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The team identified a finding of very low The team identified a finding of very low safety significance involving a non-cited violation of 10 CFR 50, Appendix B, Criterion lll, Design Control, because FENOC did not correctly translate the design basis of the electrical distribution system into procedures to ensure operability of offsite power during bus transfers when operating the system service station transformer (SSST) load tap changers (LTC) in the manual mode, an allowed system configuration. Specifically, the team found that procedure\'s supporting calculation did not evaluate the voltage levels on the 480 volt buses. The team determined that during some design basis events, with the tap changer in manual, voltage on the 480 volt vital bus could degrade to a level that would cause the degraded grid relays to trip, resulting in a spurious trip of offsite power. FENOC entered the issue into the corrective action program, and implemented an Operation\'s night order to ensure the LTC was maintained in automatic. The team determined that the issue was more than minor because it was associated with the Mitigating Systems Cornerstone attribute of Design Control, and adversely affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. The finding was of very low safety significance (Green) because it was a design deficiency confirmed not to result in a loss of operability or functionality. The team determined that there was not a crosscutting aspect associated with this finding because it was not indicative of current performance.was not indicative of current performance.  +
23:59:59, 30 June 2011  +
05000334  +  and 05000412  +
23:59:59, 30 June 2011  +
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00:44:09, 21 February 2018  +
23:59:59, 30 June 2011  +
Inadequate Calculations for Placing SSST LTC in Manual Mode  +