The disclosure provides a vehicle electrical system equipped with a high-voltage branch and a first low-voltage branch, which is galvanically isolated from the high-voltage branch by insulation. The low-voltage branch has at least one low-voltage line, which leads to the high-voltage branch. The low-voltage branch has a voltmeter. The voltmeter is connected in a signal-transmitting manner to the at least one low-voltage line. Furthermore, the voltmeter is set up to detect whether an absolute voltage value of the at least one low-voltage line with respect to a ground potential of the vehicle electrical system lies above a voltage limit. The voltage limit defines an absolute voltage value which is greater than the absolute value of a maximum signal voltage of the low-voltage line, which the low-voltage line has during fault-free operation.

An insulation impedance detection method includes: An inverter injects a first common-mode voltage into an alternating current side, where the first common-mode voltage is divided by an alternating current grounding insulation impedance of an alternating current cable and a direct current grounding insulation impedance of a photovoltaic unit. The inverter can obtain an impedance value of the alternating current grounding insulation impedance based on the first common-mode voltage, a voltage divided by the alternating current grounding insulation impedance for the first common-mode voltage (a second common-mode voltage on the alternating current grounding insulation impedance), and an impedance value of the direct current grounding insulation impedance. The alternating current grounding insulation impedance is detected by using a necessary device, namely, the inverter in a photovoltaic power generation system. In this way, an additional detection device is not mounted, which reduces costs and complexity of alternating current grounding insulation impedance detection.

An electric circuit according to an embodiment of the present disclosure includes only a single amperemeter configured to measure either a positive current or a negative current through a respective measurement resistance between a respective high voltage potential and a common ground potential. The respective actual measurement resistance value of the unmeasured measurement resistance is calculated by applying a respectively calculated actual measurement resistance value of the respective measured measurement resistance, a calculated actual positive isolation resistance value, and a calculated negative isolation resistance value.

A system and a method for calculating insulation resistance, and more particularly for calculating insulation resistance between a positive terminal and a negative terminal of a battery and a chassis based on voltages of the battery applied to a resistor that connects the positive terminal of the battery and the chassis and a resistor that connects the negative terminal of the battery and the chassis.

An external power feed system includes a vehicle and an external power feed device disposed outside the vehicle. The external power feed device includes an external electric leak detector configured to detect an electric leak. The vehicle includes a power supply device configured to supply electric power to the external power feed device. The vehicle includes an external power feed relay. The external power feed relay is disposed between the external power feed device and the power supply device when the external power feed device is connected to the vehicle. The vehicle includes a controller configured to control the external power feed relay such that the external power feed relay is turned off when the external electric leak detector detects an electric leak.

A circuit includes: an isolation power module, a first and second sampling modules, a first and second sampling points, a processor. A first terminal of the first sampling module is connected to a positive electrode of a battery pack and first terminal of a positive switch module, a second terminal of the first sampling module is connected to a negative electrode of the battery pack and a first terminal of the negative switch module, a third terminal of the first sampling module is connected to a first reference voltage end; a first terminal of the second sampling module is connected to a second terminal of the positive switch module and a positive electrode of the isolation power module, a second terminal of the second sampling module is connected to a second terminal of the negative switch module and a negative electrode of the isolation power module.

An electric leakage detection apparatus for a battery included in an electric vehicle transmits a first voltage corresponding to a voltage between a negative terminal of the battery and a chassis of the electric vehicle to an analog-to-digital converter through a capacitor. The electric leakage detection apparatus transmits a second voltage corresponding to a voltage between a positive terminal of the battery and the chassis to the analog-to-digital converter through the capacitor. The analog-to-digital converter outputs digital signals indicating the first voltage and the second voltage using the negative terminal as the ground. The electric leakage detection apparatus determines the first voltage and the second voltage based on the digital signals, and detects an electric leakage between the battery and the chassis based on the first voltage and the second voltage.

An insulation layer formation method comprises: a first step in which a surface treatment is applied to a base material to form thereon a high-resistance layer having high electric resistivity; a second step in which metal plating parts are formed on the base material that has undergone the first step in such a manner as to allow a high-resistance layer to be formed thereon; and a third process in which a high-resistance layer is formed on the base material that has undergone the second step.

Disclosed are discloses an insulation detection circuit for voltage balance, comprising a bus battery, a bus positive voltage dividing circuit, a bus negative voltage dividing circuit, a differential amplification circuit and a MCU module. The bus battery is respectively connected with the bus positive voltage dividing circuit and the bus negative voltage dividing circuit, the bus positive voltage dividing circuit and the bus negative voltage dividing circuit is respectively connected with the differential amplification circuit, and the differential amplification circuit being connected with the MCU module; the bus battery is configured for supplying power to each module; the bus positive voltage dividing circuit is configured for converting a positive voltage of the bus from high voltage to detectable low voltage; the bus negative voltage dividing circuit is configured for converting a negative voltage the bus from high voltage to detectable low voltage.

Provided is a distributed insulation detection device for a multi-stage DC system. A basic insulation combination module is configured to detect a ground insulation fault of the multi-stage DC system, a sampling module is configured to collect voltage data and/or leakage current data of the multi-stage DC system, to transmit the collected voltage data and/or the leakage current data to an intelligent control module for data processing, to control a resistance value of the basic insulation combination module and a resistance value of an intelligent resistance switching network module, so as to adjust a total balance resistance of the distributed insulation detection device for the multi-stage DC system.