Common metal support for outdoor CTs and VTs
Common metal support for outdoor CTs and VTs
(OP)
I am working on the project - 44 kV outdoor switchgear where conceptual design provided an installation of three CTs plus three VTs on the same support - steel structure.
CTs will be series connected as usual. My question is how far PTs have to bi installed from the CTs i.e CT-R, CT-Y and CT-B transformer.
Is there any standard rule regulating that case...
CTs will be series connected as usual. My question is how far PTs have to bi installed from the CTs i.e CT-R, CT-Y and CT-B transformer.
Is there any standard rule regulating that case...






RE: Common metal support for outdoor CTs and VTs
RE: Common metal support for outdoor CTs and VTs
RE: Common metal support for outdoor CTs and VTs
If they are the same phase they can touch each other as long as the mounting of one device does not bring grounded components within the other device's phase-ground clearance.
There may be a need to have some separation to allow connecting test leads or ground leads.
RE: Common metal support for outdoor CTs and VTs
Have you considered a combined CT/VT unit?
Regards
Marmite
RE: Common metal support for outdoor CTs and VTs
For our units (Ritz dry-type), the VTs and CTs at 46kV are essentially the same height and have similar voltage grading, thus we advise customers to leave 1-2 inches between units of the same phase.
For other designs that may have significant height differences or differences in construction and voltage grading, more space may be needed. For instance, if you were using oil-filled CTs and VTs, the CTs would typically be head-type (live tank) designs and the VTs would be tank-type (dead-tank) designs. This means that the upper ground plane on the VTs would likely be well at 30-50% of the bushing height of the CT and the lower live part of the CT would be 25% or so down the VT insulator grading. In that case, you would really need to get guidance from the manufacturer.
Marmite...depending on the standard and country, combined units below 115 kV are usually much more expensive that using discrete dry-type units.
RE: Common metal support for outdoor CTs and VTs
Regards
Marmite