Switch cabinet insulation state evaluation method based on partial discharge and temperature joint detection

Abstract

The invention discloses a partial discharge and temperature joint detection-based switch cabinet insulation state evaluation method, which comprises the following steps of: respectively installing an ultrasonic sensor and an infrared temperature sensor on the inner walls corresponding to the top and four side surfaces of a switch cabinet, an ultrasonic sensor and an infrared temperature sensor are installed in a cable chamber of the switch cabinet, partial discharge data of the switch cabinet are measured, infrared temperature data of the switch cabinet are measured, a partial discharge evaluation factor is calculated, a temperature evaluation factor is calculated, and the insulation state of the switch cabinet is evaluated. The method has the advantages that the insulation state of the switch cabinet is evaluated through the partial discharge evaluation factor and the temperature evaluation factor, and then online detection of the insulation state of the switch cabinet is achieved.

Description

Technical Field

[0001] The invention belongs to the field of power equipment detection, and in particular relates to a switch cabinet insulation state evaluation method based on partial discharge and temperature joint detection. Background Art

[0002] Switchgear is an indispensable and important equipment in the power system. Its main functions include grid control, circuit switching, and power equipment protection. The safe and stable operation of the switchgear is of great significance to ensure the reliability of the power supply of the entire power grid. However, due to factors such as processing technology, transportation collision, and electrothermal aging, insulation defects are prone to occur in the three-phase cable joints and the inside of the insulation material of the switchgear. Under the action of the operating voltage, the electric field distortion occurs at the insulation defect of the switchgear, so that the electric field strength in this area exceeds the breakdown field strength of the insulation material, resulting in partial discharge, which in turn leads to insulation degradation and affects the operating life of the switchgear. Traditional switchgear insulation status detection mainly relies on regular inspections by staff, but this method has the disadvantages of long detection cycle, high detection cost, low maintenance efficiency, and affecting the normal operation of equipment. In addition, manual regular inspections cannot perform real-time detection of the insulation status of the operating switchgear, which often leads to insulation faults in the switchgear cannot be discovered in time.

[0003] In view of the shortcomings of the existing detection methods, the present invention proposes a switch cabinet insulation state evaluation method based on partial discharge and temperature joint detection, which uses ultrasonic sensors and infrared temperature sensors to obtain the detection data of partial discharge and operating temperature of the switch cabinet, and uses the obtained detection data to calculate the partial discharge evaluation factor and the temperature evaluation factor, thereby evaluating the insulation state of the switch cabinet. The evaluation method proposed by the present invention is simple to operate and can realize online detection of the insulation state of the switch cabinet. Summary of the invention

[0004] The invention discloses a switch cabinet insulation state evaluation method based on partial discharge and temperature joint detection, which is used to realize online detection of the switch cabinet insulation state.

[0005] The technical solution of the present invention is as follows:

[0006] The first step is to install an ultrasonic sensor and an infrared temperature sensor on the top and the inner walls corresponding to the four sides of the switch cabinet respectively, and install a total of five ultrasonic sensors and five infrared temperature sensors in the switch cabinet; the five ultrasonic sensors are numbered as UT1, UT2, UT3, UT4, and UT5 respectively, and the five infrared temperature sensors are numbered as IR1, IR2, IR3, IR4, and IR5 respectively; wherein the center frequency of the ultrasonic sensor is 40kHz, the ultrasonic dynamic range is 60dB, and the linear error is less than or equal to ±5%, the resolution of the infrared temperature sensor is 384*288, the temperature measurement range is -20℃~300℃, and the temperature measurement error is less than or equal to ±1℃;

[0007] The second step is to install an ultrasonic sensor and an infrared temperature sensor in the cable room of the switch cabinet; the ultrasonic sensor in the second step is numbered as UT6, and the infrared temperature sensor in the second step is numbered as IR6; the specifications and models of the ultrasonic sensor and the infrared temperature sensor are exactly the same as those of the ultrasonic sensor and the infrared temperature sensor in the first step;

