Knowledge of the hottest cable fault locator

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Knowledge of cable fault locator

cable fault locator is a comprehensive cable fault detection instrument, which can test the high resistance flashover fault, high and low resistance grounding, short circuit, cable disconnection, poor contact and other faults of cables. The cable fault locator is equipped with an acoustic locator, which can be used to accurately determine the precise position of the fault point. It is especially suitable for testing power cables and communication cables of various models and voltages. 1. Directly buried cable 2 Hammering (pulse) method 3 Time domain reflectometry 4 Arc reflection method 5 Fast fault detector 6 The first response

detection mode

cable fault locator adopts a variety of detection modes and applies the most advanced electronic technology achievements of the contemporary era. Using computer technology and microelectronics technology, it has the characteristics of high intelligence, complete functions, wide range of use, accurate testing, convenient use and so on. The design of locator to detect aircraft cable fault is very important in civil aviation maintenance; According to the characteristics of aircraft cable, a method that can effectively test and diagnose it - low voltage pulse method is proposed, and the defect detection and positioning device of aircraft cable is designed by using single chip microcomputer and CPLD technology; The locator is mainly composed of three parts: signal acquisition circuit, system control circuit and human-computer interaction circuit; At the same time, two sets of vibration products are used, which not only ensures the high-speed signal acquisition, but also meets the low-speed processing of the system. It has the characteristics of low cost, portability and dexterity, accurate testing and so on; At the same time, in addition to being applied to aircraft cable maintenance, it can also be further applied to short-distance cable testing defect detection in telecommunications, power and other departments Working principle

the power cable fault tester is composed of three main parts: the host of the power cable fault tester, the cable fault locator, and the cable Pathfinder. The host of the cable fault tester is used to measure the nature of the cable fault, the total length and the approximate position of the cable fault point from the test end. The cable fault locator determines the exact location of the cable fault point based on the approximate location of the cable fault point determined by the host of the cable fault tester. For buried cables with unknown direction, it is necessary to use a Pathfinder to determine the underground direction of the cable. The basic method of power cable fault testing is to apply high-voltage pulse to the faulty power cable to produce breakdown at the cable fault point. When the cable fault breakdown point discharges, electromagnetic waves are generated externally and sound is emitted at the same time. The working principle of the application of arc reflection method

(secondary pulse method) in cable fault location: first, a high-voltage pulse with a certain voltage level and energy is applied to the faulty cable at the test end of the cable, so that the high resistance fault point of the cable will break down and ignite an arc. At the same time, add low-voltage pulse for measurement at the test end. When the measurement pulse reaches the high resistance fault point of the cable, it encounters an arc and reflects on the surface of the arc. When arcing, the high resistance fault becomes an instantaneous short-circuit fault, and the low-voltage measurement pulse will have obvious impedance characteristic changes, making the waveform of flashover measurement become the low-voltage pulse short-circuit waveform, making the waveform discrimination particularly simple and clear. This is what we call the "secondary pulse method". The received low-voltage pulse reflection waveform is equivalent to a waveform in which the core is completely short circuited to the ground. Superimpose the low-voltage pulse waveform obtained when releasing the high-voltage pulse and when not releasing the high-voltage pulse. The two waveforms will have a divergence point, which is the reflection waveform point of the fault point. This method combines the low-voltage pulse method with the high-voltage flashover technology, making it easier for testers to determine the location of the fault point. Compared with the traditional test method, the advantage of the secondary pulse method is to simplify the complex waveform in the impulse high-voltage flashover method to the simplest low-voltage pulse short-circuit fault waveform, so the interpretation is extremely simple and the fault distance can be accurately calibrated. The triple pulse method

uses the double impact method to prolong the arc burning time and stabilize the arc, which can easily locate high resistance faults and flashover faults. The triple pulse method has advanced technology, simple operation, clear waveform, fast and accurate positioning. At present, it has become the mainstream positioning method of high resistance fault and flashover fault. The third pulse method is an upgrade of the second pulse method. Its method is to first measure the reflected waveform of the low-voltage pulse without breaking down the fault point of the tested cable, then use the high-voltage pulse to impact the fault point of the cable to generate an arc, trigger the medium voltage pulse when the arc voltage drops to a certain value to stabilize and extend the arc time, and then send the low-voltage pulse to obtain the reflected waveform of the fault point, After the superposition of the two waveforms, it can also be found that the divergence point is the corresponding position of the fault point. Because the medium voltage pulse is used to stabilize and prolong the arc time, it is easier to obtain the waveform of fault point than the secondary pulse method. Compared with the secondary pulse method, the triple pulse method does not need to choose the synchronous duration of the arc, and the operation is also simpler. Relevant applications

in the power industry and some industries using cables, especially in some complex power systems, it is very difficult to find the fault of underground cable lines. However, the continuous emergence of equipment with diverse functions and simple operation in this regard can not only reduce the high cost of fault detection, but also reduce the inevitable long-term power failure when it is difficult to find cable faults, which brings a lot of convenience to troubleshooting. Direct buried cable

