Method for protector to detect disconnection of neutral line using third harmonic

A protection device and sub-harmonic technology, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve problems such as abnormalities that are difficult to find

Active Publication Date: 2008-05-14
BEIJING SIFANG JIBAO AUTOMATION +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] In the past, it was mainly relied on observing the abnormality of the AC voltage waveform in the sampling report printed by the protective device before putting into operation to judge that the voltage circuit was abnormal before further inspection, but it was still difficult to f

Method used

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  • Method for protector to detect disconnection of neutral line using third harmonic

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Embodiment Construction

[0020] During normal operation, the UA, UB, and UC three-phase voltages in the system are symmetrical, and there are basically no 3U0 and third harmonics. Self-produced 3U0=UA+UB+UC≈0, the protection will not trip.

[0021] A detailed description will be given below with reference to the accompanying drawings, wherein UA, UB, and UC refer to the A-phase voltage, B-phase voltage, and C-phase voltage actually measured by the protection device. TV refers to all AC voltages involved in measurement and metering in the secondary circuit of the power system.

[0022] Self-produced 3U0=UA+UB+UC, which is the zero-sequence voltage synthesized by the protection device, and is used to distinguish the zero-sequence direction for the zero-sequence direction protection.

[0023] The voltages of points A, B, and C relative to their reference points are UA, UB, and UC voltages. Different situations have different reference points.

[0024] The TV loop has four wires Ua, Ub, Uc, and UN. Wh...

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Abstract

The invention relates to a method for protecting a relay in a electric system field. The invention discloses a method for applying a third harmonic to detect line breaking in a midline of a TV in a device for protecting an electric system. The method mainly includes the following steps: under the condition without starting, Fourier algorithm is used for obtaining a UA, a UB, a UC and a third harmonic of a self-generated 3U0; when the third harmonic of any voltage is larger than 4V for 30s successively, the device for protection gives an alarm and not locks the tripping function for protectionin a short circuit. The three harmonic detected by the self-generated 3U0 is more sensitive. Through practice, the invention is capable of determining the line breaking condition of the midline timely and accurately.

Description

technical field [0001] The invention relates to the field of electric power systems, and more specifically relates to a method for detecting disconnection of a neutral line in a voltage loop of a power system. Background technique [0002] Transmission line is the basic equipment for power generation and transmission in the power system, and occupies a very important position in the power system. Before the line is put into operation or during operation, if the neutral line UN of the TV secondary circuit is disconnected and a ground fault occurs on the transmission line, the self-generated zero-sequence direction may be incorrect, which will lead to incorrect action of the protection. If the disconnection of the neutral line of the voltage circuit can be detected in time, it is very important to ensure the reliable power supply of the power system, the safety, stability and economic operation of the power system. [0003] In the past, it was mainly relied on observing the a...

Claims

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Application Information

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IPC IPC(8): H02H7/26
Inventor 赵志宏魏会利秦应力黄少锋张月品伍叶凯姚斌
Owner BEIJING SIFANG JIBAO AUTOMATION
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