Abstract
A capacitive coupling sensor for partial discharge detection with the fusion of high voltage XLPE cable joint is designed in this paper. The sensor is to address partial discharge signals leading to transmission attenuation and external interference causing poor field detection sensitivity. First, a coaxial waveguide transmission model was established of high-frequency electrical signals in the body and joint. The result showed that the signal transmission attenuation was minimized while the sensor electrodes were closely attached to the outer semi-conductive layer of the body. Second, the equivalent circuit model was constructed of the capacitive coupling sensor fused with the 110 kV straight passing joint. The specific installation location, main structure size, detection bandwidth, and sensitivity of the sensor in the joint area were determined, which was to maximize the coupling output signal amplitude and transfer function amplitude. Finally, a lightning surge voltage test was carried out with the integration of the fusion of the joint voltage thermal cycling. Simulation and measurement show the following: while the sensor is installed in the cable metal sleeve break and the electrodes are closed to the overall semi-conductive layer, there is excellent performance for partial discharge detection in the frequency range of 1–300 MHz, with a sensitivity of 5 pC.
Highlights
The power grid may have abnormal operating events including insulation breakdown and line shutdown if the high voltage cable insulation defects cannot be detected in time (Zhou et al, 2014; Fang, 2018)
The internal structure of the cable joint is much more complex than that of the cable body, taking the cable model YJLW03-Z 64/110 1 × 800 as an example, high frequency partial discharge signal is analyzed with distance transmission in the cable body
The high frequency electrical signals in high voltage XLPE cable can be considered as a coaxial waveguide in the form of a uniform transmission line
Summary
The power grid may have abnormal operating events including insulation breakdown and line shutdown if the high voltage cable insulation defects cannot be detected in time (Zhou et al, 2014; Fang, 2018). Partial discharge detection is an important technical means to discover potential insulation defects of high voltage XLPE cable joint in an efficient manner. PD detection still faces the problems of weak signals, complex and variable waveforms, and susceptibility to external electromagnetic interference (Zhao, 2018; Xie et al, 2019) These problems hamper the accurate sensing and effective identification of PD signals. A simulated field defect PD test using a patch type partial discharge sensor built into both sides of the joint shield was conducted (Luo et al, 2018). This study designs a capacitive coupling sensor fused with high voltage XLPE cable joint, based on the principle of capacitive coupling, and combining with the characteristics of high partial discharge at the joint.
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