Study For The Closed-loop Testing Method For Distribution Network Faulty Line Selection Device And Its Platform Development

With the maturity of line selection technology for small current grounding, various line selection devices for small current grounding based on different line selection principles were widely adopted in distribution automation system. However, the correct operating rate of line selection devices in field is not satisfying. Because of the randomicity of distribution network fault scenarios and the simplicity of conventional network testing method, the real performance of devices based on different line selection criteria under complex fault conditions cannot be inspected online or offline via conventional methods. At the same time, due to the lack of reasonable defect analysis method, the real accuracy of the facility is not transparent to the user. Therefore, the study on inspecting the performance of line selection devices for small current grounding based on different line selection principles has become hotspot and difficulty among current studies.Regarding the blind points existing in current line selection principle for small current grounding, and the application field of line selection devices for small current grounding, a system of small current grounding was built in RTDS(Real Time Digital Simulator) at first. The complex fault scenarios were studied to cover the blind points of fault selection devices. Based on this, a closed-loop test platform was built for line selection devices for small current grounding, where the analog signal were maximized to true fault level and transferred to the target device to examine its performance. The line selection results under different fault scenarios were recorded. The dynamic model comparison tests were conducted on the closed-loop testing platform, which tested the line selection properties of the devices. The results were analyzed through comparing with the results achieved on the closed-loop test platform. The correctness of the built small current grounding system and the accuracy of signal output of closed-loop test platform were verified. Finally, the performance evaluation method of small current grounding devices based on Logistic regression model was studied. The main and secondary factors that caused the low accuracy rate of small current grounding devices were analyzed and the numerical examples showed that the proposed method can be used as a reference for selecting the network fault line selection equipment.