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Waveform sine principle based transformer excitation flow recognition method

A technology of excitation inrush current and identification method, which is applied in the direction of instruments, measuring electric variables, measuring current/voltage, etc., can solve the problem of large influence of CT saturation on second harmonic braking delay time and broken angle

Inactive Publication Date: 2009-05-27
BEIJING JIAOTONG UNIV
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Problems solved by technology

[0005] The purpose of the present invention is to overcome the defects in the above protection schemes, and propose a transformer excitation inrush current identification method based on the principle of waveform sine degree, which can better solve the long-standing second harmonic braking delay in high-voltage power transmission systems And the problem that the discontinuity angle is greatly affected by CT saturation

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  • Waveform sine principle based transformer excitation flow recognition method

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Embodiment Construction

[0014] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0015] Such as figure 1 As shown, the present invention proposes a transformer excitation inrush current identification method based on the principle of waveform sine degree, and the method includes the following steps:

[0016] First, starting from step S101, the protection device samples all the currents on each side, and the instantaneous sampled value of the obtained current is stored in the sampling queue;

[0017] In step S102, calculate the instantaneous value of the differential current and make a difference on the current to weaken the influence of the DC component;

[0018] Step S103 calculates S(t) by using the differential current sampling current value after the difference and the instantaneous value of the previous quarter cycle;

[0019] The S104 step uses the S(t) value obtained in S103 to calculate the mathematical expectatio...

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Abstract

The invention relates to a transformer excitation inrush current recognize method based on wave-shape sine theory, wherein it uses the sine function character of normal operation, short circuit, and external circuit short; the excitation inrush current contains non-periodical component, and the distant angle has no sine character; via comparing the sine degrees, it can judge inrush current and short circuit. The invention defines and calculates out the wave-length non-sine degree sigmaS (t); comparing the wave-length non-sine degree and non-sine preset value sigmaSZd, to judge the inrush current and short circuit current; when the transformer is idle and closes gate, there is inrush current, sigmaS (t) is higher than preset value sigmaSZd; opening judging condition, closing protecting; when the transformer has short circuits, sigmaS (t) is lower than sigmaSZd, it will open protection. The invention has accurate judge and phase-divert brake, with significant effect on CT saturation.

Description

technical field [0001] The invention relates to a power system, and more specifically relates to a transformer excitation inrush current identification method based on the principle of waveform sine degree, which belongs to the technical field of transformer protection. Background technique [0002] In power system, longitudinal differential protection is often used in transformer protection system, and transformer excitation inrush current and internal short-circuit fault are still the key issues of current transformer differential protection. The transformer differential protection currently in operation is mainly composed of the excitation inrush current discontinuity angle and the second harmonic braking principle, but the effect in practical application is not very ideal. Its refusal to move (should act but not act) and malfunction (action should not act) will cause serious damage to the transformer and cause great economic losses. [0003] The principle of second harm...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/045H02H3/32G01R19/00
Inventor 和敬涵李静正欧灶军
Owner BEIJING JIAOTONG UNIV
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