Bushing CT Grounds
Bushing CT Grounds
(OP)
I've never seen a cutaway of a bushing CT or had the opportunity to take one apart.
Is the iron core of the bushing CT grounded to the breaker frame? Or, is it insulated from the case? If grounded, it seems like this would affect leakage flux due to another low reluctance path being present.
Does it make sense to check insulation resistance on bushing CTs between the secondary winding and ground or the primary bus and secondary? I can see how resistance between a primary and secondary is useful for a wound PT or CT where the windings are in close proximity, but I'm not sure if it's necessary on a bushing CT.
Is the iron core of the bushing CT grounded to the breaker frame? Or, is it insulated from the case? If grounded, it seems like this would affect leakage flux due to another low reluctance path being present.
Does it make sense to check insulation resistance on bushing CTs between the secondary winding and ground or the primary bus and secondary? I can see how resistance between a primary and secondary is useful for a wound PT or CT where the windings are in close proximity, but I'm not sure if it's necessary on a bushing CT.






RE: Bushing CT Grounds
Resistance checking between pri and sec is probably a waste of time. Between sec and ground will be like chekcing the lead resistance to ground.
If the BCTs are potted in an aluminum shell or case, then resistance check between sec and case may be worth the effort.
About the only other resistance check that could find potential problems would be between BCTs. In many cases there are more than one BCT stacked on the bushing.
RE: Bushing CT Grounds
Usually CT secondray winding is checked for insulation resistance with 1 kV megger, with acceptance value of 500 Meghohms.
RE: Bushing CT Grounds
RE: Bushing CT Grounds
RE: Bushing CT Grounds