Silicon rubber composite insulator degradation state monitoring method based on Lissajous image features

Abstract

The invention discloses a silicon rubber composite insulator degradation state monitoring method based on Lissajous image features, the method is mainly suitable for online real-time monitoring of the degradation state of a silicon rubber insulator, and the method comprises the following specific steps: (1) measuring to obtain the input voltage and leakage current of a healthy insulator; (2) constructing a Lissajous image by using the input voltage and the leakage current signal; (3) extracting characteristic parameters of the healthy insulator Lissajous image; (4) carrying out normalization processing on the voltage and current data of the insulator to be detected; and (5) calculating a degradation comprehensive monitoring coefficient CMI and evaluating the degradation state of the insulator. According to the method, the degradation state of the insulator can be monitored on line in real time, and compared with the prior art, the execution cost is lower, the efficiency is higher, and the method has important significance for accurately evaluating the degradation severity of the silicone rubber composite insulator.

Description

Technical Field

[0001] The invention belongs to the field of insulator degradation state monitoring and diagnosis, and in particular relates to a method for monitoring the degradation state of a silicone rubber composite insulator based on Lissajous image features. Background Art

[0002] Silicone rubber composite insulators are widely used in my country's power transmission lines and EMU trains because of their excellent pollution resistance. Their insulation status directly affects the reliability of power supply. Under the synergistic effect of pollutants and atmospheric environments such as high temperature, rain, and air pressure, the insulation properties of silicone rubber composite insulators will continue to deteriorate, resulting in reduced insulation performance. In severe cases, flashover accidents may even occur, causing the insulator to be broken down, seriously affecting the reliability of power supply and the safety of life and property of residents. Since most insulators have high voltage levels and are installed in narrow spaces or high altitudes, inspection is inconvenient. And the priority of replacing insulators varies depending on the degree of degradation. Therefore, real-time understanding of the degradation status of silicone rubber composite insulators is of great significance to ensuring sustainable, safe and reliable power supply.

[0003] At present, the detection of insulator degradation still mainly relies on traditional electrical detection methods, including insulation resistance test, withstand voltage test, dielectric loss angle measurement, etc. Unfortunately, these parameters will only change after the insulator material has seriously deteriorated. It is difficult to detect the slight degradation of the insulator, and the detection sensitivity is low. In recent years, scholars have developed several new detection technologies suitable for the degradation of insulators, including microwave detection, scanning electron microscopy analysis, infrared spectroscopy analysis, etc. Unfortunately, these methods need to be carried out under power outage conditions and cannot achieve the purpose of real-time monitoring of the insulator state. In addition, equipment such as microwave detection sources and scanning electron microscopy sources are relatively expensive, which has become an important factor restricting its further promotion.

[0004] Therefore, studying new detection methods for the degradation state of silicone rubber composite insulators, realizing real-time grasp of the degradation state and reducing and improving its detection sensitivity to the initial degradation state is of great significance for staff to formulate maintenance strategies in a timely manner and reduce the accident rate caused by insulator degradation. Summary of the invention

[0005] In order to solve the problems of low sensitivity, high cost, and inability to detect in real time in the current silicone rubber composite insulator detection methods, the present invention provides a silicone rubber composite insulator degradation state monitoring method based on Lissajous image features.

[0006] The technical solution adopted by the present invention is as follows:

[0007] 1. A method for monitoring the degradation state of a silicone rubber composite insulator based on Lissajous image features, characterized in that the degradation state of the silicone rubber composite insulator is monitored by online measuring the instantaneous values ​​of the insulator input voltage and leakage current through the following steps:

[0008] Step 1: Measure the input voltage and leakage current of healthy insulators

[0009] At the beginning of the insulator operation, the input voltage and leakage current of the insulator are measured by voltage transformer and current transformer. It is assumed that their instantaneous values ​​are expressed as u(t)=U0 cos(ωt) and i(t)=I0 cos(ωt+θ), where t is the measurement time and θ is the phase difference between the leakage current and the input voltage.

