Understanding the Sympathetic Inrush Phenomenon in the Power Network using Transformer Explorer

An in-service transformer in a substation may experience sympathetic inrush phenomenon due to startup inrush current from an incoming transformer, energized into the network. The startup inrush causes a half cycle voltage dip in either cycle, thereby developing an asymmetrical flux distribution in the nearby transformers in service. The paper discuses about sympathetic inrush current events, originating in a Swedish distribution network due to energization of transformers in same, or neighboring network. These events were further observed to be potentially detrimental to the network operation as well as to the health of the transformers. An in-house online monitoring tool- Transformer Explorer was deployed for continuous data acquisition and capture of the anomalous events including sympathetic inrush. The impact of the transformer following such event is also briefly discussed, based on the combined diagnostic observation made by PSCAD simulation tool and Transformer Explorer.