METHOD OF DETERMINING POINT AND DISTANCE TO SINGLE-PHASE GROUND FAULT IN 6-35 kV ELECTRIC NETWORKS WITH ISOLATED OR COMPENSATED NEUTRAL POINT

摘要

FIELD: electrical engineering.;SUBSTANCE: invention relates to methods of locating damages in 6–35 kV electric networks with isolated or compensated neutral. Essence: relay protection device is installed with possibility of recording phase currents and voltages of each connection of distribution device, as well as with possibility of fixation of single-phase short circuits to ground in each connection of distribution device, determination of location and calculation of distance to place of single-phase ground fault. Ballast resistance is connected to reserve cell of distribution device bus section, in which there is a ground fault. High-voltage breaker of the backup cell is switched on, providing short-circuit current flow in the undamaged phase through the ballast resistance of the short-circuited value and time. Mutual reactive resistances of the damaged connection are taken into account when calculating the distance to single-phase ground fault according to the expression l_{1 =} | Im (U₁) ∙ Re (I₁) - Im (I₁) ∙ Re (U₁) | / {[Re² (I₁) + Im²(I₁)] ∙ | x_l + x_m∙ (I₂ + I₃) /I₁|}, where Re (I₁) and Im (I₁) Is real and imaginary values of fixed current I₁ ground fault of the damaged phase of the line; Re (U₁) and Im (U₁) Is the real and imaginary values of the detected voltage of the damaged phase of the line; I₂ and I₃ - fixed currents of undamaged connection phases with single-phase ground fau x_m is specific resistance of mutual induction of phases of damaged connection; x_l is proper specific reactive resistance of the damaged phase.;EFFECT: technical result is fast and accurate determination of distance to single-phase ground fault location.;1 cl, 1 dwg