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

2. 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

3. 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

4. Part 1 : Today Users Requirements Impact of Electrical Disturbances
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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

5. Part 1 : Today Users Requirements Features of the CERN Protection System
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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

6. Part 1 : Today CERN Protection System Policy Protection Schemes
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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

7. Part 1 : Today CERN Protection System Policy Control & Monitoring System
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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 )
October 24th, 2012
Review of the Project for the Consolidation and Upgrade of the CERN Electrical Distribution System

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

9. Part 1 : Today CERN Protection System Hardware Distribution by Networks
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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

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

11. Part 1 : Today CERN Protection System Hardware Distribution by Networks
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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

12. Part 1 : Today CERN Protection System Hardware Distribution by Networks
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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

13. 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

14. 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

15. 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

16. 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

17. Part 1 : Today State of CERN Protection System … in summary
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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

18. Part 1 : Today Critical Points Electromechanical Relays
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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

19. Part 1 : Today Critical Points Static Relays
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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

20. Part 1 : Today Critical Points Digital Relays
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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

21. Part 1 : Today Critical Points Major Issues of Protection Selectivity
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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

22. Part 1 : Today Critical Points Major Issues of Protection Selectivity
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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

23. Part 1 : Today Critical Points Major Issues of Protection Selectivity
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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

24. Part 1 : Today Critical Points Lack of Preventive Maintenance
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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

25. Part 1 : Today Critical Points … in summary
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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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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