Voltage Standardization From a Consulting Engineer´s Point of View

The author points out certain reasons why specifications for purchased equipment have not followed the manufacturers´ existing standards and recommends certain changes in standards for system and apparatus voltages. The importance of having transformers interchangeable as step-up and step-down units is pointed out and, by means of five per cent taps above and below rated voltages in both windings, it is proposed to obtain sufficient flexibility for such interchangeable use. The paper gives a comparison between transformers designed as suggested above and transformers designed according to the manufacturers´ recommendations, and the suitability of the suggested tap range is pointed out. A recommendation is also made that the number of ratings of oil circuit breakers should be reduced.