THE WORLD'S LARGEST PARTICLE PHYSICS RESEARCH LABORATORY is used by more than 5000 physicists from research institutes worldwide. The Organisation Européenne pour la Recherche Nucléaire (CERN; Geneva, Switzerland), or the European Organization for Nuclear Research, is an intergovernmental organization with 20 member states. CERN designs, installs and runs the necessary particle accelerators that provide the particle beams to experimental areas. The physical location of these multiple accelerators actually straddles the Swiss-French border.

ELECTRICAL NETWORK

The CERN electrical network is supplied by Énergie de l'Ouest-Suisse (EOS), the Swiss regional grid company, through a 130-kV transmission line, and by Réseau Transport de l'Électricité (RTE), the French national grid company, through a 400-kV transmission line. Thus, there are two network injection substations. Owned and operated by CERN, the main Prévessin site (France) is a 400/66/18-kV substation with 490 MVA installed. The Meyrin site (Switzerland) is a 130/18-kV substation, where the high-voltage equipment is owned and operated by Services Industriels de Genève (SIG), the Geneva local power distributor, and the medium-voltage equipment is owned and operated by CERN.

When the accelerators are operating, CERN is fed through the 400-kV RTE supply. There is significant power consumption during accelerator operation, and the large peak-active power requirements of the Super Proton Synchrotron (SPS) accelerator are not available from the 130-kV network. During accelerator maintenance (winter shutdown), power is provided through the 130-kV SIG/EOS network. Switching the general services network from one source to the other is performed twice a year without interruption to the supply. The accelerators are not powered when the supply is from the 130-kV line.

NETWORK OPERATION

The Large Hadron Collider (LHC) accelerator is the most demanding and powerful accelerator ever built. It is supplied through five 66-kV underground cable links from the Prévessin substation. The energy is transformed to 18 kV in main substations at five separate locations and distributed to the users in the LHC tunnel and the surface buildings. The end users' equipment is mainly supplied at 400 V.

The remaining accelerators are supplied from an 18-kV distribution network through underground cable links or utility galleries built under the sites. The 18-kV network is designed to supply and operate all equipment in the accelerators in accordance with specific load characteristics, such as pulsed loads, stable loads, Meyrin site general services, Prévessin site general services, the SPS accelerator and experimental areas.

Accelerator components, like magnet power rectifiers and radio-frequency generators for accelerating cavities, generate large fluctuations of active and reactive power, as well as large harmonic currents that can be injected back into the network. For example, the SPS accelerator has an 18-second cycle pulse where the power consumption varies by 150 MW, when operated at 450 GeV beam energy.

To limit the network voltage swing and harmonic pollution, the network is separated into several sectors. Sectors containing large quantities of magnet rectifiers are equipped with compensating and filtering systems. Fluctuations of reactive power consumption are compensated with saturated reactors or thyristor-controlled reactors (TCRs). Harmonic currents are eliminated with harmonic filters, which simultaneously generate the necessary reactive power with capacitor banks.

The CERN power network is monitored by a supervisory control and data acquisition (SCADA) system. CERN awarded electrical network control centre and substation automation contracts to EFACEC (Matosinhos, Portugal) to provide SCADA, distribution management system (DMS) and other IT systems, as well as remote terminal units (RTUs) for substation automation, to integrate CERN's existing protection relay systems.

The CERN base load is around 40 MW, while the mean power reaches 130 MW in summer time with the Proton Synchrotron (PS) and SPS accelerators in operation and a peak power of around 200 MW to 210 MW, as these are pulsed machines. With the LHC in operation, the mean power increases to 230 MW. The expected annual electricity consumption will reach some 1000 GWh when all accelerators are in operation. The LHC, with beam injection expected for mid-November 2009, will gradually reach its nominal consumption of 390 GWh per year, more than one-third of CERN's nominal consumption.

SCADA/DMS SYSTEM

The electrical equipment on CERN's power distribution network is monitored with a SCADA/DMS system, which provides the technical infrastructure control room operators and electrical operational personnel with remote monitoring and control facilities. In addition to SCADA, this system offers the following:

• Interfacing with other systems, including third-party supervision systems (turnkey electrical systems like 150-MVAR TCR reactive power compensation systems), based on International Electrotechnical Commission (IEC) 870-5-10x protocol

• Network topology processing, aiming to identify energized and non-energized branches of the network through network coloring by power sources, voltage levels and other categories

• Module for state estimator and power flow calculations, aiming to provide calculated data, such as current flows, voltage levels, power flows and losses, based on real-time network state and effective measurements (this network topology database is currently being populated)

• Interfacing with CERN in-house-developed front-end computers

• Connection of the SCADA system, through a message handler, to the CERN technical infrastructure monitoring system provides the following:

  • SUBSTATION AUTOMATION SYSTEMS

    Injection of information to the LHC accelerator's alarm service

  • Consolidated information from various technical domains like cooling, ventilation, cryogenic plants and security systems

  • Tools for managing the reactions to major breakdowns to reduce the accelerators' downtime

  • Link to the computer-aided maintenance management system to generate maintenance orders to the various contractors in charge of maintenance and operation

  • Sharing of information with the detector control systems in the experimental areas.

