FIELD: electrical engineering.
SUBSTANCE: invention relates to relay protection and automation of electrical networks and is intended to automatically remove overvoltage in an electrical network with an isolated neutral without disconnecting overhead lines (OHL) with a single-phase ground fault (SPGF). Each of OHL outgoing from the power source is connected through an isolation transformer. For an isolation transformer, the possibility of synchronous switching of the primary and secondary windings according to the star scheme is provided by means of the first switching device with remote control. The contacts of the first switching device are open in the normal state of the electrical network. At the same time, phase-by-phase shunting of the input and output terminals of the isolating transformer is provided by means of normally closed contacts of the second switching device with remote control. The contacts of the second switching device open when a double ground fault current (DGF) flows in OHL with SGF, during a short-term connection to the ground of one of the two phases of the low-voltage busbars of the power transformer through a low-resistance grounding resistor. Simultaneously with this normally open contact of the second switching device ensure that the neutral of the secondary winding of the isolation transformer supplying power to OHL with SGF is connected to the ground through a high-resistance resistor. After elimination of SGF on OHL, a command is formed to remotely return the contacts of the first and second switching devices to their original position, thereby ensuring the connection of the restored OHL to the power source bypassing the isolating transformer.
EFFECT: increasing the reliability of the power grid equipment, as well as ensuring high reliability and safety of power supply to consumers.
1 cl, 1 dwg
