A method and system for detecting distributed partial discharge in power cables

Abstract

The invention relates to the technical field of cable fault detection; a method and system for detecting distributed partial discharge of power cables are provided; the invention classifies cables according to different environments in which the cables are distributed, the service time and the degree of aging of the insulation layer, and weights the cables according to the importance of the above characteristics; and sets detection devices according to different classification positions; performs temperature, sound, light intensity and gas detection before current pulse detection; and preliminarily determines the cable partial discharge position according to the results of the above detection; and then controls the current pulse detection device to perform further detection and determination; and the detection accuracy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cable fault detection, and in particular to a method and system for detecting distributed partial discharge of power cables. Background Art

[0002] Partial discharge of cables is an important reason for the insulation breakdown of high-voltage electrical equipment. When the power equipment is in operation, it is necessary to strengthen the detection of the power equipment, and to repair or replace it when the local discharge reaches a certain level. Cables are important power transmission and signal transmission equipment in the power system. Many of them are installed underground or high in the wild. Due to the harsh environment, the insulation layer on the outside of the cable often ages, thus forming partial discharge. The invention patent with publication number CN117949794A discloses a cable partial discharge fault detection method. The model is adaptively focused on the characteristic areas of four different types of partial discharges, so as to quickly obtain the location of partial cable discharge. The invention patent with publication number CN117949794A discloses a cable partial discharge fault detection method. The model is adaptively focused on the characteristic areas of four different types of partial discharges, so as to quickly obtain the location of partial cable discharge. The invention patent CN118033336A discloses a power grid partial discharge monitoring device based on gas detection; it can detect initial partial discharge and partial discharge of closed switches by detecting gas, thereby improving the accuracy of partial discharge detection; and when a cable undergoes partial discharge, in addition to changes in electrical pulses and dielectric loss, it is often accompanied by changes in light, heat, noise, gas pressure and chemical changes; and as recorded in the above-mentioned prior art; currently, the detection of cable partial discharge is generally carried out by a current pulse method; however, when an outdoor cable undergoes partial leakage, it is often not possible to detect it in time by the current pulse method; and excessive use of the current method itself for detection will waste resources. Summary of the invention

[0003] A distributed partial discharge detection system for power cables; it includes a cable partial discharge current detection system; the cable partial discharge current detection system uses a pulse current method to detect cable partial discharge of an electrical device; the cable partial discharge current detection system includes a voltage source U with one end of the cable grounded; a resistor R and a load device C are arranged on the cable path of the voltage source U; there are multiple load devices into which the final current flows; the voltage source U is connected to the load through a line and current is transmitted; if partial discharge occurs in a certain section of the line; a coupling capacitor C is connected in parallel at both ends of the cable K It is coupled into the current path; at the same time, a coupling impedance Z and a detector connected to the coupling impedance Z are connected in series in the coupling capacitor circuit to convert the current at both ends of the cable into voltage to detect the local discharge position; if the voltage is abnormal, local discharge occurs.

[0004] Furthermore, a local current discharge detection device is provided, and the cable local discharge current detection system cooperates with the local current discharge detection device; the local current discharge detection device includes a detection box, a moving rod, guide rails I and II; the cable local discharge current detection system is placed in the detection box; the detection box is arranged on the moving rod; the moving rod cooperates with guide rails I and II; the moving rod moves on guide rails I and II; the local current discharge detection device is moved by the moving device, and a local current discharge detection device control device is provided; the movement of the local current discharge detection device is controlled.

[0005] Furthermore, it also includes a cable partial discharge position monitoring system; the cable partial discharge position monitoring system monitors and analyzes the discharge position of the cable; if it is determined that the probability of discharge current breakdown at the cable position is greater than a preset value; an instruction is sent to the partial current discharge detection device.

