An infrared zero measurement method for disc-shaped suspension porcelain insulators of DC transmission lines

Abstract

The present invention provides an infrared zero measurement method for a disk-type suspended porcelain insulator of a DC transmission line, and the method includes the following specific steps: obtaining an infrared spectrum of a DC porcelain insulator; extracting temperature distribution data of an iron cap in the spectrum; calculating the temperature distribution difference in the iron cap, and obtaining the average temperature difference, temperature range and variance of the iron cap; calculating the temperature distribution difference between the iron caps, and obtaining an average temperature difference curve and an adaptive parameter curve; calculating a judgment parameter; and determining a degraded insulator according to the judgment parameter. The present invention combines the average temperature difference, range and variance of the iron cap; and calculates an adaptive parameter curve to obtain a judgment parameter, which is used to accurately judge whether a disk-type suspended DC porcelain insulator is degraded.

Description

Technical Field

[0001] The invention relates to the technical field of infrared detection of disc-shaped suspended porcelain insulators of direct current transmission lines, and in particular to a method for realizing zero-value degradation detection of direct current porcelain insulators by analyzing infrared thermal images thereof. Background Art

[0002] Insulators are a common type of electrical insulation equipment, which are widely used in power generation, transmission, transformation and distribution equipment. During long-term operation, insulator strings are affected by a variety of complex factors such as mechanical loads, overvoltage, acid rain, lightning strikes, icing, strong winds, ultraviolet rays, dirt, temperature and humidity changes, etc. The electrical and mechanical properties of insulators will gradually decline, resulting in degradation. Degraded insulators cannot withstand normal electromechanical loads, which may lead to partial discharge, surface slip, longitudinal insulation breakdown, explosion, string drop and other phenomena, posing a huge hidden danger to the safe and stable operation of the power system.

[0003] DC porcelain insulators are high-voltage external insulation devices serving DC transmission and distribution networks. The particularity of their operating conditions determines the particularity of their structures. DC porcelain insulators are quite different from the common insulation devices in AC transmission and transformation systems. Conventional AC insulator detection methods cannot accurately and effectively detect DC porcelain insulators. With the maturity of DC transmission and distribution technology, the application of DC porcelain insulators is becoming more and more extensive, and the detection problem of DC porcelain insulators is becoming increasingly prominent.

[0004] At present, there are many kinds of insulator deterioration detection methods, and the main methods for porcelain insulator detection include spark gap method, insulation resistance method, voltage distribution method, leakage current method, infrared thermal imaging method, ultraviolet imaging method, ultrasonic method, etc. Among them, infrared thermal imaging method is the most commonly used non-contact live detection method. Its principle is to judge the degree of deterioration of the insulator based on the heating characteristics of the insulator.

[0005] At the power equipment maintenance site, the usual infrared detection method is to take infrared images of the target equipment, analyze the temperature anomalies in the image, and determine the deteriorated insulators through diagnostic criteria. However, the existing infrared detection method for porcelain insulators is developed from the experience of on-site detection of AC porcelain insulators and is not suitable for DC porcelain insulator deterioration detection. Summary of the invention

[0006] The purpose of the present invention is to provide a DC porcelain insulator detection method, which can solve the problem that the current AC porcelain insulator infrared detection method is not suitable for the DC porcelain insulator infrared detection field, and fill the gap in the DC porcelain insulator infrared detection method.

[0007] The technical solution of the present invention:

[0008] Compared with the existing infrared detection technology for insulators, the present invention creatively proposes an infrared detection method applied to DC porcelain insulators, which has high technical advancement and wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1 is a flow chart of the method of the present invention;

[0010] Fig. 2 is an infrared spectrum of the case described in the present invention;

[0011] Figure 3 is the average temperature distribution curve of the insulator string shown in the case;

[0012] Figure 4 is the extreme difference distribution curve of the insulator string shown in the case;

[0013] Figure 5 is a variance distribution curve of the insulator string shown in the case;

[0014] FIG6 is a curve showing the average temperature difference distribution of the insulator string shown in the case;

[0015] Figure 7 is the adaptive parameter curve used in the case;

[0016] FIG8 is a multi-dimensional and multi-scale fusion judgment parameter curve and a degradation judgment result of the case calculation. DETAILED DESCRIPTION

[0017] The following will be combined with the accompanying drawings in the examples of the present invention to clearly and completely describe the technical solutions in the examples of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] As shown in FIG1 , a DC porcelain insulator infrared detection method provided in the present invention specifically comprises the following steps:

[0019] Step 1: Obtain infrared spectrum of DC porcelain insulator string;

[0020] Step 2: Extract the temperatures of all the porcelain insulator caps in the graph of step 1;

[0021] Step 3: Calculate the temperature distribution difference inside the iron cap;

[0022] Step 4: Calculate the temperature distribution difference between iron caps;

[0023] Step 5: Calculate the multi-dimensional and multi-scale fusion judgment parameters;

[0024] Step 6: Determine the number and location of deteriorated porcelain insulators.

