A study of separable connector switching performance on a low current circuit

A growing number of reports from users indicate an unexpected degree of difficulty in switching low current circuits with separable insulated connectors. Seeming to contradict this is laboratory experience that decreasing the connector switching current increases considerably the switching reliability with typical test circuits and power factors. Studies performed to date have not established any cause for the seeming higher failure rate on low current circuits and have not explained the apparent dichotomy between the field and laboratory experience. An elbow switching failure that occurred at Wisconsin Public Service Corporation was of the type that seemed to be typical of those described for low current circuits. Its remote location and interruptible load provided an opportunity to perform in-situ measurements while live switching was performed. A number of switching tests were then performed on this circuit where the failure had occurred with all circuit parameters monitored by recording instrumentation. Test results and data analysis indicate that the phenomena causing the failures may be more than the typically considered parameters of current magnitude and power factor.<>