[0006] Furthermore, it also includes a cable grading system; the cables are graded according to the environment in which the cables are distributed, the time the cables are used, and the degree of aging of the cable insulation layer; the cables are divided into grades I, II, and III; and preliminary inspections are carried out on cables of different grades at different locations based on the grading results.

[0007] Furthermore, the preliminary detection of the cable uses a preliminary retrieval system; the preliminary retrieval system includes a temperature detection device, a sound detection device, a light intensity detection device, and a gas pressure detection device.

[0008] Furthermore, temperature detection devices, sound detection devices, light intensity detection devices, and gas pressure detection devices are respectively arranged at different positions of the cable; and different numbers of detection devices are distributed to cables of different levels at different positions according to the cable grading system.

[0009] Further; the temperature detection device detects the temperature around the cable insulation layer; the temperature of the cable when it is working normally is set to T0; the detected temperature is T; the detected temperature and the comparison result are transmitted to the cable partial discharge position monitoring system.

[0010] Furthermore; the sound detection device detects the temperature around the cable insulation layer; the sound decibel when the cable is working normally is set to α0; the detected sound decibel is α, and the detected sound distribution and comparison results are transmitted to the cable partial discharge position monitoring system; and a noise elimination system is provided on the sound detection device to prevent the influence of other noises.

[0011] Furthermore, the light intensity detection device detects the light intensity around the cable insulation layer; and sets the normal light intensity during the day to Σ0; and sets the sudden strong light intensity to Σ; and transmits the detected light intensity to the cable partial discharge position monitoring system.

[0012] Further, a gas pressure detection device detects the gas pressure around the cable insulation layer. The gas pressure during normal operation of the cable is set as P0, and the detected gas pressure is P. The detected gas pressure and the comparison result are transmitted to the cable partial discharge location monitoring system.

[0013] Further, weight grading is performed on three indicators for classifying the cable, namely the environment where the cable is distributed, the usage time of the cable, and the aging degree of the cable insulation layer. Let the environment where the cable is distributed be Ω, the usage time of the cable be t, and the aging degree of the cable insulation layer be Η. The weight coefficients are set as 0.2, 0.2, and 0.6 respectively. When 0.2Ω + 0.2t + 0.6Η < M, the cable is classified as Class I; when 0.2Ω + 0.2t + 0.6Η > M, the cable is classified as Class II; when 0.2Ω + 0.2t + 0.6Η > 2M, the cable is classified as Class III.

[0014] Further, different numbers of temperature detection devices, sound detection devices, light intensity detection devices, and gas pressure detection devices are installed corresponding to Class I, Class II, and Class III of the cable grading.

[0015] Further, when detecting a Class III cable, if (T - T0) / T0 > 0.5 detected by the temperature detection device; (α - α0) / α0 > 0.5 detected by the sound detection device; (P - P0) / P0 > 0.2 detected by the gas pressure detection device; (Σ - Σ0) / Σ0 > 0.2 detected by the light intensity detection device or when one of the above results appears, the detection result is transmitted to the cable partial discharge location monitoring system.

[0016] Further, when detecting a Class II cable, if (T - T0) / T0 > 0.8 detected by the temperature detection device; (α - α0) / α0 > 0.8 detected by the sound detection device; (P - P0) / P0 > 0.4 detected by the gas pressure detection device; (Σ - Σ0) / Σ0 > 0.3 detected by the light intensity detection device or when one of the above results appears, the detection result is transmitted to the cable partial discharge location monitoring system.

[0017] Further, when detecting a Class I cable, if (T - T0) / T0 > 1.2 detected by the temperature detection device; (α - α0) / α0 > 1.2 detected by the sound detection device; (P - P0) / P0 > 0.6 detected by the gas pressure detection device; (Σ - Σ0) / Σ0 > 0.3 detected by the light intensity detection device or when one of the above results appears, the detection result is transmitted to the cable partial discharge location monitoring system.

