Transformer energisation after network blackout

According to ENTSO-E Network policy 5, responsibility for system restoration after a blackout is on the shoulders of Transmission System Operators (TSOs). They are advised to have a firm plan in place for regular testing of system restoration functionality. Part of the network restoration includes energising transformers to supply various underlying grids. However, transformer energisation after a blackout is complex and there is a significant risk for network restoration to fail because the network is quite weak in the first phase of the process and due to specific transformer behaviour. This paper will focus on relevant items in regard to energising transformers and an alternative robust ‘soft-energisation’ methodology to supply transformers simultaneously after a network blackout. A qualitative assessment is made for the ‘classical’ and ‘soft-energisation’ methodology for network restoration purposes. Also, feasibility studies are elaborated