Summary Rich Bauer, Senior Reliability Engineer Event Analysis Subcommittee – LL Update March 04, 2014

Identify Relay Programming Errors to Prevent Unintended Operations A relay programming error allowed a circuit breaker to reclose following a SCADA open command to the circuit breaker This programming error led to the triggering of a SPS, tripping generation Human Error was a factor in the relay programming error Peer reviews can be a useful tool to find errors in relay programming/settings

Substation Ground Mat High Resistance A number of exothermic welds were not made to the ground mat during the construction of a substation by the contractor The lack of welds led to high resistance between different areas of the ground mat A close in ground fault, coupled with a battery ground, allowed high AC currents to flow on the Station DC system The AC fault current flowing on the DC system, caused numerous equipment failures in the station These equipment failures resulted in Misoperations that led to the loss of 2000MW of generation Thorough inspection of contract work and initial ground grid testing to ensure adequate ground grid resistance are useful tools for prevention/detection of this type of station ground grid problem

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