Plan

Feasibility

A technical feasibility study must be conducted on the strategy for the replacement of a current transformer. The options to be considered are refurbishment or replacement. Technical considerations also include the importance of the transformer, current problems and failures, uprating, and condition of windings and major components like tap changer, bushings, cooling system, etc.

The challenge with replacement projects is finding the best time to replace. If too late the transformer can fail in service and cause damage to adjacent equipment. If too early, then full utilization of the asset is not realized. 

It is thus important that a critical analysis is carried out to determine the risks and best opportune time to replace. Other considerations include planned outages in the time frame scheduled for replacement. Aligning to planned outages will reduce further downtime to replace only the transformer. This may also influence when the transformer should be replaced. Other factors to consider are similar fleet and interchangeability. If there is more than one transformer then one new can be purchased as a spare awaiting replacement or when a potential failure is imminent.

Refurbishment versus replacement is always a question that needs to be answered. This is usually priced driven but also depends on the capabilities at hand for refurbishment. For countries where the major transformer manufacturers do not have repair facilities the local capabilities must be critically reviewed in terms of quality and failure records. If these are inadequate it is then worth spending more to get a quality product that will last/exceed the designed life.

Capital

Power transformers are very expensive assets and replacement/refurbishment must be planned well in advance to ensure that adequate budgeting can be made for the expenditure. On average depending on location, capabilities and the size of the transformer, the following time frames must be taken into consideration.