Arc suppression in moderate voltage DC grid for solar PV applications

Abstract

Arc is formed in circuit breakers and switches during contact separation of high energy circuits. Arc suppression in those circuits is required to prevent damage to the contacts of the circuit breakers/ switches and to reduce the generation of heat in the vicinity of the contact. Such arcing also forms new chemical compounds around the air that includes oxides of nitrogen, ozone etc. Contact surface of the switch is eroded thereby enhancing the contact resistance when closed. In case of alternating current (ac), arc interruption takes place during natural zero current crossing that occurs twice in a cycle. In case of dc as there is no zero crossing, so arc extinguishing process is difficult and expensive. That is why DC circuit breakers are expensive and larger in size with respect to AC circuit breakers of same ratings. Also, during switching operation in DC system, dangerously high oscillatory voltage is generated due to inductive and capacitive parameters of the line. As solar PV generates DC voltage which is normally converted to AC before connecting to load. So an inverter is necessary for such conversion, that consumes power to the tune of 10% of its rating. The main challenge for transmitting DC directly to load through transmission line is the effective arc interruption. In this paper, a low cost efficient arc interruption circuit has been proposed for solar PV based DC system, which will drastically reduce the cost of generation, transmission and distribution.