Increase Effectiveness Functioning of Protection against Single-Phase Ground Fault Electrical Networks Medium Voltage

The article presents the results obtained by studies of the functioning stability of protection against mining enterprise distribution networks single-phase ground faults of 6-10 kV. Analysis of the received results allowed to determine that, in the conditions of significant discontinuity of 6-10 kV network configuration, the currently applied protection against single-phase ground faults does not allow to provide the necessary sensitivity and selectivity of revealing the damaged connection. Application of the separating transformers on outgoing lines with a high capacitive current share ratio in the total ground fault current will increase sensitivity of the protection operation on the outgoing connections. It was found out that, in the event of short-term single-phase ground faults, current protection fails due to the lack of possibility of recording the protection operation algorithms of the zero sequence current value change in the damaged line. A functional scheme and an action algorithm allowing not only to provide a reliable protection operation in the conditions of short-term ground faults, but to implement the function of detecting the hazardous and non-hazardous short circuits and select the protection actuation mode on the basis of this data have been developed. The efficiency of the developed algorithm was confirmed by simulation modeling results.