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A method and device for determining the optimal phase-separated closing time of a large-capacity main transformer

A determination method, large-capacity technology, applied in the direction of circuit devices, emergency protection circuit devices, emergency protection circuit devices for limiting overcurrent/overvoltage, etc.

Active Publication Date: 2020-09-22
STATE GRID SICHUAN ELECTRIC POWER CORP ELECTRIC POWER RES INST +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the limitations of equipment manufacturing technology, the existing excitation inrush current suppression methods still have relatively large defects in actual engineering

Method used

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  • A method and device for determining the optimal phase-separated closing time of a large-capacity main transformer
  • A method and device for determining the optimal phase-separated closing time of a large-capacity main transformer
  • A method and device for determining the optimal phase-separated closing time of a large-capacity main transformer

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Embodiment 1

[0096] A method for determining the optimal phase-separated closing time of a large-capacity main transformer, comprising the following steps:

[0097]Determine the dielectric strength decrease rate k of the circuit breaker contact gap during the movement of the contact when the circuit breaker is closed p , and the maximum slope k of the applied voltage waveform between the contact ports of the circuit breaker m ; The rate of decline in dielectric strength is the absolute value of the ratio of the pre-breakdown voltage between the contact ports of the circuit breaker and the time;

[0098] Comparing the rate of decrease in dielectric strength k p and the maximum slope k of the voltage waveform m , according to k p and k m Calculate the minimum pre-breakdown voltage of the transformer based on the size relationship between them;

[0099] The optimal target closing angle is calculated according to the minimum pre-breakdown voltage of the transformer and the preset closing ...

Embodiment 2

[0109] According to the typical parameters of SF6 circuit breakers and the field measured parameters of the Sichuan-Tibet interconnection project, the breakdown field strength of the circuit breaker port is selected as 28.6kV / mm, the closing speed when the contacts are close is 3.2m / s, and the system voltage before closing It is 230kV, and it can be obtained that the switching time of the closing resistor caused by the pre-breakdown phenomenon is 0ms-2.05ms. In actual engineering, due to the voltage at both ends of the circuit breaker, when the circuit breaker is closed, although the mechanical contacts have not yet touched, the electrical circuit will be conducted due to the insulation breakdown between the contacts, and this pre-breakdown The characteristics will greatly change the switching time of the closing resistor and have a significant impact on the accuracy of the phase selection closing. The present invention corrects the closing resistor access time based on the pr...

Embodiment 3

[0162] Taking the first no-load closing operation of the main transformer in Batang substation as an example, the main transformer of this station has been demagnetized before no-load closing, and the residual magnetism of the main transformer can be considered to be zero. The strength is 30kV / cm, and the action speed is 9.8m / s. The best closing time of A, B, and C three phases can be calculated as: 11.21ms, 14.57ms, and 15.78ms respectively, and the operation and simulation are carried out according to the closing time Calculation, the actual wave recording and simulation curve of inrush current can be obtained as Figure 7-Figure 8 As shown, the busbar voltages of Jiangda Station, Mangkang Station and Leiwuqi Station of Tibetan power grid are as follows: Figure 9 shown.

[0163] Compared Figure 7-Figure 9 It can be seen that the simulation results are basically consistent with the actual wave recording results, the three-phase inrush current is controlled between 100A-20...

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Abstract

The invention discloses a method for selecting large-capacity main transformer optimal split-phase closing time. The method comprises the following steps sequentially: defining an absolute value of aratio of pre-breakdown voltage among circuit breaker contacts to a time as insulation strength diminution rate of a contact gap, expressing as kp; defining a maximum slope of an impressed voltage waveform between contact ports of a circuit breaker as km; comparing the insulation strength diminution rate kp and the maximum slope km of the voltage waveform, and calculating an optimal target closingangle. A high-capacity main transformer optimal split-phase closing time selection method is provided. When the method is applied, according to a circuit breaker closing characteristic, the optimal target closing angle of a transformer phase selection switching-on strategy can be derived theoretically under a requirement of considering circuit breaker mechanical operation time dispersion based onconsidering circuit breaker operation discreteness and a pre-breakdown characteristic, and increasing amount of access time of a closing resistor caused by pre-breakdown phenomenon can be quantized and obtained, thereby accurately evaluating the pre-breakdown characteristic of the circuit breaker on the magnetizing inrush current.

Description

technical field [0001] The invention relates to the field of safety and stability guarantee measures for power systems, in particular to a method and device for determining the optimal phase-separated closing time of a large-capacity main transformer. Background technique [0002] Harmonic overvoltage is mainly due to the two aspects of standing wave effect and resonance amplification effect of the harmonic component in the excitation inrush current transmission through the line, and the overvoltage generated at the end of the weak connection system with long line and light load. In order to suppress the risk of overvoltage, the best way is to suppress the magnitude of the magnetizing inrush current at the source. At present, there are two main methods to suppress the transformer excitation inrush current: one is to control the closing time of the transformer, also known as phase-selection closing; the other is to suppress the inrush current by switching on and off the closi...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H9/00H02H9/02
CPCH02H9/002H02H9/02
Inventor 魏巍刘莹梅生伟丁理杰陈颖
Owner STATE GRID SICHUAN ELECTRIC POWER CORP ELECTRIC POWER RES INST
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