Capacitive current switching capability of air-insulatedof air-insulated high voltage pantograph disconnectors

In some configurations a busbar has to be energised and de-energised by means of air-insulated pantograph disconnectors. The switching capability of the disconnectors is limited to 500mA based on the correlation with tests on GIS disconnectors. Due to different reasons, many of the 380kV substations in the system under consideration had to be extended. The lengths of the air-insulated busbars became longer than 500m. Assuming, that the average capacitance of an air-insulated busbar amounts to 15pF/m, the corresponding capacitive currents significantly exceed the maximum value of 500mA as suggested by IEC 62271-102. At currents higher than 1A, the arc tends to burn continuously [1] and to create a thermal channel which is typically driven upwards. Very long arcs may possibly lead to…