Switch cabinet partial discharge accurate positioning detection method based on single sensor

Abstract

The invention discloses a switch cabinet partial discharge accurate positioning detection method based on a single sensor, and belongs to the technical field of power equipment partial discharge detection. Comprising the following steps: arranging a single ultrasonic sensor at the central position of the bottom surface of the switch cabinet according to the structural characteristics of the switch cabinet and the propagation characteristics of discharge signals so as to cover the monitoring range of the whole switch cabinet; collecting refraction and reflection data of ultrasonic waves in a transmission process in the switch cabinet, and establishing an ultrasonic attenuation model after normalization processing; in the ultrasonic signal propagation process, according to the ultrasonic attenuation condition, typical signal grade ranges of different switch cabinet areas are calibrated in advance through experiments, and a position database is formed; and the partial discharge position is positioned through two-parameter cooperation of the signal amplitude and the equivalent propagation distance y. According to the detection method, the limitation that multiple sensors need to work cooperatively in the prior art is broken through, the system structure is simplified, the cost is reduced, and meanwhile the operation convenience is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of partial discharge detection of power equipment, and particularly relates to a precise positioning detection method for partial discharge of a switch cabinet based on a single sensor. BACKGROUND

[0002] The switch cabinet is a crucial power distribution and control device in the power system and is widely used in many scenes such as power conversion, distribution and protection. In actual operation, the internal components and insulation system of the switch cabinet are subjected to the combined action of high voltage, large current and complex electromagnetic environment for a long time. Such harsh working conditions can easily induce partial discharge, which seriously affects the performance and service life of the switch cabinet. Therefore, it is of great practical significance to monitor the related state of the partial discharge of the switch cabinet in real time and accurately predict its service life.

[0003] At present, the existing partial discharge detection technologies for switch cabinets mainly include the pulse current method, the ultrasonic detection method and the ultra-high frequency method. However, these detection methods still have the following common problems: 1) The above-mentioned detection methods all need at least four sensors to work cooperatively to realize the positioning detection of the partial discharge source, which increases the system complexity, detection cost and maintenance difficulty; 2) Through in-depth investigation of the factory field operation status and a large amount of data analysis, it is found that in the actual application of the sensor monitoring of the partial discharge of the switch cabinet, the detection accuracy can only be positioned to the specific cabinet, and the specific position of the fault occurrence cannot be accurately identified, which to some extent affects the accuracy of fault diagnosis and the maintenance efficiency.

[0004] Therefore, the existing technologies have certain limitations in the detection accuracy of partial discharge, system cost and operation convenience, and it is urgent to design a detection method that simplifies the system, reduces the cost and efficiently locates the partial discharge. SUMMARY

