Transformer longitudinal error protecting method with maximum side zero sequence ratio brake

Abstract

This invention discloses a longitudinal deviation protection method for a transformer with the largest side zero sequence rate brake, which weights a brake current representing through current in the longitudinal difference protection and the maximum value in the zero sequence current of the earth side of the neutral points in the transformer and sums to get a brake current with zero sequence current, which is used to get the phase rate brake element with the differential current of a related phase, when the differential current is greater than the brake current with the zero sequence current and the smallest action current, the action signal of the rate brake element of said phase is output.

Description

technical field [0001] The invention relates to a relay protection method of a power system, in particular to a transformer longitudinal difference protection method with maximum-side zero-sequence ratio braking. Background technique [0002] The current longitudinal differential protection of power transformers consists of components such as differential quick-break, ratio differential, excitation inrush current detection, and over-excitation detection. According to DL / T 684-1999 "Large Generator Transformer Relay Protection Setting Calculation Guidelines", the block diagram of transformer differential protection is shown in figure 1 As shown, the wiring example of longitudinal differential protection principle is shown in Figure 2. Usually using a current transformer for Y 0 Y / Δ transformation is performed on the three-phase current on the side to eliminate the influence of zero-sequence current. Obviously, after the transformation, each current does not contain the zer...

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Problems solved by technology

[0005] The technical problem to be solved by the present invention is aimed at Y 0 The side three-phase current conversion method cannot completely eliminate the influence of zero-sequence current, and a transformer longitudinal differential protection method with maximum side zero-sequence ratio braking is provided. The maximum value of the zero-sequence current on the neutral point grounding side (or branch) is weighted and summed to form the braking current containing zero-sequence current, and the braking current containing zero-sequence current and the differential current of the corresponding phase are used to form this phase Ratio braking element, when the differential current is greater than the braking current including zero-sequence current and greater than the minimum operating current, output the action signal of the ratio braking element

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