Study On The Corresponding Relation Between Growth Of Electrical Trees And Partial Discharge Characteristics In LDPE

With the growing demand for electricity in the world, the installed capacity of generating equipment is continuously increasing. The proportion of new energy power generation is also becoming larger with the popularize of environmental awareness among people. In virtue of the variety of power generation, the longer distance from power transmission, the growing demand for ecological environment protection, making the overhead lines, power cable lines and gas insulated pipes three hybrid transmission modes become the mainstream of electricity transmission in the future. Which proves a huge demand for the requirement and application of power cable. However, the electrical treeing is the key factor in restricting the development of the long and safe operation of power cable, and partial discharge is the most effective means in cable insulation state detection. Important technical support for safe and stable utilization of power cable can be demonstrated, in case that the initial and developing state of electrical trees can be estimated and diagnosed with the partial discharge detection on it.On the basis of the previous studies in which the self consistent of electrical tree growth and partial discharge had been proved, this passage, according to the model of long channel partial discharge, is mainly elaborating the mathematical analysis on the ideal needle plate electrode system, the discussion on the propagation distance of partial discharge, the discharge capacity of partial discharge pulse, and the change mechanism of ?-q-n patterns.We carried out electrical tree initiation and partial discharge combined experimental system on LDPE specimens with the voltage of 8k V applied. Theelectrical tree shapes in the whole process from the tree initiation to the critical breakdown and the partial discharge data were completely recorded. On the basis of different stages of electrical tree growth, the ?-q-n patterns of corresponding partial discharge were analyzed. The partial discharge extinction phenomenon, the secondary growth of electrical trees and the phenomenon happened in the breakdown of critical electrical trees were also further explained.Finally, we made the partial discharge characteristics analysis and ?-q-n patterns comparative analysis of electrical trees in different conductivity types.Continue the conductive mechanism study of electrical trees on the basis of the single channel model, summarized that the growth rate of non conducting electrical trees is in proportion to the growth rate of the quantity of partial discharge. While the growth rate of conductive electrical trees which has grown near the earth electrode is in proportion to the change rate of the electrical tree tip field strength.Which proved theoretical support for the theory--the LDPE aging degree can be evaluated by the channel conductivity measure of the electrical tree.