Low-voltage overhead line fault detection device and method

Abstract

The invention provides a low-voltage overhead line fault detection device and method, and relates to the technical field of power detection. Comprising the steps that a plurality of split core type current transformers clamp and measure the current of an overhead conductor, a lead-out wire collects output signals of each split core type current transformer into a circuit of a next stage, the output signals are transmitted through the lead and finally reach a current gathering ring, the current gathering ring synthesizes and amplifies sampled secondary current, a current synthesized current value is obtained, and the current synthesized current value is calculated. And carrying out fault detection judgment. By adopting a non-contact measurement mode, direct contact with a cable or a line is avoided, the safety and durability of equipment are improved, the fault detection precision is improved by adopting a multi-point detection mode, accurate positioning of a fault occurrence position is realized by analyzing a signal output by a current gathering ring, the fault detection precision and efficiency are improved, and the fault detection accuracy and efficiency are improved. And reliable monitoring and protection are provided for a low-voltage power line.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power detection, and in particular to a low-voltage overhead line fault detection device and method. Background Art

[0002] my country's low-voltage distribution network generally adopts three-phase four-wire power supply. The low-voltage line fault finding device can quickly, safely and accurately find the fault point when a grounding or short-circuit fault occurs in the low-voltage line. It is of great significance to improve the reliability and safe operation of power supply of the power grid, improve the quality of service, and reduce the economic losses caused by long-term faults of low-voltage lines. Among them, the insulation transformation of the line can effectively reduce the probability of phase-to-phase short circuit and grounding of the conductor, and greatly improve the reliability of power supply in the substation area. At present, the traditional low-voltage line fault finding adopts the "all-staff departure, carpet search" line patrol method, which is time-consuming and inefficient. In addition, when encountering line branching, it is necessary to check each branch, or climb the pole to check the current to determine the faulty branch. The process takes a long time and there is a risk of people falling and getting injured.

[0003] In the prior art, after a fault occurs in a transformer substation, the first task is to determine the type of fault, by checking the fuse or measuring the leakage current to determine whether it is a short circuit or a ground fault; then determine the approximate location of the fault point. The usual practice is to divide the low-voltage line into several sections and determine the fault point by testing the power transmission in sections. In the process of segmenting the low-voltage overhead line, workers need to repeatedly climb the pole, remove the wire connection points, and restore the wire connection. The work efficiency of the workers is low and the risk is high. The average time for a single pole climbing and the removal and binding of the wire connection points is 50 minutes, and long-term work on the pole is very likely to cause a fall from a height and electric shock.

[0004] At present, the low-voltage lines in the foreground are long, and the fire points are numerous and complex. The operation and maintenance personnel need to manually judge and find the location of the fault point. When the low-voltage overhead lines fail, it is easy to make mistakes and it is time-consuming and labor-intensive. The risk of falling from a height and electric shock is extremely high, and the specific location of the fault point cannot be determined in time. Summary of the invention

[0005] The main purpose of the present invention is to provide a low-voltage overhead line fault detection device and method to solve the problems in the prior art that the specific location of the fault point cannot be determined in time during line fault detection and the specific location of the fault point and the detection process has low safety.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a low-voltage overhead line fault detection device, comprising: a plurality of clamp-on current transformers, used to clamp and measure overhead conductors; each clamp-on current transformer is provided with a lead-out wire at the lower end, and the other end of the lead-out wire is connected in parallel and then connected in series with the corresponding current focusing ring through a wire, so as to perform multi-point monitoring and determine the fault point of the same section of three-phase four-wire conductor line. .

[0007] In the preferred embodiment, an insulating clamp is installed on the insulating handle at the lower end of the clamp-on current transformer, an insulating telescopic rod is provided at the lower end of the insulating clamp, the lower end of the insulating telescopic rod is fixedly connected to the insulating rod by bolts, and an insulating clamp opening and closing controller is provided at the bottom of the insulating rod.

[0008] In the preferred embodiment, the lead wire and the conductor are wound with insulating material; the insulating clip is fixed to the insulating handle at the lower end by a buckle.

