Form peak valley detection method for identifying internal and external faults of ultra high voltage direct current transmission line

Abstract

The invention relates to a form peak valley detection method for identifying the internal and external faults of an ultra high voltage direct current (UHV DC) transmission line, comprising the following steps: after a fault occurs to a DC line, starting a starting element; using Karenbauer transform to perform electromagnetic decoupling on the two-pole DC voltage transient signal detected at the relay-installed place of a rectifier side to obtain an aerial mode voltage; after 5ms of the occurrence of a fault, using Top-Hat and Bottom-Hat operators to compute disperse aerial mode voltage signals of which the sampling interval is 0.1 and the sampling length is 50; extracting the peak and valley data contained in the aerial mode voltage signals to obtain a computing result which is two groups of data the length of which is 50, and solving the absolute values of the two groups of data, wherein the solved maximum value of the absolute values of the two groups of data is the maximum peak valley value of the aerial mode voltage. The fault is distinguished to be an internal fault or an external fault according to the value of the maximum peak valley value. A large number of simulation results show that the method of the invention has good effect.

Description

technical field [0001] The invention relates to the technical field of relay protection of electric power systems, in particular to a peak-valley detection method for identifying internal and external faults of ultra-high voltage direct current transmission lines. Background technique [0002] At present, traveling wave protection is widely used in the world as the main protection of HVDC transmission line protection. It uses the current and voltage traveling waves transmitted at the moment of fault to form ultra-high-speed line protection. Moreover, DC line protection provided by ABB and SIEMENS is adopted in most projects. Its protection is based on the current gradient, voltage traveling wave conversion rate and voltage traveling wave mutation as the criterion, but its protection is easily affected by transition resistance, especially when an external fault occurs, the fault traveling wave passes through the smoothing reactance at the end of the DC line If the voltage co...

AI Technical Summary

Problems solved by technology

Its protection is based on the current gradient, voltage traveling wave conversion rate and voltage traveling wave mutation as the criterion, but its protection is easily affected by transition resistance, especially when an external fault occurs, the fault traveling wave passes through the smoothing reactance at the end of the DC line If the voltage conversion rate is reduced, it will easily cause protection malfunction or refusal to operate, which will have a great impact on the stable operation of the DC system.

Therefore, the main protection of the DC system based on the change rate criterion is easily affected by transition resistance, noise interference, fault distance, etc.

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