Frequency-tuned resonant test systems for HV on-site testing of XLPE cables and SF6 insulated apparatus

The principle, that a high-voltage test should simulate operational stresses, is valid for on-site tests too. Therefore, a high-voltage AC test considers the possible failure mechanisms of the insulation correctly, whereas a DC test cannot fulfil this principle for AC apparatus. However, an on-site AC test of XLPE high-voltage cables and SF₆ insulated systems (GIS, GIT) demands both, a quite high test voltage and a high test power. Therefore, traditional test transformers or also resonant circuits with tuneable reactors become too heavy, but a frequency-tuned resonant circuit of variable frequency can solve the problem. The paper describes the characteristics, the design and the frequency-tuned circuits for on-site partial discharge measurement. It is demonstrated that on-site tests at variable frequency have many advantages-they can be handled easily, can be completed by partial discharge measurement, and offer the chance for efficient HV on-site testing in the future