ML14176A336
| ML14176A336 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 03/23/1987 |
| From: | Ashe F NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Rubin S NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| Shared Package | |
| ML14176A337 | List: |
| References | |
| AEOD-E703, NUDOCS 8704060521 | |
| Download: ML14176A336 (2) | |
Text
March 23, 1987 AEOD/E703 MEMORANDUM FOR:
Stuart D. Rubin, Chief Reactor Operations Analysis Branch Office for Analysis and Evaluation of Operational Data THRU:
Matthew Chiramal, Chief Engineering Section Reactor Operations Analysis Branch Office for Analysis and Evaluation of Operational Data FROM:
Frank Ashe, Engineer Engineering Section Reactor Operations Analysis Branch Office for Analysis and Evaluation of Operational Data
SUBJECT:
LOSS OF OFFSITE POWER DUE TO UNNEEDED ACTUATION OF STARTUP TRANSFORMER PROTECTIVE DIFFERENTIAL RELAY The enclosed engineering evaluation report is forwarded for your information.
The report provides information concerning loss of offsite power to emergency buses at H. B. Robinson Unit 2. The evaluation is considered to be generically applicabTe o pTants with auxiliary power system designs that transfer auxiliary loads, including emergency buses, from a unit auxiliary transformer to an alternate transformer following a reactor trip/turbine generator trip. As illustrated by the Robinson event, loss of power to emergency buses can occur during a transfer of auxiliary loads and may be caused by unneeded actuation of a startup or reserve power transformer protective differential relay. This unneeded actuation of a protective differential relay may be caused by direct current (DC) saturation of a current transformer (CT) which forms a part of the differential relay circuitry. The safety concern is that the offsite power (preferred power source) to the emergency buses could be lost at a time when needed to operate safety-related electrical equipment.
A review of related information obtained from the Sequence Coding and Search System data base did not result in the identification of any other reported event where DC saturation of a CT was a concern. However, as indicated by the Robinson event, grid system conditions at the time of the transfer along with a higher than usual auxiliary load in-rush current may well be determining factors for a given operating plant.
For this reason, susceptibility to DC 3704060521 870323 PDR ADOCK 05000261 P
Stuart D. Rubin
- 2 saturation of CTs associated with power transformer protective differential relay circuitry could potentially exist at other stations. In view of this conclusion and since IE has issued an information notice addressina the Robinson event, the report suggests that NRR consider this event as appropriate in ongoing licensing reviews. In addition, it is suggested that consideration be given to incorporating the Robinson event into the next revision of the Standard Review Plan. The report also suggests that these activities focus on the potential for the occurrence of DC saturation of CTs attendant to startup or reserve power transformer protective differential relay circuitry.
Frank Ashe, Engineer Engineering Section Reactor Operations Analysis Branch Office for Analysis and Evaluation of Operational Data
Enclosure:
As stated DISTRIBUTION:
PDR AEOD SF ROAB CF FAshe MChiramal SRubin WLanning KBlack MWilliams FHebdon CHeltemes OFC : ROAB
- SC:ROAB
- BC:ROAB r ~~~~--- ---------------
t NAME : FAshe:as
- MChiramal : SRubin DATE :
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- 3{/87
- 3//87 OFFICIAL RECORD COPY