Method and circuit arrangement for the insulation testing of test pieces with large intrinsic capacitance and for the localisation of faults in power cables

摘要

A description is given of a method and circuit arrangement for the insulation testing of test pieces with large intrinsic capacitance and for the localisation of faults in power cables The method is characterised in that the high-voltage transformer is electronically driven on its primary side via a charging capacitor with a very low frequency voltage, which is overlaid with a higher frequency, and that on the secondary side of the high-voltage transformer, the component with the higher frequency is synchronously filtered out (demodulated), and that the high secondary voltage with low frequency is fed to the test piece, and that the measuring device is connected with the test piece via a switching device in the pulse-free period to the high-voltage transformer. The circuit arrangements for carrying out the method provide essentially for the primary-side driving of the high-voltage transformer in the form of pulse packets or in the form of a slowly changing voltage with superimposed square-wave pulses. Provided for demodulation on the secondary side of the high-voltage transformer is either a voltage-dependent resistor or spark gaps or a motor-driven, rotating synchronous switch.