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A High-Resistance Fault Detection Method Using the Differential Sum of Squares of Line-Mode Currents

A technology for line-mode current and high-resistance faults, applied in the direction of measuring electricity, measuring devices, measuring electrical variables, etc., can solve problems such as insufficient sensitivity, and achieve the effect of high sensitivity and strong reliability

Active Publication Date: 2017-06-13
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved in the present invention is to overcome the problem of insufficient sensitivity of the traditional high-resistance fault detection method, and propose a high-resistance fault detection method using the sum of squares of line-mode current differences

Method used

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  • A High-Resistance Fault Detection Method Using the Differential Sum of Squares of Line-Mode Currents
  • A High-Resistance Fault Detection Method Using the Differential Sum of Squares of Line-Mode Currents
  • A High-Resistance Fault Detection Method Using the Differential Sum of Squares of Line-Mode Currents

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Embodiment 1

[0056] The simulation system diagram is as follows figure 1 As shown, the line length l PM = 150km, l MN = 150km, l NQ =220km. The sampling rate is 20kHz. Assuming that a phase-A ground fault occurs at a distance of 149km from the M side of the line MN, the initial fault angle is 5°, and the transition resistance is 50Ω. At this time, the line-mode current waveform and the sum of the squares of the line-mode current difference obtained at the M terminal M (k) Waveform such as figure 2 and image 3 shown.

[0057] Such as Figure 4 As shown, the three calculation values ​​in this example are S M (1) = 114.2, S M (2) = 121.5, S M (3)=121.3, all greater than 90, can be detected within 0.15ms.

Embodiment 2

[0059] The simulation system diagram is as follows figure 1 As shown, the line length l PM = 150km, l MN = 150km, l NQ =220km. The sampling rate is 20kHz. Assume that a phase-to-ground fault occurs on the line MN 75km away from the M side, the initial fault angle is 90°, and the transition resistance is 50Ω. At this time, the line-mode current waveform and the sum of the squares of the line-mode current difference obtained at the M terminal M (k) Waveform such as Figure 5 and Figure 6 shown.

[0060] Such as Figure 7 As shown, the three calculation values ​​in this example are S M (1) = 4604, S M (2) = 4592, S M (3)=4785, all greater than 90, can be detected within 0.15ms.

Embodiment 3

[0062] The simulation system diagram is as follows figure 1 As shown, the line length l PM = 150km, l MN = 150km, l NQ =220km. The sampling rate is 20kHz. Assuming that a phase A ground fault occurs on the M side of the line MN 20km away from the M side, the initial fault angle is 45°, and the transition resistance is 50Ω. At this time, the line-mode current waveform and the sum of the squares of the line-mode current difference obtained at the M terminal M (k) Waveform such as Figure 8 and Figure 9 shown.

[0063] Such as Figure 10 As shown, the three calculation values ​​in this example are S M (1) = 1033, S M (2) = 1718, S M (3)=1722, all greater than 90, can be detected within 0.15ms.

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Abstract

The invention relates to a high-resistance fault detection method utilizing linear-mode current difference quadratic sum and belongs to the power system relay protection technical field. The method comprises the following steps that: under a sampling rate of 20kHz, a measuring end is utilized to obtain three-phase current sampling values, so that linear-mode current is obtained; difference of two adjacent linear-mode current sampling values is calculated; the quadratic sum of the difference value of the linear-mode current in a power frequency period before a current value is obtained, so that a discrete sequence SM (K) of the quadratic sums of the difference of the linear-mode current can be obtained; and if three quadratic sums of the difference of the linear-mode current which are obtained through continuous calculation after a high-resistance fault occurs, are respectively larger than a threshold value, protection is started. As indicated by theoretical analysis and a large quantity of simulation, the high-resistance fault detection method utilizing linear-mode current difference quadratic sum of the invention can reliably detect high-resistance faults, and has high sensitivity, is not influenced by system oscillation.

Description

technical field [0001] The invention relates to a high-resistance fault detection method using the differential square sum of line-mode currents, and belongs to the technical field of electric power system relay protection. Background technique [0002] Our country has a vast land area and complex topography. The line may cause high-resistance faults due to insulator flashover, lightning strikes, and mountain fire flame discharges to the line. When a high-resistance fault occurs, due to the large transition resistance, the sudden change in fault current is small, and the current waveform is extremely irregular, the voltage drop is also small, and the three-phase voltage is almost symmetrical. [0003] When a common short-circuit fault occurs, a large fault phase current and zero-sequence current will be generated, and the corresponding traditional protection device can reliably operate to remove the fault. However, when a high-resistance grounding fault occurs on the line, ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/00
Inventor 束洪春余多高利杨竞及
Owner KUNMING UNIV OF SCI & TECH