[0025] The specific process is as follows:

[0026] (1) After obtaining the infrared spectrum of the DC porcelain insulator string, analyze the spectrum shooting effect, determine the spectrum detection value, and use manual or automatic methods to extract the temperature distribution of the insulator iron cap area in the spectrum;

[0027] (2) Calculate the mean E, range R and variance D of each iron cap temperature distribution, and draw the mean curve Ec, range curve Rc and variance curve Dc composed of each iron cap temperature distribution;

[0028] (3) Calculate the average temperature difference curve ΔEc between the iron caps. The calculation method is shown in formula ①

[0029]

[0030] ①

[0031]

[0032] In formula ①, n is the number of insulator strings in the analyzed infrared spectrum. In this case, n is 33. The insulator numbering direction is from the conductor side to the tower side;

[0033] (4) Construct the adaptive parameter curve Zc. The calculation method is shown in formula ②

[0034] ②

[0035] In formula ②, T is the thermodynamic ambient temperature of the shooting scene, which is 290.65 in this case; RH is the relative humidity of the shooting scene, which is 0.969 in this case; a is the temperature correction coefficient, which is 9.8×10 -4 ; k is the humidity correction factor, in this case k is 0.88;

[0036] (5) Calculate the determination parameter ξ according to formula ③

[0037] ③

[0038] In formula ③, ε is the temperature difference threshold, which is 0.5 in this case; γ is the extreme difference threshold, which is 0.838 in this case; σ is the variance threshold, which is 0.066 in this case; d is the offset coefficient, which is 0.14 in this case; the calculated value of the judgment parameter corresponds to the insulator one by one, and when the judgment parameter ξ>0, the corresponding insulator piece is determined to be a degraded insulator.

[0039] After calculation, it can be seen from Figure 8 that in the infrared spectrum shown in the case, the 1st, 2nd, 3rd, 10th, 12th, and 14th upper string insulators are deteriorated insulators.

Claims

1. A method for infrared zero measurement of a disk-type suspension porcelain insulator of a DC transmission line, characterized in that: The following steps are involved: S1. Obtain infrared spectrum of DC porcelain insulator string; S2. extracting the temperatures of all porcelain insulator caps in the obtained spectrum; S3. Calculate the temperature distribution difference inside the iron cap: Specifically, the mean E, range R and variance D of each iron cap temperature distribution are calculated, and the mean curve Ec, range curve Rc and variance curve Dc composed of each iron cap temperature distribution are drawn; S4. Calculate the temperature distribution difference between iron caps: (1) It is necessary to calculate the average temperature difference curve of the iron cap, the average temperature difference curve ΔEc, and the calculation method is shown in formula (1) In formula (1), n ​​is the number of insulator strings in the analyzed infrared spectrum, and the insulator numbering direction is from the conductor side to the tower side; (2) It is necessary to construct an adaptive parameter curve, the adaptive parameter curve Zc, and the calculation method is shown in formula (2): In formula (2), T is the thermodynamic ambient temperature of the shooting scene; RH is the relative humidity of the shooting scene; a is the temperature correction coefficient; k is the humidity correction coefficient; S5. Calculate the judgment parameter, as shown in the following formula In formula (3), ε is the temperature difference threshold; γ is the extreme difference threshold; σ is the variance threshold; d is the offset coefficient, Ec i is the i-th item in the mean curve, Rc i is the i-th item in the range curve, Dc i is the i-th item in the variance curve; the calculated value of the judgment parameter corresponds to the insulator one by one. When the judgment parameter ξ>0, the corresponding insulator piece is determined to be a deteriorated insulator. S6. Determine the number and location of deteriorated insulators.

2. The infrared zero measurement method for a disk-type suspension porcelain insulator of a DC transmission line according to claim 1 is characterized in that: The requirements for obtaining the infrared spectrum of the DC porcelain insulator string include: (1) Ensure that all insulator caps of the insulator string being photographed are clearly visible (2) The thermodynamic temperature and relative humidity at the time of shooting must be available.

3. The infrared zero measurement method for a disk-type suspension porcelain insulator of a DC transmission line according to claim 1 is characterized in that: The temperatures of all porcelain insulator caps in the extracted spectrum include (1) Only includes all the iron caps of the target insulator string to be analyzed; (2) The extraction method may be manual or automatic; (3) The extraction area is all or most of the pixels of the iron cap in the infrared spectrum.

4. The infrared zero measurement method for a disk-type suspension porcelain insulator of a DC transmission line according to claim 1 is characterized in that: The calculation of the temperature distribution difference in the iron cap includes: (1) The average value of each iron cap temperature data needs to be calculated; (2) The range of temperature data for each iron cap needs to be calculated; (3) The variance of each iron cap temperature data needs to be calculated; (4) The mean curve, range curve, and variance curve are curves in which the mean, range, and variance of each iron cap are arranged in the order of the insulator serial number.

5. The infrared zero measurement method for a disk-type suspension porcelain insulator of a DC transmission line according to claim 1 is characterized in that: The calculation parameters include: (1) Corresponding temperature difference threshold, range threshold, and variance threshold are required; (2) The judgment parameter corresponds to the insulator serial number to form a judgment parameter curve.

6. The infrared zero measurement method for a disk-type suspension porcelain insulator of a DC transmission line according to claim 1 is characterized in that: The number and location of deteriorated insulators can be determined by judging the parameter curve and the corresponding serial number of the insulator.

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