[0008] The third step is to measure the partial discharge data of the switch cabinet:

[0009] The method for measuring partial discharge data is: using the ultrasonic sensor in the first step and the second step to measure the partial discharge signal inside and around the switch cabinet, unit: dB, sampling time: 100s, sampling frequency: 200kHz;

[0010] Get the maximum value U of the partial discharge signal measured by each ultrasonic sensor Ai , unit: dB, i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6};

[0011] Get the average value U of the partial discharge signal measured by each ultrasonic sensor Pi , unit: dB, i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6};

[0012] Obtain the probability density U of the extreme points of the partial discharge signal measured by each ultrasonic sensor Mi , i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6};

[0013] The maximum value U of the partial discharge signal Ai The calculation formula is:

[0014] U Ai =max{U i1 ,Ui2 ,...,U in} (1)

[0015] Where U Ai is the maximum value of the partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB; U in is the nth partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB, n=2×10 7 ;

[0016] The average value U of the partial discharge signal Pi The calculation formula is:

[0017]

[0018] Where U Pi is the amplitude of the partial discharge signal measured by the ultrasonic sensor numbered UTi, in dB; n is the total number of sampling points of a single ultrasonic sensor, n = 2 × 10 7 ; U ik is the kth partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB;

[0019] The probability density U of the extreme point of the partial discharge signal Mi The calculation formula is:

[0020]

[0021] Where U Mi is the probability density of the extreme value point of the partial discharge signal measured by the ultrasonic sensor numbered UTi; m i is the number of extreme points of the partial discharge signal measured by the ultrasonic sensor numbered UTi; n is the total number of sampling points of a single ultrasonic sensor, n = 2 × 10 7 ;

[0022] Step 4: Measure the infrared temperature data of the switch cabinet;

[0023] The measuring method of measuring infrared temperature data is: using the infrared temperature sensors in the first and second steps to take infrared thermal images of the inside and the surrounding environment of the switch cabinet, each infrared temperature sensor takes 10 infrared thermal images, a total of 60 infrared thermal images are taken, and the shooting interval is 10 seconds;

[0024] Obtain the maximum temperature T of the three-phase cable joint of the switch cabinet from the infrared thermal image A , T B , T C , where T A is the maximum temperature of the A-phase cable connector, unit: °C; TB is the maximum temperature of the B-phase cable connector, unit: °C; T C The maximum temperature of the C-phase cable connector, unit: °C;

[0025] Obtain the maximum temperature T of the inner wall of the switch cabinet from the infrared thermal image H and the minimum temperature T L , unit: ℃;

[0026] The ambient temperature T of the switch cabinet is obtained from the infrared thermal image. E , unit: ℃;

[0027] The calculation formula for the maximum temperature of the three-phase cable connector of the switch cabinet is:

[0028]

[0029] Where, T A , T B , T C They are the maximum temperatures of the A-phase, B-phase and C-phase cable joints of the switch cabinet, in °C; T Ai , T Bi , T Ci are the maximum temperatures of the switch cabinet A-phase, B-phase, and C-phase cable joints obtained from the infrared spectra recorded for the i-th time by the infrared temperature sensors numbered IR1 to IR5;

[0030] The maximum temperature of the inner wall of the switch cabinet is T H and the minimum temperature T L The calculation formula is:

[0031]

[0032] Where, T H , T L They are the highest and lowest temperatures of the inner wall of the switch cabinet, in °C; T Hi , T Li are the highest temperature and the lowest temperature of the inner wall of the switch cabinet obtained from the infrared spectra recorded for the i-th time by the infrared temperature sensors numbered IR1 to IR5;

[0033] The ambient temperature T of the switch cabinet is obtained in the infrared thermal image E The calculation formula is:

[0034]

[0035] Where, T E is the ambient temperature of the switch cabinet, unit: °C; T Eiis the ambient temperature of the switch cabinet obtained from the i-th infrared spectrum record of the infrared temperature sensor numbered IR6;

[0036] Step 5: Calculate the partial discharge assessment factor α;

