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Locking method for voltage regulation and compensation for magnetizing inrush current of voltage transformer

A technology for compensating transformers and excitation inrush currents, applied to electrical components, emergency protection circuit devices, etc., can solve the problem of small second harmonic content, reduce the sensitivity of transformer differential protection, and the second harmonic braking criterion cannot be effectively blocked Differential protection and other issues

Active Publication Date: 2018-06-08
长园深瑞继保自动化有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] With the increase of the working magnetic flux density of the power transformer, the second harmonic content in the inrush current will become smaller and smaller, making the traditional second harmonic braking criterion unable to effectively block the differential protection
There have been many transformer misoperation events caused by this in practical engineering applications. If only relying on reducing the setting value of harmonic braking coefficient, the sensitivity of transformer differential protection will be reduced.
At the same time, in the application of UHV voltage regulation and compensation transformers, the excitation inrush current is extremely low, and the second harmonic content is about 5% to 8%. The traditional excitation inrush current criterion cannot effectively block the differential protection, and there is a possibility of malfunction

Method used

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  • Locking method for voltage regulation and compensation for magnetizing inrush current of voltage transformer
  • Locking method for voltage regulation and compensation for magnetizing inrush current of voltage transformer
  • Locking method for voltage regulation and compensation for magnetizing inrush current of voltage transformer

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Embodiment 1

[0079] Example 1: During the empty charging process of the voltage regulation and compensation transformer, its second harmonic content may be lower than 10%. Therefore, when empty charging, it is easy to malfunction when using a conventional inrush current judging device. At this time, use The inverse time floating excitation inrush current threshold presents threshold self-adaptive characteristics, which can effectively reduce the risk of misoperation of voltage regulation compensation, variable emptying and charging; in addition, on the basis of second harmonic judgment, the DC component, third harmonic, The asymmetry of the waveform is judged, and the device can be effectively blocked to ensure that the protection does not malfunction during empty charging.

Embodiment 2

[0080] Embodiment 2: During the empty charging process of the voltage regulation and compensation transformer, the differential current inrush coefficient may be lower than the threshold. At this time, the harmonic content of the high and low sides of the transformer is greater than the threshold. Since the present invention judges that the differential current does not satisfy the inrush current blocking In this case, the phase current inrush threshold of each side is increased, so the protection will be effectively blocked, and the differential protection will not malfunction.

[0081] The invention can not only ensure the quick action when the airdrop is in the fault zone, but also ensure the reliable locking through the floating threshold when the internal fixed value of the excitation inrush current is near.

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Abstract

The invention provides a method for voltage regulation and compensation for magnetizing inrush current locking of a voltage transformer, relates to a method for relay protection of a power system andespecially relates to a method used for voltage regulation and compensation for magnetizing inrush current locking in an ultra high voltage power grid. The method includes calculating phase current ofdifferent sides of the voltage transformer and DC component, fundamental wave, second harmonics, third harmonics and waveform degree of asymmetry of different current of longitudinal differential phases of the voltage transformer, calculating a floating magnetizing inrush current comprehensive locking constant value; according to the above calculation result, calculating inrush current coefficient comprehensive criterion and comparing the criterion with the floating magnetizing inrush current comprehensive locking constant value, and giving a harmonic content mark; using fundamental current for calculation and setting a split-phase action mark; identifying whether it is magnetizing inrush current or interior failure according to the calculated split-phase action mark and the magnetizing inrush current locking mark and implementing protection over the voltage transformer. The method can ensure the quickness of no-load input when in-zone failure occurs and can also ensure reliable locking through a floating threshold when a value is approximate to the magnetizing inrush current interior constant value.

Description

technical field [0001] The invention relates to a method for relay protection of a power system, in particular to a method for blocking excitation inrush current of a voltage regulation compensation transformer in an extra-high voltage power grid. Background technique [0002] In order to improve the efficiency of transformers and reduce their size, autotransformers are generally used for large-capacity EHV grades. Using autotransformers in UHV power grids has the advantage of improving system stability. The UHV autotransformer usually consists of a main transformer and a voltage regulation compensation transformer. Its unique configuration puts forward new requirements for the inrush current blocking differential protection. [0003] When the transformer is powered on with no load or the voltage is restored after the external fault is removed, the magnetic flux in the transformer core increases sharply, the core is saturated instantly, and a large excitation inrush current ...

Claims

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Application Information

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IPC IPC(8): H02H7/045
CPCH02H7/045
Inventor 石磊周浩张广嘉刘瑞春陆兆沿李松泽
Owner 长园深瑞继保自动化有限公司
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