Effects of Continuous Operating Voltage Stress and AC Energy Injection on Current Sharing Among Parallel-Connected Metal–Oxide Resistor Columns in Arrester Banks

The capacitors of series compensation (SC) installations have to be protected against overvoltages by surge arresters. Since very high amounts of energy must be handled under fault conditions, many parallel metal-oxide (MO) resistor columns are typically arranged in arrester banks, which are also designated as metal-oxide varistors (MOVs). It is known that in rare cases, single MO resistor columns fail in consequence of excessive energy injection. It is so far an unsolved question as to whether it is allowed to replace such arresters by new ones because of possible electrical aging effects of the remaining, healthy arresters. The presented investigations indicate that the aging affects do have an impact on the residual voltage of the investigated MO resistors, but with only negligible impact on current sharing among individual columns (e.g., of a bank). Therefore, the replacement of single arresters seems to be possible at least for the investigated type of MO resistors.