Experimental investigations of overvoltages in 6 kV station service cable networks of thermal power plants

The paper presents the results of experimental investigations of overvoltages on 6 kV isolated neutral station service cable networks of thermal power plants. On the basis of these investigations, certain measures are proposed for limiting overvoltages and for the reliability of station service of thermal power plants. The cables are shielded and have three leads with cross-linked insulation. The shield was grounded at both ends. The overvoltages were recorded with capacitive voltage measurement systems made at the Nikola Tesla institute. Wideband capacitive voltage measurement systems recorded a flat response from below power frequencies to 10 MHz. Investigations of overvoltages were performed for: appearance and interruption of metal earth faults; intermittent earth faults; switching operation of HV motors switchgear; switching operation of transformers switchgear; and transfer of the network supply from one transformer to another.