A DC voltage protection method suitable for AC-DC hybrid power grid

Abstract

The invention discloses a direct current voltage protection method applicable for an alternating current and direct current hybrid power grid. The formula that the absolute value of Up-Un is smaller than Uset1 is judged to be interpolar short circuit criterion P1, the formula that the absolute value of Up+Un is greater than Uset2 is judged to be grounded short circuit criterion P2, the formula that Up+Un is greater than Uset3 is judged to be negative electrode grounded short circuit criterion P3, the formula that Up+Un is smaller than -Uset3 is judged to be positive electrode grounded short circuit criterion P4, and the formula that the absolute value of Up+Un is greater than Uset3 is judged to be single-phase grounded short circuit criterion P5, and direct current voltage protection is carried out by judging whether the above five criteria are established. The direct current voltage protection method disclosed by the invention serves as backup protection of alternating current grounded short circuit, also can serve as backup protection of direct current single-pole grounded short circuit and interpolar short circuit, and provides fault pole selection information of direct currentshort circuit.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a DC voltage protection method suitable for an AC-DC hybrid power grid. Background technique [0002] my country's low-voltage power grid generally adopts a small-current grounding method. When a grounding short circuit occurs, it is difficult to effectively identify the fault due to weak zero-sequence current and unstable arc. Although the three-phase line voltage is symmetrical after a single-phase ground short circuit, the system can maintain operation, but if the fault persists, it may develop into a phase-to-phase short circuit and affect the safe operation of the power grid. Therefore, in the small current grounding system, the single-phase grounding short circuit also needs to be detected in time. In AC systems, common single-phase ground fault detection methods can be divided into steady-state analysis methods, transient analysis methods, a...

AI Technical Summary

Problems solved by technology

However, in medium and low voltage DC systems, there is generally no special DC harmonic protection. After an AC fault occurs, it is difficult to reduce the impact of the fault on the DC system through the existing DC protection configuration, and DC protection needs to be improved.

Images