[0009] In the preferred solution, the number of turns of the focusing ring is adjusted according to actual needs.

[0010] In a preferred embodiment, the insulating telescopic rod is adjusted in length by means of a bolt.

[0011] In a preferred embodiment, the insulating clamp opening and closing controller is configured to be wavy.

[0012] A low-voltage line fault detection method, characterized in that it is applicable to a low-voltage overhead line fault detection device according to any one of claims 1 to 7, comprising: S1: Divide the same section of low-voltage three-phase four-wire overhead conductor at the measurement point into several sections, and use the section-by-section test power transmission method to determine the fault point; S2: Multiple clamp-on current transformers are extended and retracted through their respective insulating telescopic rods. After the line height is determined, the insulating clamp opening and closing controller clamps the line so that the line is placed on the top of the clamp-on current transformer. The current of each phase on the conductor is sampled in phases to obtain the secondary current, and each clamp-on current transformer clamps a conductor of the same polarity. S3: The corresponding current focusing ring synthesizes and amplifies the sampled secondary current to obtain the current synthesized current value; wherein the secondary currents of each clamp-on current transformer are connected in parallel according to polarity; S4: According to the current composite current value, the detection result is obtained and the fault type is determined; if the current composite current value is greater than the preset current value, it is determined that there is a ground fault at the measuring point, and then the next measuring point is detected and processed accordingly; S5: Repeat the operations of S3-S4 to determine the fault interval, and use the clamp-on current transformer to measure each phase.

[0013] In the preferred solution, judging the fault type further includes: if the composite current value is zero, that is, the sum of the current values ​​is zero, then there is no fault in the power supply line at the measurement point.

[0014] In the preferred solution, the data sizes of different phases are compared, and the ground fault phase is the phase with the larger collected reading; The fault types include short circuit, open circuit and grounding; The preset current value is 5A, and the corresponding measuring wire diameter is not less than 4mm 2 .

[0015] The present invention provides a low-voltage overhead line fault detection device and method, including multiple clamp-on current transformers that clamp and measure the current of overhead conductors, and lead-out conductors that collect the output signals of each clamp-on current transformer into the circuit of the next stage, and transmit them through the conductors, and finally reach the focusing ring, which synthesizes and amplifies the sampled secondary current to obtain the current synthesized current value and perform fault detection and judgment. The non-contact measurement method avoids direct contact with cables or lines, improves the safety and durability of the equipment, and the multi-point detection method improves the accuracy of fault detection. By analyzing the signal output by the focusing ring, the accurate positioning of the fault location is achieved, the accuracy and efficiency of fault detection are improved, and reliable monitoring and protection are provided for low-voltage power lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 is a structural diagram of a fault detection device of the present invention; Figure 2 It is a structural diagram of the clamp-on current transformer of the present invention; Figure 3 It is a schematic diagram of the overall process of fault detection of the present invention; Figure 4 The insulating telescopic rod of the present invention is connected by bolts; Figure 5 It is a schematic diagram of fault finding in the application of the present invention.

[0017] In the figure: a clamp-on current transformer 1; an insulating handle 1-1; an insulating clamp 1-2; an insulating telescopic rod 1-3; an insulating rod 1-4; a bolt 1-5; an insulating clamp opening and closing controller 1-6; a lead wire 2; a wire 3; and a focusing ring 4. DETAILED DESCRIPTION

[0018] Example 1 like Figure 1-5 As shown, a low-voltage overhead line fault detection device includes multiple clamp-on current transformers 1 for clamping and measuring overhead conductors; each clamp-on current transformer 1 is provided with a lead wire 2 at the lower end, and the other end of the lead wire 2 is connected in parallel and in series with the corresponding focusing ring 4 through a wire 3, so as to perform multi-point monitoring on the same section of a three-phase four-wire conductor line and determine the fault point.

