NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
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NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
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 buried underground, and the laying distance from several meters to a few kilometers, the scene The environment is complicated. In addition to high quality requirements for cable fault testing equipment, the overall quality of technicians is also very strict.
Common cable fault types have low resistance failures, high-resistance short-circuit ground faults, and three kinds of flashing failures. For different types of cable faults, the filling point detection method adopted is greatly different. The following is simple to introduce you to the high voltage cable fault detection method. Traditional high voltage cable fault detection methods mainly include the following two categories: bridge method and pulse method.
First, the bridge method This is a classic method of the ranging from the power cable. This method is relatively simple, but it is necessary to know data such as cable length in advance, and only apply to low-resistance and short-circuit failures. However, in actual operation, the fault is often high resistance and flashing failure. It has a small bridge current due to high fault resistance, so a general sensitivity instrument is difficult to detect.
Second, pulse method 1, pulse current method This method is safe, reliable, and simple wiring. The method is to break the cable fault point with high pressure breakdown, using the instrument to collect and record the current line wave signal generated by the fault, according to the time of the current wave signal to return to the fault point to return to the fault point. The method is coupled to the pulse current with a transformer, and the waveform is simpler, safer.
This method also includes two types of straight flashing and flaking. Different from the pulse voltage method, the capacitance voltage divider is different, and the pulse current method is placed in parallel to the low pressure test using the linear current coupler, and the high-voltage circuit has no direct electrical electrical connection, and the recording instrument and the operator are used. , Especially safe and convenient. So people generally use this method.
2, the pulse voltage method This method can be used to measure high resistance and flashing failure. First, the cable failure is broken down on a DC or pulse high voltage signal, and then the time required to return to the time of the measurement point and the fault point by recording the discharge pulse. An important advantage of the pulse voltage method is that it is not necessary to use high-resistance and flashing failure, directly utilizing the instantaneous pulse signal generated by the fault breakdown, the test speed is fast, and the measurement process is also simplified.
3, pulse return method for the failure of low-impedance and circuit type, using low-pressure pulse reflection method to measure the cable failure and straightforwardly directly, only by observing the time difference of the transfer pulse by observing the time difference of the transfer pulse by observing the time difference of the emission pulse by observing the time difference of the transfer pulse by observing the time difference of the transfer pulse by observing the time difference of the transfer pulse by observing the time difference of the transfer pulse by observing the time difference of the transfer pulse by observing the time difference of the fault point reflection and the emission pulse by observing the time difference of the transfer pulse. A low pressure pulse is injected into the cable while the pulse propagates to the fault point, and the pulse is reflected back to the measurement point. The time difference of the emission and reflection pulse is recorded by the instrument, and only the distance of the fault occurrence point can be calculated to know the pulse propagation speed.
The method is simple and intuitive, and it is necessary to know the raw data such as cable length, and can identify the position of the cable connector and the branch point according to the reflected waveform. The above is several commonly used high-voltage cable fault detection methods, do you learn? Pay attention to Xiaobian, there will be more exciting content waiting for everyone! .
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