[0037] The calculation formula of partial discharge assessment factor α is as follows:

[0038]

[0039] Step 6: Calculate the temperature evaluation factor β;

[0040] The temperature evaluation factor β is calculated as follows:

[0041]

[0042] Step 7: Evaluate the insulation status of the switchgear;

[0043] When α≤0.5 and β≤0.5, the insulation state of the switch cabinet is good;

[0044] When 0.5<α≤1 or 0.5<β≤1, the insulation state of the switch cabinet is abnormal;

[0045] When α>1 or β>1, the switch cabinet has an insulation fault; BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention relates to a flow chart of a method for evaluating the insulation status of a switch cabinet based on joint detection of partial discharge and temperature. DETAILED DESCRIPTION

[0047] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation processes;

[0048] The first step is to install an ultrasonic sensor and an infrared temperature sensor on the top and the inner walls corresponding to the four sides of the switch cabinet, respectively. A total of five ultrasonic sensors and five infrared temperature sensors are installed in the switch cabinet, and the five ultrasonic sensors are numbered as UT1, UT2, UT3, UT4, and UT5, respectively. The five infrared temperature sensors are numbered as IR1, IR2, IR3, IR4, and IR5, respectively. The center frequency of the ultrasonic sensor is 40kHz, the ultrasonic dynamic range is 60dB, and the linear error is less than or equal to ±5%. The resolution of the infrared temperature sensor is 384*288, the temperature measurement range is -20℃~300℃, and the temperature measurement error is less than or equal to ±1℃;

[0049] The second step is to install an ultrasonic sensor and an infrared temperature sensor in the cable room of the switch cabinet, the ultrasonic sensor in the second step is numbered as UT6, the infrared temperature sensor in the second step is numbered as IR6, and the specifications and models of the ultrasonic sensor and the infrared temperature sensor are exactly the same as those of the ultrasonic sensor and the infrared temperature sensor in the first step;

[0050] The third step is to measure the partial discharge data of the switchgear;

[0051] The method for measuring partial discharge data is: using the ultrasonic sensor in the first step and the second step to measure the partial discharge signal inside the switch cabinet and the surrounding environment, unit: dB, sampling time: 100s, sampling frequency: 200kHz,

[0052] Get the maximum value U of the partial discharge signal measured by each ultrasonic sensor Ai , unit: dB, i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6};

[0053] Get the average value U of the partial discharge signal measured by each ultrasonic sensor Pi , unit: dB, i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6};

[0054] Obtain the probability density U of the extreme points of the partial discharge signal measured by each ultrasonic sensor Mi , i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6};

[0055] The maximum value U of the partial discharge signal Ai The calculation formula is

[0056] U Ai =max{U i1 ,U i2 ,...,U in} (9)

[0057] Where U Ai is the maximum value of the partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB; U in is the nth partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB, n=2×10 7 ;

[0058] The average value U of the partial discharge signal Pi The calculation formula is:

[0059]

[0060] Where U Pi is the amplitude of the partial discharge signal measured by the ultrasonic sensor numbered UTi, in dB; n is the total number of sampling points of a single ultrasonic sensor, n = 2 × 10 7 ; U ik is the kth partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB;

[0061] The probability density U of the extreme point of the partial discharge signal Mi The calculation formula is:

[0062]

[0063] Where U Mi is the probability density of the extreme value point of the partial discharge signal measured by the ultrasonic sensor numbered UTi; m i is the number of extreme points of the partial discharge signal measured by the ultrasonic sensor numbered UTi; n is the total number of sampling points of a single ultrasonic sensor, n = 2 × 10 7 ;

[0064] Step 4: Measure the infrared temperature data of the switch cabinet;

[0065] The measuring method of measuring infrared temperature data is: using the infrared temperature sensors in the first and second steps to take infrared thermal images of the inside and the surrounding environment of the switch cabinet, each infrared temperature sensor takes 10 infrared thermal images, a total of 60 infrared thermal images are taken, and the shooting interval is 10 seconds;

