HITACHI GE Hitachi Nuclear Energy - NRC: Home Page · 2015-10-06 · 6, 8, and 19 for GE-Hitachi Nuclear Energy Advanced Boiling Water Reactor Design Certification Rule Renewal Application

HITACHIGE Hitachi Nuclear EnergyJerald G. HeadSenior Vice President, Regulatory Affairs

3901 Castle Hayne RoadP0 Box 780 M/C A-18Wilmington, NC 28402-0780USA

T 910 819 5692F 910 362 [email protected]

Docket number: 52-045MFN 15-073

September 25, 2015

U.S. Nuclear Regulatory CommissionDocument Control DeskWashington, DC 20555-0001

Subject: NRC Request for Additional Information Letter Number 1 Related to Chapters6, 8, and 19 for GE-Hitachi Nuclear Energy Advanced Boiling Water ReactorDesign Certification Rule Renewal Application - GEH Response to RAI 08.02-2

Reference:

1. Letter from USNRC to Jerald G. Head, GEH-, Subject: Request for AdditionalInformation Letter Number 7 Related to Chapter 8 For GE-Hitachi Nuclear Energy,Advanced Boiling Water Reactor Design Certification Rule Renewal Application,June 10,2015

In regard to the Requests for Additional Information transmitted in your June 10, 2015 letter,Reference 1, please find attached GEH's response to RAI 08.02-2. Enclosure 1 contains thecomplete response. Enclosure 2 contains the DCD markups associated with this response.

If you have any questions concerning this letter, please contact Peter Yandow at 910-81 9-6378.

MFN 15-073Pae2o2

I declare under penalty of perjury that the foregoing information is true and correct to the bestof my knowledge, information, and belief.

Sincerely,

Jerald G. HeadSenior Vice President, Regulatory Affairs

Commitments: No additional commitments are made in this response.

Enclosures:

1. GEH Response to RAI 08.02-2

2. GEH Response to RAI 08.02-2 - ABWR DOD DRAFT Revision 6 Markups

cc: Adrian Muniz, NRCKevin Nunes, GEHDavid Hinds, GEHPeter Yandow, GEHHugh Upton, GEHPatricia Campbell, GEHShailesh Sheth, GEHErik Kirstein, GEHJames Parham, GEH002N9996

Enclosure 1

MFN 15-073

GEH Response to RAI 08.02-2

MEN 15-073 Page 1 of 7Enclosure 1

NRC Request for Additional Information 08.02-2:

In Request for Additional In formation (RA/) response dated August 29, 2014(Agencywide Documents Access and Management System (ADAMS) Accession No.ML14241A558), GE Hitachi Nuclear Energy, the applicant, discussed its response toRAI 08.02-1 concerning the recent operating experience that involved the loss of one ofthe three phases of the offsite power circuit (single-phase open circuit condition) atByron Station and the loss of 2 phases at Forsmark, Sweden.

Based on the review of applicant's response, staff identified the following issues:

Enclosure 1, "Description of the Protection Design Features not included in DCD"states:

This section explains the design features of the protective relays that provide formonitoring and alarms for detecting the loss of one or more phases or a groundin the electrical system at the UA T or RAT inputs and on the safety-relatedmedium voltage busses and alarming in the Main Control Room so that operatorscan take manual action, as appropriate, and initiate corrective actions to addressthe loss of phase condition.

Enclosure 1, "Summary of Monitoring and Alarms Design Features" states:

Because the ABWR offsite and onsite high and medium voltage circuits will bemonitored and alarmed in the Main Control Room, operators can take manualaction, as necessary, and initiate corrective actions to address a loss of phasecondition.

Enclosure 2, DCD, Section 8.3.1.1.6.3, "Bus Protection" states:

6.9 kV bus incoming circuits have inverse time over-current, ground fault, busdifferential and under-voltage protection. The under-voltage monitoring isresponsive to all three phases. The monitoring is effective for both load sheddingand emergency diesel start and protection of the safety-related bus loads forgrounds and loss of one or more phases.

