Frequent operational switching in quarry distribution networks with voltage 6-10 kV change their parameters in a wide range. This causes possible changes in the magnitudes of earth fault currents for individual feeders and for the whole substation, as a whole ...

Of the many variants of earth protection devices, the optimal one for distribution networks is the zero-sequence power direction relay with electronic contactless circuit.

The study of transients of a certain level or phase of voltage at moments of short-circuit at multiple repetition is complicated by a number of difficulties: 1) short-circuit must occur each time at a given phase of voltage network; 2) the time of the closed state of the circuit (network) must exceed the duration of the transient with the subsequent automatic recovery of network parameters; observation or photographing the beginning of the leading edge of the transient process becomes impossible, since the entire process is conducted mainly with the help of cathode oscilloscopes.