Electrical Lockout Steps: NF C18-510 Procedure [2026]

Electrical lockout/tagout is the prevention measure that must always be prioritized before working on an electrical installation or facility: it eliminates the risk. It is a procedure whose objective is to de-energize and secure the section of the installation where personnel will carry out electrical work. This procedure is governed by the NF C18-510 standard: it is a central topic in electrical authorization training. Electrical lockout consists of 5 steps + a preparation step which we will detail below.

The steps of electrical lockout per NF C18-510

For a BC-authorized professional, Low Voltage lockout follows 6 steps:

• Pre-identification
• Separation
• Locking/Securing
• Identification
• Voltage Absence Test (VAT)
• Grounding + Short-circuiting (MALT + SC)

De-lockout follows the reverse order. It involves going back through the same steps to reconnect the installation to the electrical network.

Before starting a lockout procedure, you must have:

• Your PPE: a face shield, insulating gloves and an insulating mat for Low Voltage, all of which you have verified
• A lockout padlock
• A voltage absence tester
• A grounding and short-circuiting device if necessary
• A lockout certificate

Pre-identification

It consists of analyzing the electrical architecture of the site:

• Locate the installation to be locked out
• Identify visible and concealed network elements
• Check for sensitive sources, such as backup generators (their presence requires grounding)
• Identify other potential hazards
• Record this information in the lockout certificate

Separation

It consists of separating the installation from all voltage sources. On all active conductors:

• By opening a disconnector (off-load)
• By unplugging the equipment
• By removing fuses from a fuse holder
• Separation devices include:
• Disconnectors
• Power sockets
• Fuses
• Withdrawable devices
• Control, protection or emergency shutdown devices

Locking/Securing

Its purpose is to lock the device in the open position and prevent any switching:

• Immobilization of the device
• Signage and locking device (padlock or lock): To lock out a device, a physical locking device such as a lockout padlock must be used. Various lockout equipment is available to secure lockout devices, including lockout hasps and cables, valve accessories, pneumatic connectors, electrical sockets or circuit breakers. Lockout padlocks allow equipment to be locked at multiple closure points and can be locked by several people.
• A sign prohibiting operation of the device with the name of the person who performed the lockout, along with the date and phone number

Identification

It aims to verify with certainty that the separated and locked device is indeed the source of the circuit concerned by the work. VAT is not reliable for this purpose. Identification requires:

• Knowledge of the geographical layout
• Consultation of plans and diagrams
• Knowledge of the installations and their characteristics
• Reading of signs and labels
• Visual identification when it is possible to trace the conduit from the separation point

Voltage Absence Test (V.A.T.)

It involves verifying the absence of voltage on all active conductors, as close as possible to the work location, using a voltage absence tester.

Warning! Even though technically the VAT can be performed using a simple voltmeter, it must be carried out using a voltage absence tester. The proper functioning of this device must be verified before and after the voltage absence test.

Grounding (MALT) and Short-Circuiting (SC)

MALT/SC is the ultimate protection:

• It triggers a short-circuit cutoff in case of accidental re-energization.
• It provides a discharge path:
  • In case of residual energy release
  • In case of induced voltage
  • In case of lightning

MALT and SC are not mandatory in LV except in cases of induced voltage risk, re-energization risk or with long cable runs. Grounding is required in sensitive areas: metro, hospital, etc.

Once electrical lockout is complete:

1. The lockout supervisor hands the lockout certificate to the work supervisor (authorized B2 B2V).
2. The work supervisor orders the start of work to the performing electrician (authorized B1 B1V).
3. At the end of the work, the work supervisor hands the work completion notice to the lockout supervisor.
4. The lockout supervisor de-locks the installation and produces the de-lockout certificate.