Transformer Bushings/Wall Bushings

Overview

Transformer bushings and wall bushings carry a live conductor through a grounded barrier, such as a transformer tank cover or a substation wall, without letting the voltage flash over to earth. Raptronics supplies resin-impregnated paper (RIP) and dry-type bushings by Moser-Glaser for transformer, wall and switchgear applications across MV/HV ratings.

A bushing is a small part of a large asset, but it sits at one of the highest electrical stress points in the substation. When one fails, the outage rarely stays limited to the bushing. Choosing the right insulation technology, interface and creepage distance at the specification stage avoids most of the problems that show up years later in service.

Our engineering team works with utilities, transformer OEMs, EPCs and industrial users to match the bushing to the duty: the voltage class, the current, the mounting interface, the site pollution level and the way the asset will be maintained.

Specifications

Insulation technology

Resin-impregnated paper (RIP), dry-type

Applications

Transformer, wall and switchgear

Types

• Transformer bushings

  Transformer bushings connect the windings inside an oil-filled tank to the overhead line or busbar outside it. One end sits in transformer oil and the other in air, so the design has to manage two very different dielectric environments at once. RIP bushings handle this with a capacitively graded core that spreads the electric field evenly along the insulation.

• Wall bushings

  Wall bushings take a conductor through a building wall or a partition between indoor and outdoor equipment. Both ends are normally in air, and one side may face weather and pollution while the other stays clean and dry. Getting the creepage distance right for the outdoor side is a key part of the selection.

• Switchgear bushings

  In switchgear, bushings form the interface between the switchgear and the cables, busbars or transformers connected to it. Space is usually tight, so a compact dry-type design that can be mounted in any orientation is often an advantage.

RIP bushings are built by winding paper with conductive grading layers around the conductor, then impregnating the core with resin under vacuum and curing it into a solid body. The result is a bushing with no oil inside it, which removes the risk of oil leaks and reduces the fire risk compared with oil-impregnated paper (OIP) designs.

Applications

• Power transformers

  New transformers built by OEMs, and replacement bushings for transformers already in service, where a failed or ageing bushing needs to be swapped during a planned outage.

• Substation wall penetrations

  Indoor substations and GIS buildings where conductors must pass from an outdoor yard into a building, or between rooms, through a grounded wall.

• Switchgear

  MV/HV switchgear where a compact, dry bushing simplifies the layout and removes oil from the equipment room.

Applicable standards

We carry the applicable standards for your voltage class. Please reach out with your inquiries for more details.

Frequently asked questions