CN109581150B - Cable fault location method based on spectral attenuation characteristics - Google Patents

Abstract

The invention relates to a method for locating a fault point of a cable based on a spectrum attenuation characteristic. The relationship curve between amplitude and position; calculate the corresponding intersection position of the two relationship curves when the amplitude is equal; take the intersection position as the starting point, collect partial discharge signals at different positions on the opposite side of the cable line and separate them out Partial discharge signal amplitude, fit the relationship curve between the PD signal amplitude and position at different frequencies, and obtain the position of the intersection point corresponding to the relationship curve when the amplitudes are equal is the PD originating point. The design of the invention is reasonable, and the test can not only be tested in the case of line power failure, but also can be tested when the line is running. The test can be performed both at the end of the line and from the middle joint of the line. The test results are accurate, convenient and suitable for Wide range of occasions.

Description

Cable fault location method based on spectral attenuation characteristics

technical field

The invention belongs to the technical field of power cables, in particular to a cable fault point location method based on spectrum attenuation characteristics.

Background technique

With the advancement of the transformation and upgrading of the power supply system focusing on the urban power supply network, the cableization rate of transmission lines with voltage levels of 110kV and above has increased rapidly. seem particularly urgent. Partial discharge, as the main manifestation of cable line insulation failure in the early stage, is not only the main cause of insulation aging, but also the main characteristic parameter to characterize the insulation condition. At present, the use of partial discharge live detection in the operation of high-voltage cross-linked cable lines is closely concerned at home and abroad. Technology hotspots.

At present, the more effective method for localization of cable partial discharge is the oscillating wave method. This method needs to carry out detection in the case of a power failure of the cable under test. First, the end of the cable under test is pressurized to a preset value. The capacitor resonates, and a damped oscillating voltage is generated at the end of the cable under test. The pulse reflection method is used to locate the partial discharge. This method has the following disadvantages: (1) The test needs to be carried out in the case of a power failure of the line under test. The operating conditions have requirements; (2) The test can only be performed at the end of the line under test. During the test, the signal cannot be effectively collected due to the long line length and the fast attenuation of the high-frequency partial discharge signal.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art, and to propose a method for locating fault points of cables based on spectrum attenuation characteristics, so as to solve the problems of difficulty in testing and inability to effectively collect signals due to partial discharge signal attenuation.

The present invention solves its technical problem by adopting the following technical solutions to realize:

A method for locating fault points of cables based on spectral attenuation characteristics, comprising the following steps:

Step 1. Use a data collector to collect partial discharge signals at n different positions at positions l ₁₁ , l ₁₂ . . . l _1n of the cable lines, respectively.

Step 2. Use a filter to separate out the partial discharge signal amplitudes at positions l ₁₁ , l ₁₂ ...... l _1n at frequencies f ₁ , f ₂ ;

Step 3. Fitting the relationship curves H ₁ (f ₁ ) and H ₁ (f ₂ ) of the PD signal amplitude and position at the frequencies f ₁ and f ₂ according to the distance l and the corresponding PD signal amplitude H;

Step 4. Obtain the intersection position l ₀ corresponding to the curves H ₁ (f ₁ ) and H ₁ (f ₂ ) when the amplitudes are equal;

Step 5. Take the corresponding intersection position l ₀ when the amplitudes are equal as the starting point, take the positions l ₂₁ , l ₂₂ ... l _2n on the opposite direction side of the cable lines l ₁₁ , l ₁₂ ...... l _1n to collect n respectively. PD signals at corresponding positions;

Step 6. Use a filter to separate out the partial discharge signal amplitudes at l ₂₁ , l ₂₂ ...... l _2n under the same frequencies f ₁ , f ₂ ;

Step 7, according to the distance l and the corresponding partial discharge signal amplitude H, fit the relationship curves H ₂ (f ₁ ) and H ₂ (f ₂ ) of the partial discharge signal amplitude and position at the frequencies f ₁ and f ₂ ;

Step 8: Obtaining the intersection position l corresponding to the curves H ₁ (f ₁ ) and H ₂ (f ₁ ) when the amplitudes are equal is the PD starting point.

The advantages and positive effects of the present invention are:

1. The design of the present invention is reasonable, it collects the partial discharge signal in the cable line and extracts the amplitude signal at different frequencies, establishes the characteristic parameter attenuation curve of partial discharge propagation in the cable at different frequencies, and then according to the partial discharge signal in the cable. The propagation law and spectral attenuation characteristics in the cable line realize the function of cable fault location, which can not only be tested in the case of line power failure, but also can be tested when the line is running. There are no specific requirements for the operating conditions of the line. .

2. When the present invention is testing, it can be tested at the end of the line, or it can be located in the middle of the line and tested from the middle joint of the line, so as to avoid the problem that the partial discharge signal cannot be effectively collected due to the attenuation of the partial discharge signal. The partial discharge signal is attenuated to the point that it cannot be captured due to the long propagation distance. The test results are accurate, the error is small, and the accuracy is high.

