ZnO varistor-based fault discharge device and control method thereof

Abstract

The invention discloses a ZnO varistor-based fault discharge device and a control method thereof, and the fault discharge device comprises a current transformer which is used for detecting a current in a power transmission line; a signal processor which is used for processing the current detection signal; a fault bleeder which comprises a main bleeder path and a plurality of secondary bleeder paths, the main bleeder path comprises a first quick switch and at least one ZnO piezoresistor which are connected in series, and each secondary bleeder path comprises a second quick switch and a bleederresistor which are connected in series; and a controller which is used for carrying out closing control on the first quick switch and / or each second quick switch when the current in the power transmission line is greater than the rated breaking current of the circuit breaker, so that the current of the power transmission line is less than or equal to the rated breaking current of the circuit breaker, and controlling the closed quick switch to be disconnected after the circuit breaker is disconnected. The fault discharge device can reduce the protection cost of the power grid fault and improvethe protection effect of the power grid fault on the premise of not influencing the normal operation of the power grid.

Description

technical field [0001] The invention relates to the technical field of power grids, in particular to a ZnO varistor-based fault leakage device and a control method thereof. Background technique [0002] The scale of my country's power grid continues to expand, the structure of the power grid is gradually strengthened, the application of low-impedance and large-capacity transformers in the power grid continues to increase, the capacity of single machines in the system, the capacity of power plants, and the load and load density continue to increase. The operation of the unit and the construction of the UHV transmission backbone grid have greatly improved the power transmission capacity of the main grid and enhanced the safety and reliability of the grid operation. At the same time, it has also led to a sharp increase in the short-circuit current level of each important node. When the short-circuit current occurs, the current value increases instantaneously, which is several ti...

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Problems solved by technology

[0006] 1) There is a certain loss in the series connection of FCL in the power grid, and the power consumption caused by a large number of distributed series connection in the power grid will increase with the increase of the number;

[0007] 2) The cost of new materials such as superconducting FCL is relatively high, and the economy is poor;

[0008] 3) Electronic devices in power electronic FCL have low withstand voltage level and poor stability;

[0009] 4) The current-limiting reactance of FCL is connected in series to the line to suppress the short-circuit current, but because the dynamic impedance characteristics of the line are changed, that is, the equivalent electrical distance of the line before and after the fault changes, which affects the setting of the line over-current protection

[0020] 1) The fixed resistor lacks adaptability, and it is difficult to balance the flow capacity and the discharge effect. The resistor with a small resistance value has a small rated capacity and poor flow capacity. The resistor with a large resistance value has a strong flow capacity, but the larger resistance It will increase the node voltage and the leakage effect will be poor;

[0021] 2) At the moment of short circuit, a large inrush current several times higher than the short circuit cycle current will be generated. The traditional bleeder resistor can hardly bear such a large inrush current, and it is easy to be burned out and lose the bleeder effect.

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