the CERN Electrical network protection system S. Bertolasi / J-P. Sferruzza EN Department CERN

Outline Part 1 User requirements CERN protection system policy CERN protection system hardware Critical points Part 1 The CERN Protection System Today October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Outline Part 2 Guidelines on protection schemes Improving the selectivity of the protection Improving the reliability Schedule Part 2 The CERN Protection System Tomorrow October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Users Requirements Impact of Electrical Disturbances 1/2 Each year, the CERN electrical distribution network faces around 5 short-circuits (cables, switchgears, transformers) Processes related to experiments and technical infrastructure require us to minimize disturbances on the electrical network Impact of disturbances outside CERN network on the functioning of accelerators : some experiments stop and the restart takes time. User requirements are conditionned by the impact of electrical disturbances on CERN processes. October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Users Requirements Features of the CERN Protection System 2/2 LHC design required the users to cope with voltage disturbances lasting 100 ms Very demanding requirement for the machines Today, such disturbances can lead to machine stops (depending on the voltage drop) The clearing of electrical faults must ensure a fast restart of accelerators : Priority 1 : Quick clearing, to avoid damage to equipment Priority 2 : Targeted clearing, to avoid unnecessary shutdowns increasing the time to restart Operation in closed loop configuration October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Policy Protection Schemes 1/2 Protection by Logic Selectivity is used wherever possible: To reduce the fault clearing time while seeking selectivity Because faults on the 18 kV network are detected by the protection relays of the 66 kV network Other major schemes : Time selectivity Less frequently : Differential selectivity Interlocking functions : Circuit-breaker failure To prevent the re-energizing of a fault by the Autotransfer System October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Policy Control & Monitoring System 3/3 Design principles (since 1979): 2 tripping circuits working in parallel : positive and undervoltage coil The protection relays are not installed inside the switchgear cubicles (Operation rules do not allow the switching OFF and ON of switchgears from local command but only from a remote protection relay) SCADA supervision (digital and static relays) Transient recording : within most digital relays + dedicated transient recorders in major substations (ME9, BE, BE9, SEM12, LHC 2.4.6.8) October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Hardware 1000 relays, from the 1960s to 2012 1/3 October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 Electromechanical relays < 1980s Static relays 1980s Digital relays 1990s Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 400 kV Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 Electromechanical relays < 1980s Static relays 1980s Digital relays 1990s 18 kV 400 kV Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 66 kV & 18 kV Electromechanical relays < 1980s Mostly LHC Static relays 1980s Digital relays 1990s 18 kV 400 kV Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 66 kV & 18 kV Electromechanical relays < 1980s Mostly LHC 66 kV & 18 kV Static relays 1980s SPS & NA Digital relays 1990s 18 kV 400 kV Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Including a busbar differential protection from the late 1960s Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 18 kV Including a busbar differential protection from the late 1960s 66 kV & 18 kV Electromechanical relays < 1980s Mostly LHC 66 kV & 18 kV Static relays 1980s SPS & NA Digital relays 1990s 18 kV 400 kV Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Including a busbar differential protection from the late 1960s Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 18 kV Including a busbar differential protection from the late 1960s 66 kV & 18 kV 18 kV Electromechanical relays < 1980s Mostly LHC 66 kV & 18 kV Static relays 1980s SPS & NA Digital relays 1990s 18 kV 400 kV Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Including a busbar differential protection from the late 1960s Part 1 : Today CERN Protection System Hardware Distribution by Networks 2/3 18 kV Including a busbar differential protection from the late 1960s 3.3 kV & 18 kV 66 kV & 18 kV 18 kV Electromechanical relays < 1980s Mostly LHC 66 kV & 18 kV Static relays 1980s SPS & NA Digital relays 1990s 18 kV 400 kV Safety October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today State of CERN Protection System … in summary 3/3 Critical importance of protection selectivity for fast and targeted faults clearings Electromechanical relays (20 %) SPS and North Area 18 kV networks (pulsed and stable) Meyrin Experiments (West Area) 18 kV network Safety 3.3 kV and 18 kV networks Static relays (24 %) LHC General Services 18 kV loop LHC Machine 18 kV and 66 kV networks Safety 3.3 kV network Digital relays (56 %) October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points Electromechanical Relays 1/8 Electromechanical relays are obsolete and maintenance is time-consuming Lack of spare parts is becoming critical Do not allow protection by logic selectivity Some critical electromechanical relays were already replaced by digital relays (parts of SPS & North Area, ME9 Jura substation protections) October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points Static Relays 2/8 Static relays are also obsolete (drifting of delay settings due to ageing of capacitors) The stock of spare parts has to be reconstructed