CERN's SCADA/DMS system came into operation in 2001. The system also included some RTUs for substation automation, featuring supervision, control and integration of existing third-party protection relays.

EVOLUTION

Since 2001, CERN and EFACEC have been working together to integrate new substation RTUs with the legacy systems into a truly unique industrial SCADA system, supplied and maintained by the Portuguese company.

This system manages almost all of the equipment located on CERN's electrical network, including substations on the surface and underground, as well as other network branches existing in the technical buildings throughout the site. The equipment supervised in these installations spans all voltage levels, from 400-kV circuit breakers and transformers down to 48-Vdc battery chargers. As the distribution network involves different generations of technology, the SCADA system comprises many heterogeneous hardware and software interfaces offering different methods of integration.

Altogether, the system presently manages about 160,000 signals. They cover mostly status signals but also a significant number of analog measurements and counters. Control output channels are available for remote operation of specialized substation equipment. By the time all CERN's substation equipment has been migrated, a total of 200,000 signals are expected to be managed by the SCADA/DMS system.

At the substation level, RTUs perform data acquisition and control orders execution, either by means of its input/output units or by integrating third-party devices such as protection relays, these being integrated through various protocols over serial communication links.

About CERN

Presently, CERN has 26 RTUs — each one with a local human-machine interface (HMI) — installed in ground-level substations. Therefore, authorized operators may supervise and control the substation process locally. RTUs placed at surface installations may observe several substations, so some of them are really large in terms of the output of data points.

CERN also has 31 RTUs for the underground areas of the LHC, where access conditions are limited to shutdown periods. The hardware type is based on embedded diskless technology, characterized by high availability and reduced maintenance. The underground substations are distributed along the LHC tunnels, some positioned in close proximity to the experiments.

The SCADA graphical user interface is available from the technical control room and is manned 24 hours a day throughout the year. About 30 workstations are available in the main substations to offer complete network supervision at the field level. Electrical operators use them during network reconfiguration, commissioning and maintenance operations. All systems are connected through a dedicated TCP/IP based network.

In the scope of the procurement policy, CERN purchases devices and equipment from different companies within the member-state countries, by means of supply contracts. Due to this fact, CERN has a heterogeneous set of different devices, with different interface and communication protocols. The RTUs had to be adapted to manage several communication protocols, either standard or proprietary from specific vendors, as well as various field buses.

For instance, the RTUs communicate through a JBUS protocol interface with approximately 500 digital protection relays from Schneider Electric (France). These RTUs also communicate with a wide set of other equipment, such as transformer voltage regulators, programmable logic controllers, uninterruptible power-supply systems, battery chargers, and medium-voltage network control and supervision devices. The next generation of digital protection relays based on EN 61850 will be integrated in the future.

In view of the importance of the LHC and its experiments for the international scientific community, the electrical services within CERN rely on the adopted management system, which has been developed in accordance with CERN specifications. As this is an evolving system, CERN remains focused on the migration of legacy systems to new technologies, granting the necessary implementations in order to maintain high-level standards for the operation and management of the distribution network and other important LHC infrastructure assets.

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Georges Burdet (Georges.Burdet@cern.ch) has been working for CERN since 1977 on a wide range of electronic technology for magnets power converter electronics and remote monitoring. In 1982, Burdet moved to computer technology, facing the rapid changes in operating systems and programming languages. From 1984, he was involved in the design of the LEP electrical networks monitoring system based on a CERN in-house-developed solution at the data acquisition, processing and applications levels. This solution was later deployed to cover the whole CERN site. Since 2001, Burdet has been involved in the integration of an industrial SCADA solution, and in 2006, he was appointed administrator of the CERN electrical networks supervision, SCADA.

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Organisation Européenne pour la Recherche Nucléaire (CERN), the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. With headquarters in Geneva, Switzerland, CERN's member states are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. India, Israel, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and the United Nations Educational, Scientific and Cultural Organization (UNESCO) all have observer status. Several scientists from CERN have received Nobel Prizes. Additionally, CERN attracts other Nobel laureates to its facilities.