Power & Energy Solutions

The premier renewable energy publication

Making a difference in windfarm transformers

The electric energy industry has long been a conservative business taking very deliberate and measured steps in adopting new technologies. The renewable energy markets have forced companies to adapt to a fast-paced and rapid technology development cycle. The exponential growth and the demand for more power in a smaller envelope continue to drive rapid development.

H-J has accepted these challenges and we are leading the renewable energy transformer industry with material and product development for both high and low voltage bushing applications.

New, higher power solar inverters and wind turbines are being developed and released on a regular basis. This is driving a series of fundamental changes in transformers for renewable applications:

• Solar inverter containers are open and exposed to elements,

• Converting from dry-type to liquid-filled transformers,

• Using high-temperature insulation systems and operating temperatures, and

• Increasing current ratings and the high voltages to 35 kV, 200 kV BIL class and beyond.

At H-J, we are dedicated to developing industry-leading bushing solutions by listening to our customers. Solutions for high voltage bushings include plug-in type technology for 38 kV class with 150 and 200 kV BIL options. Bushings are available with 600, 900 and 1200 A continuous current ratings. Higher voltage and BIL versions are currently under development to support industry needs. These are dry, solid, internally-shielded epoxy resin bushings. The bushing interfaces are designed in accordance with relevant IEC or IEEE Standards to provide interchangeability with different molded rubber elbow solutions in the market.

The standard operating temperature for bisphenol-A and cycloaliphatic epoxies are 105°C and 120°C. However, an important consideration with epoxies is that the maximum temperature must not be exceeded in operation. Above these temperatures the epoxy nears or enters the glass transition range (Tg) where the material is no longer rigid. This may compromise the bushing’s physical integrity and, most importantly, the sealing integrity of the bushing.

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