Author: Noyafa–CCTV Tester
Compensation of the influence of stray inductance For convenience, the moment when the second pulse begins to fall is generally regarded as the arrival time of the reflected wave at the fault point, which will obviously cause errors. The error is generally within 10 meters. In the actual test, the following methods can be used to overcome: (1) For the convenience of compensation of the influence of the anti-stray inductance, the moment when the second pulse starts to fall is generally regarded as the arrival time of the reflected wave at the fault point, which will obviously cause errors.
The error is generally within 10 meters. In the actual test, the following methods can be used to overcome: (1) Calculate the distance to the fault point from the beginning of the positive pulse of the reflected wave, rather than the moment when the pulse falls. (2) Calculate the fault point distance by the time when the reflected pulse falls, and subtract a fixed value from the result under the premise of a certain understanding of the error.
Especially when the fault point is far away, when the reflected wave from the fault point reaches the measurement point, due to the influence of propagation attenuation, the positive pulse has become inconspicuous (Figure 4.9), and the fault point distance can only be calculated by the time at which the pulse falls. Long-distance fault direct flash pulse current waveform (3) In the instrument using the automatic calculation method, the instrument is automatically compensated. (4) During the test, capacitors with small internal inductance, such as pulse capacitors, should be used as much as possible, and the connection between the capacitor and the cable (including the ground wire) should be shortened as much as possible.
For each test, use a fixed capacitor and guide wire, which will help to grasp the size of the error to accurately calculate the actual fault point distance.
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