Electric shock and arc flash kill and seriously injure workers every year. Unlike many workplace hazards, electrical energy is invisible — there is no visible warning before a contact becomes fatal. The electrical isolation permit to work is the document that forces everyone involved to confirm, before anyone starts work, that the system has been isolated, tested dead, and locked out against inadvertent re-energisation.
Getting this wrong doesn't just risk HSE enforcement. It risks lives. This guide covers the legal framework, the confirmed dead procedure, the roles of the Authorised Person and Competent Person, and the common failure modes that turn a routine job into a fatality.
The legal framework
Electrical isolation falls primarily under the Electricity at Work Regulations 1989 (EaWR), which impose absolute duties — there is no "so far as is reasonably practicable" defence for electrical work carried out on live systems where it was practicable to make the system dead.
| Legislation / guidance | Relevance |
|---|---|
| Electricity at Work Regulations 1989 | Regulation 13: work on or near dead conductors must confirm the system is dead; Regulation 14: no live working unless it is unreasonable for the work to be done dead and suitable precautions are in place |
| HSE Guidance Note GS38 | Guidance on test instruments and probes — specifies the standard for voltage testing equipment used to confirm dead |
| IET Wiring Regulations BS 7671:2018+A2:2022 | The national standard for electrical installations — relevant where work involves fixed wiring |
| Health and Safety at Work Act 1974 | Overarching duty of care to employees and others affected by the work |
Absolute duty: Regulation 13 of the EaWR is one of the few absolute duties in UK health and safety law. If an electrical system can practicably be made dead before work begins, it must be. There is no cost or inconvenience justification for live working where dead working is feasible.
The AP and CP roles
UK electrical safe systems of work are built around two defined roles. Both must appear on the electrical isolation permit.
Authorised Person (AP)
The AP is the person responsible for issuing the permit and authorising the isolation. They must have sufficient technical knowledge and experience to understand the system being isolated, to specify the correct isolation points, and to confirm that all necessary precautions are in place before signing. The AP is typically a senior electrical engineer, an electrical safety manager, or a person formally authorised in writing under a site electrical safety document.
Competent Person (CP)
The CP carries out the work. They must have the technical competence to perform the specific task safely within the limits defined by the permit. The CP accepts the permit from the AP, confirming they understand the isolation, the scope of work, and the conditions they must work within.
⚠ The AP and CP must be different individuals. The same person cannot both issue a permit and accept it as the person doing the work. This separation of roles is the control — if one person fulfils both, the independent oversight is lost.
The confirmed dead procedure: test before touch
The single most important control on any electrical isolation permit is the confirmed dead procedure — the formal sequence of steps that proves the system is not live before anyone touches it. The procedure must be recorded on the permit.
Step 1: Identify the correct isolation point(s)
Every supply to the system must be identified — including backfeed paths, UPS systems, capacitor banks, and generator supplies. A single isolation of the apparent main supply is not sufficient if there are alternative paths. The permit must list every isolation point.
Step 2: Isolate and secure
Each isolation point is switched off and locked in the off position with a padlock. Each padlock is individually owned — one lock per person working on the system, so that the system cannot be re-energised while any one person's lock remains in place. An isolation tag is applied at each point.
Step 3: Prove the test instrument is working
Before testing the isolated system, the voltage test instrument must be proved on a known live source. This is the critical step that HSE GS38 mandates — a test instrument that gives a false "dead" reading can kill. Prove the instrument works before trusting its reading.
Step 4: Test for dead
Test between all conductors — phase to phase, phase to neutral, phase to earth, neutral to earth — at the point where work will be carried out. All readings must confirm dead. A single non-zero reading means the system is not fully isolated.
Step 5: Prove the instrument again
After the dead test, prove the instrument on the known live source again. This confirms the instrument was working throughout the test and has not failed between the two proofs.
