Pulse optimization method and pulse generation circuit for improving cable fault location accuracy

Abstract

The invention discloses a pulse optimization method and circuit for improving the accuracy of cable fault distance measurement. When the pulse time domain reflection method is used for cable fault distance measurement, the pulse used for analysis is actually only the reflected pulse of the fault point. It doesn’t matter to transmit pulse, so a circuit can be designed to generate a transmit pulse voltage wave, which is connected to both ends of the primary side of the pulse transformer respectively, one of which transmits the pulse normally into the cable, and the other counteracts the injection before AD acquisition on the secondary side of the pulse transformer The transmission pulse of the cable, in this way, only the reflected pulse of the fault point in the signal collected by AD, without the transmission pulse, the waveform is simple, clear, and easy to analyze; at the same time, it does not affect the normal injection of the transmission pulse signal into the fault cable. The signal input acquisition uses an isolation pulse transformer, which can not only collect the pulse reflection signal on the cable, but also suppress interference, and has high reliability.

Description

technical field [0001] The invention relates to a pulse optimization method and a circuit for improving the accuracy of cable fault distance measurement when the pulse time domain reflection method is used for distance measurement of cable faults, and belongs to the technical field of power electronics. Background technique [0002] Cable power supply has been widely used because of its safety, reliability, and advantages of beautifying cities and industrial and mining layouts. However, with the increasing use of cables, the number of cable faults is also increasing. How to quickly and accurately detect the distance and location of the fault point and find the location of the fault point requires the inspectors to first choose a detection instrument with excellent performance and be able to correctly identify waveform. [0003] Pulse time domain reflectometry is an important method for cable fault location, which is suitable for cable fault location with low resistance and ...

AI Technical Summary

Problems solved by technology

[0005] At present, the cable fault distance meter designed based on the pulse time domain reflection method has the main shortcomings in waveform acquisition, display and analysis: the pulse voltage wave emitted by the detection instrument has a certain width, due to the output impedance of the instrument and the waveform of the cable If the impedance does not match, there will be a "smearing effect" of the transmitted pulse at the cable measurement end. When the fault point is very close to the measurement end, the reflected pulse at the fault point will overlap with the transmitted pulse, and the starting position of the reflected pulse cannot be found on the waveform. cause significant measurement blind spots, such as figure 2 In addition, the instrument collects and displays the transmitted pulse and the reflected pulse at the same time. When the fault point is far away from the measuring end, due to the attenuation effect of the cable, the amplitude of the reflected pulse at the fault point will be much smaller than the transmitted pulse. In order to improve the reflection of the fault point The pulse amplitude often needs to increase the gain of the instrument amplifier. Doing so often causes the instrument pulse signal acquisition and amplification circuit to saturate, and the so-called "blocking" phenomenon occurs, resulting in signal acquisition distortion, which is not conducive to waveform analysis.

[0006] In order to eliminate the impact of the transmitted pulse on the measurement results and eliminate the "smearing effect", there is also a patented technology that mentions an impedance balance network, such as image 3 As shown, the resistance, capacitance, inductance, pulse transformer and other components are used inside the instrument to simulate the characteristics of the cable impedance network, to achieve the matching between the internal impedance of the instrument and the cable impedance, and to achieve the purpose of eliminating the influence of the transmitted pulse. However, this method cannot solve the above preconditions The signal "blocking" problem of the amplifying circuit; at the same time, because the simulated impedance cannot completely match the real impedance of the cable, and a large number of transformer components are used, when the cable is long, the inductance and capacitance of the cable and the transformer T2 will make the emission pulse formation more serious Oscillation, resulting in messy waveform, unable to distinguish

[0007] In actual measurement, the above shortcomings will make waveform analysis difficult, difficult to determine the start time of the reflected pulse, easy to misjudgment, resulting in unnecessary economic losses

Images