Based on the above, the staff determined that the applicant did not provide sufficientdesign in formation for staff to conclude that all open phase conditions (OPCs) would beautomatically detected and alarmed in the main control room under all operatingelectrical system configurations and plant loading conditions. In addition, the applicantdid not provide sufficient design information concerning the automatic protectivefeatures that would be provided to transfer the offsite power circuits to the 6. 9 kV safetyrelated buses Division I (E), Division II (F), and Division III (G) if they are functionallydegraded due to open-phase conditions. Furthermore, the staff's review of operatingreactor licensees' NRC Bulletin 2012-0 1, "Design Vulnerability in Electric Power

MEN 15-073 Page 2 of 7Enclosure 1

System," responses and interactions with the industry representatives in various publicmeetings revealed that undervoltage detection and protection schemes cannot detect allOPCs and mitigate the consequences of OPCs under all operating electrical systemconfigurations and plant loading conditions.

There fore, the applicant is requested to provide the design basis and ITAAC informationin accordance with § 52.47, "Contents of applications; technical information," for theElectrical Engineering Branch staff to determine whether it meets the 10 CFR 50Appendix A, GDC 1 7, "Electric power systems," requirements regarding the offsitepower circuits and onsite electrical power distribution system to provide adequatecapacity and capability in view of the design Vulnerability identified in Bulletin 2012-01.The information should have sufficient details for the combined operating licenseapplicants to complete the detailed design (e.g., location of relays) and analyses (e.g.,setpoints) in final safety analysis report in accordance with §52. 79, "Contents ofapplications; technical information." In addition, GEH is requested to provide thedelineation of scope between the DCD and COL applicants in regards to the BL.

The NRC staff position for new reactors with active design safety features, reviewedunder 10 CFR Part 50 and 10 CFR Part 52, "Licenses, Certifications, and Approvals forNuclear Power Plants," the following criteria should be satisfied when evaluating OPCs:

a. The OPC should be automatically detected and alarmed in the main control roomunder all operating electrical system configurations and plant loading conditions.The _detection circuits should be sensitive enough to identify OPCs under alloperating electrical system configurations and plant loading conditions for whichthe offsite power supplies are required to be operable in accordance with planttechnical specifications (TSs) and licensing basis for safe shutdown.

b. The detection circuit should minimize spurious indications for an operable offsitepower source in the range of voltage perturbations such as switching surges,transformer inrush currents, load or generation variations, lightning strikes, etc.,normally expected in the transmission system. If there is potential for OPCs onthe high voltage and low voltage side of transformers and interconnecting onsiteauxiliary power circuits, the OPCs) should be alarmed in the main control roomfor operators to take corrective action within reasonable time. Any connectionsnot required to be evaluated, should be documented with adequate justification.In such cases, the consequences of not isolating the degraded power sourceimmediately should be evaluated to demonstfrate that any subsequent designbases conditions that require offsite power circuit (s) for safe shutdown do notcreate plant transients or abnormal operating conditions. Also, the alternatepower source(s) can be connected to the safety related buses within in the timeassumed in the accident analysis.

c. If offsite power circuit(s) is (are) functionally degraded due to open-phaseconditions, and safe shutdown capability is not assured, then the safety relatedbuses should be designed to be transferred automatically to the alternate reliable

MEN 15-073 Page 3 of 7Enclosure 1

offsite power source or onsite standby power system within the time assumed inthe accident analysis and without actuating any protective devices, given aconcurrent design basis event.

d. The design of protection features for open-phase conditions should address thefollowing:

(i) Power quality issues caused by QPCs such as unbalanced voltages andcurrents, sequence voltages and currents, phase angle shifts, and harmonicdistortion that could affect Class 1E safety-related buses. The Class 1E loadsshould not be subjected to power quality conditions specified in industrystandards such as Institute of Electrical and Electronic Engineers (IEEE)Standard (Std) 308-2001, "Criteria for Class IE Power Systems for NuclearPower Generating Stations," Section 4.5, "Power Quality," with respect to thedesign and operation of electrical systems as indicated in Regulatory Guide(RG) 1.32 "Criteria for Power Systems for Nuclear Plants."

(ii) Protection scheme should comply with applicable requirements includingsingle failure criteria for Class 1E safety-related systems as specified in 10CFR Part 50, Appendix A, GDC17 and 10 CFR 50.55a(h) (3) derived fromIEEE Std 603-1991," Standard Criteria for Safety Systems for Nuclear PowerGenerating Stations, as endorsed by RG 1.153, "Criteria for Power,Instrumentation, and Control Portions of Safety Systems."

