Auxiliary power supply for ground-mounted secondary substation - has ring-type CTs on HV feeder cable connected to rectifier/pre-regulator unit providing substation auxiliary supply.

摘要

The kiosk-type substation(2), on a buried base(1), contains a remotely controlled 3-phase HV circuit breaker(3), control cabinet(4) and HV underground cable terminations(5,6,7). The cable cores of one HV circuit (e.g. 5) pass through three ring-type CTs encased together(11), forming with the rectifier/pre-regulator box(19) the auxiliary supply unit(10). The star-connected CT secondaries terminate on studs, which are butt-connected to corresponding contacts in the rectifier box, and automatically short-circuited when the box is detached. Before rectification, CT circuits enter a pre-regulator. Pairs of thyristors, reverse-parallel connected between each secondary pair, shunt the CTs during those parts of each cycle when current exceeds that required by the auxiliary load, giving consistent supply from low(20A) to nominal full-load(400A) primary current. ADVANTAGE - Less costly than present methods.