Smart Grid restoration concepts

This paper addresses how future Smart Grid measurement, analysis and control technologies could be applied to significantly enhance methods for system restoration. The paper reviews the common phases for system restoration from system assessment, creation of restoration building blocks, expansion of islands, re-integration with neighboring systems through to customer load restoration. A number of novel restoration concepts including phasor based state and topology estimation, automatic island frequency control, virtual synchro-scopes, simultaneous line end energization, simultaneous generator synchronization, stabilization of parallel plant units and temporary low voltage operation of transmission lines are presented. The concepts in general are based upon applying smarter computer, communication and control processes while minimizing the need for capital investment in transmission equipment. These concepts will allow EHV lines to be energized at a much earlier phase in the restoration process. This in turn will allow electrical islands to be formed more rapidly with much greater capacity and geographic scope. As a consequence restoration times could be reduced from days to hours. The ideas are presented at this stage as concepts rather than methods. The concepts have been tested with very preliminary simulations and appear promising. Significant more study is required to further validate the feasibility of each concept with detailed simulations and analyses with due consideration to all the practical issues including control, communication, security, impact on protection systems, impact on operating procedures and consequences of false operations.