[0066] Obtain the maximum temperature T of the three-phase cable joint of the switch cabinet from the infrared thermal image A , T B , T C , where T A is the maximum temperature of the A-phase cable connector, unit: °C; T B is the maximum temperature of the B-phase cable connector, unit: °C; T C The maximum temperature of the C-phase cable connector, unit: °C;

[0067] Obtain the maximum temperature T of the inner wall of the switch cabinet from the infrared thermal image H and the minimum temperature T L , unit: ℃;

[0068] The ambient temperature T of the switch cabinet is obtained from the infrared thermal image. E , unit: ℃;

[0069] The calculation formula for the maximum temperature of the three-phase cable connector of the switch cabinet is:

[0070]

[0071] Where, T A , T B , T C They are the maximum temperatures of the A-phase, B-phase and C-phase cable joints of the switch cabinet, in °C; T Ai , T Bi , T Ci are the maximum temperatures of the switch cabinet A-phase, B-phase, and C-phase cable joints obtained from the infrared spectra recorded for the i-th time by the infrared temperature sensors numbered IR1 to IR5;

[0072] The maximum temperature of the inner wall of the switch cabinet is T H and the minimum temperature T L The calculation formula is:

[0073]

[0074] Where, T H , T L They are the highest and lowest temperatures of the inner wall of the switch cabinet, in °C; T Hi , T Li are the highest temperature and the lowest temperature of the inner wall of the switch cabinet obtained from the infrared spectra recorded for the i-th time by the infrared temperature sensors numbered IR1 to IR5;

[0075] The ambient temperature T of the switch cabinet is obtained in the infrared thermal image E The calculation formula is:

[0076]

[0077] Where, T E is the ambient temperature of the switch cabinet, unit: °C; T Ei is the ambient temperature of the switch cabinet obtained from the i-th infrared spectrum record of the infrared temperature sensor numbered IR6;

[0078] Step 5: Calculate the partial discharge assessment factor α;

[0079] The calculation formula of partial discharge assessment factor α is as follows:

[0080]

[0081] Step 6: Calculate the temperature evaluation factor β;

[0082] The temperature evaluation factor β is calculated as follows:

[0083]

[0084] Step 7: Evaluate the insulation status of the switchgear;

[0085] When α≤0.5 and β≤0.5, the insulation state of the switch cabinet is good;

[0086] When 0.5<α≤1 or 0.5<β≤1, the insulation state of the switch cabinet is abnormal;

[0087] When α>1 or β>1, an insulation fault occurs in the switch cabinet.

