A fault location method for outgoing lines of new energy stations based on electromagnetic time inversion method

Abstract

The invention relates to a new energy station transmission line fault distance measurement method based on an electromagnetic time inversion method, and belongs to the technical field of electric power system relay protection. The present invention sets different fault types in the transmission line area of ​​the new energy station through electromagnetic transient simulation, extracts fault currents on both sides for Karenbauer transform decoupling, extracts line-mode currents, and uses db4 wavelet to decompose line-mode components into high-frequency and low-frequency components Component, select the high-frequency d1 component for electromagnetic time inversion, which is equivalent to a current source, connect to both ends of the lossless mirror line to supply power to the line, assume the fault point, and then calculate the current energy of each hypothetical fault point, the maximum current energy corresponds to The hypothetical fault point is the actual fault point. It can be seen from the simulation verification and the measured data that the method is correct and effective. The method proposed by the invention is not affected by the higher harmonics at the station side, the weak feed characteristics of the station, and the speed frequency current of the double-fed fan, and does not need to identify the head of the traveling wave and calibrate the arrival time of the wave head.

Description

technical field [0001] The invention relates to a new energy station transmission line fault distance measurement method based on an electromagnetic time inversion method, and belongs to the technical field of electric power system relay protection. Background technique [0002] With the gradual expansion of the installed capacity of new energy power generation, in order to send out large-scale long-distance electric energy, a new energy station is established, and then connected to the power grid through a step-up transformer through a sending line. As an important channel for the transmission of clean energy, the transmission line of new energy stations is of great significance to the safe and stable operation of new energy stations and power grids. Therefore, it is very important for the safe and stable operation of new energy stations and power grids to ensure the correct and reliable operation of line protection when the transmission line fails. [0003] The fault char...

AI Technical Summary

Problems solved by technology

The new energy station contains a large number of power electronic devices. After the station's sending line fails, the fault current contains a large number of harmonics, and is affected by the power electronic device and the small moment of inertia. The fault voltage and current amplitude are low. For double-fed After the fault of the wind farm station, the main frequency of the current shifts, the operation mode of the station changes, and the input of the crowbar after the fault causes the system impedance to be unstable

Therefore, the traditional distance protection based on the full-wave Fourier algorithm is difficult to adapt to the transmission line of the new energy station, and a new protection scheme is required

Although the distance protection based on the time-domain solution of differential equation algorithm has high ranging accuracy, it ignores the influence of distributed capacitance in long-distance transmission, which reduces the ranging accuracy of long-distance transmission lines; Protection schemes are susceptible to harmonics and are time consuming

The voltage and current measured on the station side after the fault contains a large number of high-order harmonics, and the filter capacitor on the station side also plays a role in weakening the high-frequency components. Using single-ended traveling wave ranging can not accurately identify the head of the traveling wave on the station side and the reflected wave at the fault point, while installing a traveling wave device on the grid side for single-ended ranging is affected by the filter capacitor on the station side, the difference in amplitude between the reflected wave and the refracted wave at the fault point is not obvious, and it cannot be accurately identified

Since the fault location based on the single-ended and double-ended traveling wave method needs further automatic processing to calibrate the arrival time of the traveling wave, the procedure is complicated, so it is impossible to achieve accurate positioning on the sending line of the new energy station

If the transmission line failure of the new energy station cannot be accurately found and eliminated, it may bring hidden dangers to the stable operation of the power grid, causing large-scale off-grid of wind turbines, reducing the consumption of green energy, and causing serious economic losses

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