during shutdowns or after corrective maintenance Limited capability for protection by logic selectivity Poor directional functionality, critical for the LHC General services loop Static relays are faster than digital relays, thus they cannot be blocked by digital relays Digital relays: October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points Digital Relays 3/8 Software programming and chassis cabling of the digital relays : Not standardised, because of the high number of different uses (incomers, radial or loop topology, filters, etc…) More than a hundred of different programming Post-mortem analysis is time-expensive October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points Major Issues of Protection Selectivity 4/8 Operation in closed-loops In some cases, makes the fault detection more difficult, leading to a lack of selectivity Protection selectivity is crucial Logic selectivity depends on the technology of the relay Compatibility problems can be mitigate by using one protection relays technology October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points Major Issues of Protection Selectivity 5/8 Multiple sources (EDF 400 kV Prevessin, SIG 130kV Meyrin, diesel generators) Protection coordination may be difficult because short-circuit power depends on the source and configuration of the substation Blocking signals used for logic selectivity have to be sent to the appropriate protection relay to be blocked In most of the cases, only the normal configuration is taken into account Case of ME9 substation (JURA) October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points Major Issues of Protection Selectivity 6/8 An efficient fault clearing is crucial for the Transport Network because of possible interactions with the Autotransfer System (re-energizing of electrical faults) This may require inter-tripping or differential functions October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points Lack of Preventive Maintenance 7/8 Preventive maintenance is needed to ensure the proper functioning of Current measurements Cabling for relay tripping Preventive maintenance of the protection system is almost impossible today, because of The very rare machine stops The low operational capabilities of the present network The high sensitivity of the protection system due to the use of undervoltage coils, which makes the protection system very sensitive to the quality of the 48 V supply and increases the risk of accidental shutdown during interventions Blocking signals Interlock Systems rarely triggered October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 1 : Today Critical Points … in summary 8/8 Protection relays of different technologies Almost half of the hardware is obsolete Logic selectivity is limited by Hardware Substations configurations Multiple sources and Autotransfer System Maintenance issues Software not standardised Lack of preventive maintenance October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Outline Part 2 Guidelines on protection schemes Improving the protection selectivity Improving the reliability Schedule Part 2 The CERN Protection System Tomorrow October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 2 : Tomorrow Guidelines on Protection Schemes Differential Selectivity (for cables, transformers, busbars) will be used on 400 kV network 66 kV network 18 kV transport network : ME9, ME10, SEM12, ME59, BE9 In order to efficiently take into account the multiple sources, substations configurations and the Autotransfer System on the Transport Network. Logic Selectivity for the Distribution Network October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 2 : Tomorrow Improving the Protection Selectivity Consolidation of the Hardware Because of obsolescence and some protection selectivity problems, electromechanical and static relays will be replaced by digital relays The guidelines on protection schemes (see previous slide) set the target Priorities : 66 kV network LHC (especially for the General services loop) SPS and North Area October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 2 : Tomorrow Improving the Protection Selectivity New Substations Same guidelines on protection schemes Performances to be verified by Protection Coordination Studies with upstream and downstream networks Asset management also including protection schemes with blocking and interlocking signals and protection settings Short-circuits calculations tool (ETAP) October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 2 : Tomorrow Improving the Reliability Ease of Maintenance Following the network evolution, the increasing operational capability of substations will facilitate preventive maintenance and protection scheme tests Efforts towards standardisation of software programming and chassis cabling October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Part 2 : Tomorrow Schedule During Long Shutdown 1: Replacement of 66 kV network protection relays by differential protections for cables, busbars and transformers Standardisation of software programming and chassis cabling for the new substations BE91 ME59 Following years: Overhaul of static relays in LHC substations SPS and North Area Transport substation ME9 October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

Conclusion The project will improve the protection selectivity : Consolidation of the CERN protection system achieving homogeneity Revision of protection schemes with the use of differential protection relays for the Transport Network The reliability of the protection system will also be improved Replacement of obsolescent equipment Ease of Preventive Maintenance Standardisation of software and cabling Asset Management October 24th, 2012 Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System