Sub-Cyclic Damaging Ferroresonant Overvoltages in 230 kV Transmission Systems Field Experience of 230 kV Transformer-Ended Cable Feeders Failure

摘要

Extensive research and world-class standards have reported the ferroresonance phenomenon as a low-frequency temporary overvoltage with a range of voltage shape starting from 1 cycle. This paper provides a case study for a typical 230 kV transformer-ended cable feeder configuration that has experienced damaging ferroresonant overvoltages in 3/4 cycle. Ferroresonant overvoltages were recorded in two (2) different incidents and a similar 230 kV feeder configuration with magnitudes exceeding 2.75 pu in 12 ms causing a phase insulation breakdown in power transformers and a longitudinal insulation breakdown in circuit breakers. Waveform records captured at 32 samples per cycle are analyzed and used to validate a PSCAD/EMTDC model. Trigger mechanisms of this sub-cyclic ferroresonance profile are identified and preventive/protective measures are discussed based on recommendations for IEEE and IEC standards.