Differential protection method of bus sampling value based on current transformer linear transmission area

A technology of linear transfer area and current transformer, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve problems such as incorrect protection, achieve strong resistance to current transformer saturation, improve the ability, and improve the speed of action. Effect

Inactive Publication Date: 2019-02-22
NANJING UNIV OF SCI & TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, when an out-of-area fault occurs on the bus, the transformer may enter a transient saturation state due to the influence of the residual magnetism and the non-periodic component of the primary fault current, thus causing incorrect action of the protection
[0004] It can be seen from the above that there are two problems that need to be solved urgently in the existing current sampling value differential protection: the identification of faults inside and outside the zone and the correct action of the protection when the fault outside the zone turns into a fault inside the zone

Method used

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  • Differential protection method of bus sampling value based on current transformer linear transmission area
  • Differential protection method of bus sampling value based on current transformer linear transmission area
  • Differential protection method of bus sampling value based on current transformer linear transmission area

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Embodiment

[0047] In order to verify the feasibility of the criterion, a two-input and two-outlet bus fault simulation model is first built in PSCAD to obtain the fault current. The system frequency is 50Hz, and there are 24 sampling points per cycle. An out-of-area fault occurs at 0.3s, and develops into an in-area fault at 0.35s. By calculating the braking current and differential current, such as figure 1 shown.

[0048] combine figure 2 , a kind of bus sampling value differential protection method based on the current transformer linear transmission area of ​​the present invention, comprises the following steps:

[0049] Step 1: Distinguish internal and external faults according to the time difference method;

[0050] If the braking current mutation exceeds the threshold, it will be judged as a fault start, and the start time will be recorded. See the following formula for the criterion.

[0051] |i r (k)-i r (k-24)|>|i r (k-24)-i r (k-48)|+i rst

[0052] In the formula, ...

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Abstract

The invention discloses a busbar sampling value differential protection method based on a current transformer linear transmission area. The regularity rule of current transformer saturation is used, according to a current known linear transmission area position, the linear transmission area position after a cycle wave, and sampling value differential criterion judgment is applied a predicted linear transmission area. If a fault is developed in the area, sampling value differential is on exit. If sampling value differential criterion does not act, the actual linear transmission area position is used to predict the linear transmission area position of a next time, and so on until protection action or starting return. According to the method, reliable locking is achieved in external fault current transformer saturation, a conversion fault can be correctly identified, the rapid action is achieved in a current transformer linear saturation process, the sensitivity is high, and the ability of resistance to outflow current and development fault external fault point fault current shunt is improved.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a method for differential protection of bus bar sampling values ​​based on the linear transmission range of a current transformer. Background technique [0002] Compared with the conventional phasor differential protection, current sampling value differential protection has the characteristics of less calculation and faster speed. It adopts the method of repeated discrimination, that is, there are no less than S number of continuous R sampling points If the operating conditions are met, the protection will operate. The principle of sampled value differential protection greatly shortens the calculation and judgment data window required for busbar protection, and the principle of sampled value differential protection has no obvious defects, and the performance is balanced and comprehensive, which is suitable for the needs of busbar protect...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/22
CPCH02H7/22
Inventor 樊佳辉满灿孙美玲葛景朱忆洋赵雨田
Owner NANJING UNIV OF SCI & TECH
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