[0018] Furthermore, when the detection results of temperature, sound, gas pressure and light intensity are transmitted to the cable partial discharge position monitoring system, the cable partial discharge position monitoring system determines the abnormal detection position, and the partial current discharge detection device control device controls the partial current discharge detection device to move to the position and detects the partial current discharge using the above method.

[0019] The present invention classifies cables according to different cable distribution environments, usage time and insulation layer aging degree, and weights the cables according to the importance of the above characteristics; and sets detection devices according to different classification positions; performs temperature, sound, light intensity and gas detection before current pulse detection; and preliminarily determines the cable partial discharge position according to the results of the above detection; and then controls the current pulse detection device to perform further detection and determination; thereby improving the detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 It is a current pulse detection circuit.

[0021] Attached Figure 2 The figure is a diagram of a local current discharge detection device.

[0022] 1-detection box; 2-moving rod; 3-guide rail I; 4-guide rail II. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments 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.

[0024] A distributed partial discharge detection system for power cables; it includes a cable partial discharge current detection system; the cable partial discharge current detection system uses a pulse current method to detect cable partial discharge of an electrical device; the cable partial discharge current detection system includes a voltage source U with one end of the cable grounded; a resistor R and a load device C are arranged on the cable path of the voltage source U; there are multiple load devices into which the final current flows; the voltage source U is connected to the load through a line and current is transmitted; if partial discharge occurs in a certain section of the line; a coupling capacitor C is connected in parallel at both ends of the cable KIt is coupled into the current path; at the same time, a coupling impedance Z and a detector connected to the coupling impedance Z are connected in series on the coupling capacitor circuit to convert the current at both ends of the cable into voltage to detect the local discharge position; if the voltage is abnormal, local discharge occurs; a local current discharge detection device is also provided, and the cable local discharge current detection system and the local current discharge detection device cooperate; the local current discharge detection device includes a detection box, a moving rod, a guide rail I and a guide rail II; the cable local discharge current detection system is placed in the detection box; the detection box is set on the moving rod, and the moving rod cooperates with the guide rail I and the guide rail II; the moving rod moves on the guide rail I and the guide rail II; the local current discharge detection device is driven to move by the moving device, and a local current discharge detection device control device is provided; the local current discharge detection device is controlled to move; it also includes a cable local discharge position monitoring system; the cable local discharge position monitoring system monitors and analyzes the discharge position of the cable; if it is judged that the probability of discharge current breakdown at the cable position is greater than a preset value; an instruction is sent to the local current discharge detection device. It also includes a cable grading system; the cables are graded according to the environment in which they are distributed, the time they have been used, and the degree of aging of their insulation layers; the cables are divided into grades I, II, and III; and preliminary inspections are performed on cables of different grades at different locations based on the grading results; the preliminary inspection of the cables uses a preliminary retrieval system; the preliminary retrieval system includes a temperature detection device, a sound detection device, a light intensity detection device, and a gas pressure detection device; temperature detection devices, sound detection devices, light intensity detection devices, and gas pressure detection devices are respectively set at different locations of the cables; different numbers of detection devices are distributed for cables of different grades at different locations based on the grading of the cables by the cable grading system; the temperature detection device detects the temperature around the insulation layer of the cable; the temperature of the cable when it is working normally is set as T0; the detected temperature is T; the detected temperature and the comparison result are transmitted to the cable bureau The cable is provided with a partial discharge position monitoring system; the sound detection device detects the temperature around the cable insulation layer; the sound decibel when the cable is working normally is set to α0; the detected sound decibel is α, and the detected sound distribution and comparison results are transmitted to the cable partial discharge position monitoring system; and the sound detection device is provided with a noise elimination system to prevent the influence of other noises; the light intensity detection device detects the light intensity around the cable insulation layer; and the normal light during the day is set to Σ0; and the sudden strong light intensity is set to Σ; the detected light intensity is transmitted to the cable partial discharge position monitoring system; the gas pressure detection device detects the gas pressure around the cable insulation layer; the gas pressure when the cable is working normally is set to P0; and the detected gas pressure is P; the detected gas pressure and comparison results are transmitted to the cable partial discharge position monitoring system.

