Switching and protection of multiple transformer arrangement in industrial distribution system

In modern industrial electrical distributions, medium size transformers require protection systems that are faster, more reliable and selective than the systems used for their earlier counterparts. To achieve such improved performance, protection engineers will be required to further investigate the magnetic circuit and inrush current of the subject transformers. This paper provides examples of where inrush currents investigations are required for industrial system transformers, aspects of transformer and system configurations that could impact inrush currents, configuration modeling in Electromagnetic Transient Programs and the application of the analysis results in selecting transformer protection schemes that will address system´s needs. This paper shows the importance of establishing the protection configuration speed requirements, the criticality of investigating the inrush currents of transformers, a method to analyze the inrush currents and the use of such analysis in selecting protection configuration and settings.