Double-circuit line non-in-phase cross-line earth fault judgment method based on trigonometric function

Abstract

The invention discloses a double-circuit line non-in-phase cross-line earth fault judgment method based on a trigonometric function. The method comprises the steps that the fault phase voltage, the fault phase current and the zero-sequence current at the protection installing position of the line I of same-tower double-circuit lines are firstly measured the zero-sequence compensating current of the line I of the same-tower double-circuit lines is calculated, the phase angle of the fault phase voltage of the protection installing position of the line I of the same-tower double-circuit lines ahead of the zero-sequence current injected in a non-in-phase cross-line earth fault point is calculated, the fault phase voltage of the line I of the same-tower double-circuit lines within the protection setting range is calculated, and the accurate judgment on a double-circuit line non-in-phase cross-line earth fault is achieved through the amplitude characteristic of the trigonometric function of the vector relation between electrical quantities of single ends after the double-circuit line non-in-phase cross-line earth fault happens. The judgment result is not influenced by factors such as zero-sequence mutual inductance between lines, transition resistance, load currents and electric power system operation modes, and the double-circuit line non-in-phase cross-line earth fault judgment method based on the trigonometric function is applicable to same-tower double-circuit line single-end electric quantity backup protection.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a method for discriminating grounding faults of non-identical phases across lines of double-circuit lines based on trigonometric functions. Background technique [0002] The double-circuit line paralleled on the same pole has a small footprint, low cost, and stable and reliable operation when connected to the grid. It has become a common transmission line connection method in the power system. There is zero-sequence mutual inductance between double-circuit lines on the same pole, and the zero-sequence mutual inductance affects the zero-sequence compensation coefficient, thereby generating additional impedance. The additional impedance caused by the zero-sequence mutual inductance will cause the fault impedance measured by the protection device to be greater than the actual fault When a ground fault occurs near the protection setting range in the dou...

AI Technical Summary

Problems solved by technology

Since the origin of the coordinates is located on the boundary of the action characteristic circle, there is a possibility of misoperation for a ground fault at the outlet in the opposite direction of protection, and the larger the transition resistance is, the easier it is for the protection to malfunction when there is a ground fault at the outlet in the opposite direction.

[0005] Due to the strong zero-sequence mutual inductance between double-circuit lines on the same pole, the existing grounding distance protection cannot obtain the zero-sequence current of the other circuit, and the algorithm model cannot eliminate the influence of zero-sequence mutual inductance between lines. Due to the influence of zero-sequence mutual inductance, when the traditional grounding distance protection is applied to parallel double-circuit lines on the same pole, its protection range will be greatly expanded. Faults in the protection setting range often have steady-state overshoots, which makes it easy to malfunction when faults outside the protection area. It is easy to cause a large transfer of power flow and cause large-scale power outages

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