The effects of short-circuit currents in transmission and distribution networks for electrical energy are tremendous, both on the equipment and on the stability of the networks. Since short-circuits occur quite often, the short-circuit withstand capacity must be one of the main characteristics of the equipment installed.
Transformers, like series reactors, have the quality to limit the short-circuit currents to values predominantly determined by the transformer's impedance. In this way, the design of a power transformer with respect to short-circuit current withstand capacity is directed towards limitation of the current values proper as well as towards control of the forces and stresses exerted by the same short-circuit currents inside the transformer.
The final part of the distribution system at medium voltage are the distribution transformers. Distribution transformers may be oil-filled (IEC 60076) or cast resin (IEC 60076-11). DNV KEMA can perform complete type tests, which means doing all relevant tests in the High Power Lab and the High Voltage Lab. Regularly, a manufacturer offers a complete range of five distribution transformers, which can be very efficiently certified in one test performance.
Furthermore, DNV KEMA has excellent facilities to test large power transformers.