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Load transformer differential quick-break protection method

A quick-break protection and transformer technology, applied in the field of relay protection, can solve the problems of easy deep saturation, low short-circuit current level, and quick-break misoperation of differential current.

Inactive Publication Date: 2017-02-15
NANHUA UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When a serious short-circuit fault occurs outside the transformer area, the small-capacity P-class current transformer is prone to deep saturation due to the low short-circuit current level and severe residual magnetism, which will cause differential current quick-break malfunction
The setting value is set according to the unbalanced current when avoiding the external fault and the excitation inrush current when the transformer is closed with no load. Even if the setting value reaches 7~8 times the rated current, it may still malfunction

Method used

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Embodiment Construction

[0016] specific implementation

[0017] When a serious out-of-area fault occurs on the low-voltage side of a high-voltage substation, the secondary current on the high-low-voltage side is as follows: image 3 , it can be seen from the figure that the current transformer on the low-voltage side is seriously saturated, and the linear transmission region is about 4.5ms. The load transformer parameters: capacity 20MVA, high voltage side 13.8kV, low voltage side 6.3kV, impedance ratio 10.5%, YY0 wiring. The transformation ratio of the current transformer on the high-voltage side is 1500:5, and the transformation ratio of the current transformer on the low-voltage side is 600:5.

[0018] The high-voltage side current and the low-voltage side current are converted and added according to the transformation ratio, and then the differential current is calculated according to the half-wave integral algorithm. Conventional calculation, no longer a single formula) and add the results to ...

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Abstract

The invention discloses a load transformer differential quick-break protection method. The method includes low fixed value differential quick-break protection and high fixed value differential quick-break protection. The high fixed value differential quick-break protection refers to that direct outlet tripping is carried out when internal extremely serious faults occur, internal and external serious faults simultaneously occur, and external faults are transferred to internal extremely serious faults. The low fixed value differential quick-break protection refers to that the locking is carried out by the rapid time difference method based on a half-wave integration algorithm, the protection can be locked when an external fault current transformer is saturated, and rapid outlet can be carried out when internal serious faults occur.

Description

technical field [0001] The invention relates to the field of relay protection, in particular to a method for differential quick-break protection of load transformers. Background technique [0002] When a serious fault occurs inside the transformer, the general ratio differential may be blocked by the second harmonic or the discontinuity angle criterion as the excitation inrush current due to the saturation of the current transformer and the harmonics. For this reason, transformer differential current quick-break protection is set up, and current transformer saturation blocking logic is generally not added, because adding current transformer saturation detection will increase the action delay of differential current quick-break protection. When there is a serious fault in the transformer area, the differential current speed break protection action time is too long, which may seriously damage the transformer. [0003] The current transformers on the low-voltage side of load t...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/045
CPCH02H7/0455
Inventor 曾铁军李莉盛义发
Owner NANHUA UNIV