Substation transformer connection effects on sensitive industrial loads

Abstract

In electrical power distribution, it is both convenient and economical to use the open delta transformer connection to supply three-phase power to small consumers. Recently, however, problems such as rectifier failure in equipment power supplies have been attributed to this type of transformer connection. This paper presents the results of an investigation into the existence and severity of consumer problems arising from the open delta connection. It describes both theoretical and laboratory analyses of the presence of distortion in magnitude, phase angle and waveshape of the voltage and current waveforms. The analyses show that, although there are some conditions under which the open delta connection should not be used, in general the connection is suitable for supplying consumer loads.