Abstract: In a ground fault detection device, two photovoltaic strings are disconnected from a photovoltaic power generation system, measurement for one photovoltaic string is performed by a measuring instrument, and in parallel therewith, the other photovoltaic string before measurement is charged/discharged by a charging/discharging unit by executing various functions of the calculation control unit. In other words, charging/discharging of the photovoltaic string is performed in advance at the same timing as the measurement of the photovoltaic string so that the measurement can be performed immediately after the photovoltaic string is connected to the measuring instrument in a subsequent step.

Abstract: A failure detection device is a failure detection device that detects failure of a bypass diode for at least one photovoltaic string including photovoltaic cells and at least one bypass diode connected in parallel with the photovoltaic cell and disconnected from a load, including a current source circuit that supplies a current having a specified current value from a negative electrode to a positive electrode of the photovoltaic string, a voltage measurement unit that measures a potential difference between the negative electrode and the positive electrode of the photovoltaic string when the current source circuit supplies the current, and a control/determination unit that determines failure of the bypass diode based on the potential difference measured by the voltage measurement unit.

Abstract: A photovoltaic unit comprising photovoltaics for generating power by utilizing solar light and a bypass diode connected in parallel with the photovoltaics further comprises a reaction element adapted to react to a current flowing therethrough and connected in parallel with the photovoltaics and bypass diode and a blocking element connected in series with the photovoltaics. The reaction element is constructed such as to react to a current flowing therethrough when no current flows through the bypass diode while a reverse voltage is applied to the photovoltaics. The blocking element blocks a current of the photovoltaics according to the reaction of the reaction element.

Abstract: A photovoltaic power generation system comprises a photovoltaic module having a photovoltaics for generating power by utilizing solar light, a bypass diode connected in parallel with the photovoltaics, and a detection unit for detecting an open-mode failure of the bypass diode. A failure detection method comprises a detection step of detecting an open-mode failure of a bypass diode connected in parallel with a photovoltaics for generating power by utilizing solar light, the detection step detecting the open-mode failure of the bypass diode when a predetermined reverse voltage value is applied to the photovoltaics, the predetermined reverse voltage value being a voltage drop value greater than that of the photovoltaics occurring when a current having a maximum current value flows through the bypass diode.

Abstract: An object is to detect an insulation failure of a DC circuit with high sensitivity and in safety by means of a simple detection circuit. An insulation resistance measurement device of this invention is a device for measuring an insulation resistance to ground of a DC source circuit and is provided with connection terminals for connections to a positive electrode and a negative electrode of a series power supply, switch elements connected between the connection terminals and the ground potential and configured to switch connections between the connection terminals and the ground potential, resistive elements connected through the switch elements between the connection terminals respectively, and the ground potential, and a voltage detection unit for detecting voltage drops in the resistive elements.

Abstract: In a ground fault detection device, two photovoltaic strings are disconnected from a photovoltaic power generation system, measurement for one photovoltaic string is performed by a measuring instrument, and in parallel therewith, the other photovoltaic string before measurement is charged/discharged by a charging/discharging unit by executing various functions of the calculation control unit. In other words, charging/discharging of the photovoltaic string is performed in advance at the same timing as the measurement of the photovoltaic string so that the measurement can be performed immediately after the photovoltaic string is connected to the measuring instrument in a subsequent step.

Abstract: In a ground fault detection device, two photovoltaic strings are disconnected from a photovoltaic power generation system, a measurement of a first voltage value is performed for the one photovoltaic string by a first measurement unit, and in parallel therewith, a measurement of a second voltage value is performed for the other photovoltaic string by the second measurement unit by executing various functions of a calculation control unit. Thus, a capacitance relative to a ground of a measurement target is reduced. Further, the photovoltaic string is electrically separated from a load device at the time of such a measurement. Further, separate measurements are performed on the one and other photovoltaic strings in the disconnected state, and the first and second voltage values are measured in parallel.

Abstract: A ground fault detection device detects a ground fault within a photovoltaic array in a solar energy generator system including a photovoltaic string composed of a plurality of photovoltaic modules connected in series, the photovoltaic array composed of a plurality of the photovoltaic strings connected in parallel, and a load device consuming or converting electric power. The ground fault detection device includes a switching section which parallels off the photovoltaic array or the photovoltaic string by electrically disconnecting the photovoltaic array or the photovoltaic string from the solar energy generator system and a detection section which detects a ground fault in the photovoltaic array or the photovoltaic string while the photovoltaic array or the photovoltaic string is paralleled off by the switching section.

Abstract: An object is to detect an insulation failure of a DC circuit with high sensitivity and in safety by means of a simple detection circuit. An insulation resistance measurement device of this invention is a device for measuring an insulation resistance to ground of a DC source circuit and is provided with connection terminals for connections to a positive electrode and a negative electrode of a series power supply, switch elements connected between the connection terminals and the ground potential and configured to switch connections between the connection terminals and the ground potential, resistive elements connected through the switch elements between the connection terminals, respectively, and the ground potential, and a voltage detection unit for detecting voltage drops in the resistive elements.