ML20052D849
| ML20052D849 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 04/30/1982 |
| From: | Withers B PORTLAND GENERAL ELECTRIC CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8205070260 | |
| Download: ML20052D849 (5) | |
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Portland General ElechicCompany s' e Fe vn de D s
..n April 30, 1982 Trojan Nuclear Plant Docket 50-344 License NPF-1 d i 02 W):
Director of Nuclear Reactor Regulation ATTN:
Mr. Robert A. Clark, Chief Operating Reactors Branch No. 3 Sg Division of Licensing
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U. S. Nuclear Regulatory Commission 2
IS Washington, DC 20555 g
Dear Sir:
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Test Start of the Motor-Driven Auxiliary g
19 Feedwater Pump on an Emergency Diesel Generator In response to requests for additional information verbally received from members of your staff, the attachment is provided.
Included in this attachment is a discussion of the emergency diesel generator trips and how the start of the motor-driven AFW pump will affect these trips and a description of how both emergency diesel generators are, by design, inhibited from operating while connected in parallel.
This information supports that provided in the PGE letters dated January 15, 1982 and November 12, 1981.
Sincerely, Bart D. Withers Vice President Nuclear Attachment c:
Mr. Lynn Frank, Director State of Oregon Department of Energy Od D
00 4
PDR P
121 S W Sa'rnon Street. Pomand. Oegm 97204 1
Trojan Nuclear Plant Robert A. Clark
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1Dockat 50-344'
-April 30, 1982 License NPF-1 l
Page 1 of 2 Parallel Operation of the Emergency Diesel Generators i
Operation of the Trojan Nuclear Plant emergency diesel generators (EDGs) in parallel is possible as described on Page 8.3-20 of the Final Safety Analysis Report (FSAR). As discussed in this section of the FSAR, the EDGs cannot be paralleled automatically and, as will be clarified further, they can be manually paralleled only through the operation of several l
breakers.
l In the postulated case in which the motor-driven AFW pump would be
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considered necessary for Plant protection, the EDGs are expected to be l
i the sole available sources of electrical power. As shown on FSAR Figure 8.3-1 (attached), Plant Single Line Diagram, power is normally supplied to the 4.16-kV buses Al, A5, A2 and A6 through the unit substation trans-I I
formers No. I and 2 from the 12.47-kV buses H1 and H2.
During normal i
operation,' breakers 152-101, 152-501, 152-201 and 152-601 will be shut, with breakers 152-108, 152-208 and 152-506 open.
If power should be lost during this normal operating situation and an undervoltage condition occurs on bus Al (buses A2 and A6 can be con-sidered symmetric to Al and A5 for this evaluation), then EDG No. I will j
start and attain rated speed and voltage within 10 seconds. With the l
I undervoltage condition existing on Al and with the EDGs at rated speed and voltage, breaker 152-101 will automatically open and breaker 152-108 will then automatically shut such that EDG No. 1 is supplying only the a
Al bus. At this point, breaker 252-103 will be open due to H1 under-l voltage relay trip logic.
4 In order to energize the A5 bus, the following actions must then occur.
First, breaker 152-101 must be.. hut; this is allowed once breaker 152-108
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is shut and breaker 152-501 is already shut. These breaker operations are conducted at the control board in the control room. At this time,
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the motor-driven AFW pump could be started.
i The EDGs could be paralleled if breakers 152-201, 152-601 and 152-506 were also closed. Breakers 152-201_and 152-601 would be operated in 4
the same manner as breakers 152-101 and 152-501, respectively. In this
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reference lineup, EDG No. 1 is supplying Al and A5, and EDG No. 2 is supplying A2 and A6.
The EDGs would then be paralleled if breaker' t
152-506 is manually shut; however, due to undervoltage trip logic for breaker 152-506, this breaker cannot be shut while an undervoltage condition exists on both 12.47-kV buses H1 and H2.
In order to shut breaker 152-506 and parallel the EDG in this case, either bus H1 or H2
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would also have to be energized in order to clear the undervoltage trip on breaker 152-506.
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r Paralleling the EDG requires the manual operation of several breakers.
I Even in the case where an undervoltge condition does not exist on buses H1 and H2 such that breaker 152-506 can be shut, paralleling the l
EDGs requires the manual operation of three separate breakers. Each i
breaker operation also requires two separate actions, selecting the close position on the control switch and turning the synchronizing switch to
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Troj:n Nuclcsr Plant Rsbart A. Clark Dockst 50-344~
April 30, 1982 License NPF-1 Page 2 of 2 the on position. These breaker operations would be conducted at the control board in the control room where a mimic bus would show if these two power sources were paralleled.
