B Pages AB20 & AB2 1). CALCULATION PAGECALCULATION NO. 19-AN-28 REVISION NO. OOR1B Attachment A PAGE NO. A8 of A136.22 Westinghouse I.L. 41-201Q, Type CV Voltage Relay, December 1988(Appendix B Page AB22).6.23 Reliance A-C Motor Performance Data No. EO1 I 1A-B-007, June 1977 (Appendix B Page AB23).6.24 Exelon Procedure MA-MW-772-702 Rev. 0, Calibration of Voltage Protective Relays (Appendix B Page AB24).6.25 NTS Manual No. 812-01, NTS Series 812 Timing Relay, March 1999 (Appendix B Pages AB25 -AB26).6.26 IEEE Std 141-1993, IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (Appendix B Page AB27).6.27 IEEE Std 242-2001, IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (Appendix B Page AB28).6.28 IEEE Std C37.91-2008, IEEE Recommended Practice for Protection and Coordination ofIndustrial and Commercial Power Systems (Appendix B Page AB29).6.29 Calculation 19-AN-7, Rev. 11, Protective Relay Settings for 4.16kV ESF Switchgear (Appendix BPage AB30).6.30 Fitzgerald, A. E., Kingsley Jr., Charles, and Umans, Stephen D. Electric Machinery. Sixth Edition.New York: McGraw-Hill, 2003 (Appendix B Page AB31 -AB33).6.31 Calculation 19-AN-3, Rev. 16D, Protective Relay Settings for 4.16kV ESF Switchgear 7.0 IDENTIFICATION OF COMPUTER PROGRAMS7.1 Microsoft Word 2003 (Text only), S&L Computer No. ZD6585, Program No. 03.1.286-1.0. 7.2 Advanced AC Electrical Load Monitoring System (ELMS-AC PLUS) Ver 1.2, S&L ComputerNo. 8809, Program No. 03.7.379-1.2. 7.3 Mathcad Version 14.35, S&L Computer No. ZL8156, Program No. 03.7.548-1435.

8.0 CALCULATIONS

8.1 The minimum allowable voltage for the new LDVR actuation has been selected as follows:8.1.1 Selection of Limiting Breakdown Torque8.1.1.1 Motors running at reduced voltages have reduced torque output proportional tothe square of the voltage ratio. Therefore, Equation 2.1.2 is used to determine the breakdown torque at reduced voltage.%TBD@Vreduced =rate 2°/TBD@Vw V. ,.atd )The minimum allowable voltage to preclude motor stall at the 4.16kV level hasbeen determined as follows: CALCULATION PAGECALCULATION NO. 19-AN-28 REVISION NO. 001B Attachment A PAGE NO. A9 of A13Vminallowed = 4000V %TBD@Vited , where Vmin.allowed = Vred.ced(See Section 5.1.3)Induction motors are typically utilized in constant-speed applications, andbecause Pmotor = Tmotor 01, the motor BHP is proportional to the motor torque(Ref. 6.30). Therefore, for motors running above rated power, the BHP (fromReferences 6.8 and 6.9) as a percent of motor rated power is used forTBD@Vreduced. Motor TBD Vrated TBD@ Vreduced

• Vmin allowed(%) (%) (V)Aux. Bldg. Vent Sys. Exh Fans 248 100 2540.0Component Cooling Pumps 238 100 2592.8Centrifugal Charging Pumps 270 115 2610.5Aux. Bldg. Vent Sys. Sup. Fans 267 108.3 2547.5Containment Spray Pumps 248 100 2540.0Aux. FW Pumps 270 100 2434.3RHR Pumps 279 100 2394.7SI Pumps 262 100 2471.2ESW Pumps 250 109.6 2648.5Control Room Chillers 244 100 2560.7*TBDvw,ýd is proportional to the motor BHP from References 6.8 & 6.9, for motors runningbelow rated HP 100% torque is used for conservatism.

