A method and a monitoring device for selectively determining a partial system leakage capacitance in an ungrounded power supply system having a main system and at least one partial system. An extended insulation monitoring system is configured for determining an overall system leakage capacitance of the power supply system; an extended insulation fault location system for determining an ohmic and a capacitive partial test-current portion of a partial test current captured in the respective partial system; and an impedance evaluation system for determining a partial insulation resistance and a partial system leakage capacitance for each partial system to be monitored are provided. For preventing the entire ungrounded power supply system from being switched off, the fundamental idea of the present invention is advantageously based on identifying in which partial system a critical increase of a partial system leakage capacitance has taken place.

An insulation detector for highly accurately detecting or measuring, with a simple configuration, insulation resistance of a load or an apparatus to a ground or a housing and connected to an electric apparatus including one or both of an intra-apparatus capacitor and a battery, the insulation detector including an intra-insulation detector capacitor, a voltage detecting unit that detects a voltage of the intra-insulation detector capacitor, and a current-path forming switch for connecting the ground or the housing, the intra-apparatus capacitor, and the intra-insulation detector capacitor in series and forming a current path including insulation resistance of the electric apparatus. The insulation detector measures the insulation resistance by measuring a time constant of a change in the voltage of the intra-insulation detector capacitor. A capacitance value of the intra-insulation detector capacitor is a value negligible in the measurement of the insulation resistance compared with a capacitance value of the intra-apparatus capacitor.

Electrical bus isolation is detected for an electrified vehicle having a DC power source connected to positive and negative buses. The positive bus is connected to chassis ground, and a resulting first current is sensed that flows through a negative bus leakage resistance and a balanced leakage resistance. The negative bus is connected to chassis ground, and a resulting second current is sensed that flows through a negative bus leakage resistance and a balanced leakage resistance. The positive and negative bus leakage resistances are estimated in response to respective ratios of the first and second currents. A larger one of the estimated bus leakage resistances is selected as a balanced leakage resistance. Failure of a device connected to a bus (such as a wiring cable or a fuel cell) is predicted in response to predetermined decreases in the estimated balanced leakage resistance over time.

A method and device for determining insulation resistances in a motor vehicle. The device includes a control device which, in at least two measuring intervals, controls a respective operating state of at least one power converter of the motor vehicle, which is conductively connected to the traction energy store. The device further comprises a measuring device having a measuring terminal, which is conductively connected or connectable to least one DC voltage pole of an electric traction energy store of the motor vehicle, and a ground terminal which is conductively connected or connectable to a reference potential of the motor vehicle. The measuring device, in the at least two measuring intervals, respectively measures a conductance between the measuring terminal and the ground terminal. The device further comprises a calculation device, which determines the insulation resistances as a function of the at least two measured conductances and the operating states controlled.

A method and device for determining a division of a total insulation resistance and of a total system leakage capacitance in an ungrounded power supply system. The basic idea is to determine how the total insulation resistance is divided into partial insulation resistances and how the total system leakage capacitance is divided into partial system leakage capacitances between the active conductors of the ungrounded power supply system from displacement voltages measured between each of the active conductors of the ungrounded power supply system based on values determined in advance for the total insulation resistance and for the total system leakage capacitance of the ungrounded power supply system. By evaluating the displacement voltages in terms of their changes in amplitude, their frequency and their phasing, conclusions can be drawn as to the division of the total insulation resistance and of the total system leakage capacitance between the individual active conductors.

A method for measuring insulation resistance in an inverter that has a DC link circuit and a bridge circuit, connected to the DC link circuit, for driving an AC current via a bridge center tap is disclosed. The method includes connecting the bridge center tap to a grounding point, successively connecting, by way of the bridge circuit, the bridge center tap that is connected to the grounding point to two points of the ungrounded DC link circuit that differ in terms of voltage, and measuring the current flowing from the two points that differ in terms of voltage to the grounding point. The two points of the ungrounded DC link circuit that differ in terms of voltage are selected from a group of points that includes at least one intermediate voltage point of the DC link circuit in addition to two end points of the DC link circuit, such that the voltages present between the two points that differ in terms of voltage and the grounding point do not exceed a predefined voltage limit value.

An insulation detection method includes: a first and second equivalent resistances are calculated; the less one of the first and second equivalent resistances is taken as a first insulation resistance, which is an insulation resistance of the high voltage circuit on the side where the battery pack locates relative to the reference potential terminal; when the first insulation resistance is normal, the switch unit is closed, and a second insulation resistance is calculated according to the first and second equivalent resistances, voltages of a first and second sampling point when the switch unit is closed; the second insulation resistance is an insulation resistance of the high voltage circuit on the side where the load locates relative to the reference potential terminal; the insulation state of the high voltage circuit on the side where the load locates is determined according to the second insulation resistance.

An inverter for a photovoltaic apparatus, which includes a DC section, a DC/AC conversion section, an AC section and a control section. The DC section includes a plurality of DC input channels each including a DC/DC converter electrically connected between input terminals and the output terminals of the DC input channels. The inverter includes a measuring circuit arrangement adapted to measure an isolation resistance of the photovoltaic strings electrically connected with the DC input channels, when the inverter operates in predefined test conditions.

A circuit includes: an isolation power module, a first sampling module, a first sampling point, a second sampling module, a second sampling point, 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.

The present application discloses an insulation detection circuit, a method and a battery management system. The circuit includes: a first voltage dividing module, where, one end of the first voltage dividing module is connected to a positive electrode of a power battery to be detected, and the other end of the first voltage dividing module is connected to a first isolation module and a second voltage dividing module respectively; the second voltage dividing module, connected to a negative electrode of the power battery to be detected; the first isolation module, connected to one end of a sampling module; the sampling module, where, the other end of the sampling module is connected to one end of a signal generating module; the signal generating module, where, the other end of the signal generating module is connected to power ground; and the processing module.