About the need to disconnect double earth faults without time delay

The study is devoted to the analysis of real emer-gency operation in the circuit with isolated neutral of 10 kV on the example of the case which took place in Ko-stroma Region from the emergence of single-phase earth fault. The analysis which was carried out using the method of phase coordinates established the sequence of events succession, their influencing each other, and also revealed what served as the reason of damage of the equipment of transformer substation of 10/0.4 kV, the damages of the property and equipment of consum-ers of the village of Yakovlevo of Kologrivsky Region of Kostroma area. The purpose of the study was to show high danger of consequences of double short circuits on the earth in networks with isolated neutral and need of their shutdown without time delay. The tasks were to carry out the analysis of difficult emergency operation on the example of the case which arose in the Kostroma Region in the network of 10 kV in 2014; to consider the accident emergence reasons; the sequence of emer-gency events development and their influencing at each other. Considered case shows that for the improvement of the quality and safety of power supply, and also pre-vention of long judicial proceedings it is necessary to distinguish double short circuits on the earth in a net-work from two-phase short circuits accurately, to dis-connect double short circuits on the earth without time delay, to disconnect both feeders with short circuits on the earth if those are available on substation, that the protection against double short circuits on the earth es-tablished on a separate feeder received information on emergency operation on other feeders of substation.