Single-ended protection method for HVDC transmission line based on specific frequency voltage

Abstract

The invention relates to a specific frequency voltage-based non-unit protection method for a high-voltage DC transmission line. Judgement of internal and external faults is achieved by using the magnitude of non-unit specific frequency voltage change of the high-voltage DC transmission line; and the method comprises the following steps of protecting and collecting a voltage signal of a rectifier side of a high-voltage DC transmission system in real time and extracting specific frequency voltage by using a discrete Fourier algorithm (DFT) of a sliding window, wherein a specific frequency is a parallel resonance frequency of DC filters at two ends of the DC line; calculating an average voltage value as shown in the specification within 3ms, judging whether the average voltage value meets a protection starting criterion or not, and if the average voltage value is greater than a protection starting threshold value, starting protection; calculating a specific frequency voltage change coefficient VC; setting a protection judgement threshold value VCset, comparing the voltage change coefficient with the protection judgement threshold value VCset, thereby achieving identification of the internal and external faults of the high-voltage DC transmission line.

Description

technical field [0001] The invention relates to the field of relay protection for super / ultra-high voltage direct current transmission in power systems, in particular to a method for single-ended protection of high voltage direct current transmission lines based on specific frequency voltages. Background technique [0002] High voltage direct current (HVDC) transmission has been widely used in long-distance power transmission and power system interconnection due to its advantages of large transmission capacity, low loss, and flexible control. HVDC transmission lines often cross complex terrains and operate in extreme climate environments, and the probability of failure is high, which seriously threatens the safe and reliable operation of HVDC transmission systems. [0003] Traditional HVDC transmission line protection mostly uses traveling wave protection as the main protection, undervoltage protection and current differential protection as backup protection. Traveling wave...

AI Technical Summary

Problems solved by technology

[0004] Aiming at the above-mentioned deficiencies in the protection of traditional high-voltage transmission lines, "Single-ended voltage natural frequency method for fault location of ±800kV DC transmission lines" and "Transient protection of ±800kV UHV DC terminal protection method, but there are problems such as extremely high requirements on the sampling frequency and processing capacity of the device, low energy and low reliability of the signal used for discrimination

"High-voltage direct current transmission line full-line quick protection using single-ended current" and "Protection scheme for high-voltage direct current transmission lines based on transient AC current" are based on the DC filter link composed of a smoothing reactor and a DC filter in the DC transmission line Based on the difference in impedance characteristics between internal and external faults, a single-ended protection method for DC transmission lines is proposed based on the transient current characteristics. Small, susceptible to shunt saturation, protection schemes suffer from insufficient reliability and sensitivity

"High-voltage DC transmission line full-line quick-moving protection using filter branch current" proposed a protection method that uses specific frequency current in the DC filter branch to realize full-line quick-moving protection. The protection sensitivity is high, but this method does not consider the distribution of the line Capacitive current, and when the line is long, there is a problem that it is impossible to accurately distinguish the fault at the end of the line from the fault outside the inverter side

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