Questions:

a. Explain the design features that would be provided for the OPCs to beautomatically detected and alarmed in the main control room under all operatingelectrical system configurations and plant loading conditions.

b. Describe the design features that would be provided in the event that offsitepower circuit(s) is (are) functionally degraded due to open-phase conditions, andsafe shutdown capability is not assured, then the safety related buses should bedesigned to be transferred automatically to the alternate reliable offsite powersource or onsite standby power system within the time assumed in the accidentanalysis and without actuating any protective devices, given a concurrent designbasis event.

c. Provide an ITAAC that demonstrates and verifies the following, includingsetpoints:

* Monitoring/detecting/Alarming in the control room in the event of the OPCs.

* Automatically separates the Class 1E safety-related buses from the off-sitepower source and transfers safety-related loads to the unaffected offsitepower source or the emergency diesel generators.

MFN 15-073 Page 4 of 7Enclosure 1

GEH Response

Sum m ar

As stated, GEH responded to RAI 08.02-1 and provided information regarding certaindesign features that address elements of NRC Bulletin 2012-01. Since the RAIresponse was submitted and since issuance of RAI 08.02-2, the NRC issued in final theStandard Review Plan Branch Technical Position (BTP) 8-9, "Open Phase Conditions inElectric Power System," Revision 0, July 2015. In this response, changes were made tothe DCD markups that were provided in the response to RAI 08.02-1. DCD Section8.3.1.1.6 changes from the RAI 08.02-1 response has been marked up as part of thisresponse.

Detailed GEH Responses to Each Question

a. Explain the design features that would be provided for the OPCs to beautomatically detected and alarmed in the main control room under all operatingelectrical system configurations and plant loading conditions.

As previously described, the ABWR electrical system is normally aligned with themajority of the plant electrical load carried by the Unit Auxiliary Transformers (UATs)and one safety buses normally aligned to the Reserve Auxiliary Transformer (RAT). Toensure that an open phase condition (OPC) is automatically detected and alarmed inthe main control room (MCR) under all operating electrical system configurations andplant loading conditions, the plant transformer protective relaying will be designed todetect loss of phasing (one or more OPC). This scheme will operate on both the highvoltage offsite power feeds to the transformers and the medium voltage secondary side.This monitoring is in addition to the traditional three phase absolute voltage monitoring,absolute current monitoring, and differential current monitoring.

Additionally, detection of an unbalanced phase condition on the UAT and RAT will bedetected on each of the safety related buses. The unbalanced phase condition will beautomatically detected and alarmed in the MCR under all operating electrical systemconfigurations and plant loading conditions.

This description of the protective relaying, which defines the performance criteria andfunctional design requirements of the system, will be added to the ABWR DesignControl Document (DCD), Tier 2, Sections 8.2.4.6 and 8.3.1 .1 .6 (previously revised inRAI 08.02-1 response).

MEN 15-073 Page 5 of 7Enclosure 1

b. Describe the' design features that would be provided in the event that offsitepower circuit(s) is (are) functionally degraded due to open-phase conditions, and safeshutdown capability is not assured, then the safety related busses should be designedto be transferred automatically to the alternate reliable offsite power source or onsitestandby power system within the time assumed in the accident analysis and withoutactuating any protective devices, given a concurrent design basis event.

Unit Auxiliary Transformers

In the normal lineup (all loads on the UATs except for one safety bus on the RAT), thefollowing would occur in the event of a fault (including loss of phase, which is easily andreliably detected on a loaded transformer) on any one of the UATs:

* The switchyard, main generator, and UAT medium voltage breakers opening.

* The safety bus originally on the UATs will fast transfer to the RAT and onepredetermined set of Power Generation/Plant Investment Protection (PG/PIP)buses will also fast transfer to the RAT.

* The plant will scram and the main turbine will trip.

These events and the safety bus fast transfer are alarmed, but otherwise no operatoraction is necessary to protect the safety-related electrical loads. Operator action will befocused on scram recovery and monitoring the correct sequencing of the safetysystems. The event will be mitigated by the safety bus and one set of PG/PIP buses. Ifthe fast transfer of the safety bus is not successful, the safety bus feeders will open, theEmergency Diesels Generators (EDG) will start automatically, and the loads will besequenced as described in DOD Tier 2, Chapter 8.

