Transformer over-excitation protection method with angle compensation for voltage amplitude

Abstract

The invention relates to a method for compensating a voltage amplitude for over-excitation protection at a secondary voltage deviation angle of a voltage transformer of a large power transformer, particularly to a transformer over-excitation protection method with angle compensation for voltage amplitude. The method comprises the following steps that: (1), with an alternating-current sampling loop, a three-phase voltage and a system frequency of a transformer are collected and the collected voltage and frequency are inputted into a CPU of a protection device; (2), the CPU calculates a voltageamplitude compensation value and a compensated voltage; and (3), according to the obtained compensated voltage and the collected system frequency, an over-excitation multiple of the transformer is calculated and whether the transformer is in an over-excitation state is determined, wherein the over-excitation multiple is larger than or equal to 1.2, the transformer is determined to be in an over-excitation state. With the method provided by the invention, the voltage for over-excitation protection of the transformer can change with the system in real time to avoid misoperation of over-excitation protection.

Description

technical field [0001] The invention relates to a method for compensating the voltage amplitude for overexcitation protection at the secondary voltage offset angle of a voltage transformer for a large power transformer, in particular to a transformer overexcitation protection method using the angle compensation voltage amplitude. Background technique [0002] Large-scale transformer over-excitation protection is used as the main protection with time-delay action. Its action principle is to collect the transformer voltage and corresponding frequency in real time, and judge whether the transformer is over-excited by detecting the ratio of voltage to frequency (U / F). Determines whether the over-excitation protection trips at the outlet. [0003] At present, the transformer over-excitation protection voltage is mainly obtained from the three-phase voltage on the secondary side of the transformer voltage transformer, and the frequency is mainly obtained from the secondary voltage...

AI Technical Summary

Problems solved by technology

In the overexcitation protection criterion, the voltage adopts one of the three phases and the one with the larger amplitude among the three-phase voltages. This method will cause the secondary failure of the voltage transformer when the system fails once or the voltage transformer fails twice. The neutral point of the secondary side voltage shifts, and there is a problem that the non-fault phase voltage rises. According to the overexcitation protection criterion, the excitation protection will malfunction when the frequency remains unchanged and the voltage increases, causing serious accidents in the power system.

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