Abstract
The paper proposes an algorithm of a mathematical model of devices for digital protection from single-phase earth faults in 6-10 kV networks with automatic change of setpoint. It is achieved using the Mealy machine (Moore machine) for formalization and automatization of designing digital logic devices to determine a value of current single-phase earth fault and insulation conditions of 6-10 kV production networks at mining enterprises. The obtained flow-graph of the algorithm and the graph of the Mealy machine for digital devices are the basis for development of the control program, which defines the order for device operation. The developed algorithm for automatic determining the single-phase earth fault current in the 6-10 kV network provides the basis for developing a method and the device for automatic determining the single-phase earth fault current in the 6-10 kV network with an unambiguous definition of the necessary functional elements and their relationships.