The working principle of the developed monitoring system is to assess comprehensively the insulation status of DC feeder cable through monitoring discharge signal and DC leakage current signal.

This paper proposes a detecting method of the unarmored cable insulation by using DC leakage current, which transforms the synchronous measurement of the cable input-output current into a precise measurement of the input current, so as to simplify the detecting method and enhance the precision of the current measurement.

Analysis and treatment for anomaly of direct-current leakage of generator stator winding caused by hydrogen cooler fault;

A simple method of detecting leakage current to ground;

Technological analysis of measuring leakage current under condition of exerting DC voltage on winding ends for 200MW generator stator windings;

Design of on-line monitoring for leak current of insulating casing;

The average leak current is less than 0.

Adding a appropriate amount of SiO2 to ZnO ceramics leads to incrcase a value and voltage gradient of the varistor, to decrease leakage current and to raise withstanding surge current, that results in making ZnO varistors with excellent performance.