It should be noted that the safety bus feeders are independently monitored, whatever,the status of the UATs and RAT. Specifically, the safety buses are normally loaded (bythe Reactor Building Cooling Water System, Reactor Service Water System andchillers) such that a fault (including a phase loss) is easily and reliably detected. Theresult will be a fast transfer at the safety bus level. The same as above, if the fasttransfer is successful, the safety electrical loads will sequence to the RAT. If the fasttransfer is not successful, the EDGs will be started automatically and the safetyelectrical loads will be sequenced on to the safety buses as part of the EDG loadingsequence.

MEN 15-073 Page 6 of 7Enclosure 1

Reserve Auxiliary Transformer

The RAT is also monitored for faults and loss of phase, as described above and adetected fault/loss of phase will be appropriately alarmed in the MCR. The detectedfault/loss of phase will prohibit a fast transfer to the RAT. No operator action isnecessary since most loads are normally on the UATs and the connected safety busfeeder fault/loss of phase detection will fast transfer that bus to the UAT. No plant scramor turbine trip will result, and the operator actions that would be taken would be toinitiate repair of the RAT.

In the case where the OPC protection circuitry fails to isolate the offsite power sourcefrom the safety related buses, and the feeder breaker is allowed to close, theunbalanced phase condition detection circuitry located on the safety related busesprovides protection to the safety related buses. This protection scheme will cause theoffsite supply breaker to open, thereby provide for defense against a single failure of theoffsite power OPC.

An unsuccessful fast transfer of the UAT to RAT on a particular bus will result in theassociated diesel starting and sequencing the loads as a loss of power/no LOCA event.A fault/loss of phase on the RAT should be reliably detected and alarmed since thetransformer is normally loaded by the connected safety bus. Even if a fault is notdetected in normal operation, as soon as the fast transfer loads the RAT, the loss ofphase will be detected at both the transformer protective relaying and at the safety buslevel as described above.

In all these scenarios, the safety buses will not "see" a loss of phase nor require anyimmediate operator action. Finally the individual safety bus loads are protected againstOPC or faults such that their breakers will individually open to protect the motor, orpower center (as with any individual load fault). At the individual load level, singlephasing is reliably detected and the safety loads are therefore protected twice (at thebus level and at the individual load level), independent of the transformer protection.

MFN 15-073 Page 7 of 7Enclosure 1

c. Provide an ITAAC that demonstrates and verifies the following, includingsetpoints:

* Monitoring/detecting/Alarming in the control room in the event of the OPCs

* Automatically separate the Class 1E safety-related busses from the off-site power source and transfers safety-related loads to the unaffectedoffsite power source or the emergency diesel generators.

Rather than retain the COL Information Item in the FSAR, ITAAC items will be added toDCD, Tier 1, Section 2.12.1, to address the monitoring, detecting, alarming in thecontrol room, and the transferring of loads in the event of the OPC.

Impact on DCD:

The DOD changes in Tier 1 and Tier 2 are as shown on the attached markups. Thesemarkups change some of the markups provided in the response to RAI 08.02-1, asdiscussed above.

Enclosure 2

MFN 15-073

GEH Response to RAI 08.02-2

ABWR DCD DRAFT Revision 6 Markups(Note: Some changed pages are shown as Revision 5 to expedite NRC

review and will be revised to Revision 6 after approval of response.)

25A5675AC Revision 5

ABWR Design Control Document/Tier 2

Table 1.9-1 Summary of ABWR Standard PlantCOL License Information (Continued)

Item No. Subject Subsection

5.10

6.1

6.2

6.3

6.4

6.5

6. 5a

6.6

6.7

6.7a

6.8

6.9

6.9a

6.10

6.11

7.1

7.2

7.3

7.4

7.5

8.1

8.2

8.3

8.4

8.5

8.6

8.7

8.8

8.9

8.10

RIP Installation and Verification During MaintenanceProtection Coatings and Organic Materials

Alternate Hydrogen Control

Administrative Control Maintaining Containment Isolation

Suppression Pool Cleanliness

Wetwell-to-Drywell Vacuum Breaker Protection

Containment Penetration Leakage Test (Type B)

