Electrical isolation process flowchart (identify to re-energise)

What the electrical isolation process flowchart (identify to re-energise) process is

Electrical isolation is the work that happens before electrical work: taking a circuit from live to a state that is proved dead, secured against re-energisation and documented, so that the person opening the enclosure is protected by something other than an assumption. The trigger is a work request that names a point of work rather than a job title, because it is the point of work, not the job, that decides which conductors have to be dead. The chart below follows one isolation end to end: identifying the circuit and every supply that can reach it, deciding whether the work can be done dead at all, switching off and isolating at a device meant for isolation, locking off and posting a caution notice, proving the voltage indicator and testing at the point of work before proving the indicator again, applying earths where the voltage demands them, issuing the permit to work, and then unwinding the whole thing in the same order under the same control.

This chart is about electrical energy, and about one circuit at a time. It is not a general lockout/tagout procedure: a machine that also stores pneumatic, hydraulic, thermal, chemical or gravitational energy needs a multi-energy isolation procedure with its own energy source inventory, and this chart deliberately covers only the electrical half of that. It is also not the work method. What happens inside 'Do the work inside the permit limits' belongs to the job's own procedure. This chart marks the low-voltage/high-voltage fork at the earthing decision, but the switching programmes, approach boundaries and network control high-voltage jobs need belong to a high-voltage working procedure sitting above this one. Two boundaries are worth marking on your own copy: where isolation for maintenance hands over to the maintenance work order, and where a job that cannot be done dead leaves this chart altogether. Treat all of it as a starting point to be adapted under your organisation's own safety rules, the regulations that apply where you operate and review by a competent person.

Four decisions carry the process. 'Can the work be done dead?' sits in the Senior authorised person lane because it is a judgement about the system and about what the law allows, not a preference of whoever is holding the tools, and it is deliberately split in two by the follow-up, 'Is live work unreasonable to avoid?', so the case for working live has to be made twice before it is accepted. 'Stored energy or a second supply present?' sits with the isolator, the only person standing at the board, and it loops back to the isolation step rather than forward. 'Circuit proved dead?' decides whether anything else happens at all, and its failure branch runs all the way back to identification, because a circuit that reads live after a correct isolation was usually the wrong circuit or had a supply nobody drew. The last decision, 'Installation safe to re-energise?', sends defects back to the work under a re-issued permit rather than letting a deadline argue with an installation that is not ready.

What this flowchart covers

In this template

• Five swimlanes (Requester / job owner, Responsible manager, Senior authorised person, Authorised person / isolator and Competent person doing the work) across seven phases: identify, decide the method, isolate and secure, prove dead, earth and permit, work, and restore and verify
• The identification loop most isolation procedures assume away: "Identify the circuit and its supply sources" feeding "Circuit positively identified?", whose Doubt branch goes back to identification rather than on to a switch
• A two-stage live-working test rather than one yes or no: "Can the work be done dead?" hands anything that cannot to "Is live work unreasonable to avoid?", and an Unavoidable answer leaves the chart at "Control live work under a separate document"
• Isolation drawn as three steps in the isolator's lane: "Switch off and isolate at the correct point", "Lock off and post the caution notice", and a "Stored energy or a second supply present?" decision that loops back to isolation when the answer is Present
• Prove-test-prove as three rows, not one: "Prove the voltage indicator on a known source", "Test every conductor at the point of work" and "Re-prove the indicator on the known source", with a "Circuit proved dead?" branch that returns to identification when voltage is found
• Earths where the voltage demands them, "Issue the permit to work to the worker", who runs "Re-prove dead before touching the conductors", a "Testing needs the circuit re-energised?" decision issuing a test authorisation or sanction for test, and an unwind that cancels, removes earths and locks, and re-energises

When to use this template

• You are writing or reissuing a safe isolation procedure and need the identification, isolation, proving and permit steps agreed by everyone who touches them
• A near miss, a shock or a wrong-circuit isolation has been reported, and you need to see where the identification and proving steps actually failed
• You are training or authorising electricians and want one picture of what an authorised person does, what a competent person does, and where the two hand over
• Auditors or an insurer have asked how you control work on electrical systems, and the answer today is spread across a permit book, a rule book and habit
• You run low-voltage systems alongside high-voltage plant and need one chart that shows exactly where an isolation stops being routine and is handed to the high-voltage switching procedure

How it works

1. Rename the lanes to your roles

   This chart uses Requester / job owner, Responsible manager, Senior authorised person, Authorised person / isolator and Competent person doing the work. Most sites do not have all five. Where one person is both the isolator and the worker, merge those lanes and be honest about it, then decide what independent check replaces the handover you have just removed.

2. Write your own identification rule onto the first decision

   'Circuit positively identified?' means nothing until you say how. Name the drawings, schedules and labelling that count as evidence, say who may prove a circuit by switching it, and state what happens when the board's labelling and the drawing disagree. Add the second supplies your site actually has: generators, UPS, photovoltaic inverters and rings fed from both ends.

