9.0 Electrical Systems

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Objectives1. State the purposes of the following:

a. Emergency Power Supply System (EPSS)b. Normal Power Supply System System (NPSS)c. Class 1E Uninterruptible Power Supply System (EUPS)d 12 Hour Uninterruptible Power Supply System (12UPS)

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d. 12-Hour Uninterruptible Power Supply System (12UPS)e. Non-Class 1E Uninterruptible Power Supply System

(NUPS)f. Station blackout diesel generators (SBODGs)

2. Describe the major differences between the electrical system design of the US-EPR and those of currently operating PWRs.

EPSS• 6.9-kV buses always supplied from

switchyard via EATs (no fast transfer necessary)

• 4 divisions• Each EAT feeds 2 divisions• Each EAT is alternate to the other

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Each EAT is alternate to the other• Alternate feed capability between divs. 1 &

2, 3 & 4• Each division has standby EDG• 2 diesels per EPGB• Each division can be supplied by an

SBODG via manual lineup

Emergency Power (EPSS)

4Figure 9-1 (Sheet 1)

• EAT• Standby EDGs• Connections to

SBODG

Figure 9-1 (Sht 1),Divisions 1 & 2

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• Alternate feed (example)

NPSS• Main generator supplies switchyard, but

not onsite distribution• 13.8-kV buses always supplied from

switchyard via NATs (no fast transfer necessary)

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• 4 trains• Each NAT feeds 2 trains• Each NAT is also an alternate supply• 2 trains have SBODGs• Each SBODG-backed bus can supply either

of 2 EPSS divisions via manual lineup

Normal Power (NPSS)

7Figure 9-3 (Sheet 1)

• Main Generator

• NATs• SBODGs• Connections

to EPSS

EUPS

• Supplies safety-related loads

• 4 divisions supplied from EPSS

• Each division:– 2 100%-capacity 480-Vac/250-Vdc battery

h

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chargers

– 250-Vdc 2-hr battery

– 250-Vdc/480-Vac inverter

– Several ac/dc & dc/dc converters

Class 1E Uninterruptible Power Supply (EUPS)

9Fig. 9-2 (typical of all divisions)

12UPS

• Supplies nonsafety-related loads– SBODG auxiliary loads & control power for

aligning SBODGs to NPSS & EPSS

– I&C support of severe accident mitigation

• 2 trains supplied from NPSS

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• 2 trains supplied from NPSS

• Each train:– 480-Vac/250-Vdc battery charger (1 spare)

– 250-Vdc 12-hr battery

– 250-Vdc/480-Vac inverter

– Several ac/dc & dc/dc converters

12-Hr Uninterruptible Power Supply (12UPS)

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Fig. 9-4

NUPS• Supplies nonsafety-related loads needed to

remain operational for investment protection

• 2 trains supplied from NPSS

• Each train:

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Each train:– 480-Vac/250-Vdc battery charger (1 spare)

– 250-Vdc battery

– 250-Vdc/480-Vac inverter

– Several ac/dc & dc/dc converters

– Supplies CRDMs via 2 sets of in-series reactor trip breakers

Non-Class 1E Uninterruptible Power Supply (NUPS)

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Figure 9-5

SBO Considerations

• Worst-case coping duration per RG 1.155: 8 hrs

• No coping analysis necessary; SBODGs meet 10CFR50.63 & RG 1.155 req’ts for lt t AC

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alternate AC sources:

– Not normally connected

– Low potential for CCF with EDGs

– Can be connected to EPSS buses w/in 10 min

– Sufficient capacity for SBO coping

SBODGs• Located in separate areas of the switchgear

building

• Separate support subsystems

• Start on undervoltage on associated NPSS buses

Manually loaded

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• Manually loaded

• Major SBO loads:– Division 1 & 4 EFW pumps

– HVAC for MCR, SBO equipment

– Selected I&C

– MCR lighting

– MSRTs