Confirmed Dead Procedure — Permit Checklist
- All supply points to the system identified, including backfeed and stored energy paths
- System isolated at all supply points — switches open and locked
- LOTO padlocks applied at each isolation point — one lock per person
- Isolation tags applied and displayed at each isolator
- Test instrument proved on known live source before testing
- System tested dead — all phases, neutral, and earth tested at point of work
- Test instrument proved on known live source after testing
Lock-out tag-out (LOTO): what the permit must record
LOTO is the physical implementation of isolation — it is not just a concept, it is a specific set of hardware steps that must be taken and recorded. The permit must confirm:
- Isolation points: Every switch, circuit breaker, isolator, or other device that has been opened to isolate the system, identified by panel number, circuit reference, or location
- Lock ownership: The name of every person who has applied a personal padlock to a LOTO hasp at each isolation point
- Tag information: What the tags say, when they were applied, and by whom
- Stored energy: Whether capacitors have been discharged, whether UPS bypass has been confirmed, whether any mechanical energy stores (springs, counterweights) have been secured
If multiple people are working on the same system, each person must apply their own padlock. The hasp allows multiple locks — the system cannot be re-energised until every lock has been removed, which means every person must have confirmed they are clear of the system.
Arc flash: the hazard the permit must address
Arc flash — the release of energy from an electrical fault — produces temperatures exceeding 20,000°C, a pressure wave, molten metal, and intense UV radiation. Arc flash incidents cause severe burns, blast injuries, and fatalities at distances of several metres from the fault point.
Even on a correctly isolated system, arc flash risk may be present during the isolation process itself — switching under load, operating circuit breakers, or working near adjacent live conductors. The permit must specify:
- Whether any part of the work requires approach to or operation of live equipment
- The arc flash PPE required for any such approach (minimum flash-rated face shield, arc-rated coveralls, insulating gloves rated to the system voltage)
- The incident energy level at the point of work, if a formal arc flash study is available
PPE is the last resort: Arc flash PPE does not prevent an arc flash — it limits the injury. The primary control is correct isolation and confirmed dead procedure. PPE protects against residual risk only.
What an electrical isolation permit must include
Electrical Isolation Pre-Authorisation Checks
- Isolation confirmed at all relevant supply points — including backfeed and stored energy
- Equipment tested dead with calibrated test instrument (proved before and after)
- LOTO devices applied — padlocks and tags in place at every isolation point
- Isolation certificate signed and displayed at the isolator
- Stored energy sources identified and discharged or mechanically secured
- All personnel briefed on isolation boundaries and limits of the permit
Common mistakes to avoid
- Testing dead without first proving the instrument. A faulty test instrument gives a false "dead" reading. Prove before and after — every time, without exception.
- Single-point isolation on a system with backfeed. Isolating at the main board does not isolate a system that has a local generator, UPS, or a supply from a neighbouring circuit. Every feed path must be identified and isolated.
- Verbal isolation — no locks, no tags. Switching off a circuit breaker and telling the operator "it's off" is not isolation. Without a lock, anyone can re-energise the system. Physical locking is mandatory.
- Using a single shared padlock. If multiple people are working on the system, each person must have their own lock. A single shared lock that one person removes means the system can be re-energised while others are still on it.
- Not recording stored energy. Capacitor banks, UPS batteries, and spring-loaded mechanisms can retain lethal energy after the main supply is isolated. These must be identified, discharged, and confirmed on the permit.
- Assuming an adjacent system is also isolated. The scope of the permit covers only the system identified. Adjacent panels and circuits may be live. The permit must clearly define the isolation boundaries.
Download a free electrical isolation permit template
We've produced a free Electrical Isolation Permit to Work template in Word (.docx) format, available in both a pre-filled version (standard hazards and controls already populated) and a blank version.
Electrical Isolation Permit to Work — Free Template
Covers the Electricity at Work Regulations 1989 and HSE GS38. Pre-filled with standard LOTO controls, confirmed dead checks, and arc flash PPE. Editable Word (.docx) format.
For all permit types, visit the templates page.
Beyond paper: managing electrical isolation permits digitally
Electrical isolation incidents often come down to a failure in the permit process — a step missed, a boundary misunderstood, a lock not applied. Paper permits cannot enforce sequence or flag incomplete steps. PermitDesk generates electrical isolation permits digitally, with the confirmed dead checklist built in, the AP and CP sign-off captured as named digital signatures, and a full timestamped audit trail automatically stored.
Issue your first electrical isolation permit in under 2 minutes
PermitDesk handles the drafting. The AP and CP sign off digitally. Full audit trail included.
Start your free 14-day trialRelated reading
→ What is a permit to work? A plain-English guide
→ Hot Works Permits: a complete guide for site managers
→ Working at Height Permits: WAH Regs 2005, rescue plans & harness inspection
→ Confined Space Entry Permits: atmospheric testing & standby person requirements
→ Excavation & Ground Works Permits: CDM 2015 & service strikes
→ Lifting Operations Permits: LOLER 1998 & Appointed Person duties