3. State the two tests for live working

   Live working has to clear three conditions together: that it is unreasonable for the conductor to be dead, that it is reasonable to work on it live, and that suitable precautions prevent injury. Write down the categories your organisation accepts, name who may authorise them, and record where that authorisation is written. A permit to work is not it: that document says the equipment is dead.

4. Name your isolation devices and your locks

   Say which devices count as points of isolation and which do not, because a local control switch or an emergency stop is neither. Then set the rule for locks and keys: one lock, one key, held by the person relying on it, multi-hasp where several people are protected, and a caution notice that names who applied it and when.

5. Put your prove-dead sequence on the chart

   Write down the instrument, the proving unit or known source, the points tested and the combinations tested, and the requirement to prove the indicator immediately before and immediately after. Test equipment should be made for the job: fused leads, finger barriers and minimal exposed metal at the probe tips. Then say who repeats the test at the point of work.

6. Decide your earthing and safety-document rules

   State the voltage at which earths become mandatory, where they are applied relative to the point of work and every point of isolation, and who records their positions. Then define the documents: what a permit to work covers, when a sanction for test or your own low-voltage test authorisation is used instead, who may issue and cancel each, and how a permit is returned and by whom.

7. Walk it against a real isolation

   Take two recent jobs, one routine and one where something went wrong, and trace them through the chart with the people who did them. Any step described in the room that is not drawn, and any box everyone admits they skip, is the finding worth acting on before you publish this as your own procedure.

Frequently asked questions

What are the steps in an electrical isolation process?

A work request names the point of work; the isolator identifies the circuit and every supply, and the authorised person decides whether the work can be done dead. Anything that cannot leaves this chart under a separate live-working authorisation. The outage is agreed, the circuit is isolated and locked off, and any stored energy or second supply is dealt with. The voltage indicator is proved, conductors are tested at the point of work, and the indicator is proved again. Earths are applied where the voltage demands them, the permit is issued, and the worker re-proves dead before touching anything. Work proceeds inside the permit limits; live testing runs under a test authorisation or sanction for test before dead work resumes. The permit is signed back, the installation is checked safe to re-energise, earths and locks are removed by whoever applied them, and the circuit is re-energised.

What does proving dead mean, and why prove the tester twice?

Proving dead is a test that the conductors at the point of work carry no voltage, made with an instrument you have just shown to be working. The sequence is prove, test, prove: check the indicator on a proving unit or a known live source, test the circuit, then check the indicator on the known source again. The second check is the one people skip and the one that matters, because an indicator that failed silently during the test would otherwise have shown exactly what a dead circuit shows. Test at the point of work rather than at the isolator, and test every combination the system can present, so induced voltage and back-feed are found rather than assumed away. The instrument matters too: a two-pole voltage indicator made for the purpose has fewer failure modes than a multimeter on the wrong range, and its leads should carry fuses, finger barriers and a minimal exposed tip.

Is electrical isolation the same as lockout/tagout?

They overlap but they are not the same thing. Lockout/tagout is the wider discipline of controlling every hazardous energy source on a machine before servicing it: electrical, pneumatic, hydraulic, thermal, chemical, and gravitational or stored mechanical energy such as springs and suspended loads. Electrical isolation is the electrical part of that, and it carries requirements the others do not, principally the requirement to prove the conductors dead with a tested instrument and, above a certain voltage, to earth them. In practice a machine isolation runs a multi-energy procedure with an energy source inventory, and this chart is what happens inside its electrical branch. Keeping them as separate documents is deliberate: it stops an electrical isolation being treated as a whole-machine isolation, which is how people are injured by the stored energy nobody listed.

When is it acceptable to work on a live circuit?

Rarely, and only against a written justification. In Great Britain the Electricity at Work Regulations 1989 set three conditions that must all be met before live work on or near a conductor where danger may arise: unreasonable in all the circumstances for it to be dead, reasonable for the person to be at work on or near it while live, and suitable precautions taken to prevent injury. In the United States, NFPA 70E takes a similar line: energised work is justified only where de-energising would add hazards or is infeasible, and it runs under a documented energized electrical work permit except exempt tasks such as testing, troubleshooting and voltage measuring by a qualified person. Fault-finding and commissioning that cannot be done dead is the usual case; schedule pressure is not one. This chart's permit to work states equipment is dead, so it never authorises live work.

Who may isolate a circuit, and who removes the lock and the earths?

Isolation is competent-person work, and most organisations formalise that by appointing authorised persons in writing for defined equipment and voltages, with a senior authorised person for high-voltage switching and for issuing safety documents. The rule that does the real work is custody: the person who applies a lock keeps its unique key and is the person who removes it, and where several people are protected the isolator is multi-hasped so the last lock off is the last person out. The same applies to earths, whose positions are recorded on the safety document, and to the permit itself, which is issued by the person who established the safe condition, returned by the holder and cancelled by the issuer once the site is clear. Removing somebody else's lock should be an exceptional, written, senior-authorised procedure, not something a supervisor does at the end of a shift.