[0025] Further, weight grading is performed on three indicators for cable grading, namely the environment where the cable is distributed, the time of cable use, and the aging degree of the cable insulation layer. Let the environment where the cable is distributed be Ω, the time of cable use be t, and the aging degree of the cable insulation layer be Η. Set the weight coefficients to be 0.2, 0.2, and 0.6 respectively. When 0.2Ω + 0.2t + 0.6Η < M, the cable is classified as Grade I; when 0.2Ω + 0.2t + 0.6Η > M, the cable is classified as Grade II; when 0.2Ω + 0.2t + 0.6Η > 2M, the cable is classified as Grade III.

[0026] Further, different numbers of temperature detection devices, sound detection devices, light intensity detection devices, and gas pressure detection devices are installed corresponding to Grades I, II, and III of the cable grading.

[0027] Further, when detecting Grade III cables, if (T - T0) / T0 > 0.5 detected by the temperature detection device; (α - α0) / α0 > 0.5 detected by the sound detection device; (P - P0) / P0 > 0.2 detected by the gas pressure detection device; (Σ - Σ0) / Σ0 > 0.2 detected by the light intensity detection device or when one of the above results appears, the detection result is transmitted to the cable partial discharge location monitoring system.

[0028] Further, when detecting Grade II cables, if (T - T0) / T0 > 0.8 detected by the temperature detection device; (α - α0) / α0 > 0.8 detected by the sound detection device; (P - P0) / P0 > 0.4 detected by the gas pressure detection device; (Σ - Σ0) / Σ0 > 0.3 detected by the light intensity detection device or when one of the above results appears, the detection result is transmitted to the cable partial discharge location monitoring system.

[0029] Further, when detecting Grade I cables, if (T - T0) / T0 > 1.2 detected by the temperature detection device; (α - α0) / α0 > 1.2 detected by the sound detection device; (P - P0) / P0 > 0.6 detected by the gas pressure detection device; (Σ - Σ0) / Σ0 > 0.3 detected by the light intensity detection device or when one of the above results appears, the detection result is transmitted to the cable partial discharge location monitoring system.

[0030] Further, after the detection results of temperature, sound, gas pressure, and light intensity are transmitted to the cable partial discharge location monitoring system, the cable partial discharge location monitoring system determines the abnormal detection location; and the local current discharge detection device control device controls the local current discharge detection device to move to this location to detect the local current discharge by the above method.

