Turn-to-turn short protection zero-sequence impedance discriminating method for parallel reactor

Abstract

A zero-sequence impedance method for judging the turn-to-turn short circuit of parallelly connected reactors is disclosed. The high-end current and voltage and low-end current of said reactors are sampled. After A / D conversion and data processing, the real-time current, voltage and angle are obtained, which are compared cycle by cycle to obtain current variation. If the current variation is greater than a predefined value, disturbance exists in the electric power system. Three phase currents and three phase voltages are respectively added to obtain the zero-sequence current and zero-sequence voltage. The zero-sequence voltage is divided by the zero-sequence current to obtain a zero-sequence impedance. If the zero-sequence meets an equation, said short circuit exists.

Description

technical field [0001] The invention belongs to the field of power systems, in particular to a zero-sequence impedance discrimination method for inter-turn short-circuit protection of shunt reactors for main equipment of ultra-high voltage and ultra-high voltage (750kV) power systems. Background technique [0002] With the development of the power system, 500KV transmission lines are gradually increasing, and the ground capacitance of long-distance ultra-high voltage transmission lines is large. In order to absorb this capacitive reactive power and limit the overvoltage of the system, for lines using single-phase reclosing, In order to limit the submerged capacitor current and improve the success rate of reclosing, a three-phase-to-ground shunt reactor should be installed at both ends of the transmission line or in the substation at one end. A small reactor (or current-limiting reactor) is installed at the neutral point of the transformer, which can play the role of compensa...

AI Technical Summary

Problems solved by technology

During this process, the transient current contains rich high-order harmonics, and there is an energy exchange between the reactor and the line-to-ground capacitance. Therefore, the proportion of inter-turn short-circuit faults caused by harmonic overheating and severe micro-vibration of shunt reactors is relatively high.

The number of shunt reactors operating in domestic and foreign power systems has increased sharply, but the reliability, real-time performance and sensitivity of its protection criteria have not been high due to the inductive electrical reasons of its single winding for inter-turn power protection. Fault monitoring is very limited

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