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Method for detecting internal and external faults of ultra high voltage direct current transmission lines based on pole wave mathematical morphology spectrum

A UHV DC, mathematical form technology, applied in the direction of measuring electricity, measuring devices, measuring electrical variables, etc., to achieve the effect of simple calculation method, effective algorithm and accurate conclusion

Active Publication Date: 2012-07-18
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Its protection is based on the current gradient, voltage traveling wave conversion rate and voltage traveling wave mutation as the criterion, but its protection is easily affected by transition resistance, especially when there is an external fault, the fault traveling wave passes through the flat wave at the end of the DC line. For reactors and DC filters, the voltage conversion rate is reduced, which is likely to cause malfunction or refusal of protection, which has a great impact on the stable operation of the DC system
Therefore, the main protection of the DC system based on the change rate criterion is easily affected by transition resistance, noise interference, fault distance, etc.

Method used

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  • Method for detecting internal and external faults of ultra high voltage direct current transmission lines based on pole wave mathematical morphology spectrum
  • Method for detecting internal and external faults of ultra high voltage direct current transmission lines based on pole wave mathematical morphology spectrum
  • Method for detecting internal and external faults of ultra high voltage direct current transmission lines based on pole wave mathematical morphology spectrum

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] (1) After the DC line fails, the starting element starts immediately, and reads the positive DC voltage collected at the protection installation U + ( k ) and DC current I + ( k ), according to the formula: P + ( k )=Z P I + ( k ) -U + ( k ), to obtain the polar wave voltage, its waveform is as image 3 shown;

[0037] (2) According to wavelet transform: , carry out 4-layer wavelet transform on the positive line polar wave voltage, extract the high-frequency part of each layer, and add them together to obtain the high-frequency feature quantity of the polar wave voltage with a frequency spectrum above 3125Hz (sampling frequency 100kHz) PG + ( k );

[0038] (3) According to the formula ( )and ( ), calculate the high-frequency characteristic quantity of positive line wave voltage PG + ( k ) positive semi-axis mathematical form spectral value : g is a half-sine structural element, and the scale r is selected as 9; Represents the open...

Embodiment 2

[0044] Embodiment 3: The structure and parameters of the power transmission system are the same as in Example 1, and the steps of monitoring and identifying faults are the same as in Example 1.

[0045] The phase A ground fault of the AC bus on the inverter side of the DC transmission line is faulty, and the transition resistance is 5 ohms. The sampling short data window length is 5ms, and the sampling frequency is 100kHz; when the polar wave voltage is subjected to 4-layer wavelet transformation, the spectrum of the high-frequency transient quantity of the polar wave voltage obtained by extracting the high-frequency part of each layer and adding them is above 3125Hz ;Calculate the high-frequency characteristic quantity of positive line wave voltage PG + ( k ), the positive semi-axis mathematical form spectrum value, the scale r is selected as 9.

[0046] The integral value sought SPS =0.3246<50, it is judged as an out-of-area fault.

Embodiment 3

[0047] The present invention performs simulation verification for different types of out-of-area faults and different grounding resistances of transmission lines, and obtains the integral of the form spectrum value along the scale of the structural element SPS , the results are shown in the table below:

[0048]

[0049] In the table, A-G means A-phase ground fault, B-G means B-phase ground fault, C-G means C-phase ground fault, A-B means AB phase short-circuit fault, A-C means AC phase short-circuit fault, B-C means BC phase short-circuit fault, AB- G means AB two-phase short-circuit ground fault, AC-G means AC two-phase short-circuit ground fault, BC-G means BC two-phase short-circuit ground fault, ABC-G means three-phase short-circuit ground fault.

[0050] Principle of the present invention is:

[0051] When a fault occurs outside the area, the generated voltage traveling wave reaches the transient voltage traveling wave at the protection installation through refrac...

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Abstract

The invention provides a method for detecting internal and external faults of ultra high voltage direct current transmission lines based on pole wave mathematical pattern spectrum. The method is characterized in that when a direct current (DC) line fault occurs, a starting component is started, according to positive pole line DC voltage U+(k) and DC I+(k) which are collected by a protection installation location, pole wave voltage of a positive pole line is obtained, and the positive pole line pole wave voltage is subjected to wavelet transform, pole wave voltage high frequency characteristic quantity PG+(k) of a high frequency portion of the positive pole line pole wave voltage is extracted. The pole wave voltage high frequency characteristic quantity is calculated by means of mathematical morphology, a mathematical morphology spectrum value of the pole wave voltage high frequency characteristic quantity is obtained, structure element scale needed is selected, and the mathematical morphology spectrum value is subjected to integration operation along abscissa axis structure element scale. Internal and external faults are distinguished according to the integration operation value. The method has the advantages of being sensitive in identifying the internal faults, reliable in identifying the external faults and applicable to the popularization and the usage in direct current transmission line systems.

Description

technical field [0001] The invention relates to a form spectrum detection method for identifying internal and external faults of UHV DC transmission lines based on polar wave transient quantities, and belongs to the technical field of power system relay protection. Background technique [0002] At present, traveling wave protection is widely used in the world as the main protection of HVDC transmission line protection. It uses the current and voltage traveling waves transmitted at the moment of fault to form ultra-high-speed line protection. Moreover, DC line protection provided by ABB and SIEMENS is adopted in most projects. Its protection is based on the current gradient, voltage traveling wave conversion rate and voltage traveling wave mutation as the criterion, but its protection is easily affected by transition resistance, especially when there is an external fault, the fault traveling wave passes through the flat wave at the end of the DC line. For reactors and DC fi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/02
Inventor 束洪春万雄彪田鑫萃
Owner KUNMING UNIV OF SCI & TECH
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