Description of drawings

Figure 1 is a graph showing the relationship between the spectral transfer function of the partial discharge signal and the line length.

Detailed ways

The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

The design idea of the present invention is as follows: the partial discharge inside the power cable is a broadband signal containing abundant high-frequency components, the frequency of the partial discharge signal is generally in the range of tens to hundreds of megahertz, and the frequency spectrum of the partial discharge signal is generally in the range of tens to hundreds of megahertz. The relationship between the transfer function and the line length is shown in Figure 1. The invention collects the partial discharge signal in the cable line and extracts the amplitude signals at different frequencies, establishes the characteristic parameter attenuation curve of the partial discharge propagation in the cable at different frequencies, and then according to the propagation of the partial discharge signal in the cable line The law and spectrum attenuation characteristics realize the function of cable fault location.

Based on the above design idea, the method for locating the fault point of the cable based on the spectral attenuation characteristic of the present invention includes the following steps:

Step 1. Use a data collector to collect partial discharge signals at n different positions at positions l ₁₁ , l ₁₂ . . . l _1n of the cable lines, respectively.

Step 2. Use a filter to separate out the partial discharge signal amplitudes at the frequencies of f ₁ , f ₂ at l ₁₁ , l ₁₂ ...... l _1n .

Step 3. Fit the relationship curves H ₁ (f ₁ ) and H ₁ (f ₂ ) of the PD signal amplitude and position at different frequencies f ₁ and f ₂ according to the distance l and the corresponding PD signal amplitude H .

Step 4: Obtain the corresponding intersection position l ₀ of the curves H ₁ (f ₁ ) and H ₁ (f ₂ ) when the amplitudes are equal.

Since the originating position of the PD signal must be located on the right side of the intersection position _l0 , and according to the propagation law of the PD signal, the PD signal is symmetrically propagated to both sides with the originating point as the midpoint.

Step 5. Take the corresponding intersection position l ₀ when the amplitudes are equal as the starting point, and collect n samples from the positions l ₂₁ , l ₂₂ ... l _2n on the opposite direction side of the cable lines l ₁₁ , l ₁₂ ...... l _1n PD signals at different locations.

Step 6: Use the filter to separate out the partial discharge signal amplitudes at the same frequencies f ₁ , f ₂ again at l ₂₁ , l ₂₂ ...... l _2n ,

Step 7. Fit the relationship curves H ₂ (f ₁ ) and H ₂ (f ₂ ) between the PD signal amplitude and the position at the frequencies f ₁ and f ₂ according to the distance l and the corresponding PD signal amplitude H.

Step 8: Obtaining the intersection position l corresponding to the curves H ₁ (f ₁ ) and H ₂ (f ₁ ) when the amplitudes are equal is the PD starting point.

Through the above steps, the occurrence position of the partial discharge signal can be obtained.

What is not described in the present invention applies to the prior art.

It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive, so the present invention includes but is not limited to the embodiments described in the specific implementation manner. Other embodiments derived from the scheme also belong to the protection scope of the present invention.

Claims (1)

1. a cable fault point location method based on spectrum attenuation characteristic is characterized in that comprising the following steps: Step 1. Use a data collector to collect partial discharge signals at n different positions at positions l ₁₁ , l ₁₂ ...... l _1n of the cable lines respectively; Step 2. Use a filter to separate out the partial discharge signal amplitudes at positions l ₁₁ , l ₁₂ ...... l _1n at frequencies f ₁ , f ₂ ; Step 3. Fitting the relationship curves H ₁ (f ₁ ) and H ₁ (f ₂ ) of the PD signal amplitude and position at the frequencies f ₁ and f ₂ according to the distance l and the corresponding PD signal amplitude H; Step 4. Obtain the intersection position l ₀ corresponding to the curves H ₁ (f ₁ ) and H ₁ (f ₂ ) when the amplitudes are equal; Step 5. Take the corresponding intersection position l ₀ when the amplitudes are equal as the starting point, take the positions l ₂₁ , l ₂₂ ... l _2n on the opposite direction side of the cable lines l ₁₁ , l ₁₂ ...... l _1n to collect n respectively. PD signals at corresponding positions; Step 6. Use a filter to separate out the partial discharge signal amplitudes at l ₂₁ , l ₂₂ ...... l _2n under the same frequencies f ₁ , f ₂ ; Step 7, according to the distance l and the corresponding partial discharge signal amplitude H, fit the relationship curves H ₂ (f ₁ ) and H ₂ (f ₂ ) of the partial discharge signal amplitude and position at the frequencies f ₁ and f ₂ ; Step 8: Obtaining the intersection position l corresponding to the curves H ₁ (f ₁ ) and H ₂ (f ₁ ) when the amplitudes are equal is the PD starting point.

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