Transmission Perspec..

Incident No.2 – Reduced Capability
• A 500MVA 275/132/22kV autotransformer was taken out of
service for a scheduled tap changer maintenance over a
weekend. This transformer had a design where the diverter is
physically sitting on top of the 132kV bushing. During
inspection, problems were identified on the diverter switches.
• Instead of removing only the diverter switch, the contractor
removed the complete set of bushing and diverter. In attempting
to re-install, the equipment was mishandled and the bushing got
damaged. No spares could be found for this old design.
• The transformer was then modified to run on a fixed tap
position.