A users view of specifications [power transformers]

In a typical transformer project there are a great number of specifications of ever increasing detail, from the initial identification of the electrical parameters by the grid system designer, through the enquiry documents and tender documents which form the primary interface between the customer and suppliers, to the suppliers specifications for sub components and ultimately to the drawings from which parts and assemblies are actually made. It is an interesting feature of this process that information is added at each stage, so the grid system designer needs to have no practical knowledge of how a transformer is made but he must have a clear idea of what electrical parameters are important to the operation of the grid and what values thy should have. Equally the transformer winder must be very skilled at turning a winding schedule into several tons of accurately formed copper and paper but needs to know nothing of post-fault overload conditions. Making a transformer that will work efficiently over a very long period of time delivering secure supplies of electricity is a team effort. The various forms of specification involved can be seen as the official means of communication between the team members. The author discusses specification types, National Grid Company specification policy, works testing and long term reliability, functional versus design specifications, and alternative approaches to minimising lifetime cost