Phase relevant current differential protection method

Abstract

The invention relates to the power system relay protection field, in particular to a phase relevant current differential protection method. In order to improve the motion sensitivity of differential protection at the time of internal failure and the brake reliability at the time of external failure to the most extent, the invention adopts the technical scheme. A phase relevant current differential protection method adopts the circuital phase relevant current differential protection criterion: Im+KIn cos Phi>Idz. In the formula, Im and In respectively represent current phasor collected and calculated to be obtained at two sides in the current differential protection and Phi is an angle between Im<&> and In<&>. When the angle of Im<&> is larger than the angle of Im<&>, it is positive. The positive direction of Im<&> and In<&> is from busbar flow to a component to be protected. K is brake coefficient. Idz is the fixed threshold of the current differential protection. The invention is mainly applied to the power system relay protection.

Description

technical field The invention relates to the field of electric power system relay protection, in particular to a phase-related current differential protection method. Background technique Current differential protection is one of the most widely used protection principles in power systems. The current differential protection principle is based on Kirchhoff's current law, that is, the sum of the currents flowing to a node is zero. This principle is known as a fast protection with absolute selectivity. The traditional current differential protection adopts the method of ratio braking, relying on the braking effect of the braking current, so that the setting value of the protection action changes with the change of the current passing through the protected element. However, this braking method also has inherent disadvantages: when the braking coefficient is small, the braking performance is low when an external fault occurs, which may cause malfunction of external faults and...

AI Technical Summary

Problems solved by technology

However, this braking method also has inherent disadvantages: when the braking coefficient is small, the braking performance is low when an external fault occurs, which may cause malfunction of external faults and reduce the reliability of relay protection; When the dynamic coefficient is large, the braking performance is relatively high when there is a fault in the zone, and it will affect the sensitivity of the current differential protection when there is an internal fault.

In addition, the traditional current differential protection may have misoperation problems when there is a fault outside the zone and the current transformer is saturated, while the sensitivity of the current differential protection when the fault passes through the transition resistance in the zone still needs to be improved and developed.

Images