[0005] The purpose of the present application is to solve the problems of low detection accuracy of partial discharge, high system cost and poor operation convenience in the prior art, and to provide a precise positioning detection method for partial discharge of a switch cabinet based on a single sensor. The method can break through the limitation of the traditional technology that needs multiple sensors to work cooperatively, and only uses one sensor to quickly and accurately position the switch cabinet, and can monitor the equipment state in real time.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: a precise positioning detection method for partial discharge of a switch cabinet based on a single sensor, comprising the following steps: S1, determining the position of a single sensor: According to the structural characteristics of the switch cabinet and the propagation characteristics of the discharge signal, a single ultrasonic sensor is arranged at the center of the bottom surface of the switch cabinet to cover the entire monitoring range of the switch cabinet. S2, an ultrasonic attenuation model is established: In the actual propagation process, the ultrasonic signal encounters objects and reflects and refracts. The refracted and reflected data of the ultrasonic signal in the propagation process in the switch cabinet are collected, and an ultrasonic attenuation model is established after normalization processing. The normalization processing process is to fit the ultrasonic propagation time and propagation distance data into a curve related to time and distance. The expression of the ultrasonic attenuation model is y = 626.06x + 0.2712, wherein 626.06 is the normalized ultrasonic propagation speed, x is the actual propagation time, 0.2712 is the distance caused by time delay, and y is the equivalent propagation distance. S3, dividing the ultrasonic attenuation level: In the propagation process of the ultrasonic signal, according to the ultrasonic attenuation condition, the typical signal level range of different switch cabinet regions is pre-marked through experiments to form a position database: The pre-marked typical signal level range is divided into six levels according to the dBμV value of the signal intensity, each level corresponds to different switch cabinet regions and typical discharge types, and also reflects the equivalent propagation distance range of the discharge source. The specific signal level division results include the following: The 1st level signal intensity (0~20dBμV) appears in the edge of the cabinet or the external interference region, representing environmental noise or slight surface discharge, and the equivalent propagation distance is greater than 1.0m; The 2nd level signal intensity (21~35dBμV) appears in the side wall insulator or low voltage terminal, which is corona discharge or floating potential, and the equivalent propagation distance is 0.8~1.0m; The 3rd level signal intensity (36~50dBμV) is at the busbar connection or the circuit breaker shell, indicating poor contact or local breakdown, and the equivalent propagation distance is 0.6~0.8m; The 4th level signal intensity (51~65dBμV) occurs at the circuit breaker contact or cable terminal, representing insulation deterioration or metal particle discharge, and the equivalent propagation distance is 0.4~0.6m; The 5th level signal intensity (66~80dBμV) appears at the high voltage conductor connection point or the grounding switch, which is usually arc discharge or serious insulation defect, and the equivalent propagation distance is 0.2~0.4m; The 6th level signal intensity (greater than 80dBμV) occurs in the sensor adjacent area, which is usually direct arc or metal short circuit, and the equivalent propagation distance is less than 0.2m; S4, double-parameter cooperative positioning of partial discharge position: Based on the captured ultrasonic signal, the ultrasonic sensor extracts the propagation time x and signal amplitude 𝐴, and calculates the equivalent propagation distance y through the attenuation model y=626.06x+0.2712. The signal level is determined based on the signal amplitude 𝐴. The corresponding area of ​​the signal level classification result table obtained in step S3 is directly queried and its rationality is verified in combination with the equivalent propagation distance y to finally determine the location of the partial discharge.

[0007] The beneficial effects of the present invention are: 1) The detection method of the present invention overcomes the limitation of traditional technologies that usually require four or more sensors to work together to achieve partial discharge positioning detection. It can accurately detect the location of partial discharge using only a single ultrasonic sensor. Unlike traditional methods, the present invention does not rely on data fusion of multiple sensors, which simplifies the system structure, reduces costs, and improves operational convenience.

[0008] 2) In addition, traditional methods usually rely on time difference arbitrating (TDOA) technology for partial discharge detection, but TDOA technology has high requirements for time synchronization accuracy. The method of the present invention does not rely on precise time synchronization, thereby effectively avoiding this technical difficulty and improving the reliability and applicability of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a flow chart of the positioning detection method of the present invention; Figure 2 A diagram showing the sensor deployment structure for realizing positioning detection in the present invention; Figure 3 This is a diagram of ultrasonic attenuation measured in an embodiment of the present invention; Figure 4 This is a diagram of ultrasonic level division set in the detection method of the present invention; Figure 5 This is a comparison diagram of the positioning results detected by the model of the present invention and the actual discharge position. DETAILED DESCRIPTION

[0010] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0011] Example: Figure 1 As shown, the present invention provides a method for accurately locating and detecting partial discharge of a switch cabinet based on a single sensor, comprising the following steps: S1. Determine the location of a single sensor: According to the structural characteristics of the switchgear and the propagation characteristics of the discharge signal, the ultrasonic sensor should be installed in the key position where it can effectively receive the partial discharge signal; Generally, the sensor should be selected in the high electric field area where partial discharge may occur or near the device contact point to ensure that the discharge signal can be accurately captured. Experimental data shows that a single ultrasonic sensor is placed at the center of the bottom surface of the switch cabinet to cover the entire monitoring range of the switch cabinet, and can better reflect the relationship between ultrasonic attenuation and distance. In addition, it is also necessary to reduce electrical noise interference and improve diagnostic accuracy. Figure 2 The position of the dark dot is the placement position of the ultrasonic sensor.

