Bipolar parallel multi-terminal direct current power transmission system electric current modulus longitudinal differential protection method

Abstract

The invention discloses a bipolar parallel multi-terminal direct current power transmission system electric current modulus longitudinal differential protection method. The method comprises the steps that digital sampling and modulus decoupling are conducted in each converter station of the parallel system, and 1, 0-mode voltage and electric current are obtained; one point on the direct current main line is selected as the destination point of calculation, starting from each converter station, the line terminal voltage, the electric current up to the destination point are calculated segment-by-segment and the 1, 0-mode differential current is obtained through the overlay at the destination point. If the 1-mode differential current is greater than the fault threshold, the fault is an internal area fault, otherwise the fault is an external fault; if the 0-mode differential current is greater than the threshold, the fault is a positive pole grounding fault; if the 0-mode differential current is less than the threshold, the fault is a negative pole grounding fault; if the 0-mode differential current is between the positive and negative selection thresholds, the fault is an inter polar short-circuit fault. The differential protection method is fast in movement speed, high in transition resistance capability, and is not under the influence of capacitive current in distribution, and can be extended to arbitrary end parallel direct current systems, in principle can recognize the fault type and is strong in adaptability. According to the differential protection method, the required sampling rate is low, the method is easy to implement and has practical value.

Description

technical field [0001] The invention relates to the field of relay protection for direct current transmission in electric power systems, in particular to current longitudinal protection for super / ultra-high voltage direct current transmission lines. Background technique [0002] The development of double-terminal direct current transmission system in my country is becoming more and more mature, but there are problems such as single location of the sending and receiving end system of the interconnection system, and tight line channels. The multi-terminal DC transmission system has the characteristics of large transmission power, low line cost and flexible control mode of the traditional DC transmission system, and overcomes the problems existing in the double-terminal system. It is the development trend of the future DC transmission technology. The double-terminal DC transmission systems that have been built include the Italy-Corsica-Sardinia three-terminal DC system and the ...

AI Technical Summary

Problems solved by technology

Traditional differential protection is affected by distributed capacitive current, and its quick action and reliability are not high

Chinese patents CN200910022923.6 and CN201110349980.2 respectively propose DC line differential protection methods based on distributed parameter models for double-terminal and three-terminal DC transmission systems, but these methods are not suitable for multi-terminal systems, and the methods themselves cannot distinguish single-terminal Pole fault and inter-pole fault and fault pole selection

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