The Diagnosis Method And Realization Of Fault In Mid-Voltage Power Distribution

In the power networks with neutral point grounded by arc-suppression coil, the fault residual current in system could be reduced and the recovery speed of faulted phase voltage will decrease when single earth fault happens, which suppresses the damage of earth fault and arc fault and makes great contribution to medium-voltage power system protection. In usual case the work arc-suppression coil for compensating works in the state of approaching resonance. So it is also called compensated resonance power networks. In such system the single phase-to-earth fault current is small and the characteristic of fault is unobvious, which has restricted application of this neutral point grounded style. With development of technology and various mathematic tools in engineering, diverse embedded devices and algorithm for earth fault detection and location have been in application. But the model of earth fault resistor and discipline of whole earth fault process are complex and obscure, a perfect earth fault diagnose strategy that meets all kinds of circumstances hasn't yet been discovered.In this paper, the author made a detailed analysis the development process of all types of fault which caused the neutral point voltage increase, and summery the fault characteristics. Using the electromagnetic transient calculation procedures (EMTP-ATP) on the bases of the analysis of simulation results, the author find out Grounding-like fault detection method based on the the analysis of the fault development process. The method has been successfully applied to the "Process Analysis Based Fault Detection Diagnosis Device" in seven substation and one year of operating experience shows that the method is accurate and reliable.