How should cable faults be detected? What are the methods to detect power cable faults

The first is the low-voltage pulse reflection method, this method is mainly used in the detection of cable faults caused by low resistance, because when low resistance, the impedance of other points does not match the impedance of the fault point, so in the cable, the low-voltage pulse meets the fault point will appear reflected pulse, and then according to the specific propagation speed of the reflected pulse and the transmitted pulse and the calculation of the actual round-trip time difference, locate the fault point. The second is the impact high-voltage flashover method, the impact high-voltage flashover method is widely used in cable fault detection, and its principle is to apply the impact high voltage at the beginning of the fault cable, and record the data information of the voltage jump at the moment when the fault breakdown occurs.

Then, through research and analysis of the obtained data, the fault point is accurately located, and countermeasures are proposed. The bridge method has the advantage of high accuracy, simple and convenient operation, but the bridge method is not suitable for detecting high-impedance flashover faults, because the bridge current will be relatively small when the fault resistance is high, which brings difficulties to detection. In addition, the length of the cable needs to be known before the test when the bridge method is applied, and if the cross-sections of each cable and the cross-section that make up the cable route are different, they need to be calculated before the test.

Finally, there is also the secondary pulse method for detecting cable faults.

Respondent: Huatian Power.

Discuss it with the wire, it obediently don't have a situation, so I asked it to Beijing Hotel for three catties and two pots.

After the cable fails, it is generally used to determine the type of fault with a shake meter or a high resistance meter above 1500V, and then use different instruments and methods to initially measure the fault, and finally use the fixed-point method to accurately determine the fault point. Induction method, its principle is that when the audio current passes through the core of the cable, there are electromagnetic waves around the cable, because some carry electromagnetic induction receivers, when walking along the line, the sound of electromagnetic waves can be heard, when the audio current flows to the fault point, the current mutates, and the audio of the electromagnetic wave mutates, this method is very convenient for finding the low-resistance short-circuit fault between the broken phases, but it is not suitable for finding the high-resistance short-circuit and single-phase grounding fault. The principle of acoustic measurement is to use high-voltage pulses to promote the discharge of the fault point, produce a discharge sound, and use a sensor to receive this discharge sound on the ground to measure the precise location of the fault point.

(1) Acoustic measurement.

The sound wave generated by the discharge of the fault point is used to set the point, and the sound sensor detects the sound signal above the power cable, and the place with the largest sound is the location where the fault point is located, and the farther away from the fault point, the smaller the vibration sound.

2) Acousto-magnetic synchronization method.

When the fault point is flashed under the action of impulse voltage, the electromagnetic wave and vibration sound wave generated by the fault point discharge are received at the same time, and the measured signal is judged to be generated by the discharge of the fault point to accurately judge the location of the fault point.

3) Audio induction.

At one end of the circuit under test, add a certain power of low-voltage audio signal to the fault of the cable, when the measured signal is transmitted to the short circuit or disconnection point, but can not continue to be transmitted along the cable, so that there will be obvious signal size changes on both sides of the cable fault point, if the signal change is detected by the receiver above the cable path, the location of the fault point can be determined.

At the same time, the accuracy and completeness of the basic data of the cable are also very important to improve the efficiency of fault point finding, such as the direction of cable laying, the total length of the cable, and the distribution of cable intermediate joints.

Summary. Hello dear <>

The use of cable fault detection instruments is as follows: 1Preparation: Place the cable fault detection instrument on stable ground, plug it in and wait for it to warm up.

2.Connecting cable: Connect the cable to be tested to the test port of the instrument and make sure the connection is secure.

3.Set parameters: According to the type and length of the cable to be tested, set the test parameters of the instrument, such as test voltage, test frequency, etc.

4.Start Test: Press the test button on the instrument to start cable fault detection.

The instrument automatically scans the cable and displays the test results. 5.Analysis Results:

Based on the test results displayed by the instrument, the location and type of cable faults are analyzed and repaired. 6.Turn off the instrument:

When the test is complete, press the off button on the instrument, disconnect the power supply and store the instrument in a dry and ventilated place.

How to use cable fault detection instrument.

Hello dear <>

The use of cable fault detection instruments is as follows: 1Preparation: Place the cable fault dust detector on a stable ground, turn on the power and wait for the warm-up.

2.Connecting cable: Connect the cable to be tested to the test port of the instrument and make sure the connection is secure.

3.Set parameters: According to the type and length of the cable to be tested, set the test parameters of the instrument, such as test voltage, test frequency, etc.

4.Start Test: Press the test button on the instrument to start cable fault detection.

The instrument automatically scans the cable and displays the test results. 5.Analysis Results:

Based on the test results displayed by the instrument, the location and type of cable faults are analyzed and repaired. 6.Turn off the instrument:

When the test is complete, press the off button on the instrument, disconnect the power supply and store the instrument in a dry and ventilated place.

