Study On Online Insulation Monitoring Method Of High Voltage Overhead Lines Based On Travelling-Wave Principle

At present, the proposed different online insulation monitoring methods of overhead ines must acquire monitoring signals from field where insulator strings are installed, the monitoring equipments installed outdoor always run in strong electromagnetic field and varied weather conditions, the equipments can not run steadily; the methods which acquire field operations of workers can not keep all-weather monitoring for all the insulator strings. The double terminals travelling-wave location principle is used in this paper, it is a new try to locate the insulator string that discharges and to estimate its insulation level by the transient wave of arc discharge which is acquired from two terminals of lines. So, the following researches are done in this paper:(1) The mechanism of generation of travelling-wave by arc discharges is analysed through using of superposition principle and arrow diagram. The arc is generated during the flashover of dry-band, when the last dry-band is flashovered by arc, the discharge circuit is closed, and the travelling-wave runs into lines. In the arrow diagram, during the period of unsteadily arc discharge, the additional source closes and opens from arrow diagram, and travelling-wave is generated every time; during the period of steadily arc, the additional source closes and never opens from arrow diagram, and travelling-wave is generated only once.(2) The simulation models of polluted insulator string with arc discharge are made up based on the mathematic model of insulator pollution flashover, the keys of model establishing are arc’s V/A characteristics and pollution layer resistance. First, pricises models are established, which contain every insulator in all kinds of condions. Simplified models are established based on the former, the string is equivalented to a cylinder and all the arcs are quivalented to one arc.(3) The transient wave acquired from double terminals is analysed. In additional web and arrow diagram, during the period of unsteadily arc, the wave contain all the initial wave of every arc and their reflected wave, during the period of steadily arc, the wave contain only the initial wave of steady arc and its reflected wave. The insulation models of different arc stages are established separately, the wave form of discharge phase have no clear, and the wave form of undischarge phases’ampitude change higher in the unsteadily arc stage, the wave form of discharge phase’s ampitude change lower, and every wave form have clear relativity in the steadily arc stage.The researches of thi paper indicate that the insulation online monitoring of polluted insulator string can be achieved by the transient current wave acquired from lines double terminals. The monitoring equipments need not be installed on towers along lines, and workers need not make field operations by this method, the labour power is saved, and the maintenance of monitoring equipments is induced clearly.