At a reduced voltage of 2648.5V (66.2% of 4000V), the breakdown torque willequal the running torque for the Essential Service Water Pump. This boundsthe 4 kV motors.8.1.1.2 Per Assumption 4.2.2, the minimum breakdown torque for the Class I E motorsat the 480 V level is 200%.8.1.1.3 The only 480 V level loads running above rated load are the Control RoomHVAC Return Fans, which are rated 40HP and run at 49HP or 122.5%(References 6.8 & 6.9).8.1.1.4 Motors running at reduced voltages have reduced torque output proportional tothe square of the voltage ratio. Therefore, Equation 2.1.2 is used to determine the breakdown torque at reduced voltage of low voltage motors running at fullload.= Vreduced 2%Tao D = I %TBD @, V., CALCULATION PAGEE CALCULATION NO. 19-AN-28 REVISION NO. 001B Attachment A PAGE NO. Al0 of A13( VMinAllow460V /TBD Q V,..d = 100= = 460V x x 200 (Section 5.1.4)='VMinAllow60v = 325.3V8.1.1.5 Equation 2.1.2 is used to determine the breakdown torque at reduced voltagefor the Control Room HVAC Return Fans: = 122.5 VinAlow460V Jx 225 (Section 5.1.4.2)SVinAiiow46V = 339.42VAt a reduced voltage of 339.42V (73.79% of 460V), the breakdown torque willequal the running torque for the Control Room HVAC Return Fan. Becausethis is higher than the limiting voltage for the 4.16kV ESF buses calculated inSection 8.1.1.1, this is the limiting voltage. Therefore, the station ELMS modelhas been analyzed to determine the 4.16kV ESF bus voltage required to ensureall 480V Control Room HVAC Return Fans are > 73.79% of rated terminalvoltage, while all other 480V ESF motors are > 70.72% (325.3Vtemnai /460V.) of rated terminal voltage. From Appendix A page AA 1 the minimumrequired voltage on each of the four buses, 141, 142, 241 & 242, are 3056.4V,3075.OV, 2914.3V and 2955.2V respectively; therefore highest minimumvoltage required on all four buses (141, 142, 241 & 242) is determined to be3075.OV (3075.OV/35 = 87.86V, Section 5.1.2) and is used as the Analytical Limit (AL).8.1.1.6 Voltage Setpoint4160 V Switchgear buses 141 (Div. 11), 142 (Div. 12), 241 (Div. 21), and 242(Div. 22).Nominal Relay Dropout Setpoint = Minimum Relay Dropout + Total NegativeError (in percent of nominal relay dropout setpoint, from Section IX.D of thebase revision) = 87.86V/(1-0.0142) = 89.13VThis equates to 89.13V*35 (PT Ratio) = 3119.55V. EC 377631 (Ref. 6.10) determined that no damage will result to permanently connected Class I E loads as a result of operation at degraded voltageconditions for the maximum allowable duration of the transients as specified inthe Technical Specifications (340 seconds) at a 4.16 kV Switchgear bus voltageof 3120V (75%). Therefore the new LDVR setpoint is 3120V/35 = 89.143Vrounded up to the nearest hundredth volt yields 89.15V.8.1.1.7 Time Delay SettingThe LDVR time delay setting needs to be long enough to prevent spurioustripping, and short enough to protect the motors from overload tripping and CALCULATION PAGECALCULATION NO. 19-AN-28 REVISION NO. 001 B Attachment A PAGE NO. All of Al3lockout due to prolonged exposure to low bus voltage (low degraded voltage). The LDVR should trip before overload relays for a sustained low bus voltagecondition. Minimum Setting CriteriaSection 8.3 of the Byron UFSAR states that the 4160 V ESF Switchgear areprotected from faults via relays (Westinghouse CO series overcurrent relays,Table 8.3-6) to disconnect faults with minimum system disturbance. Thus, theinitial time delay associated with the LDVRs 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 4.16 kV circuit breaker basedon a high impedance fault on a 480V bus fed from a protected 4.16 kV ESFbus. The longest fault clearing time has been determined to be approximately

2seconds, with additional margin of 1 second to establish the nominal setpoint (3seconds) and allow time for the bus voltage to recover.