[0019] In this embodiment, a clamp-on current transformer (usually one or more) is used to clamp and measure the current of the overhead conductor, and can monitor the current conditions of multiple conductors in real time; the lead-out conductor 2 collects the output signal of each clamp-on current transformer into the circuit of the next stage and merges the signal. The merged signal is transmitted through the conductor 3 and finally reaches the focusing ring 4. By connecting in parallel, the signals of all current transformers can be unified and integrated to obtain the monitoring signal of the entire line status. The output signal of the focusing ring 4 is used for fault detection and judgment. The non-contact measurement method avoids direct contact with cables or lines, improves the safety and durability of the equipment, and the multi-point detection method improves the accuracy of fault detection. By analyzing the signal output by the focusing ring 4, the location of the fault can be located, which improves the accuracy and efficiency of fault detection and provides reliable monitoring and protection for low-voltage power lines.

[0020] Faults are usually accompanied by abnormal current (such as overcurrent, undercurrent, short circuit, etc.). According to the changing characteristics of the current (such as abnormal conditions such as short circuit, overload, etc.), the clamp-on current transformer can accurately capture the current changes in the conductor.

[0021] This embodiment includes four clamp-on current transformers 1 .

[0022] In the preferred embodiment, an insulating clamp 1-2 is installed on the insulating handle 1-1 at the lower end of the clamp-on current transformer 1, an insulating telescopic rod 1-3 is provided at the lower end of the insulating clamp 1-2, the lower end of the insulating telescopic rod 1-3 is fixedly connected to the insulating rod 1-4 by bolts, and an insulating clamp opening and closing controller 1-6 is provided at the bottom of the insulating rod 1-4.

[0023] In this embodiment, the insulating telescopic rod 1-3 is connected to the insulating clamp 1-2 to provide a longer operating distance for the current transformer. The design of the telescopic rod can adjust the length of the current transformer as needed to adapt to wire measurements at different heights or positions.

[0024] In the preferred embodiment, the lead wire 2 and the lead wire 3 are wound with insulating material; The insulating clip 1-2 is fixed to the lower insulating handle 1-1 by means of a buckle.

[0025] The insulating clamp 1-2 is a component fixed to the lower end of the insulating handle 1-1, in order to clamp the current transformer and provide additional insulation protection to further enhance the safety of operation.

[0026] In the preferred solution, the number of turns of the focusing ring 4 is adjusted according to actual needs.

[0027] In this embodiment, the number of turns of the focusing ring 4 can be adjusted according to actual applications.

[0028] In the preferred embodiment, the insulating telescopic rod 1-3 is adjusted in length by means of a bolt 1-5.

[0029] In the preferred embodiment, the insulating clamp opening and closing controller 1-6 is configured to be wavy.

[0030] The wave-shaped design can increase the contact surface and enhance the contact force with the current transformer or the object being measured, thereby ensuring a stable clamping force and reducing the risk of slipping or falling off.

[0031] In this embodiment, a clamp-on current transformer (usually 2-4) is used to measure the operating current of the overhead line conductor. Its secondary winding is connected to the focusing ring 3 through the conductor 2, so that the operating current of the line is phase-synthesized in the focusing ring 3 after passing through the current transformer. The focusing ring 3 is composed of a multi-turn coil, which facilitates the instrument to measure the current. The measuring instrument adopts an ordinary clamp-on ammeter, which reduces the manufacturing cost of the device, reduces the difficulty of research and development, and also has the advantage of being easy to carry on site.

[0032] The secondary winding of each current transformer is connected in parallel and then in series with the focusing ring. The unbalanced current in the line is measured in the focusing ring by an ordinary clamp ammeter. The non-direct contact measurement method improves the safety of work and the durability of equipment. The focusing ring made of multi-turn coils improves the accuracy of detection and can monitor the operation of overhead lines in real time.

[0033] Detection principle: According to Kirchhoff's current law, the composite current value of each phase current Ia, Ib, Ic and In is zero. The location of the fault point is determined by measuring the unbalanced current at the measuring point.

[0034] like Figure 5 The figure shows a schematic diagram of fault finding in the present embodiment. In the present embodiment, four clamp-on current transformers 1 are preferably used. The clamp-on current transformers 1 clamp and measure the current of the overhead wires, and monitor the current conditions of multiple wires in real time. Specifically: 1) When the repair personnel installed the device on the left side of pole #2, the collected current was 11.8mA, indicating that the fault point was after the monitoring point.

