Method and device for monitoring the insulation of ungrounded DC and AC voltage networks

摘要

The invention relates to a method and a device for monitoring the insulation of an ungrounded DC and/or AC voltage network. The method includes the following steps: (a) generating a measurement DC voltage Umess= that is connected to a ground on one side for a tvar; predeterminable measuring time frame tvar; (b) generating and superposing at least one measurement AC voltage Umess˜ connected to a ground and having a measurement duration tcons with the measurement DC voltage Umess− for forming a total measurement voltage Umess; (c) feeding the total measurement voltage Umess into the voltage network to be monitored; and (d) determining an insulating resistance R= from the measurement DC voltage Umess− and an insulating impedance Z from the measurement AC voltage Umess˜. The devise is configured to carry out the above method. The method and the device are suited in particular for monitoring the insulation in electric and hybrid vehicles.

主权项

1. A method for monitoring the insulation of an unearthed DC voltage network or an unearthed AC voltage network, or an unearthed DC voltage network and an unearthed DC-AC voltage network, comprising the steps of:
(a) generating a DC measurement voltage Umess= connected on one side to ground for a predeterminable measurement period tvar; (b) generating and superpositioning at least one AC measurement voltage Umess˜ connected to ground with a periodic time tcons onto the DC measurement voltage Umess= for the purpose of forming a total measurement voltage Umess; (c) introducing the total measurement voltage Umess into the voltage network to be monitored; and (d) determining an insulation resistance R= from the DC measurement voltage Umess= and an insulation impedance Z˜ from the AC measurement voltage Umess˜; (e) measuring a total measured current Imess generated by the total measurement voltage Umess, when determining the insulation resistance R= and the insulation impedance Z˜; (f) dividing the total measured current Imess into a DC measured current Imess= and an AC measured current Imess˜; (g) determining the insulation resistance R= based on the DC measured current Imess= and determining the insulation impedance Z˜ based on the AC measured current Imess˜; (h) determining an insulation resistance R˜ and a leakage capacitance C˜ from the insulation impedance Z˜; and (i) outputting the insulation resistance R˜ as an insulation resistance of the voltage network when there is a voltage network-specific small leakage capacitance and outputting the insulation resistance R= as an insulation resistance of the voltage network, when there is a large leakage capacitance.