ML19350E628

Responds to NRC 810212 Questions Re Station Electric Distribution Voltages

ML19350E628
Person / Time
Site:	Pilgrim
Issue date:	06/16/1981
From:	Morisi A BOSTON EDISON CO.
To:	Ippolito T Office of Nuclear Reactor Regulation
References
81-129, NUDOCS 8106230370
Download: ML19350E628 (9)

Text

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s BOSTON F.DISO N COMPANY asusnAs. arrir as son ocvi.sv0= svasst 90erON, 'dAESACHUSETv3 Q219 9 A. V. MO Riel NUCLEAR OPERATIONS SUPPORT DEPARTMENT June 16,1981 BECo. Ltr. #81- 129 Mr. Thomas A. Ippolito, Chief Operating Reactors Branch #3 Division of Operating Reactors .

Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Compission Washington, D. C. 20555 License No. OPR-35 Docket No. 50-293 Further In' formation on Station Electric Distribution System Voltages

References:

1. ~ Boston Edison Letter (G. C. Andognini) gg ' A ..

to NRC (D. L. Ziemann) dated November 15, 1975.

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2. Boston Edison Letter (G. C. Andognini)

~ to NRC (T. A. Ippoli to) dated March 28, ,-f f[ 'h 1980. 9 jg"n"-,9 I98I * ~ .

3. Telecon with BECo & NRC Personnel on

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PNPS Electric Distribution, dated 'O

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February 10, 1981. gg

Dear Sir:

In a telecon discussion on February 10,1981, (Ref. 3), clarification was provided as to specific and/or alternative infomation which would be acceptable in order for your staff to complete its review of the Electric Distribution System Voltages at Pilgrim Station. As a result of this discussion, questions were fomalized and transmitted by your letter dated February 12, 1981. Our response to those questions is presented as follows:

1 Question #1:

Per Guideline 1, Reference 4, submit an analysis for the 23kV connection (second offsite source) through the shutdown transfomer to the Class IE buses .

Response

0/3 The normal operating range of Pilgrim Station's 23kV zystem voltage is beween 23.4kV and 22.23kV (23.4kV + 0% - 5",) . We have calculated and 8/  !

prouted in Table 1, voltage profiles at the safety related buses for 8106 230fh

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..  : so:JON EDISON COMPANY Mr. - Thomas A. Ippolito, Chief ~

June 16,1981

.Page 2 full load and no' load conditions on the above 23kV system range. These

- calculations 'are extremely conservative in that (i) there is no credit taken for the capacitor bank on the primary side of the shutdown-transformer (capacitor bank is installed to improve 23kV system voltage and minimize the effects of motor starting) (ii) we are assuming the shutdown transformer is supplying both the emergency buses (A5 & A6) simultaneously at full load.

This failurewould of twoonly(occur with LOCA to

2) diesel generators coincident start and with the lossbreaker the vacuum of 345kV-system, closed the by-passing the subject capacitor bank. Although these conditions occuring simultaneously is extremely improbable, we feel the resulting analysis supports our contention that the 23kV system provides adequate power at acceptable voltages to the subject safety related equipment.

Question #2:

Provide the manufacturer's recommended minimum starting voltage for all Class IE loads.

Response

Safety-related motor specifications for Pilgrim #1 require that all Class IE motors shall be capable of starting and accelerating the required loads with 80% rated nameplate voltage at the motor terminals.

This results in the following voltage at the motor terminals:

a. 4000V motors connected to the 4160V safety-related buses require 3200V at the motor terminals for starting and accelerating.

b. 460V motors connected to the 480V safety-related buses require 368V at the motor terminals for starting and accelerating.

Our review of the manufacturer's recommended minimum starting voltage for Class IE load verified the above specification requirements.

Question #3:

Provide the voltage drops from the Class IE buses to the terminals of all Class IE loads for all cases analyzed.

(Telecon Clarification)

Envelope the "all Class IE loads for all cases analyzed" into worst case.

Response

In Reference (1), Table 1 and Table 2 provide voltage profiles at the l safety-related buses for the following cases: -

a. When the station auxiliaries are supplied through the unit auxiliary trans former.

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b. When the-station auxiliaries are supplied through the startup trans-fomer.

