ML19290E878
| ML19290E878 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 03/11/1980 |
| From: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8003170253 | |
| Download: ML19290E878 (8) | |
Text
{{#Wiki_filter:I Telephone 617 366-90ll TWX 7tO-3 90 0 7 3 9 YANKEE ATOMIC ELECTRIC COMPANY a.a.2.1 7 'O = WYR 80-34 M G,1 20 Turnpike Road Westborough, Massachusetts 01581 Lc ,Y$W$~$/ ~_ March 11,1980 United States Nucl ear Regul atory Commission Washington, D.C. 20555 Attention: Of fice of Nuclear Reactor Regulation Mr. Dennis L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors
References:
(a) License No. DPR-3 (Docket No. 50-29) (b) USNRC Letter to YAEC dated December 4, 1979
Subject:
Loss of Offsite Power Survey
Dear Sir:
As requested in Reference (b), we are providing the foa l owing information. We have reviewed Yankee Atomic Power Station experiences with the offsite power system over the past 19 years of operation. During that time there has been onl y one compl ete l oss of of f site power which occurrcd on November 9, 1965 during the " Northeast Bl ackout". The Yankee Rowe pl ant was shutdown at that time. Pa r t ial losses of of f site power have been more common. El ectric power from the transmission network to the Yankee Rowe onsite electric distribution system is suppl ied by two physicall y independent circuits. One is the 115 kV Cabot Line (Y-177) and the otter is the 115 kV liarriman l ine ( Z-126 ). These lines enter the pl ant switchyard from opposite directions. Connections of these transmission lines to the transmission grid are shown in Figure 1. The connections between the onsite and offsite power systems are shown in Figure 2. Due to the configuration of the onsite power system and its connections to the offsite power system, the plant is subjected to a partial loss of of fsite power whenever one of the two 115 kV transmission lines is de-energized. If the plant is at power there will, in general, be a pl ant trip. If the line outage is schedul ed and plant conditions allow, connections can be made between onsite buses through bus tie breakers prior to taking the line out of service, 80031zo 25h p
~ U.S. Nuclear Regulatory Commission March 11,1980 Attention Of fice of Nuclear Reactor Regulation Page 2 During any plant trip, power will be lost on the buses connected to Station Service Transformer No. 1. These buses are then manually connected to al ternate sources through bus tie breakers. As this is a design condition and does not a f fect the transmission lines or the normal offsite power connections to the pl ant, these events have not been reported as partial losses of of fsite power. Detailed data on compl ete and partial losses of of f site power are provided in the attached encl osure. Pl a n t and transmission line records were reviewed in detail for the years 1965 to 1979 with a l ees detailed review for operation prior to 1965. Since the " Northeast Bl a ckou t" of November 1965, changes have been made in the monitoring and operation of the transmission grid which minimize the effects of system disturbances. We trust that you find this information satisfactory; however, shoul d you desire additional information, please contact us. Very trul y yours, YANKEE ATOMIC ELECTRIC COMPANY k p J. A. Kay Senior Engineer - Licensing IlWI/kaf Encl osures
ENCLOSURE Response to Loss of Offsite Power Survey Yankee _ Atomic Power Station Rcwe, Massachusetts The item numbers used correspond to the item numbers used in Reference (b). A. Pa r t ial Losses of Offsite Power (1 ) f (2) (3) (4) (5) (6) (7) Line i Remarks Time to lCause l (Vol tage, Frequency, Pl an t Response) Restore Date Lost l (SeeNote! '(See Notes b and c hel ow) a below) t Z-126 Line Faul t P1 ant tripped. Low Main Cool ant F1ow. 2 hr. 42 min. l06/04/63 at llarriman j 4 i e I i Y-177 Lightning P1 ant tripped. Low Main Cool ant F1 ow. I6 min. 07/10/66 l 06/24/73 Z-126 Transfer Trip ! Operator tripped pl ant on indication i1 br. 5 min. RelayOperation! of Z-126 1ine dead. t I Z-126 Lightning P1an ri p by relay operation on 1 min. l 08/31/73 l 1 Z-126 Faul t at lP1 ant tripped. Low Steam Generator } l br. 34 min. ! 05/13/75 Sherman Sta. i Level. j Z-126 Faul ty Pilet P1 ant tripped by operator a f te:- 1 oss l 5 min. 12/27/75 i Wire Relay I of Z-126 1inc. Z-126 l Line Faul t Pl a n t tripped by operator af ter l oss 6.5 min. 02/02/76 i of Z-126 l ine. i i ENCLOSURE NOTES: a. Normally two 115 kV lines are available. In each case of a partial loss of of fsite power one of these two lines was temporarily de-energized. Scheduled outages of lines for maintenance have not been considered, since the pl ant can be placed in a configuration all owing all necessary loads to be suppl ied f rom the l ine remaining in service. b. The two 115 kV lines are physically independent and reach the Yankee Rowe pl ant by separate paths and fi,n opposite directions. The protective relaying for these trans. 2ission lines is designed to clear faul ts on one line without atfecting the other line. There fore, by design, most transient events which can cause the loss of one line will not simul taneously cause the loss of the second line. c. Detailed information on vol tage and frequency behavior was not . generall y avail abl e. These outages were due to l ocalized conditions which woul d not be expected to cause extensive frequency or vol tage disturbances. ENCLOSURE B. Compl ete Loss of Of fsite Power 1. Length of Time: B,th Y-177 and Z-126 lines tripped and went dead between 1718 ar c 1722 hours. Z-126 was re-energized f rom Harriman Station (hydro) at 1740 and was re-connected to the onsite distribution system at 1755 (approximately 33 minutes af ter loss). At approximatel y 2133 hours the Y-177 line was re-energized (4 hours,11 minutes af ter the loss of power). 2. N.A., the unit was of f-line when the power loss occurred. 3. N.A. 4 As a resul t of system wide disturbances and loss of generation, the vol tages on the transmission system deteriorated rapidl y. Based on a computer study which simul ated conditions during the incident, the vol tage at Yankee Rowe at 1718 hours was down to about 93% of nominal. This study was reported in Refe*ence (B.1 ) bel ow. 5. Frequency on the transmission system was decaying prior to loss of the lines to Rowe. At 1718 the frequency was 58.3 hz. By 1722 it was down to about 54 Hz. Figure 3 shows the frequency decay during the event. This figure was taken from Reference (B.1). 6. Date: November 9,1965.
Reference:
(B.1) Eastern New York - New England Power System Behavior during Northeast Power Interruption - November 9,1965. Report to the Federal Power Commission by Eastern New York - New England System Studies Group September 15, 1966.
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