Suppression method of excitation inrush current

Abstract

The invention discloses a suppression method of an excitation inrush current. The suppression method comprises the steps of S1, sampling a plurality of points of each periodic wave of a simulation value of each circuit breaker, setting preset switch-on time, setting switch-on setting angle to be 90 degrees or 270 degrees, and setting a rated current peak; S2, acquiring actual switch-on time, a switch-on angle and a switch-on current peak when the circuit breaker is switched on, and calculating to obtain switch-on time difference and switch-on angle difference; S3, switching off the circuit breaker; and S4, correcting switch-on time to be used as next switch-on time according to the switch-on angle difference, obtaining a new switch-on angle and a circuit peak, considering excitation inrushcurrent suppression to be success when the switch-on angle approximates to the switch-on setting angle and the current peak approximates to the rated current peak, otherwise, continuing to repeat thestep S3 and the step S4. By a flexible control method, the excitation inrush current is effectively suppressed, and great convenience and flexibility are provided for a relay under various special working conditions.

Description

technical field [0001] The invention relates to a suppressing method used in the electrical field, in particular to a suppressing method for excitation inrush current. Background technique [0002] At present, when the transformer is air-dropped, the phase angles of the three-phase voltages of the system are random. If the switch is not turned on at the right time, a large inrush current will be generated. The reason for the excitation inrush current is not only related to the structure of the transformer, but also related to the size, direction and closing angle of the residual magnetism in the transformer core before closing; in addition, it is also related to the capacity of the transformer and the distance from the large power supply (that is, the distance between the transformer and the power supply). The connection impedance between the power sources), whether the transformer or current transformer is saturated, and so on. [0003] The adverse consequences of exciting...

AI Technical Summary

Problems solved by technology

[0004] 1. The relay protection device of the transformer is caused to malfunction, causing all the loads on each side of the transformer to be cut off, causing frequent failures in the operation of the transformer;

[0005] 2. If a transformer of power station A is connected to the power supply with no load, the original excitation inrush current will induce "sympathetic inrush" (sympathetic inrush) in the operating transformers adjacent to other power stations B and C in the power grid and trip by mistake, resulting in large Area blackout;

[0006] 3. The excitation inrush current with a large value will cause damage to the transformer and circuit breaker due to excessive electromotive force;

[0007] 4. Induce operation overvoltage and damage electrical equipment;

[0008] 5. The DC component in the excitation inrush current causes the magnetic circuit of the current transformer to be over-magnetized, which greatly reduces the measurement accuracy and the correct action rate of the relay protection device;

[0009] 6. A large number of harmonics in the inrush current cause serious pollution to the power quality of the grid;

[0010] 7. Cause the grid voltage to rise or drop suddenly, affecting the normal operation of other electrical equipment

Generally, each harmonic component is scientifically calculated indirectly according to the linear interval of the B-H curve. Some studies have shown that when the transformer core is deeply saturated, the actual harmonic component is sometimes 10% less than the theoretical value, which gives the transformer differential Protection has serious unforeseen consequences

In addition, because the harmonic braking amount is too low, the differential element cannot be blocked normally, and the excitation inrush current seriously affects the safety of the transformer differential protection.