ML19341D001

Adequacy of Station Electrical Distribution Sys Voltages, Indian Point Nuclear Station,Unit 2, Technical Evaluation Rept

ML19341D001
Person / Time
Site:	Indian Point
Issue date:	01/31/1981
From:	Weber D EG&G, INC.
To:	Shemanski P Office of Nuclear Reactor Regulation
References
CON-FIN-A-6429 EGG-EA-5307, NUDOCS 8103040682
Download: ML19341D001 (13)

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1 January 1981 n.. u,vg o l,i , TEC11NICAL EVALUATION REPORT, ADEQUACY OF STATION ELECTRICAL DISTRIBUTION SYSTEM VOLTAGES, INDIAN POINT NUCLEAR STATION, UNIT NO. 2, DOCKET No. 50-247 f-7

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NON-lE -- 6.9KV ~3 - bNO '3 b NO O > NO NO O NO P U NO I #3 #4 #5 #6 BUS #1 F2 - 1 LJ (3 [] ;_ SST w 'A> 6.9KV w w SST SST u v 6.9KV w w SST 2 mm 480V mm3 5-, n 480V rv m 6 lE 480V #2A L #3A C #5A U #6A U BUS . . NOC N0LJ N0LJ N0 c: NO NOL; N0' .: hDGi IEDG\ lEDG Q2 k21j \23 FIGURE 1. INDIAN POINT UNIT 2 ONE-LINE

TABLE 1 CLASS 1E EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE TERMINAL VOLTAGES (% of nominal voltage) . b Maximum" Minimum Analyzed Equipment Condition Rated Analyzed Rated Steady State Transient 440V Motors Start -- -- 80 80.45 d -- Operate 110 112e 90 92.7 -- 460V Motors Start -- -- 80 87.3d __ Operate 110 107 90 94.1 -- 480V Starters Pickup -- -- 80 -- -- Dropout -- -- 70 -- -- Operate 110 103 90 90.2 -- Other Equipment f

a. 138kV source: maximum analy.:ed = 105.6%.

b. 13.8kV source: minimum analyzed = 99.27%.

c. Licensee did not provide transient values but stated that they analyzed the start of the 900 hp Circulating Water Pumps and indicated that "the voltages at all equipment would remain above the minimum required volt-age" for the duration of the start.4

d. These values are for individual 440V and 460V motors with the lowest starting voltage under conditions of minimum grid and bus voltage.3

e. As load is applied, the voltage will decay to acceptable levels.

f. Analyzed voltages are within the operating range of the 480V battery '

chargers. Instrument buses are supplied by inverters from 125V batteries and are unaffected by any offsite occurrences.4 , I 4 l

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2. The minimum voltage occurs when the of f site 13.8kV system is at its minimum expected value of 13.7kV; the l' 13.8/6.9kV transformer is supplying 6.9kV buses 2, 3, 5, and 6, and 480V buses 2A, 3A, 5A, and 6A; and all IE loads are in operation.

3. The worst case transient voltages occur when starting o the 900 hp Circulating Water Pump and the 13.8kV system is at its minimum value and supplying maximum loads.

l 4.3 Analysis Result. Table I shows the projected worst case class lE 4 equipment terminal voltages based on the-modification in Section 4.1. 4.4 Analysis Verification. Con Ed has indicated that test equipment will be installed on all class IE 480V load center buses and MCC 26A and B during the 1980-1981 refueling outage to measure current and voltage when the plant is in operation. The values obtained will be used to calculate i voltages by the saue technique as used in the analysis and the results would be compared with the actual voltages. Review of the test results, when submitted, will determine the validity of the analysis.4 1 5.0 EVALUATION l Six revicw positions have been established from the NRC analysis guide-i' linesl and the documents listed in Section 2.0 of this report. Each 4 review position is stated below followed by an evaluation of the licensee

  .                    s ubmi t tals . The evaluations are based on completion of changes described              -

in Section 4.1. Position 1--With the minimum expected offsite grid voltage and maximum load condition, each offsite source and distribution system connection combination must be capable of starting and of continuously operating all class lE equipment within the equipment voltage ratings. 2 Con Ed has shown, by analysis, that the 138kV and 13.8kV systems have i sufficient capability and capacity for starting and continuously operating the class IE loads within the equipment voltage ratings (Table 1). However, con Ed has not provided analysis showing the capability and j

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capacity of the 13.8kV system to supply all Unit 2 and Unit 3 loads through a Unit 2/ Unit 3 tie breaker. There are no interlocks or limiting conditions of operation included in the plant Technical Specifications that prevent the use of the tie during operation of either plant. o

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Additionally, the Technical Specifications contain no limiting condi-t tions to prevent the use of one or more gas turbine generators (GTs) from supplying all required IE 480V loads via the 13.8/6.9kV transformer. Con Ed has not provided an analysis to demonstrate that the GTs are capable of starting and of continuously operating all required IE equipment within the equipment voltage rating to either Unit 2 or both units via the Unit 2/ i Unit 3 tie breaker. 4

