Automatic Reconfiguration of CERN 18 kV Electrical Distribution - the Auto Transfer Control System

Availability is key to electrical power distribution at CERN. The CERN electrical network has been consolidated over the last 15 years in order to cope with the evolving needs of the laboratory and now comprises a 200 MW supply from the French grid at 400 kV, a partial back up from the Swiss grid at 130 kV and 16 diesel generators. The Auto Transfer Control System has a critical role in minimizing the duration of power cuts on this complex electrical network, thus significantly reducing the impact of downtime on CERN accelerator operation. In the event of a major power loss, the control system analyzes the global status of the network and decides how to reconfigure the network from alternative sources, following predefined constraints and priorities. The Auto Transfer Control System is based on redundant logical controllers (PLC) with multiple remote IO stations linked via an Ethernet IP ring (over optical fiber) across the three major substations at CERN. This paper describes the system requirements, constraints and the applicable technologies, which will be used to deliver an operational system by 2020.