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Protection, defence and restoration

The electricity system consists of many components (generators, lines, transformers...), each of which can have a failure. A failure (short circuit) triggers abnormal operation (for example, characterized by very high currents) that can cause harm to people, the environment (fires) and other system components. For this reason the electricity system is "protected" through systems which are conveniently redundant and which must ensure speed and selectivity of action to isolate the component as soon as there is a failure. The protection systems are designed to protect the individual components, but do not consider stability issues of the electricity system. A disturbance in an area, in fact, could threaten continuity of the service to the whole network. To deal with such situations, the network has dedicated automated systems, which are intended to keep "alive" the electricity system and/or limit the disruption: these systems constitute the defence plan of the electricity system.

Despite the control actions by the operators and the presence of defence plans, very unfavourable situations and events can lead to blackouts, or the total or partial disruption of the electricity system. Service restoration after a blackout is a very complex and delicate operation phase, which involves transmission network operators, power plant operators and distribution network operators in a coordinated way. Service restoration is generally planned and coded by network operators in appropriate restoration plans.

RSE has developed several research activities on these issues, with the aim of greater integration between the protection and defence functions, and between the defence and restoration plans.
Protection activities include both theoretical assessments and laboratory studies and field trials, and extend to applications for electricity transmission and distribution.
The defence plans are managed through the proposal and evaluation by simulation of different strategies, taking into account the latest available technology (for example PMU/WAMS) and relevant aspects such as the ICT requirements.
Contributions to the studies on restoration concern the definition of methodologies, criteria and control functions to increase the efficiency and reliability of the service restoration process.