Damage by disconnection under low current load: A study of photovoltaic DC connectors

Photovoltaic (PV) systems are operated with long-term stability for decades. In addition to PV panels and power electronics, long-term stable wire harnesses are required. DC connectors, which are in use by the hundreds of millions in the field, must meet the highest requirements in respect of reliability and safety. These connectors, which connect the individual modules, and can also be found on the inverter and combiner boxes, are by standard not designed to be disconnected under load. However, there are practical fault conditions in which a safe and completely load-free disconnection is not feasible. For example, disconnection while the system is energized with the inverter switched off, may result in reverse power flow in a parallel string. To date, little research has been performed on the critical level for a minimum current at which damage to the connectors and thus a potential hazard occurs. In this publication, DC connectors are subjected to realistic disconnection tests at high voltages and low currents. The damage is assessed by electrical tests, visual examination of the contacts and the insulation, as well as measurements of the insulation properties.