Product Design Considerations for Minus Ambient Temperature Applications of Transformer Bushings
- Feb 11
- 1 min read
Updated: 2 days ago
In cold countries where the ambient temperature routinely drops below freezing, transformer bushings face several unique challenges to withstand dielectric, thermal, mechanical, and environmental stresses. Without adequate design considerations, extreme cold can lead to insulation degradation, thermal and mechanical failure, or complete breakdown of the bushing.
Main considerations for Product Design
Porcelain remains stable at low temperatures. However, failures are more likely to occur at the cemented joint between the porcelain and the mounting flange due to different temperature coefficient of expansion. Therefore, cementing materials & cemented joints must be validated through thermal cycling tests.
Epoxy components (test tap and oil end insulator) are to be manufactured using epoxy material suitable for minus temperatures.
Insulating oil (mineral oil or ester oil) must have low pour point & viscosity suitable for the application to prevent it from freezing.
Sealing materials (O-rings and gaskets) must remain flexible and maintain their sealing properties at the lowest expected temperatures. Sealing Materials suitable for Minus Temperatures below -30 °C includes fluoro silicon.
If mounting flange, conservator, flange extension, and electrode are either powder-coated or painted, the material used for powder coating/painting should be suitable for minus temperature application.
Indicator glass or polycarbonate sheet used for oil-level indicators are to be selected based on their ability to withstand thermal contraction and avoid cracking at sub-zero temperatures (typically down to -40 °C or lower).
Plated components (HV terminal & oil-end terminal) should use corrosion-resistant finishes (e.g. hot-dip galvanized, zinc-nickel, or tin-plated) with strong substrate adhesion to prevent flaking at low temperatures.
The hardware materials (e.g. bolts, screws, fasteners) must be resistant to corrosion which can be accelerated in some cold environments.