All CERN buildings and structures undergo an annual electrical inspection. A workshop would be included in the annual electrical inspection of the building concerned.

The regulatory framework under which electrical inspections are carried out is CERN’s Safety Code C1 and consequently Safety Instruction 24, which refers to international standard IEC 60364; the latter is supplemented by French standard NFC 15-100 for low-voltage installations and by French standard NFC 13-200 for high-voltage installations.

In addition, electrical inspections of safety lighting are carried out in accordance with CERN Safety Guideline SG EL-0-0-1. Finally, the scope, methods and content of electrical inspection reports are based on the French decree of 26 December 2011 .

CERN’s Code C1 provides a regulatory framework that sets out the safety aspects of the design, installation and operation of electrical installations.

CERN’s electrical safety rules include CERN Code C1 and Safety Instructions 5, 24 and 48. These rules apply to everyone working on the CERN site and to everyone involved in the design, operation and maintenance of electrical installations and equipment. They concern the entire CERN site (Switzerland and France).

Information on safety lighting requirements can be found in Safety Guideline EL-0-0-1.

Electrical installations must comply with CERN Safety Instruction 24 and IEC standard 60364. The most recent IEC and CENELEC standards also constitute the basic rules.

A request to remove a general emergency stop (AUG) must be made by the department concerned, with the involvement of the TSO responsible for the building and the DSO/LEXGLIMOS/EXSO of the department/experiment.

To submit a request, contact the EN-EL group by creating a ticket with the Service Desk and providing a description of the requirements, including:

• the reasons for the change;
• the countermeasures that will be required following the removal of the general emergency stop;
• an assessment of the need to install another emergency switch, in accordance with Safety Instruction 5 and French standard NFC 15-100 (chapter 465).

The HSE department (electrical-safety-specialist@cern.ch) must be informed (by the TSO of the building or by the EN-EL group) of the change, be provided with the prepared documentation and fill in a Safety Request Form to give its assessment of the change.

Safety Instruction 4, “Safety Inspections”, provides definitions of initial safety inspections and periodic safety inspections and explains the differences between them.

The electrical project manager or the CERN electrical work package manager is responsible for:

• requesting the HSE department to carry out an initial electrical inspection (electrical-verifications.service@cern.ch);
• providing all the necessary documents (see EDMS 1212097) to the HSE department;
• resolving the non-conformities identified in the inspection report within a maximum of two months;
• sending an e-mail to electrical-verifications.service@cern.ch to report on how the non-conformities have been addressed.

The following documents must be sent to electrical-verifications.service@cern.ch:

• the duly completed electrical inspection request form (EDMS 1212097);
• the desired deadline/date;
• the name of the on-site contact person who will accompany the inspector.

NB: The inspection will involve switching off devices (residual current devices, lighting) and checking the settings of circuit breakers and fuses.

In accordance with CERN’s Code C1, the HSE department manages the organisation of electrical inspections, namely:

• an initial inspection: when a new electrical installation is commissioned or the electrical structure is modified (creation or reorganisation of part of the installation, modification of the earthing system or of the short-circuit power of the source, modification or addition of distribution circuits);
• periodic inspections: carried out to inspect all installations;
• accompanied periodic inspections: carried out as an initial inspection in the context of the ELECNCSOL project.

The HSE department may also perform electrical inspections on request.

All the machine’s potential risks and the safety provisions are described in the safety notice. In the case of electrical and mechanical hazards, it is generally necessary to carry out a comprehensive lockout, including disconnection from the network and purging of residual energy.

The HSE department (electrical-safety-specialist@cern.ch) is responsible for organising electrical inspections.

Electrical inspections are carried out by specialists (HSE department or HSE department contractors).

ELECNCSOL is a joint project being carried out by the HSE department and the EN-EL and SCE-SAM services to bring electrical installations up to standard following periodic inspections.

The purpose of the SAILOR ELEC software is to centralise and structure electrical safety inspection data, making it possible to:

• plan and organise electrical inspections;
• create and integrate inspection reports;
• ensure the distribution of reports and the traceability of non-conformities;
• facilitate the monitoring and extraction of statistics.

The following modifications to an existing electrical installation require a new initial inspection:

• modification of the earthing system;
• modification of the short-circuit power of the source;
• modification or addition of distribution circuits;
• creation or reorganisation of part of an installation.

NB: Replacing an old electrical outlet with one of the same type, adding a fieldbox or adding an electrical outlet to a terminal circuit does not require another inspection. However, adding an electrical outlet to a new switchboard requires an initial inspection.