[0012] S2, establish an ultrasonic attenuation model: In the actual propagation process, ultrasonic signals will be reflected and refracted when encountering objects, which will affect the actual propagation speed and attenuation of the ultrasonic signals. The refraction and reflection data of ultrasonic signals during propagation in the switch cabinet are collected and normalized to establish an ultrasonic attenuation model. The attenuation model is fitted by 152 groups of measured data, including 30 groups of air medium propagation data and 122 groups of metal-insulation composite medium reflection data. The model is effective when the goodness of fit R² is greater than or equal to 0.93. This attenuation model is of great significance, as it not only provides key reference for discharge positioning, but also helps to improve the sensitivity and response capability of the monitoring system.

[0013] The expression of the ultrasonic attenuation model is y = 626.06x + 0.2712, where 626.06 is the normalized ultrasonic propagation speed, x is the actual propagation time, 0.2712 is the distance caused by time delay, and y is the equivalent propagation distance. Figure 3 This is done by obtaining a large amount of ultrasonic propagation time and propagation distance data, and fitting them into a curve related to time and distance. As can be seen, the R 2 value is 0.942, which has a good fitting effect.

[0014] S3, divide the ultrasonic attenuation level: During the propagation of ultrasonic signals, according to the ultrasonic attenuation, the typical signal level range of different switch cabinet areas is pre-calibrated through experiments to form a position database: The pre-calibrated typical signal level range is divided into six levels according to the dBμV value of its signal intensity, each level corresponds to different switch cabinet areas and typical discharge types, and also reflects the equivalent propagation distance range of the discharge source. The specific signal level division results include: 1st level signal intensity (0~20dBμV) appears at the edge of the cabinet or in the external interference area, representing environmental noise or slight surface discharge, with an equivalent propagation distance greater than 1.0m; The 2nd level signal strength (21~35dBμV) appears at the side wall insulator or low voltage terminal, is corona discharge or floating potential, and the equivalent propagation distance is 0.8~1.0m; The 3rd level signal strength (36~50dBμV) is at the busbar connection or circuit breaker shell, indicates poor contact or local breakdown, and the equivalent propagation distance is 0.6~0.8m; The 4th level signal strength (51~65dBμV) occurs at the circuit breaker contact or cable terminal, represents insulation deterioration or metal particle discharge, and the equivalent propagation distance is 0.4~0.6m; The 5th level signal strength (66~80dBμV) appears at the high voltage conductor connection point or grounding switch, is usually arc discharge or serious insulation defect, and the equivalent propagation distance is 0.2~0.4m; The 6th level signal strength (greater than 80dBμV) occurs in the vicinity of the sensor, is usually direct arc or metal short circuit, and the equivalent propagation distance is less than 0.2m.

[0015] S4, double-parameter cooperative positioning of partial discharge position: The ultrasonic sensor extracts the propagation time x and signal amplitude A according to the captured ultrasonic signal, calculates the equivalent propagation distance y through the attenuation model y=626.06x+0.2712, determines the signal level according to the signal amplitude A, directly queries the signal level division result table obtained in step S3 to output the corresponding area, combines the equivalent propagation distance y to check the rationality, and finally determines the partial discharge position.

[0016] The model detection result is compared with the actual discharge position to test the feasibility of the model detection: In the switch cabinet, the spatial coordinates of a partial discharge source are (0.4, 0.3, 0.5), the ultrasonic sensor measures the propagation time of the signal as 0.3974ms, and the signal amplitude is 58dBμV. The propagation time is substituted into the ultrasonic attenuation model to calculate the equivalent propagation distance as 0.52m, according to the signal amplitude 58dBμV, the signal level division table obtained in step S3 is consulted, and it is known that the signal corresponds to the 4th level signal strength area. The positioning result is as shown in Figure 5 It can be seen that the predicted PD source position displayed in blue has little difference from the actual PD source position displayed in red, so the detection model has high detection accuracy.