5 i

Position 2--With the maximum expected of fsite grid voltage and minimum load condition, each offsite source and distribution system connection combination must be capable of continuously operating the required class 1E equipment without exceeding the equipment voltage ratings. Con Ed has shown, by analysis, that the voltage ratings of the IE ~ equipment will not be exceeded. Position 3--Loss of offsite power to either of the redundant class 1E distribution systems due to operation of voltage protection relays, must not occur when the offsite power source is within expected voltage limits. EG6G Idaho, Inc., will verify, in a separate report, that the require-ments of this position are satisfied (TAC No. 10028). Position 4--The NRC letterl requires that test results verify the accuracy of the voltage analyses supplied. Con Ed indicates that test results will be available in August 1981. The proposed test is acceptable if the test values used are obtained when the 1E buses are loaded to at least 30%. Position 5--No event or condition should result in the simultaneous or consequential loss of both required circuits from the offsite power network to the onsite distribution system (GDC 17). Con Ed has analyzed the 138kV and 13.8kV connections to the offsite . power grid, and determined that no potential exists for simultaneous or consequential loss of both circuits frcm the offsite grid. Position 6--As required by GDC 5, each offsite source shared between units in a multi-unit station must be capable of supplying adequate starting and operating voltage for all required class 1E loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units. Indian Point is the site of two operating nuclear units. The prefer-red (138kV) and alternate (13.8kV) offsite sources are independently connec-ted to the onsite distribution system of each unit. However, the alternate offsite source of each unit can simultaneously supply IE loads of the other unit through a tie breaker. Con Ed has not provided an analysis for the connection. Additionally, the Indian Point Station has three gas turbine generators that could supply power to class IE loads individually or in combination to one unit or both units through the tie breaker. No voltage analysis for this supply has been provided to the NRC. ,

6.0 CONCLUSION

S The voltage analyses submitted by Con Ed for the Indian Point Nuclear Station Unit 2 were evaluated in Section 5.0 of this report. Upon the completion of changes described in Section 4.1, it was found that: 6

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1. Voltages within the operating limits of the class 1E i equipment.have not been supplied for all projected

,                                   combinations of plant load and normal offsite power grid conditions; considering an accident in one unit and the safe shutdown of the other unit.

Reconnendations:

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a. Con Ed should either provide an analysis to show

, that.one 13.8kV gas turbine generator can supply satisfactory voltage to all possible connected IE loads (on both Units 2 and 3) or have LOCA requirements in the Technical Specifications preventing their use.

b. Con Ed should either provide an analysis to show that the Buchanan 138/13.8kV tie, through the 13.8/6.9kV transformer can supply all class IE  ;

equipment to both units through the Unit 2/ Unit 3 l tie breaker considering the Buchanan grid at its I minimum expected voltage or provide LCO require-ments in the technical specifications preventing the use of this tie breaker to IE loads during ,' . operation of both Unit 2 and Unit 3.

2. Con Ed should provide LCOs in their Technical Specifi-cations which would require that the circuit breaker

control suitches located in the control room, which control the automatic transfer of the 6.9kV buses 1, 2, 3, and 4 to buses 5 and 6, be " locked out" and tagged

{' anytime the 13.8 kV source is connected to buses 5 and 6.

,                           3.      The proposed test to verify the accuracy of the analysis

} is satisfactory if the test measurements are made with ! the IE buses and MCCs loaded to at least 30% of their full load rating. If this is not possible, con Ed should demonstrate that each bus or MCC is loaded sufficiently and tne instrumentation is accurate enough

to ensure the correct readings.

4. Con Ed has determined that no potential for either a simultaneous or consequential loss of both offsite

l. power sources exists.

l, EG6G Idaho, Inc., is performing a separate review of the undervoltage i relay protection at the Indian Point Nuclear Station. This will evaluate i the relay setpoints and time delays to determine that spurious tripping of the class 1E buses will not occur with normal offsite source voltages. 7 l l

l l l l 7.0 RE FERENCES

1. NRC letter, William Gammill, to All Power Reactor Licensees (Except Humboldt Bay), " Adequacy of Station Electric Distribution Svstems Voltage," August 8, 1979. .

2. Con Ed letter, W. J. Cahill, Jr., to Director of Nuclear Regulation, October 16, 1979. .

3. Con Ed letter, W. J. Cahill, Jr., to Director of Nuclear Regulation, April 28, 1980.

4. Con Ed letter, P. Zarakas, to Director of Nuclear Regulation, August 1, 1980.

5. Telecon, L. Olsian, NRC, D. Weber, EG6G Idaho, Inc., M. Scott and t

P. Szabados, Con Ed, January 16, 1981. e 6 8}}