HV instrument transformer bushing, or terminal closure - incorporates current transformer operating tripping relay in event of earth fault

摘要

The object is to inhibit the rise of pressure inside the bushing following a HV fault to earth through the bushing flange. To achieve it a current transformer (1) is built into the bushing flange. This transformer is connected to a relay to instantaneously trip the HV circuit breakers. Further assistance in limiting pressure rise can be given by including collapsible evacuated chambers (2) between the bushing and a porcelain or plastics housing. Both methods can be applied to HV instrument transformers and through bushings.