Claims

1. A switch cabinet insulation status assessment method based on partial discharge and temperature joint detection, characterized in that The following steps are involved: The first step is to install an ultrasonic sensor and an infrared temperature sensor on the top and the inner walls corresponding to the four sides of the switch cabinet, respectively. A total of five ultrasonic sensors and five infrared temperature sensors are installed in the switch cabinet, and the five ultrasonic sensors are numbered as UT1, UT2, UT3, UT4, and UT5, respectively. The five infrared temperature sensors are numbered as IR1, IR2, IR3, IR4, and IR5, respectively. The center frequency of the ultrasonic sensor is 40kHz, the ultrasonic dynamic range is 60dB, and the linear error is less than or equal to ±5%. The resolution of the infrared temperature sensor is 384*288, the temperature measurement range is -20℃~300℃, and the temperature measurement error is less than or equal to ±1℃; The second step is to install an ultrasonic sensor and an infrared temperature sensor in the cable room of the switch cabinet, the ultrasonic sensor in the second step is numbered as UT6, the infrared temperature sensor in the second step is numbered as IR6, and the specifications and models of the ultrasonic sensor and the infrared temperature sensor are exactly the same as those of the ultrasonic sensor and the infrared temperature sensor in the first step; The third step is to measure the partial discharge data of the switch cabinet: The method for measuring partial discharge data is: using the ultrasonic sensor in the first step and the second step to measure the partial discharge signal inside and around the switch cabinet, unit: dB, sampling time: 100s, sampling frequency: 200kHz; Get the maximum value U of the partial discharge signal measured by each ultrasonic sensor Ai , unit: dB, i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6}; Get the average value U of the partial discharge signal measured by each ultrasonic sensor Pi , unit: dB, i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6}; Obtain the probability density U of the extreme points of the partial discharge signal measured by each ultrasonic sensor Mi , i represents the data measured by the ultrasonic sensor numbered UTi, i = {1, 2, 3, 4, 5, 6}; The maximum value U of the partial discharge signal Ai The calculation formula is U Ai =max{U i1 ,U i2 ,...,U in } (1) Where U Ai is the maximum value of the partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB; U in is the nth partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB, n=2×10 7 ; The average value U of the partial discharge signal Pi The calculation formula is: Where U Pi is the amplitude of the partial discharge signal measured by the ultrasonic sensor numbered UTi, in dB; n is the total number of sampling points of a single ultrasonic sensor, n = 2 × 10 7 ; U ik is the kth partial discharge signal measured by the ultrasonic sensor numbered UTi, unit: dB; The probability density U of the extreme point of the partial discharge signal Mi The calculation formula is: Where U Mi is the probability density of the extreme value point of the partial discharge signal measured by the ultrasonic sensor numbered UTi; m i is the number of extreme points of the partial discharge signal measured by the ultrasonic sensor numbered UTi; n is the total number of sampling points of a single ultrasonic sensor, n = 2 × 10 7 ; Step 4: Measure the infrared temperature data of the switch cabinet: The measuring method of measuring infrared temperature data is: using the infrared temperature sensors in the first and second steps to take infrared thermal images of the inside and the surrounding environment of the switch cabinet, each infrared temperature sensor takes 10 infrared thermal images, a total of 60 infrared thermal images are taken, and the shooting interval is 10 seconds; Obtain the maximum temperature T of the three-phase cable joint of the switch cabinet from the infrared thermal image A , T B , T C , where T A is the maximum temperature of the A-phase cable connector, unit: °C; T B is the maximum temperature of the B-phase cable connector, unit: °C; T C The maximum temperature of the C-phase cable connector, unit: °C; Obtain the maximum temperature T of the inner wall of the switch cabinet from the infrared thermal image H and the minimum temperature T L , unit: ℃; The ambient temperature T of the switch cabinet is obtained from the infrared thermal image. E , unit: ℃; The calculation formula for the maximum temperature of the three-phase cable connector of the switch cabinet is: Where, T A , T B , T C They are the maximum temperatures of the A-phase, B-phase and C-phase cable joints of the switch cabinet, in °C; T Ai , T Bi , T Ci are the maximum temperatures of the switch cabinet A-phase, B-phase, and C-phase cable joints obtained from the infrared spectra recorded for the i-th time by the infrared temperature sensors numbered IR1 to IR5; The maximum temperature of the inner wall of the switch cabinet is T H and the minimum temperature T L The calculation formula is: Where, T H , T L They are the highest and lowest temperatures of the inner wall of the switch cabinet, in °C; T Hi , T Li are the highest temperature and the lowest temperature of the inner wall of the switch cabinet obtained from the infrared spectra recorded for the i-th time by the infrared temperature sensors numbered IR1 to IR5; The ambient temperature T of the switch cabinet is obtained in the infrared thermal image E The calculation formula is: Where, T E is the ambient temperature of the switch cabinet, unit: °C; T Ei is the ambient temperature of the switch cabinet obtained from the i-th infrared spectrum record of the infrared temperature sensor numbered IR6; Step 5: Calculate the partial discharge assessment factor α; The calculation formula of partial discharge assessment factor α is as follows: Step 6: Calculate the temperature evaluation factor β; The temperature evaluation factor β is calculated as follows: Step 7: Evaluate the insulation status of the switchgear; When α≤0.5 and β≤0.5, the insulation state of the switch cabinet is good; When 0.5<α≤1 or 0.5<β≤1, the insulation state of the switch cabinet is abnormal; When α>1 or β>1, an insulation fault occurs in the switch cabinet.

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