Analysis of the Causes of MOV Faults in a Series Compensation Platform

The metal oxide voltage arrester (MOV) used for series compensation platform protection is the main protection of parallel capacitor banks, which limits the over-voltage at both ends of the capacitor bank. This article takes a case study of a series compensation MOV experiencing a fault during a line trip and re-switching to the series compensation. Based on the fault recording curve and system simulation calculation, it is shown that the energy absorbed by the MOV is lower than its maximum allowable flow capacity, and the energy overload of the MOV is not the cause of this equipment failure. Through visual inspection, electrical testing, and disassembly analysis of the faulty MOV, this study analyzes the temporary over-voltage generated by the re-switching series compensation platform when a short circuit fault occurs in the system. The accumulated energy amplifies the weak points inside the MOV, causing surface flashover of internal resistors and pressure release action. Finally, this article proposes corresponding improvement measures, suggestions, and issues to be noted.