Photovoltaic safety equipment and the National Electrical Code

Article 690-5 of the National Electrical Code (NEC) 1990 Edition requires that photovoltaic (PV) power systems mounted on the roofs of dwellings be equipped with a device that will detect ground faults in the array, interrupt the fault current, and disable the array. The design of a ground fault indicator and array disabler device that meets the requirements of the NEC for stand-alone and grid-tied systems is described. Preliminary testing revealed a low-voltage oscillation and excessive power consumption at voltages below the operating window. These problems have been resolved by a voltage monitoring relay.<>