Half-wavelength transmission line transient state quantity pilot protection method based on post-test simulation principle

Abstract

The invention relates to a half-wavelength transmission line transient state quantity pilot protection method based on a post-test simulation principle, and belongs to the technical field of power system relay protection. The method comprises the steps of: performing parameter setting on a half-wavelength power transmission line, assuming that a protected line does not have a fault, taking a power transmission line equivalent model as a reference model, calculating the voltage and the current of the tail end of the line according to the actually measured value of the voltage and the current of the measuring end and according to the voltage and current distribution rule along the line of the line model, and performing comparison and matching of the voltage and the current of the tail end of the line obtained through simulation and calculation and the actually measured voltage and current to form pilot protection based on the transmission line fault transient state quantity. The half-wavelength transmission line transient state quantity pilot protection method adopts the current modulus of the two sides of the buses M and N at the two sides of the line to respectively calculate the transient quantity of the current fault signal at the midpoint for detection, and compares with the transient quantity of currents calculated to the midpoint during normal operation and external faults to identify the faults, so that the method has high sensitivity and selectivity.

Description

technical field [0001] The invention relates to a half-wavelength transmission line transient quantity longitudinal protection method based on post-measurement simulation principle, and belongs to the technical field of electric power system relay protection. Background technique [0002] Half-wave-length alternating current transmission (half-wave-length alternating current transmission) refers to the ultra-long-distance AC power transmission technology whose power transmission distance is close to half of the power frequency wavelength. When the power frequency is 50Hz, the power transmission distance is about 3000km. As a long-distance and large-capacity AC transmission method, the half-wavelength AC transmission technology has the advantage of self-balancing reactive power throughout the line, without the need to install reactive power compensation equipment. At the same time, from the perspective of power transmission, its equivalent electrical distance is 0, theoretical...

AI Technical Summary

Problems solved by technology

For distance protection, the measured impedance of the half-wavelength line varies nonlinearly with the location of the fault point, and the spatial distance of the line and the equivalent impedance no longer tend to be linear. Severe forward overtaking problem, distance protection no longer applies

For longitudinal differential protection, after a half-wavelength line fault occurs, the electrical quantity along the line presents nonlinear and non-monotonic characteristics, and the capacitive current cannot be accurately calculated and compensated. The differential current cannot be directly obtained from the current on both sides and the capacitive compensation current. The current compensation method fails and cannot be applied to half-wavelength transmission lines

The measured impedance of half-wavelength transmission lines no longer shows a single linear change with the fault location, so traditional distance protection cannot be directly applied to half-wavelength transmission lines, and the attenuation loss of traveling waves on ultra-long lines is extremely large, making it difficult to accurately detect the head of traveling waves. Protection is also difficult to use for half-wavelength transmission line protection

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