“Virtual” power line method to correct the calculation of current ground faults in the parallel overhead transmission lines 110–220 kV

Abstract

The mutual induction between the phase wires of the different overhead power lines located close to each other causes unbalanced redistribution of currents in the line wires. This leads to emergence of the out-of-balance zero sequence current, which affects negatively on the sensitivity of the zero-sequence current protection. It is impossible to estimate such out-of-balance current by the means of typical calculation programs for short circuit currents. This paper describes the method of “virtual” lines for an extra correction of the values of zero-sequence currents during the 110–220 kV current ground faults occurring in the overhead power lines. There is an example of using this method for three 220 kV parallel overhead lines passing close to each other.