[0035] 2) The repair personnel installed the device on the right side of pole #2 and collected a current of 0, indicating that the right side of pole #2 was normal and had no faults. The repair personnel installed the device on the lower lead of pole #2 and collected a current of 13.2mA, indicating that the fault point was behind the lower lead of pole #2.

[0036] 3) The emergency repair personnel re-tested the terminal head on the main switch of the electromechanical box and found no abnormality, indicating that the fault point was inside the insulating sleeve of the lead wire under the #2 pole.

[0037] Example 2 In combination with Example 1, a low-voltage line fault detection method is further described, which is applicable to a low-voltage overhead line fault detection device described in Example 1, comprising: S1: Divide the same section of low-voltage three-phase four-wire overhead conductor at the measurement point into several sections, and use the method of segmented power transmission to determine the fault point.

[0038] S2: Multiple clamp-on current transformers 1 are extended and retracted through their respective insulating telescopic rods 1-3. After the line height is determined, the insulating clamp opening and closing controller 1-6 clamps the line so that the line is placed on the top of the clamp-on current transformer 1. The currents of each phase on the conductor are sampled in phases Ia, Ib, Ic and In to obtain the secondary current, and each clamp-on current transformer 1 clamps a conductor of the same polarity.

[0039] S3: The corresponding current focusing ring 4 synthesizes and amplifies the sampled secondary current to obtain a current synthesized current value; wherein the secondary currents of the clamp-on current transformers 1 are connected in parallel according to polarity.

[0040] S4: Use a clamp ammeter to obtain the current value of the focusing ring, obtain the detection result based on the current composite current value, and judge the fault type; if the current composite current value is greater than the preset current value, it is determined that there is a grounding fault at the measurement point, such as leakage in the phase line, and the leakage detection circuit and the leakage position form a leakage current through the earth, so that the leaking phase line can be quickly determined, and then the next measurement point is detected and corresponding processing is performed.

[0041] S5: Repeat the operations of S3-S4 to determine the fault interval, and use the clamp current transformer 1 to measure each phase, so that the leakage position can be found simply and quickly.

[0042] In the preferred solution, judging the fault type further includes: if the composite current value is zero, that is, the sum of the current values ​​is zero, then there is no fault in the power supply line at the measurement point.

[0043] In this embodiment, when a low-voltage overhead line fails, the low-voltage line is divided into several sections, and the fault point is determined by the method of segmented power transmission. First, the insulating telescopic rods 1-3 are adjusted in height to determine the line height, and the insulating clamp opening and closing controllers 1-6 clamp the line, and the four clamp-type current transformers 1 clamp and measure the current of the overhead conductor.

[0044] The detection principle of this embodiment is as follows: Based on Kirchhoff's current law, and taking into account that the impedance of the short-circuit fault point is generally much smaller than the load impedance on the line, the heterodyne current signal input by the signal collector to the line mainly flows through the short-circuit fault point and forms a loop. Therefore, the collection of the heterodyne current signal indicates that the fault point is after the detection point, otherwise the fault point is before the detection point.

[0045] In the preferred solution, the data sizes of different phases are compared, and the ground fault phase is the phase with the larger collected readings.

[0046] The fault types include short circuit, open circuit and ground fault.

[0047] The preset current value is 5A, and the corresponding measuring wire diameter is not less than 4mm2.

[0048] In this embodiment, the current sampling element is a clamp-on current transformer 1, which is used to sample the current of each phase of the low-voltage three-phase four-wire overhead conductor (one for each phase), and each current transformer must clamp one conductor with the same polarity. The two ends of the secondary winding of the current transformer must be connected to the current synthesis and amplification element according to the polarity.

[0049] The current synthesis and amplification element is a focusing ring, which synthesizes and amplifies the secondary currents of the four current transformers to facilitate the measurement of fault current. The secondary currents of the four clamp-on current transformers are connected in parallel according to polarity, and the two ends of the parallel connection are then connected to the two ends of the focusing ring.

