Method for locking zero-sequence directional elements applied to line with no transposition and double circuits on same tower

Abstract

The invention discloses a method for locking zero-sequence directional elements applied to a line with no transposition and double circuits on a same tower. The method comprises the steps of extracting the components of the positive sequence currents, the components of the negative-sequence currents and the components of the zero-sequence currents of a protected line after a longitudinal zero-sequence direction protection device is started; judging the size relation between the ratio of the components of the zero-sequence currents and the components of the positive sequence currents and a threshold value k1; judging the size relation between the ratio of the components of the negative-sequence currents and the components of the positive sequence currents and a threshold value k2 if the ratio of the components of the zero-sequence currents and the components of the positive sequence currents is smaller than the threshold value k1, judging as a ground fault when the ratio of the components of the negative-sequence currents and the components of the positive sequence currents is smaller than the threshold value k2, and opening the zero-sequence directional elements; judging as an interphase un-grounded fault when the ratio of the components of the negative-sequence currents and the components of the positive sequence currents is larger than the threshold value k2, and locking the zero-sequence directional elements. The purpose of correctly distinguishing the ground fault and an interphase fault of the line with no transposition and double circuits on the same tower can be achieved.

Description

technical field [0001] The invention relates to the field of power systems, in particular to a method for blocking zero-sequence directional elements of double-circuit lines on the same tower without transposition. Background technique [0002] At present, longitudinal zero-sequence directional protection is one of the main protections of transmission lines, which has the advantages of high sensitivity and stable zero-sequence fault network structure. When a grounding fault occurs on the transmission line, when the zero-sequence current and zero-sequence voltage at the protection installation reach the threshold value, the zero-sequence directional element is activated to distinguish the zero-sequence direction. When the zero-sequence directional elements on both sides of the transmission line are judged to be faults in the forward direction, the protection action trips. [0003] For a transmission line with uniform transposition, the three-phase parameters are symmetrical,...

AI Technical Summary

Problems solved by technology

In the actual operation of the project, it often occurs that the double-circuit line without transposition on the same tower will cause incorrect action of the longitudinal direction protection caused by the zero-sequence directional element misstarting

Images