ECCS Performance Results

ECCS Testing Requirements

Limiting Break Results

Toxic Gases

SGTS Performance

SGTS Exceeding 90 Hours of Operation per Year

PSI and ISI Program Plans

Access Requirement

Cooling Temperature Profiles for Class 1 E Digital Equipment

APRM Oscillation Monitoring Logic

Effects of Station Blackout on HVAC

Electrostatic Discharge on Exposed Equipment Components

Localized High Heat Spots in Semiconductor Material forComputing Devices

Diesel Generator Reliability

Periodic Testing of Offs Mntrn ndPoeto_ , , _ Against Design Vulnerabilities

P'rocedures Whnen a/f=Out of Service /

Offsite Power SYi tems Design Bases

Offsite Power/ ystems Scope Split

Capacity of ,'uxiliary Transformers

-.Net_.,ld

Diesel Generator Design Details

Not Used

Protective Devices for Electrical Penetration Assemblies

5.4.15.4

6.1.3.1

6.2.7.1

6.27.2

6.27.3

6.2.7.4

62.7.5

63.6.1

6.3.6 2

6.3.6.3

6.4.7.1

6.5.5.1

6.55.2

6.69.1

6.6.9.2

7.3.3.1

7.6.3 1

7.8.1

7.8.2

7.8.3

8.1.4.18.2.4.1

8.2.4.2

8.24.3 18.2.4.6I

8.3.4 3

8 3 4.4

1,9-6 1.9-6COL License Information

25A5675AA Revision 5

AB WR Design Control Document/Tier 1

Class 1 E equipment is classified as Seismic Category I.

Class 1E equipment which is located in areas designated as harsh environment areas is qualifiedfor harsh environments.

IAdd insert here. >Interface RequirementsThe portions of the EPD System which are not part of the Certified Design shall meet thefollowing requirements:

The offsite system shall consist of a minimum of two independant offsite transmission circuitsfrom the TN.

Voltage variations of the offsite TN during steady state operation shall not cause voltagevariations at the loads of more than plus or minus 10% of the loads nominal ratings.

The normal steady state frequency of the offsite TN shall be within plus or minus 2 hertz of 60hertz during recoverable periods of system instability.

The offsite transmission circuits from the TN through and including the main step-up powertransformers and RAT(s) shall be sized to supply their load requirements, during all designoperating modes, of their respective Class 1 E divisions and non-Class I E load groups.

The impedances of the main step-up power transformers and RAT(s) shall be compatible withthe interrupting capability of the plant's circuit interrupting devices.

The independence of offsite transmission power, instrumentation, and control circuits shall becompatible with the portion of the offsite transmission power, instrumentation, and controlcircuits within GE's design scope.

Instrumentation and control system loads shall be compatible with the capacity and capabilitydesign requirements of DC systems within GE's design scope.

Inspections, Tests, Analyses and Acceptance Criteria

Table 2.12.1 provides a definition of the inspections, tests, and/or analyses, together withassociated acceptance criteria, which will be undertaken for the EPD System.

2.12.1-4 2.12.1-4Electrical Power Distribution System

In Section 2.12.1, before "Interface Requirements," add the following:

Monitoring of the normal and alternate power feeds on the high voltage side of the UATand RAT using the potential and current transformers of the protective relaying used for

transformer protection is provided to detect open phase conditions, whether one, two, or

three phases, with or without accompanying ground fault.

All three phases of all the UAT or RAT shall be monitored for undervoltage, open phase,

and ground faults by the specific transformer protective relay. When an undervoltage,

open phase or ground fault is detected in any combination of one, two or three phases

by the designated UAT or RAT protective relay, the protective relay shall send an alarm

via the alarm system to the Main Control Room.

The UAT and RAT protective system relay automatically separates the Class 1 E

safety-related buses from the off-site power source and transfers safety-related loads to

the unaffected offsite power source or the emergency diesel generators.

N Table 2.12.1 Electric Power Distribution System (Continued)Inspections, Tests, Analyses and Acceptance Criteria

Design Commitment Inspections, Tests, Analyses Acceptance Criteria

23. An electrical grounding system is provided 23. Inspections of the as-built EPD System plant 23. The as-built EDP System instrumentation,for (1) instrumentation, control, and Grounding and Lightning Protection Systems control, and computer grounding system,computer systems, (2) electrical equipment will be conducted. electrical equipment and mechanical(switchgear, distribution panels, equipment grounding system, and lightningtransformers, and motors) and (3) protection systems provided for buildingsmechanical equipment (fuel and chemical and for structures and transformers locatedtanks). Lightning protection systems are outside of the buildings are separatelyprovided for buildings and for structures and grounded to the plant grounding grid.transformers located outside of the buildings.Each grounding system and lightningprotection system is separately grounded tothe plant grounding grid.