[0050] The detection principle of the low-voltage overhead line detection device is basically the same as that of the residual current operated protector. It mainly monitors the operation of the low-voltage overhead line and determines the fault point by measuring the unbalanced current of the three-phase four-wire. The residual current operated protector samples the fault current through one zero-sequence current transformer, while the low-voltage overhead line detection device uses four current transformers for current sampling.

[0051] If the composite current value of Ia, Ib, Ic and In measured by sampling is zero, it means that there is no fault in the three-phase four-wire power supply line behind the measuring point, and the fault point is on the power supply side of the measuring point. If the measurement is made at the low-voltage outlet of the transformer, it can be determined whether there is a fault in the low-voltage overhead line of the entire substation. This embodiment can be used for the detection of fault current of low-voltage three-phase four-wire lines, three-phase three-wire lines and single-phase lines.

[0052] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A low voltage overhead line fault detection device, characterized in that: include: A plurality of clamp-on current transformers (1) are used to clamp and measure overhead conductors; a lead-out conductor (2) is provided at the lower end of each clamp-on current transformer (1); the other end of the lead-out conductor (2) is connected in parallel and then connected in series with a corresponding current focusing ring (4) through a conductor (3), so as to perform multi-point monitoring on the same section of a three-phase four-wire conductor line and determine a fault point.

2. The low voltage overhead line fault detection device according to claim 1, characterized in that: An insulating clamp (1-2) is installed on the lower end of the insulating handle (1-1) of the clamp-type current transformer (1), an insulating telescopic rod (1-3) is provided at the lower end of the insulating clamp (1-2), the lower end of the insulating telescopic rod (1-3) is fixedly connected to an insulating rod (1-4) by bolts, and an insulating clamp opening and closing controller (1-6) is provided at the bottom of the insulating rod (1-4).

3. The low voltage overhead line fault detection device according to claim 1, characterized in that: The lead wire (2) and the wire (3) are wound with insulating material; The insulating clip (1-2) is fixed to the lower insulating handle (1-1) by means of a buckle.

4. The low voltage overhead line fault detection device according to claim 1, characterized in that: The number of turns of the focusing ring (4) is adjusted according to actual needs.

5. The low voltage overhead line fault detection device according to claim 2, characterized in that: The length of the insulating telescopic rod (1-3) is adjusted by means of a bolt (1-5).

6. The low voltage overhead line fault detection device according to claim 2, characterized in that: The insulation clamp opening and closing controller (1-6) is set to a wave shape.

7. A low voltage line fault detection method, characterized in that: A low voltage overhead line fault detection device applicable to any one of claims 1 to 7, comprising: S1: Divide the same section of low-voltage three-phase four-wire overhead conductor at the measurement point into several sections, and use the section-by-section test power transmission method to determine the fault point; S2: Multiple clamp-on current transformers (1) are extended and retracted through their respective insulating telescopic rods (1-3). After the line height is determined, the insulating clamp opening and closing controller (1-6) clamps the line so that the line is placed on the top of the clamp-on current transformer (1). The current of each phase on the conductor is sampled in phases to obtain a secondary current, and each clamp-on current transformer (1) clamps a conductor of the same polarity. S3: The corresponding current focusing ring (4) synthesizes and amplifies the sampled secondary current to obtain a current synthesized current value; wherein the secondary currents of the clamp-on current transformers (1) are connected in parallel according to polarity; S4: According to the current composite current value, the detection result is obtained and the fault type is determined; if the current composite current value is greater than the preset current value, it is determined that there is a ground fault at the measuring point, and then the next measuring point is detected and processed accordingly; S5: Repeat the operations of S3-S4 to determine the fault interval, and use the clamp-on current transformer (1) to measure each phase.

8. The low voltage overhead line fault detection method according to claim 7, characterized in that: Determining the fault type also includes: if the composite current value is zero, that is, the sum of the current values ​​is zero, then there is no fault in the power supply line of the measurement point.

9. The low voltage overhead line fault detection method according to claim 7, characterized in that: Comparing the data sizes of different phases, the ground fault phase is the phase with the larger collected readings; The fault types include short circuit, open circuit and grounding; The preset current value is 5A, and the corresponding measuring wire diameter is not less than 4mm 2 .

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