Pilot protection method of high-voltage direct current transmission line based on S transformation

Abstract

The invention discloses a pilot protection method of a high-voltage direct current transmission line based on S transformation. The pilot protection method comprises: collecting voltage and current of a protection element connected with positive and negative electrodes of the direct current transmission line, and filtering the voltage and the current; extracting voltage and current mutation data within a set time after a fault, and carrying out S transformation on the mutation data to obtain a complex time-frequency S matrix of voltage and current signals; calculating S transformation phase angles of the voltage and current mutations at each sampling point and a mean of the phase angle difference thereof; establishing a protection criterion of the direct current transmission line, and identifying faults inside and outside the sample space based on the S transformation phase angles of the voltage and current mutations according to the protection criterion; if the fault is a fault inside the sample space, comparing the transient energy of S transformation zero frequency bands of the voltage mutations of the positive and negative electrodes via a rectifying side protection device to judge a fault pole. The pilot protection method disclosed by the invention does not need to synchronize data on both ends of the direct current transmission line and only requires an inversion side to transmit a fault direction identification result to the rectifying side.

Description

technical field [0001] The invention relates to an S-transform-based longitudinal protection method for high-voltage direct current transmission lines. Background technique [0002] UHVDC transmission technology originated in the 1960s. Due to the rapid development of converter equipment, HVDC transmission technology has been widely used in the world in recent years. HVDC transmission has the advantages of stable power transmission, large transmission capacity, high transmission efficiency, and long-distance transmission. It has become an important way for power transmission in large energy bases and interconnection of asynchronous grids. UHV DC lines have long transmission distances, high power transmission, complex terrain, and are prone to faults caused by lightning and storms. Whether line protection can quickly and reliably detect faults is of great significance to the safe operation of DC transmission systems. [0003] The current relay protection technology for DC tr...

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Problems solved by technology

[0009] "Anovelwhole-linequick-actionprotectionprincipleforHVDCtransmissionlinesusingone-endvoltage" and "Anewwhole-linequick-actionprotectionprincipleforHVDCtransmissionlinesusingone-endcurrent" judge whether the integral value of single-end voltage or single-end current in a specific frequency band exceeds the set threshold to distinguish internal and external faults, and its action The speed is fast, but the sensitivity of the protection may not meet the requirements when a remote fault occurs on a long line

[0010] "Transient Voltage Traveling Wave Protection of HVDC Transmission Lines Based on Wavelet Transform" conducts multi-scale analysis of transient voltage on the basis of wavelet analysis, uses the high and low frequency energy differences of transient quantities to construct protection criteria, and can correctly judge faults. However, the calculation results of wavelet transform are easily affected by wavelet base selection and noise.

[0011] In summary, the existing HVDC transmission line protection methods have their own characteristics, but there is no method with fast action speed, unaffected by transition resistance and lightning interference, and high sensitivity

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