Device for detecting partial discharge in an insulation system of rotary electric machines

A device for determining partial discharge in an insulation system of a rotating electrical machine with low capacitance decoupling, the device comprising:

• a coupler as a high pass;
• an adapter device connected or connectable to the coupler, wherein the adapter device comprises:
• a frequency separating filter for dividing a decoupled signal provided by the coupler into a high frequency signal and a low frequency signal, wherein the frequency separating filter is a waveguide transformer;
• a mixer for the high frequency signal and the low frequency signal for converting the high frequency signal,
• an output where the converted high frequency signal is tapped for evaluation by an evaluation device connectable to the adapter device;
• wherein the adapter device comprises a high pass filter and a first low pass filter, wherein outputs of the frequency separating filter are connected to the high pass filter and the first low pass filter, and wherein an output of the high pass filter and an output of the first low pass filter are connected to the mixer;
• wherein the adapter device comprises a second low pass filter and comprises at least one switch downstream of the output of the high pass filter, wherein the at least one switch is switchable such that the output of the high pass filter is either connected to the second low pass filter or bypasses the second low pass filter so that the first low pass filter and the high pass filter or the first low pass filter and the high pass filter with the downstream second low pass filter are connected to the mixer.