This disclosure describes techniques for separately determining isolation resistances from nodes of a power system of an electric vehicle (EV) to a chassis of the EV. Processing circuitry may determine a first isolation resistance between a first node of the power system in the EV and a chassis of the EV, determine a second isolation resistance between a second node of the power system in the EV and the chassis of the EV, determine that the first isolation resistance or the second isolation resistance is less than a threshold resistance, and output information based on the determination that the first isolation resistance or the second isolation resistance is less than the threshold resistance.

The present disclosure discloses a detection circuit and method. The detection circuit comprises: a controller, a battery pack, a main positive switch module, a main negative switch module and at least one detection loop. The controller collects voltages of a positive electrode and a negative electrode of the battery pack and a voltage between external sides of the main positive switch module and the main negative switch module when turning on the main positive or negative switch module and after turning on any detection loop, and obtains resistance values of insulation resistors of the external sides according to resistance values of insulation resistors of internal sides of the main positive and negative switch module, as well as the voltages of the positive electrode and the negative electrode and the voltage between the external sides of the main positive switch module and the main negative switch module, which are collected twice.

An insulation resistance detection circuit and method are disclosed. The circuit includes a controller configured to: open a first relay, and close second relays, or switch an on/off status of at least one of the second relays; determine, based on a first measurement value between a positive input terminal of an inverter circuit and an earthing point, whether the positive input terminal of the inverter circuit is short-circuited or has low resistance to protective earthing; and determine, based on a second measurement value between a negative input terminal of the inverter circuit and the earthing point, whether the negative input terminal of the inverter circuit is short-circuited or has low resistance to protective earthing, where the first relay is one of in M relays and is connected to at least one impedor in parallel, and the second relays are relays other than the first relay in the M relays.

A leakage detection system for a battery pack of a vehicle may include detection circuitry having a first side connecting a positive terminal of the pack to ground and a second side connecting a negative terminal of the pack to ground, and including no more than one switch among the sides. The system may also include measurement circuitry configured to measure a voltage across a resistor of one of the sides when the switch is open and closed, and a controller programmed to output a leakage associated with the battery pack based on the voltage.

An insulation resistance detection circuit, detection method, and detection apparatus are provided. The circuit includes an alternating-current signal source, a resonant cavity, a first resistor, a second resistor, a third resistor, a fourth resistor, a first switch, and a second switch. The alternating-current signal source is sequentially connected to the first resistor, the resonant cavity, the first switch, the second resistor, and the third resistor in series to form a loop. The first resistor is connected to a positive electrode of the alternating-current signal source, and the third resistor is connected to a negative electrode of the alternating-current signal source. One end of the second switch is connected to a negative electrode of a to-be-detected battery, the other end of the second switch is connected to the fourth resistor, and the other end of the fourth resistor is connected to ground.

Methods and devices for insulation monitoring of an ungrounded IT power supply system having at least two phase conductors includes determining an insulation resistance separately for each phase conductor using a separate response value. In one embodiment of the invention, relevant current and voltage distributions are calculated. In another embodiment, a change time window is set within which a second response value is activated. In yet another embodiment, an option of shutting down/continuing operation of the IT power supply system is offered.

A fuel cell vehicle insulation resistor fault detection system, comprising: a stack, a stack pre-charge circuit, a power cell, a power distribution controller, a high voltage component, a VCU (vehicle control unit) and at least one insulation detector. The stack is connected to the stack pre-charge circuit, the stack pre-charge circuit is connected to the power cell, the power cell is connected to the power distribution controller, the power distribution controller is connected to the high voltage component and the VCU is connected to the insulation detector. When the insulation detector is used to detect whether the insulation resistor of the stack is faulty, the stack is connected to the insulation detector; when the insulation detector is used to detect whether the insulation resistor of the power cell is faulty, the power cell is connected to the insulation detector; and when the insulation detector is used to detect whether the insulation resistor of the high voltage component is faulty, the power distribution controller is connected to the insulation detector. When an insulation resistor of the fuel cell vehicle is faulty, the source of the insulation resistor fault can be located in time.

In monitoring an isolation of an ungrounded power grid an AC voltage source is connected to the power grid via at least one test resistor. A test signal with a periodic continuous voltage course with regard to ground and with a frequency is applied to the power grid by means of the AC voltage source. A leakage current flowing due to the test signal is measured; and an ohmic isolation resistance is determined from the leakage current. The frequency of the test signal is varied such that an active current part of the leakage current keeps a predetermined recommended value at varying leakage capacitances of the power grid. This provides for a desired level of accuracy at maximum speed of isolation or ground fault detection.

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.

A power-supply monitoring device includes a capacitor that is connected to an insulated electric power source to execute charging/discharging. A power-supply monitoring device including this capacitor forms a charging path for detecting deterioration in an insulation resistance of an electric power source, and detects a voltage of the capacitor when being charged through this charging path. A vehicle controller specifies an abnormal part based on whether or not the voltage of the capacitor detected by the power-supply monitoring device is within a predetermined range.