Design, simulation and testing of an EHV metal-enclosed disconnector

One of the most demanding design issues in the development of metal-clad di sconnectors for application at 500 kV and over, is to ensure the switching capabilities of the device. This paper presents the issues and processes involved from the initial desi gn through to final testing of a 550 kV disconnector. The initial work concentrated on defining the design parameters in order to minimize the risk of arc breakout. Computer analysis using 2D and 3D model ing of the contact configuration was carried out. As a following step, befo re building the disconnector, the results of the computations were validate d by a static test where the electrode arrangement was set manually at diff erent gap distances and discharges between contacts were monitored. From th e computational and test data a final contact design was optimized and a di sconnector prototype was built. Finally the capabilities for bus-charging current switching were tested in accordance with the EEC 1259 standard. The results of these tests include m easurement and comparison with EMTP simulations of the fast transient over voltages generated by disconnector operations.