Switching of shunt reactors and capacitor banks is known to cause a very high rate of rise of transient recovery voltage across the circuit breaker contacts. With improvements in circuit breaker technology, modern SF6 puffer circuits have been designed with less interrupter per pole than previous generations of SF6 circuit breakers. This has caused modern circuit breakers to operate with higher voltage stress in the dielectric recovery region after current interruption. Catastrophic failures of modern SF6 circuit breakers have been reported during shunt reactor and capacitor bank de-energisation. In those cases, evidence of cumulative re-strikes has been found to be the main cause of interrupter failure.
Monitoring of voltage waveforms during switching would provide information about the magnitude and frequency of small re-ignitions and re-strikes. However, measuring waveforms at a moderately high frequency require plant outages to connect equipment. In recent years, there have been increasing interests in using RF measurements in condition monitoring of switchgear. The RF measurement technique used for measuring circuit breaker inter-pole switching time during capacitor bank closing is of particular interest.
In this thesis, research has been carried out to investigate switching transients produced during circuit breaker switching capacitor banks and shunt reactors using a non-intrusive measurement technique. The proposed technique measures the high frequency and low frequency voltage waveforms during switching operations without the need of an outage. The principles of this measurement technique are discussed and field measurements were carried out at shunt rector and capacitor bank installation in two 275 kV air insulated substations. Results of the measurements are presented and discussed in this thesis.
The proposed technique shows that it is relatively easy to monitor circuit breaker switching transients and useful information on switching instances can be extracted from the measured waveforms. Further research works are discussed to realise the full potential of the measuring technique.
| Identifer | oai:union.ndltd.org:ADTP/265751 |
| Date | January 2008 |
| Creators | Ramli, Mohd Shamir |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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