A transformer retrofit with DuPont™ Nomex® brand paper helped improve the flexibility and reliability of a liquid-immersed unit at a hydroelectric power plant in which the original insulating cellulosic paper and oil had degenerated to a considerable degree due to aging. This transformer retrofit also reduced maintenance costs.
Engineers from ABB Halle, a world leader in transformer design, manufacture, retrofit and repair, performed a condition assessment on a transformer in a hydroelectric power plant and determined the need for a transformer retrofit.
ABB Halle’s transformer retrofit experts used a hybrid insulation system with Nomex® paper and cellulosic pressboard. They modernized the liquid-immersed 6.3 MVA (21 kV/6.3 kV) Trafo Union unit manufactured in 1982 by wrapping the conductors with Nomex® paper.
Improved operational flexibility: The use of Nomex® paper as protective insulation of the conductors enables higher overload capacity.
Enhanced reliability: This transformer retrofit with Nomex® paper enabled the rating to be upgraded from 6.3 MVA to 7 MVA, resulting in enhanced reliability under demanding operating conditions.
Reduced maintenance costs: Less maintenance will be required because Nomex® insulation shows negligibly low thermal aging over extended working lifetimes, resulting in significant improvement in oil quality.
Extended service life: Increased reliability under demanding conditions, combined with greater overload capacity and lower losses, and may lead to longer service life.
Materials Selected and Why
Nomex® paper was selected as the insulation for the conductors due to its inherent dielectric strength, ability to withstand electrical loads, excellent mechanical toughness and negligible aging over a long service life.