Yes, testing is compulsory. In particular, the inspector must test the residual current devices (RCD) and the safety lighting.

The project manager or CERN electrical work package manager must take the necessary steps to resolve the non-conformities and inform the HSE department by e-mail (electrical-verifications.service@cern.ch) about the lifting of reservations.

Buildings with no non-conformities are inspected every two years. Buildings with non-conformities are inspected every year. The buildings and structures housing the accelerators are inspected when the schedule and access restrictions permit. TSOs are notified of the date of the inspection at least one month in advance.

Each non-conformity in the periodic electrical inspection report is categorised by a suffix, e.g. “_EL”, “_SCE”, “_TSO”. The building’s TSO must take action and resolve only the non-conformities in the “_TSO” category. Non-conformities in categories other than “_TSO” will be resolved by the services concerned.

The purpose of cutting off the power, including for tests of residual current devices and safety lighting, is to check that these devices are working properly in accordance with the current regulations. A power outage notice is issued by the EN-EL or SCE-SAM electrical service in the days preceding the inspection.

In any of these situations, observe the following instructions:

• Do not touch the equipment concerned;
• Put up a hazard warning sign indicating your telephone number and the date and specifying “Do not touch, do not use”;
• Report immediately the situation by creating a ticket with the CERN Service Desk (service-desk@cern.ch), copying the electrical inspections service (electrical-verifications.service@cern.ch), the TSO and the owner of the equipment, if known.

In such cases, create a ticket with the CERN Service Desk service-desk@cern.ch), copying the electrical inspections service (electrical-verifications.service@cern.ch).

To find a building’s electrical inspection reports in EDMS:

1. Type the building number in the search bar,
2. click on the “Locations” tab,
3. click on the number of the building concerned,
4. click on the “Documents” tab,
5. click on the paragraph “Safety Inspection”.

Here you will find all the electrical inspections carried out since the building was built.

In addition to the electrical inspection, checks are carried out to ensure that the equipment installed is appropriate for the risk level of the ATEX zone concerned.

The yellow emergency stop is a device that cuts off the power supply to terminal circuits in order to ensure compliance with §465 of French standard NFC 15-100 in the event of an unexpected hazard. The departures from the power supplies disabled by the emergency stop are indicated on the sign next to the device. It is advisable to locate this type of device at all the entrances to the building. If required, a device may also be installed on each floor.

Only qualified personnel may work on electrical installations. The required qualifications are:

1. Technical skills acquired through accredited training or recognised professional experience.
2. Knowledge of the safety regulations applicable to the installations concerned.
3. Knowledge of emergency procedures and first-aid measures to be taken in the event of an electric shock.

Qualification can be based on standard UTE C 18.510 (NFC 18-510).

Such work is classified as electrical work and is covered by French standard NFC 18-510, section 9.7.2.4.1. The minimum requirements are as follows:

• The priority is to disconnect the cables (lockout).
• Make sure that the insulation of all the other cables in the cable trays remains intact.
• Use PPE (insulating gloves as a minimum) if it is not possible to disconnect all the cables in the work area.
• The person in charge must have B2/H2 electrical accreditation or equivalent.
• The other workers must have B1 electrical accreditation or equivalent.
• Follow all the other safety instructions applicable at CERN, in particular the disassembly procedures.

The above requirements do not exempt the person in charge of the work from carrying out a risk assessment, which may provide additional information.

The removal of residual current devices (RCDs) must be analysed on a case-by-case basis. Contact electrical-safety-specialist@cern.ch for assistance. In accordance with section 411.3.3 of French standard NFC 15-100: “in alternating current systems, the terminal circuits must be fitted with additional protection in the form of a residual current device (RCD) with a rated residual operating current not exceeding 30 mA, in accordance with standard 415.1, when they are connected to: sockets with a rated current not exceeding 32 A; sockets installed in places classified as being in external influence category AD4, regardless of their rated current; sockets in temporary installations, such as worksites, regardless of their rated current.”

The safety standard that applies to all Swiss sockets is SN 441011. It can be consulted on the SNV platform.

According to annex A, “risk analysis”, of Swiss standard SN 441011-1:2019, Swiss plugs and sockets for domestic and similar usage are not designed to operate permanently at their rated current. They should be subjected to only 80% of their rated current. Where the continuous load capacity requirements are higher, products complying with standard EN 60309 should be used. Contact electrical-safety-specialist@cern.ch for assistance.