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CERN Electrical Network short Description

EOS 130kV line 400kV Breaker EDF 400kV line

CERN Electrical Networks

Networks schematics
(requires HPGL Viewer)

CERN End of Year Closure
(22/12/07 - 6/01/08)

18kV Secured Network
(22/12/07 to 06/01/08)

18kV Secured Network
400kV maintenance
(07/01/08 to 16/01/08)

CERN Electrical Networks
 (Version 2005, PDF format)


Detailed description

CERN is connected to both Swiss and French National Grids:

  • 130kV line from the VERBOIS Station on the Swiss side, arriving on MeyrinSite.
    The 130/18kV Station is operated by SIG (Services Industriels de Genève)
  • 400kV line from the Bois-Tollot Station, arriving in Prévessin Site.
    400kV Grid is operated by
    RTE (Réseau de Transport d'Electricité)

    The 400kV CERN Station is operated by CERN Electrical Service.
  • These 400kV and 130kV National Grids are inter-connected (see the 1999 and 2003 situations)
  • Energy is currently supplied by EDF (Electricité de France) & EOS (énergie ouest suisse)
  • CERN Electrical Networks carry electrical energy to major sub-station via 66kV and 18kV underground links. Final loads are supplied under 18kV, 3.3kV or 400V.

    Safety Services are rescued by Diesel Generators and sensitive loads are fed through UPS systems to isolate from network perturbations or power cuts.

    Battery system provides the Auxilliary Voltage for protection & interlocks.

Related links

energie ouest suisse
EOS: énergie ouest suisse

SIG: Services Industriels de Genève

Electricite de France
EDF: Electricité de France

Réseau Transport Electricité
RTE: Réseau de Transport d'Electicité

French National

Disclaimer - © Copyright CERN - Comments & changes to EN/EL Group WebMaster . Last modified on January 2009

66kV es and 18kV distribution to CERN domain

400kV CERN Incoming

Central 66kV switchboard

Central 66kV switchboard

66kV switchboard in a LEP area

400/18kV 90MVA transformers for the SPS pulsed loads

66kV bus bars downstream the 400/66kV 110MVA transformers

66kV feeders, supplyin main sub-stations via cross-country links.

66kV substation and 66/18kV transformers in access point 2 of LHC.

CERN specificity: pulsed load

SPS Pulse shape

The SPS accelerator is based on a cyclic operation: injection of particles from PS, acceleration with the RF system while ramping the bending magnets, then slow extraction and finally dumping of the residual beam. The energy stored in the main magnets is re-injected on the 18kV network. A typical cycle period is around 14.4 seconds. This figure shows the variation of active and reactive power on the main magnet 18kV bus bar, the part absorbed by the Main, North (and Auxiliary) compensators, and the remaining values on the EDF line. See the different regulation implied in these compensators.

90Mvar reactive power compensation and harmonics filter in the BE area

90MvAr Saturated reactor compensator


Compensator (90Mvar), based on a 120Mvar saturated reactor, associated with 93Mvar filters for harmonics 2, 3, 5, 7, 11, 13, 17 and HF. Under replacement by 150MVAr SVC.

The BE substation was renovated during the SPS shutdown 2000/2001. 18kV switchboards are renewed, as well as the protection and control equipment. Pictures coming soon.

Auxiliary 18Mvar reactive power compensation and harmonics filtering in BB3

18Mvar thyristor controlled reactor

18kV switchboard for Auxilliary Compensator

18kV protection relays for Auxilliary Compensator

Water cooled thyristors for Auxilliary Compensator

Auxiliary 18Mvar (TCR based) compensator in BB3, necessary to operate the SPS accelerator at higher energy level

18kV switchboard for Auxiliary compensator

Protection relays in rack as used for Auxiliary compensator

Thyristor cubicles for the Auxiliary 18Mvar compensator

Thyristor control for Auxilliary Compensator

Micene for Auxilliary Compensator


TCR electronic control from BBC, with the DAC controlled by MICENE on the left

MICENE used to interface the equipment and compute the TCR reference each main period (computed from the reactive power in the main magnet of the SPS accelerator


24Mvar reactive power compensation and harmonics filtering in the LHC sites (50Mvar in LHC site 2)

66kV Incoming in the LEP area

Compensator in the LEP area

18kV switchboard in the LEP area

Voltage regulator in LEP area

66kV switchboard and 66/18kV transformers in LHC even point (underground line coming from the BE on the right of the picture

50Mvar TCR compensator in LHC site 2, with associated filter

18kV switchboard as used for LHC compensators

Tap changer controller, associated with the reactive power compensators in the LHC even points


18kV protection relays assembled in crates and rack mounted in the SPS area

MICENE used to interface compensator equipment and to compute (each mains period) the TCR reference in order to keep stable the reactive power at the 18kV level


18kV substations

A renovated sub-station on Meyrin site, with SEPAM as protection relay

SEPAM protection relay in the BE9, one of the main 18kv sub-station

a 18kV sub-station in the SPS area (BB3)

The main switchboard in the BE, to supply the SPS Main Power Converter

Safety equipment

Diesel generator (on the top, right side) in LHC area to supply safety equipment as lift, lightning, ventilation, etc. In the middle is the 38MVA 66/18kV transformer to supply accelerator components like RF klystrons, spectrometer magnet, etc.

Diesel generator automation in the LHC area

48V battery chargers, in the LHC underground sub-stations

The permanent insulation monitoring of the 48V dc distribution network

Emergency stop interlock system in the LHC areas, also used in the renovated sub-stations

The safety lightning invertor (48VDC to 230VAC) in the LHC area

One of the PLC used in the Auto-transfer system, to supply CERN critical 18kV network from EDF or EOS

Emergency stop identification crate in the LHC area





400V distribution

A low voltage switchboard in the LHC area, with digital and analogue Io's connected to MICENE

The new generation of LV switchboards, with embedded control, connected to the CFE through fields bus



Disclaimer - © Copyright CERN - Comments & changes to TS/EL Group WebMaster . Last modified on 2 March 2008