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Description of automatic computing program of differential current of digital transformer differential protection

A differential protection and differential current technology, which is applied to emergency protection circuit devices, electrical components, etc., can solve the problem of low differential current limit criterion

Active Publication Date: 2008-06-04
BEIJING SIFANG JIBAO AUTOMATION +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Obviously, the sensitivity of the differential current limit criterion of digital transformer differential protection is much lower than that of conventional transformer differential protection.

Method used

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  • Description of automatic computing program of differential current of digital transformer differential protection
  • Description of automatic computing program of differential current of digital transformer differential protection
  • Description of automatic computing program of differential current of digital transformer differential protection

Examples

Experimental program
Comparison scheme
Effect test

Embodiment Construction

[0013] Fig. 1 shows the step flow of alarming and blocking transformer differential protection after the differential current exceeds the limit in the present invention. Set the basic side rated current I ED , the basic side current transformer secondary side load current I during detection F , to calculate the difference current I D , differential current threshold I CD .

[0014] The criterion of the procedure for judging the floating threshold of the differential current of the digital transformer differential protection is as follows:

[0015] Under the premise that there is no sudden change in the current on each side:

[0016] The discriminant formula for issuing a differential current over-limit alarm with a delay of 5S is:

[0017] I ED I F I Dφ ≥ 0.1 I CD - - ...

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Abstract

The invention discloses a converting method of differential current in differential protection for a digital substation. The method comprises the following steps: after the value of the secondary side rated current (5A or 1A) of a current transformer is multiplied by the actual measured differential current, the result is divided by the secondary side load current of the current transformer, the value of the differential current in the full loading situation is then obtained by converting. When the value of the differential current in full loading is less than 10 percent of the value of the differential current action threshold, the differential current does not exceed the restriction, and the differential protection of the digital substation can operate normally. When the value of the differential current in full loading is more than 10 percent of the value of the differential current action threshold, the differential current exceeds the restriction, thus sending an alarming signal that the differential current exceeds the restriction. When the value of the differential current in full loading is larger than 50 percent of the value of the differential current action threshold, the differential current exceeds the restriction gravely, thus sending an alarming signal that the differential current exceeds the restriction and locking the differential protection of the digital substation.

Description

technical field [0001] The present invention relates to the field of power systems, and more particularly to a method for relay protection. Background technique [0002] BCH and DCD series differential relays are widely used in conventional transformer differential protection, and its actuator is a current relay with an operating current of 225ma and an operating voltage of 1.5V. Considering that the allowable error of the current transformer is 10%, that is to say, the differential current and differential voltage on the actuator may be 10 times larger than that during normal operation in the event of an external fault. Therefore, it is required in the inspection procedure that the differential voltage on the actuator must be greater than 150mV (10% of 1.5V). [0003] As we all know, the differential current (differential voltage) of transformer differential protection is proportional to the magnitude of the load current. The work of measuring differential current (differ...

Claims

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Application Information

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IPC IPC(8): H02H7/045
Inventor 袁伯诚
Owner BEIJING SIFANG JIBAO AUTOMATION