High voltage test circuit for harmonic and impulse voltage stress

The paper deals with testing possibilities of discharge activity influence to a medium voltage cable system. It was observed that the discharge activity in insulation systems of high voltage devices is higher when the power electronic is present. The aim is to create a test circuit which will simulate the influence of superposed impulses and harmonics on power frequency to insulation system condition. Further, the selection of suitable voltage and current sources, including their position in test circuit, is discussed. Possibility of using nanocrystalline core for proposed test circuit was verified by measurement of amplitude frequency characteristic. The influence of harmonics and effect of impulses which are generated by power electronics to discharge activity was investigated. The discharge activity was observed on Trichel cylinder and on sample which simulates medium voltage cable with small cavity in insulation. The various distortions of sinusoidal voltage were applied to the test objects. At the same time the partial discharge activity was measured and processed by software to evaluate partial discharge parameters.