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. sonvow EossON COMPANY

-Mr. Thomas A. Ippolito, Chief June 16,1981

- Page 3 These voltages 'are calculated for nonnal operating ranges of 345kV grid system voltage with no load and. full load conditions.

We have calculated the voltage drops from the Class IE buses to the ter-minals of Class IE loads. Voltage drops are given-in the attached Table 2.

Based on these voltage drops and voltage profiles given in Table 1 and Table 2 of Reference (1), we have calculated the voltages at the terminals of the safety-related loads for the worst case condition. Calculations verify that the voltages at the terminals of safety-related loads are within the operating ranges of the equipment.

Question #4:

Define the plant operating mode and the loading of the Class IE buses for the conditions identified as " Full Load" and "No Load"in Reference 2, Table 2.

(Telecon C1arification)

BECo can provide its own definitions for " full load" and "no load".

Response

Full-Load LOCA condition with preferred offsite power (345kV) available.

This means all RHR and Core Spray pumps are running and most of the station auxiliaries are connected.

No-Load flinimum loads required during refueling outage ;eriod when the station auxiliaries are supplied through the 345kV offsite power system.

Question #5:

Per Guideline 3, Reference 4, provide an analysis of the effect on all Class IE equipment when starting and running the largest non-Class IE load when the Class IE buses are heavily loaded during a LOCA. Also submit a transient analysis for bulk Class IE load starting (no sequential loading) during a LOCA. The analyses should confirm that the second-level of undervoltage protection relays do not drop out during these load starting conditions.

The starting of the largest non-Class IE load will have an effect on the Class IE bus voltage regardless of the load location.

Response

Case 1: Effect on all Class IE equipment when starting and_ running the largest non-Class IE load when the Class IE buse, are heavily loaded during LOCA.

At Pilgrim Station Unit #1, the Class IE loads are connected to the "X" winding of the startup and unit auxiliary transformers.

The largest non-IE load (Reactor Feedwater Pumo, 5000 HP) is

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i soeroN EoisoN COMPANY Mr. Thomas A. Ippolito, Chief

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June 16, -1981 Page 4 connected to the "Y" winding of the startup and unit auxiliary transformers.

Startup and unit auxiliary transformers are three winding transfomers.

with one primary and two secondary windings (X and Y).

During the LOCA condition with 345 kV system available, the auxiliary loads are supplied through the startup transformer. In order to determine the effect of starting the largest non-IE load on Class IE buses, the equivalent circuit of the three windino startup transformer has been developed. (Please refer to: " Elements of Power Systems Analysis" by William D. Steventon; Second Edition; Page 169.)

In Pilgrim Station #1, the largest non-IE load is the Reactor Feedwater Pump which has the following rating:

Rated HP - 5000 @ 4000V Full Load Amp - 578 amps Starting Current - 37555 amps Starting KVA - 27.0 MVA With the minimum voltage at the 4160V bus during LOCA condition, ,the-voltage drop at the Class IE buses for starting the argest non-IE load on the Y winding of startup transformer is about 55V for less than 9 seconds. This voltage drop will not effect the Class IE systems and The second-level of undervoltage relays will not drop out.

Case 2: Transient analysis of bulk Class IE load starting during LOCA.

To analyze this condition, we have considered the simultaneous starting of all Class IE loads (RHR and Core Spray pumps) with Class IE buses fully loaded with' a minimum voltage at the 345kV grid.

Due to starting of bulk Class IE loads during LOCA condition, the voltage drop at the 4160V safety-related buses will be about 300 volts for less than 6 seconds.

Due to the duration of this voltage drop, the second-level of undervoltage relays will not drop out during the starting of these loads.

This study verifies that the onsite datribution system in conjunction with offsite power sources has sufficient caoacity and capability to automatically start, as well as operate, all requireo Class IE loads within their required voltage ratincs. There will be no spurious tripping from the offsite sources due to:

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(i) short-term voltage degradation of she offsite power source; (ii) starting and running the largest non-class IE load when the Class IE buses are heavily loaded during LOCA; (iii) starting of bulk Class IE loads during LOCA.

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. 2 eastoN rossoN CIMPANY.