24. MCR alarms, displays and controls provided 24. Inspections will be conducted on the MCR 24. Displays and controls exist or can befor the EPD System are as defined in Section alarms, displays and controls for the EPD retrieved in the MOR as defined in Section2.12.1. System. 2.12.1.

25. RSS displays and controls provided for the 25. Inspections will be conducted on the as-built 25. Displays and controls exist or can beEPD System are as defined in Section RSS displays and controls for the EPD retrieved on the RSS as defined in Section2.12.1. System. 2.12.1.

w

S0

U,

5.m

0

ci

0

(0

5.

Add ITAAC here.e

a00a0

0n

ea

Add the following ITAAC:

Table 2.12.1 Electric Power Distribution System

Design Commitment Inspections, Tests, Analyses Acceptance Criteria26. Monitoring of the high voltage side An analysis of the transformer protection An analysis demonstrates:

of the normal power feed (attached scheme will be performed to verify theto the UATs) and the alternate following: a. The correct location of the currentpower feed (attached to the RAT) and potential transformers for eachusing the potential and current a. Protective relay current and UAT and RAT transformertransformers of the protective potential transformers have been protection relay.relaying used for transformer correctly located. b. Protective relay set points ensureprotection is provided to detect b. Relay set points can provide that the monitoring systems canopen phase conditions, whether adequate detection. adequately detect open phaseone, two, or three phases, with or conditions in any combination ofwithout accompanying ground the three phases, with or withoutfault. accompanying ground faults, on

the high-voltage side of the UATand RAT transformers.

c. The trip setpont is sufficient toprovide detection of open phaseconditions while minimizingspurious indications underconditions which may be normallyexpected in the transmissionsystem.

27. All three phases of all the UATs or A test will be performed on the as-built Using simulated signals, at the designatedRAT shall be monitored for monitoring system, using simulated protective relay set points in anyundervoltage, open phase, and signals, to demonstrate that, at the combination of the three phases, the as-ground faults by the specific designated protective relay set points, built UAT and RAT monitoring systemstransformer protective relay. When each UAT and RAT monitoring system initiate an alarm in the Main Control Room.an undervoltage, open phase or alarms in the Main Control Room.ground fault is detected in any _____________________________________

Design Commitment Inspections, Tests, Analyses Acceptance Criteriacombination of one, two or threephases by the designated UATs orRAT protective relay, the protectiverelay shall send an alarm via thealarm system to the Main ControlRoom.

28. Each UAT and RAT protective A test will be performed on each as-built Using simulated signals, at the designatedsystem relay automatically UAT and RAT protective system relay, protective relay set points in anyseparates the Class 1E safety- using simulated signals, to demonstrate combination of the three phases, the as-related buses from the off-site that, at the designated protective relay set built UAT and RAT monitoring systemspower source and transfers safety- points, each UAT and RAT monitoring initiate a transfer of loads.related loads to the unaffected system transfers loads.offsite power source or theemergency diesel generators.

29. Each safety bus shall be monitored A test will be performed on the as-built Using simulated signals, at the designatedfor an unbalanced phase condition, monitoring system, using simulated protective relay set pointsthe source of which is provided by signals, to demonstrate that, at theoffsite power source. When an designated protective relay set points, a. Each UPO is detected andunbalanced phase condition (UPC) each UPC is detected and opens the UAT b. UAT and RAT feeder breakers tois detected a protective relay shall and RAT feeder breakers to the safety the safety bus open.send an alarm via the alarm bus.system to the Main Control Room,and send a trip signal to the offsitepower feeder breaker

30. Protective relaying used for An analysis of the safety related bus An analysis demonstrates:protection of the 6.9 kV safety protection scheme will be performed torelated buses is provided to detect verify the following: a. The correct location of the currentopen phase conditions, whether and potential transformers for eachone, two, or three phases, with or a. Protective relay current and of the safety related buses.without accompanying ground potential transformers have been b. Protective relay set points ensurefault. correctly located, adequate detection and protection

_______________________ b. Relay set points can provide of safety related loads in the event

Design Commitment ] Inspections, Tests, Analyses Acceptance Criteriaadequate detection and protectionof safety related loads. of an open phase conditions in anycombination of the three phases,

with or without accompanyingground faults, on the high-voltageside of the UAT and RATtransformers.

