The product is mainly used in coal mine with explosive dangerous gas (methane mixture). The power supply system with rated voltage of 10 kV, 6 kV, rated frequency of 50 Hz and non-direct grounding of three-phase AC neutral point is used to control, measure and protect the power supply system with rated voltage of 10 kV, 6 kV, rated frequency of 50 Hz and non-direct grounding of three-phase AC neutral point.