Simulation Studies on MOV Protection Configurations in Low Voltage AC Power Circuits using ATP

This paper is aimed at the effect of surge protection device (SPD) arrangement towards the overvoltage under Differential Mode and Common Mode of operation. Metal Oxide Varistor (MOV) as a type of SPD for lightning surge is used due to its excellent protective ability. The lightning source used in this simulation is an impulse with 10 kA current amplitude and current wave $8/ 20 \mu \mathrm{s}$. Analysis is carried out when the lightning strikes the three-phase system with different mode of protection. The result shows that in normal condition, MOV acts as an open circuit, while during lightning surges, it acts as a short circuit to discharge the high current to the Ground. Differential Mode consists of four MOVs which are connected between Line to Line and to Ground (3L-G). Common Mode consists of three Metal Oxide Varistors at which each SPD is connected between Lines to the Ground (L-G). Based on simulation results, both overvoltage protections have their strength and weaknesses. It is found that in Differential Mode, the burden of the SPD only occurs on the SPD that connect between L-G when all phases are subject with lightning surges, while in Common Mode, the burden exists at all SPDs. A higher energy-handling capability of SPD is needed for the LG SPD in Differential Mode, and a higher rating of varistor shall be used at each lines in Common Mode to avoid failures.