GB experience and its relevance to the pending European market redesign
Ever since the early days of electric power, which was characterised by small local networks, the trend has been towards greater integration, resulting in the large, centrally-managed transmission networks we see today. Whilst the ownership structures have varied over the years and from country to country (private vs public, vertically integrated vs unbundled), the picture has been one of power flowing, often over large distances, from large scale generators connected to the high voltage grid to consumers connected to the low voltage grid, with a central system operator balancing the generation and consumption in real time.
In that world, operators of lower voltage distribution networks have played a passive role in system operations with largely unidirectional flows of power across their networks from grid supply points to end consumers, leaving the realtime balancing of the national system to the Transmission System Operator (TSO) on the higher voltage network. The Distribution System Operators (DSOs) have concentrated instead on connecting customers and maintaining and reinforcing the network, with real-time operations focused mainly on network outage and fault management.