Patent ID: 8659858

Claim:
A photovoltaic power generating device, comprising: a plurality of photovoltaic strings; a current collecting box serving to collect electric power from the photovoltaic strings; and a power conditioner supplied with the electric power from the plural current collecting boxes, and having an inverter for converting the electric power into the alternating current power, wherein the current collecting box includes: a first detector that provides detection outputs to detect a ground fault in each of the photovoltaic strings; a first calculator that calculates the mean value of a plurality of outputs from the first detector by obtaining the plural outputs from the first detector; a first judgment circuit that determines the presence of the ground fault by comparing the mean value calculated by the first calculator with a set value, and the power conditioner includes: a second detector that provides detection outputs to detect a ground fault in a connecting cable between the current collecting box and the power conditioner; a second calculator that calculates the mean value of a plurality of outputs from the second detector by obtaining the plural outputs from the second detector; and a second judgment circuit that determines the presence of the ground fault by comparing the mean value calculated by the second calculator with a set value, wherein the number of output values in detection outputs used for calculating the mean value by the first or second calculator is changed according to detection outputs supplied from the first or second detector, and wherein the number of output values in detection outputs used for calculating the mean value by the second calculator is larger than the number of output values in detection outputs used for calculating the mean value by the first calculator.