DC isolator

The best designed machinery in this universe is the human body. It has an excellent built-in self-defense and self-repair system. Even that highly intelligent system needs occasional repair and maintenance. And so does every manmade system, including solar PV installations. Within the solar installation is the inverter which receives Direct current (DC) from solar strings as input and puts out Alternating Current (AC) to the grid on the output end. During installation, routine maintenance and emergencies it is necessary to isolate the panels from the AC side, and hence, a manually operated isolating switch is placed between the panels and the inverter input. Such a switch is called a DC isolator because it provides DC isolation between the photovoltaic panels and the rest of the system.

This is an essential safety switch and is mandated in each photovoltaic power system according to IEC 60364-7-712. The corresponding British requirement comes from BS7671 – Part 712.537.2.1.1, which states “To allow maintenance of the PV convertor, means of isolating the PV convertor from the DC side and the AC side must be provided”. Specifications for the DC isolator itself are given in the “Guide to the Installation of PV Systems”, section 2.1.12 (Edition 2).