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A Instantaneous Fault Discrimination Method Using Restoration Voltage Delay Half-period Superposition to Detect Beat Frequency

A technology for transient faults and voltage recovery, applied in fault location, electrical digital data processing, special data processing applications, etc., can solve problems such as power system secondary fault impact, achieve easy implementation, broaden the application range and prospects

Active Publication Date: 2017-04-12
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved in the present invention is to avoid the problem that the power system is impacted by the secondary fault caused by the failure of reclosing after the fault of the transmission line, and proposes a method for distinguishing instantaneous faults by using half-period delay of the recovery voltage to superimpose and detect the beat frequency

Method used

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  • A Instantaneous Fault Discrimination Method Using Restoration Voltage Delay Half-period Superposition to Detect Beat Frequency
  • A Instantaneous Fault Discrimination Method Using Restoration Voltage Delay Half-period Superposition to Detect Beat Frequency
  • A Instantaneous Fault Discrimination Method Using Restoration Voltage Delay Half-period Superposition to Detect Beat Frequency

Examples

Experimental program
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Effect test

Embodiment 1

[0031] Embodiment 1: as figure 1 The simulation system model of 500kV transmission line with shunt reactor is shown, the line to be protected is MN, and the line length is L PM = 150km, L MN = 358km, L NQ =220km, shunt reactor reactance X L =1680.56Ω, X n =434Ω. The sampling rate is 20kHz. According to the line parameters, the frequency of the free oscillation component formed between the capacitive and inductive components is calculated as ω=265.78Hz, and the oscillation period is τ=23.6ms;

[0032] Assuming that a phase A grounding transient fault occurs on the line MN 50km away from the M terminal, the normalized fault phase voltage waveform u obtained by the measurement terminal M at this time M (k) if figure 2 shown by figure 2 It can be seen that the time when the fault occurs is 0.3s, and the time when the circuit breaker is disconnected is 0.4s;

[0033] Starting 200ms after the disconnection of the circuit breaker, the disconnected phase voltage value obtai...

Embodiment 2

[0035] Embodiment 2: as figure 1 The simulation system model of 500kV transmission line with shunt reactor is shown, the line to be protected is MN, and the line length is L PM = 150km, L MN = 358km, L NQ =220km, shunt reactor reactance X L =1680.56Ω, X n =434Ω. The sampling rate is 20kHz. Now suppose that a phase-A permanent ground fault occurs on the line MN 50km away from terminal M. At this time, the normalized fault phase voltage waveform u obtained by measuring terminal M is M (k) if Figure 7 shown by Figure 7 It can be seen that the time when the fault occurs is 0.3s, and the time when the circuit breaker is disconnected is 0.4s;

[0036] Starting 200ms after the disconnection of the circuit breaker, the disconnected phase voltage value obtained by the measuring terminal is superimposed on the voltage value 10ms before the current value to obtain the superimposed voltage waveform u M1 (k), such as Figure 8 shown;

[0037] Using discrete Fourier transform, ...

Embodiment 3

[0038] Embodiment 3: asfigure 1 The simulation system model of 500kV transmission line with shunt reactor is shown, the line to be protected is MN, and the line length is L PM = 150km, L MN = 358km, L NQ =220km, shunt reactor reactance X L =1680.56Ω, X n =434Ω. The sampling rate is 20kHz. Now suppose that a phase-A grounding transient fault occurs on the line MN 160km away from terminal M, at this time, the normalized fault phase voltage waveform u obtained by measuring terminal M M (k) if Figure 9 shown by Figure 9 It can be seen that the time when the fault occurs is 0.3s, and the time when the circuit breaker is disconnected is 0.4s;

[0039] Starting 200ms after the disconnection of the circuit breaker, the disconnected phase voltage value obtained by the measuring terminal is superimposed on the voltage value 10ms before the current value to obtain the superimposed voltage waveform u M1 (k), such as Figure 10 shown;

[0040] Using discrete Fourier transform, ...

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Abstract

The invention relates to an instantaneous-fault identification method for beat frequency detection adopting recovery-voltage delay one-half cycle superposition and belongs to the field of power system relay protection. The method includes that for an electric transmission line with two ends provided with paralleling reactors, calculating the free oscillation component frequency omega and the oscillating period tau according to line parameters and compensation degree of the paralleling reactors; when line failure occurs and at the moment starting from 200ms after a breaker is disconnected, superposing disconnected-phase voltage values acquired by a measuring end and voltage values of current values 10ms ago, and extracting frequency omega j (j=1,2,3) of superposed waveforms within three sliding time windows by the aid of discrete Fourier transformation, wherein each of the sliding time window is 2 tau in length; respectively comparing and extracting size relation of the omega j and the omega, and if the extracted frequency is equal to the calculated free oscillation frequency, judging to be instantaneous fault, or otherwise, judging to be permanent fault. As is show in a great deal of simulation tests and verification, the instantaneous-fault identification method is reliable and efficient.

Description

technical field [0001] The invention relates to a method for discriminating instantaneous faults by superimposing and detecting beat frequency by half-period delay of recovery voltage, and belongs to the technical field of electric power system relay protection. Background technique [0002] As an effective measure to ensure safe power supply and stable operation of the power system, automatic reclosing technology has been widely used in EHV power grids. Operation experience shows that most of the faults on EHV overhead transmission lines are transient faults. After the fault arc is extinguished, the coincident line disconnects the phase to restore the normal operation of the system, which can greatly improve the reliability of power supply. The current automatic reclosing device is still blindly reclosing after the circuit breaker trips, and has not yet discriminated between transient faults and permanent faults. There is still a risk of reclosing failure causing the power ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/08G06F19/00
Inventor 束洪春杨竞及高利曹璞璘
Owner KUNMING UNIV OF SCI & TECH
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