Method for identifying excitation inrush current based on amplitude-comparison criterion

Abstract

The invention relates to a method for identifying excitation inrush current based on an amplitude-comparison criterion. When duration time as shown in formula I is greater than time T3, time T8 is delayed, time T5 is spread, and a mark of time T3 with respect to formula II exists within the time T5; or when duration time as shown in formula II is greater than time T3, time T8 is delayed, time T5 is spread, and a sampling mark of time T3 with respect to formula I exists within the time T5; and the current is considered as a fault, and the amplitude-comparison criterion is open, wherein epsilonis a threshold value. The method of the invention can be used for avoiding the operation failure or the false operation of transformer protection equipment, and protecting the safe and stable operation of the power system.

Description

technical field [0001] The invention relates to a method for identifying excitation inrush current and fault current in transformer differential protection. Background technique [0002] In order to ensure the safe operation of the transformer, it must be equipped with differential protection, and the excitation inrush current of the transformer has always been a major hidden danger of the misoperation of the transformer differential protection. [0003] The principles commonly used to identify inrush current include: [0004] Use the waveform identification method to identify the excitation inrush current, that is, use the ratio of the integral value of the positive and negative half-wave vector sums in one cycle of the differential current to the integral value of one cycle to identify. In essence, only even or odd harmonics are generally used. The function does not reflect the asymmetry of the waveform from the essence of the waveform, which has a certain impact on the m...

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Problems solved by technology

[0004] Use the waveform identification method to identify the excitation inrush current, that is, use the ratio of the integral value of the positive and negative half-wave vector sums in one cycle of the differential current to the integral value of one cycle to identify. In essence, only even or odd harmonics are generally used. The function does not reflect the asymmetry of the waveform from the essence of the waveform, which has a certain impact on the misjudgment of the differential protection during airdrop

[0005] Utilize the waveform symmetry method-the waveform asymmetry k value to identify the excitation inrush current and the fault. The principle requires a high sampling rate of the device, and the asymmetry k value is difficult to adjust due to the influence of the system, and a capacitor is connected to the low voltage side of the transformer. It is difficult to find a suitable value of k when

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