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Modern circuit breakers (CBS) may be susceptible to catastrophic failure possibly because they are designed to be more highly stressed than earlier CB designs with multiple interrupters per pole. Improved performance is obtained with dielectrically well-designed interrupters by taking advantage of advanced controlled switching to achieve a reignition-free window during opening to minimize the risk of nozzle puncture. On occasion, CB owners may wish to check whether equipment is performing satisfactorily and whether controllers are producing reliable and repeatable stress control. The monitoring of voltage waveforms during switching using established methods will provide information about the magnitude and frequency of small reignitions and restrikes. However, waveform measurements at a moderately high signal frequency require plant outages to connect specialized equipment. A nonintrusive measurement technique has been developed to measure the high- and low-frequency voltage waveforms occurring during reactor switching operations without the need for an outage. Results of tests performed in the laboratory and in a 275-kV substation demonstrating the capability of this new method to detect reignitions are presented.
Date of Publication: April 2012