METHOD FOR DETERMINING SINGLE-PHASE FAULT OF FEEDER TO GROUND IN MEDIUM VOLTAGE CABLE NETWORKS

摘要

FIELD: power engineering.;SUBSTANCE: invention relates to electric power engineering and can be used for remote determination in on-line mode of damage point at all types of single-phase earth faults in cable networks with voltage of 6–10 kV. Essence: fixing at feeder input phase voltages u_A, u_B, u_C and zero sequence current 3i_0. Detecting damaged phase. Using n feeder models in phase coordinates with given different values of distance to single-phase ground fault l_f1, l_f2, … l_fn, where n≥3. Single-phase ground fault is simulated in each feeder model on the detected damaged phase. Input of measured phase voltages u_A, u_B, u_C. Input phase currents of each model are transformed to zero-sequence input currents 3î₀₁=î_A1+î_B1+î_C1, 3î₀₂=î_A2+î_B2+î_C2, 3î_0n=î_An+î_Bn+î_Cn. Separating the zero sequence current at the input of feeder 3_i0 and input zero-sequence currents 3î₀₁, 3î₀₂, …3î_0n of each feeder model high-frequency components. At the specified time interval of observation from the moment of occurrence of earth fault of the value of the discrepancy is determined ε₁, ε₂, … ε_n high-frequency zero-sequence current components at input of feeder 3i₀ and high-frequency components of zero-sequence input currents of each model 3î₀₁, 3î₀₂, …3î_0n. Obtained discrepancy values are used to approximate dependence ε=ƒ(l_s) and calculating distance to prospective point of damage l_f.calc, at which value of discrepancy ε minimum.;EFFECT: high accuracy of determining the point of damage.;1 cl, 6 dwg