A new method of condition monitoring on electrical contact endurance of power switch
Prediction of the remaining electrical endurance of a power switch is important for the reliable performance of power switches. The erosion of contact material is one of the most important indexes for the electrical life of a contact. Previous methods of contact material life prediction are introduced. They mainly consider the relationship between erosion volume and current amplitude. A new idea is presented to diagnose the life of electrode material from the waveform characteristics of the make and break currents. LabVIEW is used to sample and store the current and voltage signals. Current waveforms, break/make current arc duration and contact resistance are discussed. As a result, the occurrence probability of fluctuating phenomena of the break current, contact resistance and make arc duration change with the number of contact operations. The break arc duration is determined by the break current.
Interruption life of vacuum circuit breakers
Over the past few years, there has been an increased interest in the number of short circuit interruptions a vacuum circuit breaker is capable of before excessive wear occurs on the contacts. Several methods have been proposed for recording or extrapolating the interruption life of vacuum circuit breaker contacts and these have resulted in many different claims. As a means of reconciling these, and for providing a common ground for axial magnetic type vacuum circuit breaker contacts, a recommendation is made for a new means of measuring contact life. This new method is based on the interruption level and the amount of time in which the arcing between the contacts occurs. This is then compared against test results for vacuum circuit breaker contacts from Cooper Power Systems.
Electrical endurance and reliability of circuit-breakers-common experience and practice of two utilities
Tests carried out for HV and MV equipment are described. They have been designed to represent an equivalent stress level designed to represent an equivalent stress level borne over 25 years in a modern system and provide a good compromise between cost and representativeness. Twenty years of experience shows that the tests make it possible to satisfactorily check aspects of dimensioning relevant to reliability and to give the operator a quantified guarantee. >