ML19294A929
| ML19294A929 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 02/20/1980 |
| From: | Counsil W NORTHEAST UTILITIES |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| TAC-12672, NUDOCS 8002260146 | |
| Download: ML19294A929 (8) | |
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February 20, 1980 Docket No. 50-336 Director of Nuclear Reactor Regulation Attn:
Mr. R. Reid, Chief Operating Reactors Branch #4 U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Reference:
(1)
R. Reid letter to W. G. Counsil dated November 27, 1979.
Gentlenen:
Millstone Nuclear Power Station, Unit No. 2 Loss-of-Offsite Power In Reference (1), the NRC Staf f requested that Northeast Nuclear Energy Company (NNECO) provide information pertaining to complete or partial loss-of-offsite power events at Millstone Unit No. 2.
Please find attached NNECO's response to the Ref erence (1) requests.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPAh"I f(19th W. G. CounsiT Vice President Attachment I
8002260 j
DOCKET NO. 50-336 ATTACHMENT MILLSTONE NUCLEAR POWER STATION, UNIT No. 2 LOSS-OF-OFFSITE POWER FEBRUARY, 1980
A.
For loss of off site power where less than all of f site power was lost:
Question 1 How many circuits to the of f site network are normally available and how many were lost during the event?
Respo nse In accordance with 10CFR50, Appendix A, Criterion 17, Millstone Unit No. 2 takes credit for two off site power circuits being normally available to the plant.
Specifically, these two circuits consist of two separate 345KV switchyard connections, one feeding Reserve Station Service Transformer (RSST) 15G-21S and the other feeding RSST 15G-22S.
See the attached Drawing labeled 25200-91001, Sheet 1 of 2, Rev. 14.
Table I indicates which circuit was lost during each event.
Question 2 What was the cause of the event?
Response
Refer to Table I.
Question 3 Why did some other lines not fail when some did fail?
Res po nse The of fsite power supplies (2-345KV circuits) are electrically connected in the 345KV switchyard through a combination of circuit breakers.
When a fault occurs on one of the two of fsite power sources, one cr more circuit breakers will trip to isolate the faulted circuit and keep the remaining of fsite circuit intac t and inservice.
Question 4 Was any voltage increase or decrease experienced just prior to or during the outage? If so, y ease give datails, voltcges reached, affects, etc.
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Response
Our records did not indicate any voltage increase or decrease being experienced just prior to or during the disturbance events listed in Table I.
Question 5 Was any frequency decay experienced just prior to or during the outage?
If so, please give details, lowest frequency reached, decay rate, af f ects on equipnent operation, etc.
Response
Frequency decay greater than or equal to 0.5 Hz. is normally recorded for any disturbance event on our transmission system. Our records did not indicate the presence of frequency decay for any of the disturbance events listed in Table I.
Question 6 How long was power unavailable from the circuit?
Response
Ref er to Table 1.
Question 7 Date of Event.
Respo nse Ref er to Tcble I.
B.
For losses of all offsite power:
Question 1 How long was the power of f ? How long for partial recovery? Please give details.
Response
Ref er to Table I.
-3_
Question 2 If turbine trip occurred, how soon af ter did loss of of f site power occur?
Response
A review of our records indicate that this event, turbine trip with subsequent loss of of fsite power has not occurred at Millstone Unit No. 2 to date.
Question 3 If power was covered promptly (10 minutes or less), was it due to automatic or manual actions?
Response
In Table I, letters preceded by the time of day indicate whetber action was automatic (letter R) or manual (letters S and M).
The letter R indicates operation was performed by relay, letter S indicates operation was performed by supervisory and letter M indicates operation was performed manually.
Question 4 Was any voltage increase or decrease experienced just prior to or during the outage?
If so, please give details, voltages reached, af f ects, etc.
Response
Our records did not indicate any voltage increase or decrease being experienced just prior to or during the disturbance events listed in Table I.
Question 5 Was any frequer.cy decay experienced just prior to or during the outage?
If so, please give details, lowest f requency reached, decay rate, af f ects on equipment operation, etc.
Response
Frequency decay greater than or equal to 0.5 Hz. is normally recorded for any disturbance event on our transmission system. Our records did not indicate the presence of frequency decay for any of the dis-turbance events listed in Table I.
. Question 6 Date of Event.
Response
Refer to Table I.
TADLE I
OSS - Out of Service R - Operation of Relay LOOP - losn of Offsite Power M - P.anual Operation MILLSTONE UNIT 2 - 0FFSITE POWER DISTURBANCES 12/26/75 to 11/1/79 RSST - Reserve Station Service S - Operation of Transformer Supervisory a
Partial Loss loss Restor.
Restor.
Tors 1 1DOP Of Of Of Of Duration Duration LOOP To To RSST ICOT
>SGT RSST Partial For Date Plant Plant 15G-21S 150-220 ISG-213 15C 223 Recovery Complete Cause of Disturbance (time)
( t irse)
(time) time)
Recovery X
R0406 S0514 68 min 8/10/76 X
R05.l1 R0521+
< 1 min X
P0634 R0634+
< 1 min
-Salt contamination on insulators at MP 15G X
B0648 R0618+
< 1 min X
R0653 MOF 67 min X
R0806 M0809 3 min X
PO901 MlOO4 F10938 S 1247 24 hrs. -
~
(8/11/76 (8/11/76) 37 min.
5/10/77 X
P.0547 R0547+
< 1 min Unknown 5/31/77 X
R1100 R1105 5 nin Unknown 8/10/77 X
RO153 S0618 4 hrs-25 min Unknown 12/16/77 X
R1558 R1615 17 nin 383 Line primary relay problem at Millstone - ISC 2/I'/80 Rev. 2
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