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Single phase earthing wire selection method for small earthing current system

A small grounding current, single-phase grounding technology, applied in the direction of measuring electricity, measuring electrical variables, instruments, etc., can solve problems that affect the detection effect and difficulties of the device

Inactive Publication Date: 2008-07-09
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Since the working frequency is very close to the harmonic frequency, it is very difficult for the detector to filter out the harmonic signal and extract the external working signal.
These all affect the detection effect of this device

Method used

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  • Single phase earthing wire selection method for small earthing current system
  • Single phase earthing wire selection method for small earthing current system
  • Single phase earthing wire selection method for small earthing current system

Examples

Experimental program
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Embodiment Construction

[0014] figure 1 Shows how the three output terminals of the signal generator are respectively connected to the phases a, b, and c of the secondary sides of the voltage transformer TV on the bus. The relay protection measures the three-phase voltages of a, b, and c on the secondary side of the TV. When the voltage of one phase drops and the voltage of the other two phases rises, it can be judged that a single-phase grounding short circuit occurs in the power system, and the phase of the voltage drop is Failures are different. When the relay protection detects that a single-phase ground short circuit occurs, the signal generator sends a signal to the fault phase through the secondary side of the TV figure 2 The pulse signal shown

[0015] If the signal generator sends a sinusoidal AC signal, the greater the power of the sinusoidal AC signal, the greater the current amplitude of the signal; the greater the current amplitude of the signal, the more conducive to the detection of...

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Abstract

The method includes signal generator and signal detector. When relay protection detects short circuit of grounding in single phase occurs, signal generator through TV secondary side sends impulse signal to fault phase. Pulse width of impulse signal is less than 5 ms and impulse cycle is larger than 20 ms. width of impulse and impulse cycle are adjustable through hand regulation or self-regulation. With certain time period, signal generator sends out N kinds of impulse signals I different cycle, where N is greater than or equal to 2.

Description

(1) Technical field [0001] The invention relates to the field of relay protection of power systems, in particular to a fault line selection method for single-phase ground short-circuit in a small ground current system. (2) Background technology [0002] The power system in which the neutral point of the power transformer is not directly grounded is called a small ground current system. When a single-phase ground short circuit occurs in this kind of system, there is no fault circuit, no short circuit current will be generated, the relay protection of the power system may not trip, and the power system is allowed to continue to run for a period of time. Because there is distributed capacitance in the power line, although the distributed capacitance is not too large, capacitive current is generated at the single-phase ground point, which is also harmful to the power system. Therefore, when a single-phase ground short circuit occurs in this kind of system, the relay protection ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/02
Inventor 李晓明
Owner SHANDONG UNIV
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