Fractal dimension-based ultrahigh voltage DC transmission line boundary element method

A UHV DC and fractal dimension technology, applied to electrical components, emergency protection circuit devices, etc., can solve problems such as the influence of the change rate of directional traveling waves, DC protection devices refusing to operate, and easy to malfunction

Active Publication Date: 2011-06-15
KUNMING UNIV OF SCI & TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, relevant data show that the currently used DC line traveling wave protection has the problems of easy misoperation and noise interference to varying degrees.
Or due to problems such as the change rate of directional traveling wave being affected by the transition resistance, sometimes the existing DC protection device will refuse to operate

Method used

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  • Fractal dimension-based ultrahigh voltage DC transmission line boundary element method
  • Fractal dimension-based ultrahigh voltage DC transmission line boundary element method
  • Fractal dimension-based ultrahigh voltage DC transmission line boundary element method

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Experimental program
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Embodiment Construction

[0067] Simulation model such as figure 1 As shown, a positive grounding fault occurs at a distance of 150km from the protection installation, the grounding resistance is 1Ω, the time window length is 2ms, and the sampling frequency is 100kHz.

[0068] (1) After the DC line fails, the starting element starts immediately, according to the formula:

[0069] (1)

[0070] Find the line-mode voltage , the line-mode voltage waveform is as Figure 4 as shown in (a);

[0071] (2) Fractalize the line-mode voltage and find its fractal dimension D , whose sampling frequency f 100kHz, sample sequence length n for 200 points. The present invention adopts box dimension as the method for finding fractal dimension, establishes time series: , ,…, , ( i= 1,2,…, n ) for the i The sampling value of a sampling point.

[0072] (3) Take the time scale as r ( , in the present invention r =50) divide the time series into time period: , ...

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Abstract

The invention discloses a fractal dimension-based ultrahigh voltage DC transmission line boundary element method. When a DC line fails, after a protective element is started, a line-mode voltage is calculated by utilizing a phase-mode transformation theory according to DC voltages of two electrodes at a protection arrangement position; and a discrete line-mode voltage signal with the sampling sequence length of 200 points is selected, and fractals are measured by adopting a box dimension method to calculate a fractal dimension D for distinguishing an internal failure from an external failure. In the method, sampling frequency is 100 KHz, a time window is 2 ms, a required data length is relatively shorter and the influence of a control system is avoided. Various failures in the full-length range of the line can be accurately identified by the method. The method ensures relatively higher resistance to transition resistance, and is not influenced by interference and highly practical.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a method for boundary elements of UHV DC transmission lines based on fractal dimension. Background technique [0002] The transmission power of the DC transmission line is large. After the line fails, the line protection device must remove the fault as soon as possible, otherwise it will cause a great impact on the entire system and pose a threat to the safe and stable operation of the system. General power frequency protection operates slowly and takes a long time, which is difficult to meet the requirements of DC transmission line protection. At present, traveling wave protection is widely used in the world as the main protection of high-voltage DC line protection. Its single-ended protection is based on the mutation amount and change rate of voltage traveling wave and the gradient of current change as the criterion. It has ultra-high-speed action...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/26
Inventor 束洪春安娜田鑫萃张广斌孙士云刘可真曹璞璘万雄彪贺婷方毅
Owner KUNMING UNIV OF SCI & TECH
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