it is very time-consuming to detect faults in underground direct buried cables and underground residential power distribution (URD) systems, which will cause very inconvenient power cuts to users, and some technologies may also damage cables. For some equipment with high technical requirements, its operation is more complex, and only operators with strict training can use it, which brings a lot of inconvenience to the promotion and application of this kind of technical equipment. Therefore, the selection of appropriate technology depends partly on the knowledge of cable system design understood by the designers of fault detectors, and also partly on the understanding of professional technical knowledge in this regard by equipment and operators. With appropriate equipment and professional technology working on site, it is the first step to detect faults quickly and effectively. Hammering (pulse) method

many power companies use hammering (pulse) method. This technology is the most effective in detecting high resistance faults in a simple cable system. Hammering method includes using a pulse or impulse voltage to impact the power-off cable. When an effective high-voltage pulse impacts the fault area, the fault point will flashover and produce a hammering sound that can be heard by the operator along the cable surface. However, detecting cable faults often requires several hammers, and repeated impacts may damage the cable

however, according to dennisminier, the administrator in charge of electrical installation and maintenance of Seattle lighting company in the United States, because this method is simple and easy, they have always used hammering method to detect cable faults. Time domain reflectometry

(TDR) is a low-voltage arc reflection technology that is displayed by changing the pulse reflection generated on the cable structure. This pulse reflection is recorded on the screen of TDR and compared with the characteristic graph (the characteristic graph recorded before the fault) or with the characteristic graph made by the sound phase on the same cable line. The distance of the fault point is determined by the figure that France has stopped the use of primary plastic shaped scattering points. TDR method is one of the most effective methods to detect low resistance faults. The problem is that the graphical analysis of TDR requires trained and experienced operators to perform analysis operations

high resistance faults and complex systems require equipment to have a higher energy level. Some methods of high voltage arc reflection, such as digital arc reflection method and differential arc reflection method, require special equipment and strictly trained operators. Arc reflection method

due to the complexity of arc reflection method, hammering method is still the most common application technology. This technology is relatively simple, without special instruments and skilled analysts. The new instrument is multifunctional, and the potential damage of the cable can be minimized by hammering

the time of using pulses on cables should be as short as possible, and it can improve the efficiency of fault detection, which is the common goal of many power companies. In the underground direct buried cable and the simple underground residential power distribution system, there are currently two devices that can achieve the above two goals. Fast fault detector

a device called fast fault detector (FFF) was developed by the American Electric Power Research Association in Palo Alto, California. This FFF can detect the waveform emitted by the fault when the cable is arcing for the first time before the circuit is powered off, and the captured waveform is processed and stored in the FFF monitor, which is connected to the usual disconnection point in the URD system. This device has two sensors to monitor the transient faults on both sides of a circuit. When a fault occurs, the time interval between the two transient peaks gives the distance to the fault point. FFF can update the hardware of the experimental machine for a long time and work automatically without strict training of operators. This cheap device can be installed in the URD circuit as a permanent monitoring instrument to detect the faults. In other words, after the fault occurs, the device can be used as a detection tool. Since the device uses the voltage pulse of the cable rated value or lower than the rated value for one-time impact after the fault, and the discharge is only carried out once, the chance of cable damage is minimal

only one FFF is required for each single-phase open radial or ring circuit, while a device is required for each phase of the 3-phase system. The fault location information can be sent to the remote control communication computer center of the headquarters of the power company through RS-232 interface. The first response

another device is called the firstresponse device, which is a battery powered hammer high-voltage coupler and a single hammer to form a cable radar system to isolate the faulty cable section between transformers, and can measure the distance to the fault point. The device adopts digital arc reflection technology and requires a high-energy filter when detecting. High resistance faults in complex systems often produce interference signals, which interfere with detection through some connectors and star connected taps. Therefore, higher energy is needed to quickly and accurately identify faults. Special power transmission lines and complex network systems are usually equipped with manholes and pipelines, which may accumulate a lot of water. Therefore, in cities and industrial areas, these complex network systems often produce many cable faults caused by water. Because the characteristic of water is like a insulator, it is very difficult to detect water fault, that is to say, it is difficult to detect the exact fault point of flashover. In order to detect flashover, the voltage level or the capacitance of the pulse generator must be increased until breakdown can be caused. To find out the water fault of paper insulated lead clad cable (PILC) and extruded insulated cable, the energy level causing flashover needs to be as high as 5400j, which is several times higher than the energy required to detect urn fault. Accordingly, it is required to install filters to effectively protect instruments and operators from the danger of high voltage

Baltimore gas and power company (BGE), located in central Maryland, is applying that the decline in imports does not mean that the utilization rate of foreign equipment has fallen. An advanced fault/cable analysis system -- biddledart-6000, manufactured by AVO company, has won

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