Differential current protection
Differential current protection
(OP)
Hi, I´d like to know about the use of trafo´s for differential current protection, I´m working with a 6600 HP @ 6000KV AC 3 phase-60hz ring motor and it have one 100:5A trafo in each power supply line as a differential current protection, my question is, why I have to use this 100:5A trafo since the nominal current is arround 600A?
many thanks!
many thanks!





RE: Differential current protection
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Differential current protection
RE: Differential current protection
RE: Differential current protection
Good info by aolade… A couple of side notes are, 1) for a window CT, it’s important to keep the stator-coil external leads {1+4} routed symmetrically through the per-phase cores so currents cancel in normal operation. [100:5 ratio provides significantly more current sensitivity than a pair of 600:5 CTs.]
Note though, that differential-mode {87M} CTs are worthless for independently sensing motor running-overload [51/49] current, so can’t be applied in “all-in-one” motor protection.