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Inrush current recognition method and low-voltage and medium-voltage quick disconnection protection method utilizing same

A technology of quick-break protection and identification method, applied in the direction of protection reacting to overcurrent, measurement of current/voltage, measurement device, etc., can solve problems such as inability to meet equipment and protection requirements

Inactive Publication Date: 2012-12-05
XJ ELECTRIC +2
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  • Abstract
  • Description
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Problems solved by technology

Furthermore, the present invention also provides a medium and low voltage quick-break protection method based on the inrush identification method, which is used to solve the problem that the existing protection method cannot meet the equipment and protection requirements

Method used

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  • Inrush current recognition method and low-voltage and medium-voltage quick disconnection protection method utilizing same
  • Inrush current recognition method and low-voltage and medium-voltage quick disconnection protection method utilizing same
  • Inrush current recognition method and low-voltage and medium-voltage quick disconnection protection method utilizing same

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Embodiment Construction

[0038] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0039] Embodiment of Inrush Current Identification Method

[0040] This embodiment provides a method for identifying inrush current and fault current by phase.

[0041] There are two criteria for judging when an overcurrent occurs, namely: the second harmonic blocking criterion, which uses the second harmonic content in the current to identify the inrush current, as shown in formula (a);

[0042] I op.2 >K 2 *I op.1 (a)

[0043] In formula (a), I op.2 is the second harmonic in the current, I op.1 is the fundamental wave in the current, K 2 is the set second harmonic braking coefficient;

[0044] Waveform comparison principle Locking criterion, such as formula (b); use the comparison between the first half cycle and the second half cycle of the waveform after current differentiation to identify the excitation inrush current. The purpose of differentia...

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Abstract

The invention relates to an inrush current recognition method and a low-voltage and medium-voltage quick disconnection protection method utilizing same. The technical scheme includes that a secondary harmonic locking criterion and a locking criterion by a waveform comparison principle are adopted to judge phases or logics on the basis of self quick disconnection overcurrent criteria of a circuit (while keeping the direction and low-voltage locking selective), phase-separation locking is realized, and the inrush current recognition with a low-voltage open criterion is adopted and differentiates magnetizing inrush current from fault current of an air-dropped distribution transformer when the circuit in a power distribution network is manually closed or repeatedly closed. Accordingly, reliability of quick disconnection protection is guaranteed while speediness of the quick disconnection protection is ensured.

Description

technical field [0001] The invention relates to the field of relay protection, in particular to an inrush current identification method and medium and low voltage quick-break protection using the inrush current identification method. Background technique [0002] At present, there are a large number of distribution transformers installed in the medium and low voltage lines in the distribution network (such as 10kV) power system (see figure 1 ), at the instant of closing or reclosing of the line, the excitation inrush currents generated by each distribution transformer are superimposed on the line and reflected back and forth, resulting in a complex electromagnetic transient process. When the number and capacity of distribution transformers on the line increase to a certain extent, the exciting inrush current will be large and the time constant will be large. For the current quick-break protection in the two-stage current protection, due to the need to take into account the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R19/165G01R31/08H02H3/08
Inventor 吴水兰印吉景许云龙刘洋游建军刘星
Owner XJ ELECTRIC
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