Benefits of Permanent Travel Measurement in High Voltage Circuit Breaker Online Monitoring

Abstract

The benefits of Condition Based Maintenance have been widely recognized for a long time. In recent years the focus shifted to its implementation. Since the resources for monitoring investments were not unlimited, the asset managers devoted their attention primarily on transformer monitoring at first, letting the condition monitoring of circuit breakers somehow fall behind (as evidenced in specific details from the CIGRE enquiry 2004-2007). Finally, circuit breakers are now getting more monitoring attention. In deciding which parameters should be kept under scrutiny to accurately assess the circuit breaker condition, travel measurement is one of the most discussed topics. Measuring the opening/closing coil current and the commutation of auxiliary contacts is essential, inexpensive and quite straightforward. Installing SF6 gas density monitoring, in addition to an already installed threshold gas relay, finds its motivation in environmental gas leakage regulations. The measurement of travel curves requires the permanent installation of a proper transducer and additional fitting work, which has an impact on the cost of the monitoring system. Supporting the best decision whether to go for it or not, the benefits in terms of monitoring assessment are analyzed in this paper. Starting from the influence of contact travel on circuit breaker performance, typical parameters that can be derived from this measurement are analyzed and compared in relation to possible circuit breaker problems. Considerations are provided as to where to take the movement from and how to rescale the input signal. Some indications are also given on how to select a proper travel transducer and DC/DC converter power supply, what to pay attention to from an electrical as well as from a mechanical point of view to enhance reliability and measurement accuracy.