THE RESPONSE OF MOV AND SIC ARRESTERS TO STEEP-FRONT LONGER DURATION CURRENT PULSES

An 80 m section of 138 kV transmission cable is used to produce pulses with voltages of several hundred kilovolts, currents greater than 20,000 A and voltage risetimes equal to approximately 50 ns. This line pulser is used to test the response of MOV and gapped SiC surge arresters to steep-front, high current, 1.4 microsecond duration pulses. The typical arrester voltage during a pulse consists of a very strong initial "overshoot" voltage spike, followed by a nearly constant "residual" voltage which lasts to the end of the pulse. The "overshoot" voltage is believed to be related to the inductance of the arrester/divider circuit; this voltage increases linearly with peak current and is about the same for the MOV and SiC arresters. The "residual" voltage indicates the protection offered by the arrester due to its voltage clamping action and is larger for the SiC arrester. Replacing the arrester by a similarly sized aluminum tube allows the inductive portion of the response to be removed, and the true arrester response is then seen to be quite fast.