Cable fault detection instrument is a device used to detect cable fault, mainly including the following:1Cable Partial Discharge Detector:

It is used to detect partial discharge of cables and can help find the location of cable faults. 2.Cable Insulation Resistance Tester:

It is used to test the insulation resistance of the cable, and it can be judged whether the cable insulation is normal. 3.Cable Fault Locator:

It is used to locate the location of the fault of the electric old digging cable, and the fault point can be quickly found. 4.Cable Gland Partial Discharge Detector:

It is used to detect partial discharge of cable glands and can help pinpoint the location of splice faults. 5.Cable Fault Diagnosis Scatter Tunnel:

With a variety of detection functions, the attendant can perform a comprehensive fault diagnosis of the cable.

1. Distinction between wires and cables.

Wire specifications generally refer to cable specifications. There is no strict boundary between "wire" and "cable". Generally, the products with a small number of cores, small product diameter and simple structure are called wires, those without insulation are called bare wires, and the others are called cables; The larger conductor cross-sectional area (more than 6 square millimeters) is called a large wire, the smaller one (less than or equal to 6 square millimeters) is called a small wire, and the insulated wire is also called a cloth wire.

2. Common cable faults.

1) Wire surface marking - According to the national standard, the wire surface should have the continuous mark of the manufacturer's name, product model and rated voltage. This is conducive to finding the manufacturer in time when problems occur during the use of wires, and consumers must pay attention to this when purchasing wires. At the same time, consumers should pay attention to whether the name of the manufacturer, product model, and rated voltage indicated on the certificate are consistent with the printed mark on the surface of the wire, so as to prevent counterfeit products.

2) Appearance of wires - Consumers should pay attention to the appearance of wires when purchasing wires, the appearance of wires should be smooth and flat, the insulation and sheath layers should not be damaged, the logo printing should be clear, and there should be no greasy feeling when hand-molding wires. From the cross-section of the wire, the thickness of the insulation or protection of the Otomo sleeve should be uniform on the entire circumference of the wire, and the core should not be deviated, and the insulation or sheath should have a certain thickness.

Conductor wire diameter - consumers should pay attention to whether the conductor wire diameter is consistent with the cross-section indicated on the certificate of the joint notice when purchasing wires, if the conductor cross-section is too small, it is easy to cause short circuits due to wire heating. It is recommended that the wires used in household lighting lines should be square millimeters and above; Household appliances with large power such as air conditioners and microwave ovens should use wires with square millimeters or more.

3) Standardized use - the wiring should be standardized, the fixed line is best to use BV single-core wire through the pipe, pay attention not to touch the wire when wiring, do not touch the wire when decorating the room; Do not have a joint in the middle of a course; Do not touch the wire when connecting to the electrical box (box); In addition, household appliances with large electricity consumption, such as air conditioners, should be powered by a separate wire; It is best to keep a certain distance between the wires used for weak and strong currents.

Common faults in cable lines include mechanical damage, insulation damage, insulation moisture, insulation aging and deterioration, overvoltage, cable overheating faults, etc. When the above fault occurs in the line, the power supply of the faulty cable should be cut off, the fault point should be found, the fault should be checked and analyzed, and then repaired and tested.

Precise location of cable faults is usually carried out in the following 4-step sequence:

Determine the type of fault point.

According to the nature of the fault, cable faults can be divided into low-resistance grounding or short-circuit faults, high-resistance grounding or short-circuit faults, disconnection faults, disconnection and grounding faults, and flashover faults.

Select the appropriate method and the corresponding instrument according to the type of fault.

It is tested with different test methods for different fault types. For example, for high-impedance faults, the flash method can be used to locate the fault.

Coarse bite. There are two kinds of rough positioning methods: bridge method and wave reflection method. At present, the wave reflectometry locator is more popular.

However, there are several cable faults that are difficult to find by wave reflection method, such as insulation defects in high-voltage cable sheaths, steel tape armored low-pressure cables, PVC cables, and short cables that cannot be located. In addition, some high-resistance breakdown points cannot be broken down under impulse voltage and are difficult to locate.

Precise pointing. Cable faults can be accurately pinpointed in the following four methods:

1) Acoustic measurement method: It is discharged by the high-voltage pulse generator to the fault cable, the fault point produces an arc, and produces a discharge sound, in the case of direct burial of the cable, the first wave, the acoustic probe of the fixed-point instrument picks up the first wave signal and amplifies it through the headset or meter output.

2) Step voltage method: It is mainly aimed at the external sheath insulation of the cable has the requirements of the outer sheath grounding fault point, now for some directly buried low-voltage cables, wire core grounding faults, can also use the step voltage legal point.

3) Electromagnetic method and audio method: use electromagnetic wave fixed point or use audio legal point, that is, use the change of electromagnetic wave signal or audio signal before and after the cable fault to determine the fault point.

4) Acousto-magnetic synchronization method: It is a comprehensive application of acoustic measurement method and electromagnetic wave method.