The discovery and fixed-point work of cable failure has always been a big problem in the electrical scale, mainly because the cable is buried underground, and the laying distance from several meters to a few kilometers, the site is complex. In addition to the high quality requirements for cable fault testing equipment, the discovery and fixed-point work of cable failure have always been a big problem in the electrical scale, mainly because the cable is deeply buried underground, and the laying distance from a few meters to a few kilometers, and the on-site environment is complex. . In addition to high quality requirements for cable fault testing equipment, the overall quality of technicians is also very strict.
Let's take a look at how to make a high-voltage cable failure lookup work. There are three common cable faults: low resistance faults, high-resistance short-circuit ground faults and flash faults. Different types of cable failures have different fault point detection methods.
High-voltage cable fault Find conventional methods mainly include both bridge methods and pulse methods. First, the pulse current method This method is safe and reliable, the wiring is simple. The method is to use high-pressure breakdown cable fault points, collect and record the current line wave signal generated by the fails, depending on the time of the current wave signal at the measurement end and the fault point round trip.
This method is coupled with transformer, and the waveform is simple and safe. This method also includes a straight flash and a flashing method. Unlike the pulse voltage method, the voltage sampling is used for voltage sampling, and the pulse current method is placed in parallel with a linear current coupler in a low pressure test ground, and there is no direct electrical connection with the high-voltage circuit, for recording instruments and operators. Safe and convenient.
So people usually use this method. Second, the pulse voltage method This method can be used to measure high resistance and flash failure. First, the DC or pulse high voltage signal is down from the cable failure, and then the time required to measure the distance between the measuring point and the fault point.
An important advantage of the pulse voltage method is that there is no need to be burned on high resistance and flash failure, directly utilizing the instantaneous pulse signal generated by fault breakdown, the test speed is fast, and the measurement process is simplified. Third, pulse return method for low resistance and circuit type failure, using low pressure pulse reflection method to measure cable failure than said bridge method simply, only the time difference of the fault point reflection and transmit pulse can be measured. During the test, a low-pressure pulse is injected into the cable. When the pulse propagates to the fault point, the reflection is reflected, and the pulse is reflected back to the measurement point.
Using the instrument records the time difference of the emission and reflection pulses, as long as the speed of the pulse is known, the distance of the fault occurrence point can be calculated. This method is simple and intuitive, and it is not necessary to know that raw data such as cable length can also be identified according to the reflected waveform to identify the position of the cable connector and the branch point. The normal high voltage cable fault is high resistance fault, and the fault point distance is measured by high pressure flashing method.
This method is tested by cable fault. 1, the wiring method first completes the high-voltage flashing wiring as required; then use the double clip test line to connect the sampler with the rangefinder host, and then place the sampler in the high-voltage capacitor ground line. 2, when the device is operated, the sampling method selects the flashing, the pulse width is default, the cable type selection physical type, the read accuracy is default.
Use the high voltage device to discharge the cable, then click the orange sampling button on the right, the device starts sample until the sample is sampled, and then the sample button is stopped again. 3, study the waveform, move the roof to the start and end point of the waveform, read the waveform, and automatically measure the distance of the fault point in the upper left corner. The above is the full content of the high-voltage cable fault finding, have you learned? Don't forget to pay attention to Xiaobian! More exciting, let us continue.
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