Open phase fault detection (OPFD) has been at the forefront of protection concerns since the January 30, 2012 open phase event at Exelon’s Byron Unit 2. The cause of this open phase event was the failure of the C-phase insulator stack for the Unit 2 System Auxiliary Transformer (SAT) revenue metering transformer.
On February 28, 2012 another event occurred at the Byron Plant. A mechanical failure of 345 kV under-hung porcelain insulator on Unit 1 SAT A-frame structure failed due to a manufacturing defect. The 345kV line fell to the ground causing a phase-to-ground fault which tripped the SAT lockout scheme causing the 6.9 kV busses to fast transfer to the UAT, and the ESF busses to be de-energized and subsequently reenergized by the diesel generators. These failures have highlighted the need for detecting open-phase conditions that can occur in the power delivery system.
The PSStech OPP System can be used to detect, alarm, and actuate in response to single and double open phase conditions in the offsite power circuit(s). Based on a field-proven system tested in May 2014, the OPP System is specifically designed to detect open phase conditions on industry-recognized types of transformers where an open phase under no-load or lightly-loaded conditions is undetectable by traditional voltage or current measurements.