[0017] The detection method of the present application breaks through the limitation of the traditional technology that usually needs four or more sensors to work cooperatively to realize the positioning detection of partial discharge, and only a single ultrasonic sensor can realize the accurate detection of the position of partial discharge; unlike the traditional method, the present application does not need to rely on data fusion of multiple sensors, simplifies the system structure, reduces the cost, and improves the operation convenience.

[0018] The above description is only to illustrate the technical solutions of the present application but not to limit the present application. Other modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art should be covered in the scope of claims of the present application as long as they are not deviated from the spirit and scope of the technical solutions of the present application.

Claims

1. A single-sensor based method for accurately locating and detecting partial discharge in a switch cabinet, characterized by: The following steps are involved: S1. Determine the location of a single sensor: According to the structural characteristics of the switch cabinet and the propagation characteristics of the discharge signal, a single ultrasonic sensor is placed at the center of the bottom surface of the switch cabinet to cover the monitoring range of the entire switch cabinet; S2. Establish ultrasonic attenuation model: During the actual propagation process, ultrasonic signals will be reflected and refracted when encountering objects. The refraction and reflection data of the ultrasonic wave during its propagation in the switch cabinet are collected and normalized to establish an ultrasonic attenuation model. The normalization process is to fit the ultrasonic wave propagation time and propagation distance data into a curve related to time and distance. The expression of the ultrasonic attenuation model is: y = 626.06x + 0.2712, where 626.06 is the normalized ultrasonic propagation velocity, x is the actual propagation time, 0.2712 is the distance caused by time delay, and y is the equivalent propagation distance; S3. Classification of ultrasonic attenuation levels: During the propagation of ultrasonic signals, based on the ultrasonic attenuation, the typical signal level ranges of different switchgear areas are pre-calibrated through experiments to form a location database: The pre-calibrated typical signal level range is divided into six levels based on the dBμV value of its signal strength. Each level corresponds to a different switchgear area and typical discharge type, and also reflects the equivalent propagation distance range of the discharge source. The specific signal level classification results include the following: Level 1 signal strength (0-20dBμV) occurs at the edge of the cabinet or in external interference areas, indicating ambient noise or slight surface discharge, with an equivalent propagation distance greater than 1.0m. Level 2 signal strength (21-35 dBμV) appears at the side wall insulator or low-voltage terminal, which is corona discharge or suspended potential, with an equivalent propagation distance of 0.8-1.0 m. Level 3 signal strength (36-50dBμV) is at the busbar connection or circuit breaker housing, indicating poor contact or partial breakdown, with an equivalent propagation distance of 0.6-0.8m. Level 4 signal strength (51-65 dBμV) occurs at the circuit breaker contacts or cable terminals, indicating insulation degradation or metal particle discharge, with an equivalent propagation distance of 0.4-0.6 m. Level 5 signal strength (66-80dBμV) occurs at the high-voltage conductor connection point or grounding switch, usually due to arc discharge or severe insulation defects, with an equivalent propagation distance of 0.2-0.4m. Level 6 signal strength (greater than 80dBμV) occurs in the vicinity of the sensor, usually due to direct arcing or metal short circuits, with an equivalent propagation distance of less than 0.2 meters. S4. Dual-parameter collaborative localization of partial discharge locations: Based on the captured ultrasonic signal, the ultrasonic sensor extracts the propagation time x and signal amplitude 𝐴, and calculates the equivalent propagation distance y through the attenuation model y=626.06x+0.2712. The signal level is determined based on the signal amplitude 𝐴. The corresponding area of ​​the signal level classification result table obtained in step S3 is directly queried and its rationality is verified in combination with the equivalent propagation distance y to finally determine the location of the partial discharge.

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