Reliability Standard: VAR-002-3
Violation Risk Factor: Medium
Violation Severity Level: Severe
Issue: Tampa Electric Company (TEC), a GOP, Self-Reported a violation of VAR-002-3 R2. TEC discovered that it did not maintain the bus voltage per the required schedule at Polk Power Station for a period of 7 hours and 30 minutes and that TEC's operator failed to notify the TOP of deviations from the provided voltage schedule.
On April 13, 2015, the Polk Power Station 230 kV bus dropped below the voltage schedule 238 kV lower limit during startup, which initiated a low bus voltage alarm that was acknowledged by the system operator. Because none of the station's units were online at the time, the station was exempt from maintaining the voltage schedule. The voltage recovered to 238.1 kV, but the alarm did not reset because the voltage was still below the value necessary to reset the alarm. The Polk Unit 4 and Polk Unit 2 combustion turbines were subsequently brought online with their AVRs set to automatic. The station bus voltage subsequently dropped below 238 kV but the system operator did not notice because the alarm was obscured by other log entries.
Finding: FRCC found the violation posed a minimal risk to BPS reliability. TEC's generator voltage deficiency did not exceed 0.4 percent of the voltage schedule. Moreover, the two generating units operated with their AVR in automatic mode during the period of the violation. The duration of the violation was April 13, 2015 (when the Polk Power Station 230 kV bus dropped below the voltage schedule while CT 4 was online, at 11:05 a.m.) through April 13, 2015 (when the Polk Power Station 230 kV bus returned to the voltage schedule at 6:35 p.m.). FRCC considered internal compliance program to be a mitigating factor.
FERC Order: Issued May 31, 2016 (no further review)