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

One of the most demanding design issues in the development of metal-clad disconnecters 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 design through to final testing of a 550 kV disconnector. The initial work concentrated on defining the design parameters in order to minimise the risk of are breakout. Computer analysis using 2D and 3D modelling of the contact configuration was carried out. As a following step, before building the disconnector, the results of the computations were validated by a static test where the electrode arrangement was set manually at different gap distances and discharges between contacts were monitored. From the computational and test data, a final contact design was optimised and a disconnector prototype was built. Finally the capabilities for bus-charging current switching were tested in accordance with the IEC 1259 standard. The results of these tests include measurement and comparison with EMTP simulations of the fast transient overvoltages generated by disconnector operations