25A5675AK Revision 6

AB WR Design Control Document/Tier 2

(4) Capacity of switchgear, power centers with their respective transformers, motor

control centers, and distribution panels is equal to or greater than the maximum

available fault current to which it is exposed under all design modes of operation until

the fault is cleared.

Interrupting capability of the Class I E switchgear and MCC breakers is selected to

interrupt the available short-circuit current at the circuit breaker load terminals. Short

circuit analysis will be performed in accordance with IEEE 141 and/or other

acceptable industry standards or practices to determine fault currents. See Subsection

8.2.3(16) for interface requirement.

Power center transformers are sized and impedances chosen to facilitate the selection of low-

voltage switchgear, MCCs and distribution panels, which are optimized within the

manufacturer's recommended ratings for interrupting capacity and coordination of over-current

devices. Impedance of connecting upstream cable is factored in for a specific physical layout.

8.3.1.1.6 Circuit Protection

8.3.1.1.6.1 Philosophy of Protection

Simplicity of load grouping facilitates the use of conventional, protective relaying practices for

isolation of faults. Emphasis has been placed on preserving function and limiting loss of Class

lIE equipment function in situations of power loss or equipment failure.

Breaker coordination analysis will be performed in accordance with IEEE 141, 242 and/or other

acceptable industry standards or practices.

Circuit protection of the Class 1E buses is interfaced with the design of the overall protection

system.

8.3.1.1.6.2 Grounding Methods

Station grounding and surge protection is discussed in Section 8A. 1. The medium voltage (6.9

kV) system is low resistance grounded except that each diesel generator is high resistance

grounded to maximize availability.

See Subsection 8.3 .4.14 for COL license information pertaining to administrative control for

bus grounding circuit breakers.

8.3.1.1.6.3 Bus Protection/--unbalanced phase condition /and unbalanced phase

Bus protection is as foll°ows'f-1

(1) 6.9 kV bus in ?ming circuits have inverse time over-current ground fault, bus

differential, d under-voltage protection. The undervoltag •onitoring is responsive

to all three phases. The monitoring is effective for both load shedding~ and emergency

8.3-14 8.3-14Onsite Power Systems

25A5675AK Revision 6

AB WR Design Control Document/Tier 2

diesel start and protection of the safety-related bus loads for grounds and loss of one

or more phases.

(2) 6.9 kV feeders for power centers have instantaneous, inverse time over-current and

ground fault protection.

(3) 6.9 kV feeders for heat exchanger building substations have inverse time over-current and ground fault protection.

(4) 6.9 kV feeders used for motor starters have instantaneous, inverse time over-current,

ground fault and motor protection.

(5) 480V bus incoming line and feeder circuits have inverse time over-current and

ground fault protection.

(6) Nonsafety-related buses A4. B4. C4. and the new H bus are monitored by their ownprotective relays and will trip power to the safety-related buses on detection of

abnormal voltages and frequency. including loss of one or more phases and ground

conditions.

8.3.1.1.6.4 Protection Requirements for Diesel Generators

Protective devices of the diesel generators meet all requirements of IEEE-603. When the diesel

generators are called upon to operate during LOCA conditions, the only protective deviceswhich shut down the diesel are the generator differential relays, and the engine over-speed trip.

These protection devices are retained under accident conditions to protect against possible,

significant damage. Other protective relays, such as loss of excitation, anti-motoring (reverse

power), over-current voltage restraint, low jacket water pressure, high jacket water temperature,

and low-lube oil pressure, are used to protect the machine when operating in parallel with the

offsite power system, during periodic tests. The relays are automatically isolated from the

tripping circuits during LOCA conditions when there is a concurrent LOPP signal. However,

all of these bypassed parameters are annunciated in the main control room (Subsection

8.3.1.1.8.5). The bypasses and protective relays are testable and meet all IEEE-603

requirements, and are manually reset as required by Position 1.8 of Regulatory Guide 1.9. No

trips are bypassed during LOPP or testing. See Subsection 8.3 .4.22 for COL license

information.

Synchronizing interlocks are provided to prevent incorrect synchronization whenever the dieselgenerator is required to operate in parallel with the preferred power supply (see Section 5.1.4.2of IEEE-741 ). Such interlocks are capable of being tested, and shall be periodically tested per

Section 8.3 .4.23).

Onsite Power Systems 8318.3-15