An evaluation has also been performed to determine how of ten buses A5 and A6 are powered from the EDG. A5 and A6 are powered from the EDG during the Periodic Operating Test (POT) for Pressurizer / Pressurizer Heater Functional Testing, and the test interval for this POT is once every 18 months. Besides this, buses A5 and A6 could potentially be powered from the EDG in the event of the loss of offsite power or a 12.47-kV or 4.16-kV system fault. These events have not occurred to date and are expected to occur only infrequently, if at all. In order to further assure that an inadvertent paralleling of the EDG due to operator error cannot occur in these cases, the Plant Operating Manual Off-Normal Instructions for 12.47-kV and 4.16-kV system faults and temporary loss of onsite power and the Emergency Instruction for plant operation af ter loss of normal and preferred power will include precautions for reenergizing buses A5 and A6.
Page 8.3-20 of the FSAR states that this system is designed to meet the requirements of Safety Guide 6.
Section D.4.d of Safety Guide 6 states the following:
"If means exist for manually connecting redundant load groups together, at least one interlock should be provided to prevent an operator error that would parallel their standby power sources."
An interlock is not installed'on breaker 152-506 to prevent such a paralleling operation, but it is not considered necessary to have an interlock since paralleling requires the manual operation of several breakers as discussed above. This is not a case in which the system is in noncompliance with the FSAR and its commitment to Safety Guide 6, nor is this an unreviewed safety question since Page 8.3-20 of the FSAR also describes the method by which the diesel generators can be manually connected in parallel. In addition, this system design was previously accepted in the Safety Evaluation Report for the Trojan Nuclear Plant dated October 7, 1974.
In order to clarify the FSAR in this regard, Chapter 8 will be revised in the Updated FSAR to reflect the extent to which breaker 152-506 meets Safety Guide 6.
ELD /4sh6A27
Trojsn Nucitar Plant Robart A. Clark Dockst 50-344 April 30, 1982 License NPP-1 Page 1 of 2 Emergency Diesel Generator Trips The following table lists the emergency diesel generator trips:
Relay Type Setpoints Differential relays Minimum pickup at 0.2 A at 10% slope Overcurrent relays Variable with voltage - 2560 A at 100% volt-age to 640 A at 0% voltage Ground time overcurrent Transformer set at a 10-to-1 ratio with 1.5 A setpoint on secondary corresponding to 15 on primary Field overcurrent/ loss Setpoint high (overcurrent) - 100 mV; set-of field device point low (loss of field) - 10 mV Voltage balance relay Supervi
.s the above overcurrent relays to prevent spurious overcurrent trips due to blown fuses on the secondary of the poten-tial transformers Lockout relays None: units tripped by associated relays as described in Attachment 2, Page 2 Engine overspeed 1050-1060 rpm Engine underspeed None (no relay is installed)
Underfrequency None (no relay is installed)
Low lube oil pressure 20 psi High crankcase pressure 1-in. water As discussed on Page 8.3-42 of the FSAR, two lockout relays, diesel generator lockout and diesel engine lockout, are provideo for each unit.
Any of the following abnormal conditions will operate these elays, which will initiate a trip of the appropriate diesel generator output breaker 152-108/208:
1.
Diesel Generator Lockout Relays, 186-lD1 and 186-2D1 Diesel generator phase overcurrent with voltage restraint supervised by voltage balance relays.
Diesel generator neutral overcurrent relays.
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Diesel generator loss-of-excitation relay.
Troj:n Nucissr Plant Robert A. Clark Dockst 50-344 April 30, 1982 License NPF-1 Page 2 of 2 2.
Diesel Engine Lockout Relays,186-lD2 and 186-2D2 Diesel generator differential relay operation (deacti-vated in auto start mode).
Engine overspeed relays.
Engine fail-to-start relays.
High crankcase pressure / low lube oil pressure (deacti-vated by safety injection signals).
Many alarms are available to the operator to indicate potential problems with the emergency diesel generators. These alarms are listed on Pages 8.3-46 through 8.3-49 of the FSAR.
The only emergency diesel generator trip that could be affected by the start of the AFW pump is the overcurrent trip should voltage be unexpec-tedly low.
Since locked-rotor amps for the AFW pump motor is 862 amps, it would not affect this overcurrent protection. Note that in the case of the AFW pump start, no trips would be deactivated, nor setpoints adjusted.
Overcurrent protection should also be considered for the AFW pump motor breaker 152-510. The instantaneous overcurrent trip of 2000 amps would not be affected since the motor would only have a maximum of 862 locked-rotor amps. Based on the characteristic time curves for this breaker and the locked-rotor amps of 862 amps, a long-time overcurrent trip would occur in 5.4 seconds at 100% voltage and in 7 seconds at 75 percent I
voltage (lowest expected); however, the overcurrent condition due to starting the AFW pump is expected to recover in less than 2 seconds and so will not affect these overcurrent trips.
i ELD /4sh6A29