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10kV cable online distance measurement method based on sheath current traveling wave time-frequency composite analysis

A technology of sheath current and distance measurement method, which is applied in the direction of measuring electricity, measuring devices, short-circuit testing, etc., and can solve the problems of urban power grid operation efficiency, voltage rise, and complicated distribution of cable feeder branches that affect the quality of power supply for users.

Active Publication Date: 2020-12-15
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, due to the many branches and complex distribution of cable feeders, affected by human external forces, environmental factors, and backward technology and equipment, once a failure occurs, it will seriously affect the quality of power supply for users and the operating efficiency of the urban power grid.
At present, about 80% of the fault types that occur in distribution network cables are single-phase ground faults. After a single-phase ground fault, the system can operate with faults for a period of time, but due to the increase of the non-fault relative ground voltage, the system will remain faulty for a long time Operation will seriously threaten the insulation of the line and the normal operation of the equipment

Method used

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  • 10kV cable online distance measurement method based on sheath current traveling wave time-frequency composite analysis
  • 10kV cable online distance measurement method based on sheath current traveling wave time-frequency composite analysis
  • 10kV cable online distance measurement method based on sheath current traveling wave time-frequency composite analysis

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Experimental program
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Effect test

Embodiment 1

[0081] Embodiment 1: as figure 1 The simulation model of the 10kV distribution network cable is shown, and the branch L is set 1 A single-phase ground fault occurs at a distance of 3km from the head end of the line, the total length of the line is 15km, the transition resistance is 0.01Ω, and the sampling frequency is 800kHz. Due to the occurrence of a ground fault, the duration of the traveling wave is 0.5 to 0.7 power frequency cycles, so the present invention takes The time window data of 10ms after the fault occurred was used as the analysis signal. The FFT-MUSIC algorithm is used to analyze the fault location signal I ∑ (The sum of the three-phase cable sheath current) is used for spectrum analysis, and the corresponding spectrum is as follows image 3 shown.

[0082] According to the spectrum analysis, the stable Δf is approximately 3.125×10 4 Hz, substituting Δf into Equation (21), we can get the initial separation as:

[0083] 3.152 km. Substituting the ranging r...

Embodiment 2

[0095] Embodiment 2: as figure 1 The simulation model of the 10kV distribution network cable is shown, and the branch L is set 1 A single-phase ground fault occurs at a distance of 5km from the head end of the line, the total length of the line is 15km, the transition resistance is 10Ω, and the sampling frequency is 800kHz. Due to the occurrence of a ground fault, the duration of the traveling wave is 0.5 to 0.7 power frequency cycles, so the present invention takes the fault The time window data of 10 ms after the onset was used as the analysis signal. The FFT-MUSIC algorithm is used to analyze the fault location signal I ∑ (The sum of the three-phase cable sheath current) is used for spectrum analysis, and the corresponding spectrum is as follows Figure 5 shown.

[0096] According to the spectrum analysis, the stable Δf is approximately 1.875×10 4 Hz, and substituting Δf into formula (21), the preliminary distance can be obtained as: 5.253km. Substituting the ranging r...

Embodiment 3

[0109] Embodiment 3: as figure 1 The simulation model of the 10kV distribution network cable is shown, and the branch L is set 1 A single-phase ground fault occurs at a distance of 10km from the head end of the line, the total length of the line is 15km, the transition resistance is 30Ω, and the sampling frequency is 800kHz. Due to the occurrence of a ground fault, the duration of the traveling wave is 0.5 to 0.7 power frequency cycles, so the present invention takes the fault The time window data of 10 ms after the onset was used as the analysis signal. The FFT-MUSIC algorithm is used to analyze the fault location signal I ∑ (The sum of the three-phase cable sheath current) is used for spectrum analysis, and the corresponding spectrum is as follows Figure 7 shown.

[0110] According to the spectrum analysis, the stable Δf is approximately 0.974×10 4 Hz, and substituting Δf into formula (21), the preliminary distance can be obtained as: 10.113km. Substituting the ranging...

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Abstract

The invention relates to a 10kV cable online distance measurement method based on sheath current traveling wave time-frequency composite analysis, and belongs to the technical field of force system relay protection. The method comprises the following steps: firstly, extracting three-phase sheath current and Isigma after phase-mode transformation of an extended Clarke matrix as fault distance measurement signals; secondly, performing frequency spectrum transformation on the fault distance measurement signal Isigma through an FFT-MUSIC algorithm, extracting each frequency component in the traveling wave signal, and calculating a fault rough measurement distance x by utilizing a frequency difference method formula; and finally, performing time domain analysis on the signal according to the fault initial position obtained by the frequency domain analysis method in combination with an improved lumped empirical mode decomposition algorithm, accurately judging the arrival time of the secondary reflection wave head of the fault line, and further realizing accurate fault distance measurement by utilizing the time difference among the fault point reflection wave, the opposite end reflectionwave and the initial wave head. The electromagnetic effect of a cable sheath is fully considered, the sheath current is used as the fault characteristic quantity, and the feasibility of online distance measurement is improved.

Description

technical field [0001] The invention relates to an on-line ranging method for a 10kV cable based on the time-frequency composite analysis of the traveling wave of the sheath current, and belongs to the technical field of force system relay protection. Background technique [0002] Power cables are an important part of urban power grids. With the country's transformation and development of urban power grids, power cables have been widely used due to their advantages such as small footprint, no external influence, and simple operation. However, due to the many branches and complex distribution of cable feeders, affected by human external forces, environmental factors, and backward technology and equipment, once a fault occurs, it will seriously affect the quality of power supply for users and the operating efficiency of the urban power grid. At present, about 80% of the fault types that occur in distribution network cables are single-phase ground faults. After a single-phase g...

Claims

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Application Information

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IPC IPC(8): G01R31/08G01R31/11G01R31/52G01R31/58
CPCG01R31/083G01R31/088G01R31/11G01R31/52G01R31/58
Inventor 束洪春梁雨婷宋建董俊袁小兵李航于永波
Owner KUNMING UNIV OF SCI & TECH
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