Study On Characteristics And Partial Discharge Chaos Analysis Of Electrical Treeing Propagation In XLPE Power Cables

It is a trend to use underground power cables instead of overhead transmission line in city. Because of the excellent performance, the cross-linked polyethylene (XLPE) power cable has became the main direction of development in power cable industry. The deterioration process of the XLPE power cable is very complex, the research and operation experiences showed that the bottleneck which affect the long-term operation safety of XLPE power cables is electrical treeing, it is necessary to study on the insulated aging law and mechanism of XLPE power cables, especially on the law and mechanism of treeing, it provides theory support for the manufacture, operation management and on-line diagnosis.In this paper, the XLPE power cable sample and test electrode device have be designed, it can simulate the electrical treeing in the actual XLPE cable. Results show that the test system can meet the requirements of the research on electrical treeing.The test samples are 15kV XLPE power cables, treeing test have been taken on the power frequency voltage of 12kV²1kV from the room temperature to 110℃, the influence of voltage and temperature on morphology of electrical trees have been analyzed, the partial discharge (PD)φ-q -n patterns of electrical trees have also been studied. Propagation of electrical trees was divided into four stages, maximal discharging-phase distributions H_qmax (φ) and average discharging-phase distributions H_qn(φ) in different propagation stage having analyzed, and statistical parameters derived from PD distributions. Results show that in actual XLPE power cable, the effect of voltage and temperature have the same result with needle-plate electrode system on morphology of the electrical trees, but, there are same difference in propagate process of electrical trees, and sk value of the H_qmax (φ) and H_qn(φ) decrease with the propagation of electrical trees, it can be considered as a parameter to diagnosis electrical tree propagation stage.The phenomenon of the electrical trees aging test show that deterministic chaos characteristics may exist in the trees growth, the chaos analysis results of the maximal discharging and total discharging time sequences of six group electrical trees have confirmed this conclusion, maximal Lyapunov exponent and the correlation fractal dimension of PD time sequences decrease with the increase of trees fractal dimension. It show that chaos characteristics of the electrical PD time sequences can be used as a parameter to judge the morphology characteristics of electrical trees, and the time sequence of maximal discharging is better than the time sequence of total discharging.