[0010] Step 2: Construct a Lissajous image from the input voltage and leakage current signals

[0011] According to the Euler formula, the intermediate variable t is eliminated, the correlation between the input voltage u(t) and the leakage current i(t) is obtained, and the Lissajous image representing the insulation characteristics of the insulator itself is drawn. This process can be expressed as:

[0012]

[0013] Among them, U0 and I0 are the amplitudes of the input voltage and leakage current of the healthy insulator, respectively;

[0014] Step 3: Extract characteristic parameters of healthy insulator Lissajous image

[0015] The Lissajous image is converted into a binary image, and the morphological features of the Lissajous image are extracted using digital image processing technology, including major axis, minor axis, perimeter, area and eccentricity, a total of 5 graphic features, denoted as H i , i = 1 to 5;

[0016] Step 4: Normalize the voltage and current data of the insulator to be tested

[0017] After the insulator has been in operation for a period of time or has a fault, the input voltage and leakage current of the insulator to be tested are measured under the same measurement conditions and are recorded as u1(t)=U1cos(ωt) and i1(t)=I1cos(ωt+θ1), respectively. θ1 is the phase difference between the leakage current of the insulator to be tested and the input voltage. The phase difference is normalized according to the following formulas (2) and (3) to eliminate the influence of voltage fluctuations:

[0018]

[0019] Among them, u1'(t) and i1'(t) are respectively the normalized input voltage and leakage current instantaneous values ​​of the insulator to be tested; U1 and I1 are respectively the amplitudes of the measured input voltage and leakage current;

[0020] Step 5: Calculate the comprehensive monitoring coefficient CMI and evaluate the degradation status of the insulator

[0021] The normalized insulator voltage and current data are used to construct the Lissajous figure of the insulator to be tested, and its five morphological features are extracted, which are denoted as F i , i = 1 to 5, and calculate the comprehensive degradation monitoring coefficient CMI:

[0022]

[0023] The degradation state of the insulator is evaluated according to the size of CMI. If CMI=0, it means that the insulation state of the silicone rubber insulator is normal; the smaller the CMI, the milder the degradation state of the silicone rubber insulator; the larger the CMI, the more serious the degradation state of the silicone rubber insulator.

[0024] The beneficial effect of the present invention is that the insulator input voltage and leakage current are combined and converted into a Lissajous image, and the morphological characteristics of the Lissajous image are used to monitor the degradation state of the silicone rubber composite insulator. Compared with the existing detection method, it has the following advantages:

[0025] 1) The Lissajous image of the proposed insulator contains both the input voltage information and the leakage current information of the insulator. Any slight change in its insulation state will cause the change of the Lissajous image characteristics. Therefore, it has higher sensitivity than the traditional electrical parameter detection method.

[0026] 2) The proposed technology is based on real-time measurement of insulator voltage and leakage current data, which can realize online real-time monitoring of insulator degradation status, overcoming the disadvantage that traditional electrical detection methods need to be carried out under power outage conditions;

[0027] 3) The proposed technology only needs to use the existing voltage transformer on the primary side of the insulator to measure the input voltage, and an additional current transformer is installed to measure the insulator leakage current. Compared with some existing expensive new detection technologies, the proposed technology has lower execution cost, higher efficiency, and can realize real-time monitoring of the insulator degradation status. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings:

[0030] 1. A method for monitoring the degradation state of a silicone rubber composite insulator based on Lissajous image features, characterized in that the degradation state of the silicone rubber composite insulator is monitored by online measuring the instantaneous values ​​of the insulator input voltage and leakage current through the following steps:

[0031] Step 1: Measure the input voltage and leakage current of healthy insulators

[0032] At the beginning of the insulator operation, the input voltage and leakage current of the insulator are measured by voltage transformer and current transformer. It is assumed that their instantaneous values ​​are expressed as u(t)=U0 cos(ωt) and i(t)=I0 cos(ωt+θ), where t is the measurement time and θ is the phase difference between the leakage current and the input voltage.