The contacts of the newLDVR that are part of the trip circuit are connected in series with a new NTStime delay relay connected to prevent spurious 4.16 kV bus trips whenrepowering a dead bus (References 6.11 & 6.12).The total time delay setpoint for the LDVR and NTS time delay relay is 3seconds. The LDVRs will have a time delay of 0.5 second and the NTS timedelay relays will have a time delay of 2.5 seconds.The time delay tolerance is taken from Sections 5.1.5 and 5.1.6 and the totaltime delay error is calculated below:TPE = TNE = (LDVR time delay

• tolerance)

+ (NTS time delay

• tolerance)

= 0.5s

• 10% + 2.5s
• 2% = 0.1sMaximum Setting CriteriaThe 4kV and 480V ESF motors are protected from damage, due to overcurrent, by thermal overload (TOL) relays and phase overcurrent relays. The maximumLDVR time delay is evaluated below to ensure coordination with the motorovercurrent protection.

The WO MCR chillers are the only normally running 4.16 kV loads running onBuses 141, 142, 241, and 242 that lockout following a trip. The 480V MCCmotor loads have thermal overload relays that lockout following a trip. Theremaining 4.16 kV loads and 480V switchgear loads will restart if tripped onovercurrent prior to the LDVRs disconnecting the associated bus (References 6.11 and 6.12).Calculation 19-AN-3, Rev. 16D (Ref. 6.31) established that the WO MCRChiller motor overcurrent relay would not trip for the LDVR setpoint plus totalnegative error, which equates to 1/(73.9%) = 135.32%. For a sustained undervoltage at the Loss of Voltage Relay allowable value of 65.6% (Section3.3.5.2 of Ref. 6.16), 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-5relay would trip in approximately 5 seconds. The TOL trip curves for the 480V CALCULATION PAGEI CALCULATION NO. 19-AN-28 REVISION NO. O01B Attachment A PAGE NO. A12 of A13MCC loads show a cold start minimum trip time of approximately 25 secondsfor 250% of the trip rating. Therefore, the LDVR setting should not be anyhigher than 5 seconds.LDVR Time Delay SettingIn order to have margin between the maximum allowable value and the setpointfor the time delay, the maximum allowable value is set at 3.5 seconds. Themaximum allowable value of 3.5 seconds is greater than the nominal setpoint (3seconds) plus the total positive error (0.1 seconds). The LDVR setting of 3.5seconds is acceptable because it is above the minimum setting and below themaximum setting, with margin for timing tolerances. 8.1.2 Maximum Relay ResetThe maximum reset voltage is calculated from the maximum dropout voltage and PU/DOratio as shown in Section 5.1.5:Max. Relay Dropout = Nominal Relay Dropout (DO) + TPE (in % of DO)= 89.15V * (1.0 + 0.009)= 89.95VMax. Relay Pickup = Max. Relay Dropout / PU/DO ratio= 89.95V / 0.995 = 90.40VMax. Reset Bus Voltage = 90.40V

• 35 = 3164V8.2 ResultsWith the new LDVR set at 89.15V, the LDVRs will actuate prior to any safety-related motorsstalling and thus satisfying the acceptance criteria.

The motor protection is analyzed with theLDVRs set at 89.15V and 3 seconds in ECs 389241 & 389242 (References 6.11 & 6.12) anddetermined that the motor protection, for loads that will lockout following a trip, will not tripon the normally

running, safety-related motors during a degraded voltage condition prior to theDVR 5 minute timer transferring the SR loads to the emergency diesel generators.

9.0 CONCLUSION

S AND RECOMMENDATIONS 9.1 Low Degraded Voltage Relay SettingsBased on the acceptance criteria of Section 3.0 and the calculations of Section 8.0, the following relay settings are recommended: Nom. Relay Dropout Setpoint = 89.15V [3120.25V (primary side voltage)] Nom. Relay Pickup (Reset) Setpoint = 89.15V/ 0.995 = 89.60VMaximum Relay Reset = 90.40VTime Delay Setpoint= 0.5 seconds CALCULATION PAGECALCULATION NO. 19-AN-28 REVISION NO. 001B Attachment A PAGE NO. A13 of A1319.2 Time Delay Relay SettingBased on the acceptance criteria of Section 3.0 and the calculations of Section 8.0, the following relay setting is recommended: Time Delay Setpoint = 2.5 seconds10.0 APPENDICES A) ELMS-AC Plus Load Flow ReportsB) Calculation InputC) ELMS-AC Station File ChangesD) High Impedance Fault Clearing Time}}