Claims

1. A distributed partial discharge detection system for power cables; comprising a cable partial discharge current detection system; the cable partial discharge current detection system uses a pulse current method to detect cable partial discharge of an electrical device; the cable partial discharge current detection system comprises a voltage source U with one end of the cable grounded; a resistor R and a load device C are arranged on the cable path of the voltage source U, and there are multiple load devices into which the current flows; the voltage source U is connected to the load through a line and current is transmitted; if partial discharge occurs in a certain section of the line, a coupling capacitor C is connected in parallel at both ends of the cable line K It is coupled into the current path, and a coupling impedance Z and a detector connected to the coupling impedance Z are connected in series on the coupling capacitor circuit to convert the current at both ends of the cable into voltage to detect the local discharge position; if the voltage is abnormal, local discharge occurs; a local current discharge detection device is also provided, and the cable local discharge current detection system and the local current discharge detection device cooperate; the local current discharge detection device includes a detection box, a moving rod, a guide rail I and a guide rail II; the cable local discharge current detection system is placed in the detection box; the detection box is set on the moving rod, and the moving rod cooperates with the guide rail I and the guide rail II; the moving rod moves on the guide rail I and the guide rail II; the local current discharge detection device is driven to move by the moving device, and a local current discharge detection device control device is provided; the movement of the local current discharge detection device is controlled; a cable grading system is also included; the cables are graded according to the environment in which the cables are distributed, the time the cables are used, and the aging degree of the cable insulation layer; The cables are divided into grades I, II, and III; and preliminary inspections are carried out on the cables of different levels at different positions according to the grading results; the preliminary inspection of the cables uses a preliminary retrieval system; the preliminary retrieval system includes a temperature detection device, a sound detection device, a light intensity detection device, and a gas pressure detection device; the temperature detection device, the sound detection device, the light intensity detection device, and the gas pressure detection device are respectively arranged at different positions of the cable; different numbers of detection devices are distributed to the cables of different levels at different positions according to the grading of the cable grading system; the temperature detection device detects the temperature around the cable insulation layer; Set the normal operating temperature of the cable as T0; the detected temperature is T; the detected temperature and the comparison result are transmitted to the cable partial discharge location monitoring system; the sound detection device detects the temperature around the cable insulation layer; Set the normal operating sound decibel of the cable as α0; the detected sound decibel is α, and the detected sound distribution and the comparison result are transmitted to the cable partial discharge location monitoring system; and a noise elimination system is provided on the sound detection device; Prevent the influence of other noises; the light intensity detection device detects the light intensity around the cable insulation layer; and set the normal daytime light as Σ0; and set the suddenly generated strong light intensity as Σ; the detected light intensity is transmitted to the cable partial discharge location monitoring system; the gas pressure detection device detects the gas pressure around the cable insulation layer; set the normal operating gas pressure of the cable as P0; and the detected gas pressure is P; the detected gas pressure and the comparison result are transmitted to the cable partial discharge location monitoring system; the environment where the cable is distributed, the usage time of the cable, and the aging degree of the cable insulation layer are weighted and graded; Let the environment where the cable is distributed be Ω, the usage time of the cable be t, and the aging degree of the cable insulation layer be Η; set the weight coefficients as 0.2, 0.2, and 0.6 respectively; when 0.2Ω + 0.2t + 0.6Η < M, the cable is divided into grade I; when 0.2Ω + 0.2t + 0.6Η > M, the cable is divided into grade II; when 0.2Ω + 0.2t + 0.6Η > 2M, the cable is divided into grade III; Install different numbers of temperature detection devices, sound detection devices, light intensity detection devices, and gas pressure detection devices corresponding to grades I, II, and III of the cable grading; When detecting grade III cables, if (T - T0) / T0 > 0.5 detected by the temperature detection device; (α - α0) / α0 > 0.5 detected by the sound detection device; (P - P0) / P0 > 0.2 detected by the gas pressure detection device; (Σ - Σ0) / Σ0 > 0.2 detected by the light intensity detection device or when one of the above results appears, the detection result is transmitted to the cable partial discharge location monitoring system; When testing Class II cables, if (T-T0) / T0>0.8 detected by the temperature detection device; (α-α0) / α0>0.8 detected by the sound detection device; (P-P0) / P0>0.4 detected by the gas pressure detection device; (Σ-Σ0) / Σ0>0.3 detected by the light intensity detection device or one of the above results occurs, the test result shall be transmitted to the cable partial discharge position monitoring system; When testing Class I cables, if (T-T0) / T0 detected by the temperature detection device is greater than 1.2; (α-α0) / α0 detected by the sound detection device is greater than 1.2; (P-P0) / P0 detected by the gas pressure detection device is greater than 0.6; (Σ-Σ0) / Σ0 detected by the light intensity detection device is greater than 0.3 or one of the above results occurs, the detection result shall be transmitted to the cable partial discharge position monitoring system.

2. The power cable distributed partial discharge detection system according to claim 1, characterized in that: It also includes a cable partial discharge position monitoring system; the cable partial discharge position monitoring system monitors and analyzes the discharge position of the cable; if it is determined that the probability of discharge current breakdown at the cable position is greater than a preset value, an instruction is sent to the partial current discharge detection device.

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