Foerfarande Foer upptaeckande och lokalisering av ett jordslutningsfel med stor resistans i ett eldistributionsnaet

摘要

The invention relates to detecting and locating a high-resistance earth fault of an electric power network. In the method, the substation is measured at the neutral point voltage (uU/uo) in phasor format. According to the method, the phase leg voltages of the network are measured in phasor format, the zero-sequence voltage phasor representing the neutral point voltage (uU/uo) is formed as the phasor sum of the measured phase leg voltages, the zero-sequence impedance (uZ/uo) is computed by means of a network model, whereafter the zero-sequence voltage (uU/uo) is compared in phasor format with the phasors of the network phase leg voltages (uU/uv) and the resultant zero-sequence impedance (uZ/uo) of the network, and from these computed variables are derived the fault impedances (uZ/uf) for each phase leg, whereafter the faulted leg is identified as the leg having the greatest value of the real part of the fault impedance (uZ/uf).