LOTO (Lockout/Tagout) Procedure: A Step-by-Step Guide for Electrical Work

What is Lockout/Tagout and why does electrical work need it?

Lockout/Tagout (LOTO) is a method of controlling hazardous energy. A lock physically prevents an isolating device — a circuit breaker, switch, disconnector or valve — from being operated. A tag attached to the lock identifies the person or team working and warns others not to remove it.

Electrical work needs LOTO because electricity gives no warning. A circuit that was switched off can be switched back on remotely, back-fed from another source, or charged by a capacitor or induced voltage from a nearby live line. Relying on memory, verbal agreement or a notice on the door has caused serious injuries on many sites. A lock that only the worker can remove is a simple, reliable barrier.

What must be prepared before isolation starts?

• An up-to-date single-line diagram or schematic showing every possible source of supply, including standby generators, UPS, solar inputs and interconnections.
• A written isolation plan listing each isolation point, the method of isolation and the sequence.
• An approved permit to work or isolation certificate where your site system requires it.
• Personal safety locks with a unique key for each worker, and tags showing name, company, date and contact.
• A group lock box for jobs involving several workers or crews.
• A voltage detector rated for the system voltage, with a proving unit to check it before and after use.
• Portable earths where the work or the system voltage requires them.
• Competent, authorised persons for switching, isolation and testing.

What are the steps of an electrical LOTO procedure?

1. 1Prepare: review the drawings and isolation plan, and confirm the scope with everyone involved.
2. 2Notify: inform operators and anyone affected that the equipment will be shut down and locked out.
3. 3Shut down: stop the equipment using its normal controls so it is not isolated under load.
4. 4Isolate: open every isolating device identified in the plan, including control and auxiliary supplies.
5. 5Lock and tag: apply locks and tags at every isolation point. For group work, place the keys in a lock box that each worker then locks with their personal lock.
6. 6Release stored energy: discharge capacitors and release any mechanical energy such as springs in switchgear operating mechanisms.
7. 7Prove the tester: check the voltage detector on a known live source or proving unit.
8. 8Test for dead: test every phase to earth and phase to phase at the point of work.
9. 9Re-prove the tester: confirm the detector still works, so a faulty tester does not give a false dead reading.
10. 10Earth where required: apply portable earths at the point of work on high-voltage and other systems that require it.
11. 11Try: where safe and practical, attempt to start the equipment using normal controls to confirm it cannot operate, then return controls to off.
12. 12Record: record lock numbers, isolation points and test results on the isolation certificate or permit.

The test for dead is the step that actually protects the worker. Opening a breaker and locking it proves only that the breaker is open; it does not prove that the conductors you are about to touch are dead.

How does group lockout work for larger crews?

When many people work on the same isolated system, placing a personal lock on every isolation point quickly becomes impractical. In a group lockout, the isolating authority locks each isolation point with a set of numbered locks and places those keys in a lock box. Every worker then fixes their own personal lock to the lock box. The isolation cannot be removed until every personal lock has been taken off — which each worker does only when they are personally clear of the equipment.

Which electrical hazards are often missed during isolation?

• Back-feed from generators, UPS systems, solar inverters or interconnected panels.
• Separate control or heater supplies inside the same panel.
• Stored energy in capacitors, cable capacitance and battery systems.
• Induced voltage on de-energised lines running parallel to live circuits, common on overhead line and substation work.
• Incorrect or outdated labelling of breakers and feeders.
• Shared neutrals that can carry current even when the phase conductor is isolated.

In substations and on overhead transmission lines, induced voltage deserves special attention. A line that is isolated at both ends can still carry dangerous voltage if it runs close to an energised circuit, which is why working earths at the point of work are required in addition to the main isolation.

How do you safely remove locks and re-energise?

1. 1Confirm the work is complete and tools, materials and temporary earths have been removed.
2. 2Replace guards and covers, and close panels.
3. 3Account for every worker and move them to a safe position.
4. 4Each worker removes their own personal lock from the lock box.
5. 5The isolating authority removes the isolation locks and closes the permit or isolation certificate.
6. 6Notify affected people that the equipment is being re-energised.
7. 7Re-energise following the switching sequence, then check the equipment operates normally.

What happens if a worker leaves without removing their lock?

Your procedure must define a controlled lock removal process for this situation. Typically the supervisor must make every reasonable attempt to contact the worker, confirm they are not on site or inside the equipment, inspect the work area, and obtain written authorisation from a senior manager before the lock is cut. The worker must be informed before they return to work. Cutting locks without this process defeats the whole system.

What are the most common LOTO failures?

• Relying on switching off at the control panel instead of isolating at the true energy source.
• Sharing one lock between several workers.
• Skipping the test for dead or using an unproven tester.
• Using tags alone without locks where a lock can be fitted.
• Missing a second source of supply because drawings were not checked.
• Removing locks on behalf of absent colleagues.