Mr. Thomas A. .Ippolito, Chief June :16,-.1981

'Page 5' We trust' this infomation is adequate to enable your staff .to complete its review -

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on this subject.. However, should adoi'ional information'or clarification be neces- ,..

sary,' please . feel free to contact us.  ;

- Very truly yours, i

. Attachments:

- Tables 1.and 2 l

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N l TABLE #2

. VOLTAGE DROPS FROM CLASS IE BUSES T0 THE TERMINALS OF CLASS IE LOADS FROM

~ BUS TO VOLTAGE DROP (VOLTS)

AS P-203A 5~

A5 P-203C 4.9 A5 P-215A 5.1 A6 P-203B 2.3 A6 P-215B 2.2 B1 P-110A 7.5 B2 P- 110B 7.2 B10 X19 5.4 B10 125V DC Backup.

Charger 5.7

.-810 M0-4127 9 B10 M0-4126 11 B10 P-208C 14 B14 125V DC Charger "B" 18 B14 VGTF-201B 17 B14 V-EX-1048 8

- B14 V-EX-210B 14 B 14 - P-2020 5 814 P-202E 6 B14 P-202F 6 814 P-2080 7.5 B14 , P-208E 8 B14 P-141B 7 B14 M0-3806 4.4 814 M0-3805 4.4 B15 125V DC Charger "A" 16 B15- V-EX-104A 8 B15 V-EX-210A 15 B15 P-202A 6 BIS P-202B 6.8 BIS P-202C 6.4 BIS P-208A 16 B15 P-208B 15 815 P-141A 7 BIS M0-3801 5.2 BIS M0-3800 5.3 B17 C-103A 8.8 B17 V-AC-202B 9.1 B17 V- AC-202A 9.1 817 V-AC0204A 13.6 B17 V-AC-2048 9.2 B17 M0-1400-3A 6.2 B17 M0-1400-4A 6.2 B17 MO-1400-24A 8.8 B17 M0-1400-25A 11.7 B17 M0-1001-7A 6.1 B17 M0-1001-7C 6.1 817- M0-1001-18A 5.6 B17 M0-1001-23A 7.9 B17 MG-1001-26 A 5.7

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FROM o BUS TO VOLTAGE DROP (VOLTS)

B17 M0-1001-16 A 9-B17 M0-2301-4 7.9 B17 M0-1001-34A 6.8

~ B17 M0-1001-36 A 5.9 B17 M0-1001-37A 5.8' B17 M0-1001-43C 6.2

. B 17 M0-4060B 5.7 B17 M0-4085A 5.9 817 M0-4084 5.7 -

B17 VSF-103A 8.5 B17 Y3 5.6 B18 C104A 11.3 B18 V-AC-201B 8.8 B18 V-AC-201A 7.4 B18 V-AC-204C 8.2 B18 - V-AC-204D 8.5 B18 M0-1400-38 5.9 B18 M0-1400-48 5.6 B18 M0-1400-242 9.1 B18 M0-1400-25B 14 B18 M0- 1001-78 6 B18 MO-1001-70 5.9 B18 M0-1001-18B 5.4 B18 M0-1001-238 7.0 818 M0-1001-26B 7.0 B18 M0-1001-16E 8.2 B18 M0-1301-16 5.5 B18 M0-1001-348 7.8 B18 M0-1001-36B 5.7 B18 M0-1001-43B 5.8 B18 M0-1001-430 5.8 B18 M0-4010A 5.6 B18 M0-4010B 5.6 B18~ M0-4009A 5.5 B18 M0-40098 5.3 B18 M0-4002 5.4 B18 M0-4087 5.3 818 VSF-1038 9.8 B18 Y4 5 '. 9 B20 M0-1001-29A 7.4 B20 M0-1001-298 12.4  ;

B20 M0-1001-288 12.6  !

B20 M0-1001-19 5.8 B20 M0-1001-32 5.7 B20 M0-1001-50 7.7 B20 M0-1001-50 7.6 820 M0-1001-63 5.6

-820 M0-1201-2 5.6 B20 M0-1201-80 6.0 B20. M0-220-1 5.4 B20 M0-2081 10.8 B20 M0-202-5A 8.6 B20 - M0-202-6 A 8.3

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- FROM BUS ~ TO VOLTAGE DROP-(VOLTS).

B20' .M0-202-9A 5.5 B20 M0-202-4B 12.0 B20~ M0-202-5B 8.7 B20 M0-202-6B 8.6 8 20 M0-202-98 5.5 4

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