[0033] Step 2: Construct a Lissajous image from the input voltage and leakage current signals

[0034] According to the Euler formula, the intermediate variable t is eliminated, the correlation between the input voltage u(t) and the leakage current i(t) is obtained, and the Lissajous image representing the insulation characteristics of the insulator itself is drawn. This process can be expressed as:

[0035]

[0036] Among them, U0 and I0 are the amplitudes of the input voltage and leakage current of the healthy insulator, respectively;

[0037] Step 3: Extract characteristic parameters of healthy insulator Lissajous image

[0038] The Lissajous image is converted into a binary image, and the morphological features of the Lissajous image are extracted using digital image processing technology, including major axis, minor axis, perimeter, area and eccentricity, a total of 5 graphic features, denoted as H i , i = 1 to 5;

[0039] Step 4: Normalize the voltage and current data of the insulator to be tested

[0040] After the insulator has been in operation for a period of time or has a fault, the input voltage and leakage current of the insulator to be tested are measured under the same measurement conditions and are recorded as u1(t)=U1cos(ωt) and i1(t)=I1cos(ωt+θ1), respectively. θ1 is the phase difference between the leakage current of the insulator to be tested and the input voltage. The phase difference is normalized according to the following formulas (2) and (3) to eliminate the influence of voltage fluctuations:

[0041]

[0042] Among them, u1'(t) and i1'(t) are respectively the normalized input voltage and leakage current instantaneous values ​​of the insulator to be tested; U1 and I1 are respectively the amplitudes of the measured input voltage and leakage current;

[0043] Step 5: Calculate the comprehensive monitoring coefficient CMI and evaluate the degradation status of the insulator

[0044] The normalized insulator voltage and current data are used to construct the Lissajous figure of the insulator to be tested, and its five morphological features are extracted, which are denoted as F i , i = 1 to 5, and calculate the comprehensive degradation monitoring coefficient CMI:

[0045]

[0046] The degradation state of the insulator is evaluated according to the size of CMI. If CMI=0, it means that the insulation state of the silicone rubber insulator is normal; the smaller the CMI, the milder the degradation state of the silicone rubber insulator; the larger the CMI, the more serious the degradation state of the silicone rubber insulator.

Claims

1. A method for monitoring the degradation state of silicone rubber composite insulators based on Lissajous image features, characterized in that: By measuring the instantaneous values ​​of the insulator input voltage and leakage current online, the degradation state of the silicone rubber composite insulator is monitored through the following steps: Step 1: Measure the input voltage and leakage current of healthy insulators At the beginning of the insulator operation, the input voltage and leakage current of the insulator are measured by voltage transformer and current transformer. It is assumed that their instantaneous values ​​are expressed as u(t)=U0 cos(ωt) and i(t)=I0 cos(ωt+θ), where t is the measurement time and θ is the phase difference between the leakage current and the input voltage. Step 2: Construct a Lissajous image from the input voltage and leakage current signals According to the Euler formula, the intermediate variable t is eliminated, the correlation between the input voltage u(t) and the leakage current i(t) is obtained, and the Lissajous image representing the insulation characteristics of the insulator itself is drawn. This process can be expressed as: Among them, U0 and I0 are the amplitudes of the input voltage and leakage current of the healthy insulator, respectively; Step 3: Extract characteristic parameters of healthy insulator Lissajous image The Lissajous image is converted into a binary image, and the morphological features of the Lissajous image are extracted using digital image processing technology, including major axis, minor axis, perimeter, area and eccentricity, a total of 5 graphic features, denoted as H i , i = 1 to 5; Step 4: Normalize the voltage and current data of the insulator to be tested After the insulator has been in operation for a period of time or has a fault, the input voltage and leakage current of the insulator to be tested are measured under the same measurement conditions and are recorded as u1(t)=U1cos(ωt) and i1(t)=I1cos(ωt+θ1), respectively. θ1 is the phase difference between the leakage current of the insulator to be tested and the input voltage. The phase difference is normalized according to the following formulas (2) and (3) to eliminate the influence of voltage fluctuations: Among them, u1'(t) and i1'(t) are respectively the normalized input voltage and leakage current instantaneous values ​​of the insulator to be tested; U1 and I1 are respectively the amplitudes of the measured input voltage and leakage current; Step 5: Calculate the comprehensive monitoring coefficient CMI and evaluate the degradation status of the insulator The normalized insulator voltage and current data are used to construct the Lissajous figure of the insulator to be tested, and its five morphological features are extracted, which are denoted as F i , i = 1 to 5, and calculate the comprehensive degradation monitoring coefficient CMI: The degradation state of the insulator is evaluated according to the size of CMI. If CMI=0, it means that the insulation state of the silicone rubber insulator is normal; the smaller the CMI, the milder the degradation state of the silicone rubber insulator; the larger the CMI, the more serious the degradation state of the silicone rubber insulator.

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