Inter-turn protection method for power generator

Abstract

The invention discloses an inter-turn protection method for a power generator, and the technical problem to be solved is to ensure the safe and reliable operation of inter-turn protection for the power generator while improving the sensitivity. The inter-turn protection method for the power generator adopts a steady state quantity section and a mutation quantity section of the power generator as criteria for judgment; and the steady state quantity section is used as long-term protection of inter-turn faults for the power generator, and the steady state quantity section exits by catching the first electrical transient feature of the inter-turn faults of the power generator from 20 to 60ms after start-up. Compared with the prior art, the inter-turn protection method comprises the steps of using the mutation quantity criterion which is in short-term input and can only be inputted once for sensitively and rapidly removing most of the inter-turn faults in a region, using the steady state quantity criterion for reliably removing other inter-turn faults in the region by short time delay, and simultaneously introducing a mutation quantity negative sequence forward starting element and a mutation quantity positive sequence reverse blocking element for ensuring the reliability of the mutation quantity criterion, thereby ensuring the safe and reliable operation of the inter-turn protection for the power generator while improving the sensitivity.

Description

technical field [0001] The invention relates to a relay protection method of a power system, in particular to a turn-to-turn protection method of a generator. Background technique [0002] Large-scale generator sets are one of the most important components of modern power systems. They are expensive and complex in structure. Once they fail, they will have a long maintenance period and cause huge direct or indirect economic losses to the national economy. However, as the main protection for inter-turn faults in large generators, the turn-to-turn protection of generators has always had the problems of high malfunction rate, difficulty in balancing reliability and sensitivity. Traditional generator turn-to-turn protection methods include three categories: 1) Generator turn-to-turn protection based on a dedicated longitudinal voltage transformer TV, usually combined with steady-state negative-sequence directional elements. 2) Generator transverse difference protection based on ...

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Problems solved by technology

Chinese patent application number 200510002483.X, disclosed the fault-tolerant rejudgment type negative-sequence directional blocking generator longitudinal zero-voltage turn-to-turn protection, and provided a generator turn-to-turn protection based on special longitudinal TV and conventional negative-sequence directional blocking Digital implementation scheme, this method is not much different from the traditional generator longitudinal zero-voltage turn-to-turn protection, it is composed of the steady-state quantity longitudinal zero-sequence voltage criterion and the steady-state quantity negative-sequence direction criterion, sensitive, quick and reliable The stability is affected by the setting value, which is difficult to take into account, and the influence of the algorithm error in the case of frequency offset is not considered

This scheme takes into account both the start-up sensitivity to inter-turn faults of the generator and the reliability of the actual exit, but its quick action as the main protection is not enough, and the start-up criterion has high sensitivity, and the sensitivity of the action criterion is insufficient

Chinese patent application No. 200710191300.2, which discloses the inter-turn protection of the stator dedicated to the third harmonic incremental braking, proposes to block the traditional longitudinal zero-voltage inter-turn protection with the third harmonic incremental of the longitudinal zero-sequence voltage of the generator, without losing judgment. Improve reliability under the premise of sensitivity, but there is not enough theoretical analysis and actual operation experience to prove that the third harmonic of generator longitudinal zero-sequence voltage will increase when an external fault occurs

Chinese patent application No. 02138169.0 discloses a generator turn-to-turn protection method combining floating threshold and current ratio braking. It proposes the principle of current ratio braking and floating threshold in longitudinal zero-voltage turn-to-turn protection and transverse difference protection to improve The sensitivity and reliability of these two inter-turn protections of generators have been confirmed, but the shortcoming is that the ratio relationship between the selected braking current and longitudinal zero voltage and transverse differential current needs further theoretical analysis and practical operation experience support.

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