FIELD: electric networks.
SUBSTANCE: invention relates to electric grids and is intended for rapid changeover of double fault to ground (DFTG), which develops in overhead electric network with isolated neutral in weakened single-phase faults to ground (SFTG). Technical task is solved due to the fact that in case of damage of insulation of overhead power transmission line (OTL), short-term alternate connection of phases of low-voltage buses of power transformer to ground through low-resistance earthing resistor is performed and simultaneous flow of current through low-resistance earthing resistor and opposite phases of overhead transmission lines, having SFTG. Controlling the degree of current increase in the opposite phases of the overhead transmission line, based on which the fact of the existence of the developing DFTG in the electrical network is established, after which the phase sequence order is left unchanged, connected through the automatic protection device to the low-voltage buses for the overhead transmission line, having the phase with the greatest current increase, changing the sequence of all phases for the remaining overhead transmission lines having opposite phases, with the least increase in current so that they are connected to the same phase of low-voltage buses to which the phase of the overhead transmission line having the greatest increase in current is connected. Short-term alternate connection of phases of low-voltage buses of power transformer to ground is performed periodically, at equal intervals of time, and at the beginning of each overhead transmission line a high-voltage disconnector is installed, the earthing contacts of which are connected by means of flexible insulated conductors and high-voltage plug connectors through an automatic protection device to low-voltage buses. Changing the order of alternation of phases for overhead transmission lines, having opposite phases with the least increase in current, is carried out using an autonomous robot-manipulator, by means of which the automatic protection devices installed on these overhead transmission lines are switched to an open position, and then disconnectors and installing in a similar sequence on their de-energized current-carrying parts portable protective earthing, then, with its help, on these overhead transmission lines, corresponding mutual rearrangement of pin current-carrying parts of high-voltage plug connectors relative to their fixing current-carrying parts is performed, after which, by means of an autonomous robot-manipulator, the portable protective grounding is removed from the de-energized current-carrying parts of the disconnectors and automatic protection devices and, in a similar sequence, they are transferred into the closed position, after which each of them operates in the mode of weakened SFTG.
EFFECT: rapid provision of reliable and economically feasible changeover of DFTG into weakened SFTG.
1 cl, 1 dwg
