Abstract:

The three-phase 5-pole measuring voltage transformers are installed in the mine medium voltage power network to measure the line-phase voltage and the zero-sequence voltage 3U0. They normally have to operate in grounded primary winding and therefore also contribute to the zero-sequence current component of a single-phase earth fault inside and outside the network. The article presents some results of a study of the influence of measuring transformers on the magnitude and angle of phase angle of the zero-sequence current, depending on the insulation parameters of the electrical network compared to the ground, the neutrality of the network and the number of measuring transformers connected to it when a single-phase earth fault occurs.