Power Factor Correction Capacitor Bank SWMS

Power factor correction capacitor bank installation and commissioning is high risk construction work in New South Wales because the work is carried out on or near energised electrical installations, and section 291 of the Work Health and Safety Regulation 2025 (NSW) captures it under the energised electrical category. A safe work method statement is required under section 299. SafeWork NSW is the regulator. AS/NZS 3000 governs the installation, AS/NZS 61439 the assembly, and AS 2897 the capacitor equipment itself.

A capacitor bank is the only piece of switchboard equipment in common use that **stores lethal energy as its function**. Every other component in the board is dangerous because it is connected to a source; a capacitor is dangerous because of what it is. Open the main switch and the board goes dead — the bank does not. It holds its charge, and it holds it in a can the size of a milk carton that gives no external indication of what is inside it. The trade has a habit of treating isolation as the moment safety begins. On this equipment, isolation is the moment the countdown begins.

And then the mechanism that catches even careful electricians: **voltage recovery**. A capacitor discharged to zero and confirmed at zero will climb back toward a hazardous voltage over the following minutes, on its own, with nothing connected to it. This is dielectric absorption — charge trapped in the dielectric migrating back to the plates after the surface charge has been drained. It is not a fault, it is physics, and it means a single proof of zero proves nothing about the next five minutes. Earths stay applied for the duration of the work, not just for the proving. This SWMS is authored around stored charge, recovery, the discharge resistor that fails invisibly, and the PCB dielectric fluid in cans manufactured before the late 1970s.

Hazards identified

14 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Isolate, then **discharge through the designed discharge path and prove the capacitors at zero at their own terminals** — never at the switch, never by assumption. A capacitor bank stores lethal energy as its function; the main switch does not touch it.
2. 2**Apply earths and leave them applied for the whole duration of the work** — a capacitor proved at zero recovers voltage over the following minutes by dielectric absorption, so one proof of zero proves nothing about the next five minutes. Re-prove after every break and before every re-approach.
3. 3Verify each capacitor's discharge resistor and prove the discharge actually occurred at the terminals — **a failed discharge resistor is invisible, and waiting is not proof**; time only works if the discharge path is intact, which is precisely what the failed resistor is not.
4. 4Obtain an arc flash risk assessment establishing incident energy and approach boundaries at the actual board, verify upstream protection and its settings, and close the door for any test that can be done closed.
5. 5Complete installation, termination and verification dead under Part 4.7 Div 4 ss.154 & 157; carry out step-testing that genuinely requires energisation under a documented method with a competent person and a second person present who can isolate and perform rescue.
6. 6Verify the bank's harmonic environment and detuning reactors against the actual network before energisation, confirm ventilation and ambient limits, and never energise a bank showing bulging, discolouration or venting.
7. 7Establish the manufacture date of every existing can before disturbance — **cans manufactured before the late 1970s are presumed to contain PCB dielectric until proven otherwise** — and handle, transport and dispose of them as scheduled waste under the POEO Act 1997 (NSW).
8. 8Sequence step switching to the designed timing with contactors and their pre-insertion resistors verified, and keep persons clear of the board during first energisation and step testing.
9. 9Confirm the detuning arrangement matches the site's harmonic profile before energisation and monitor for overload, overheating and audible resonance during commissioning, de-energising on any anomaly.
10. 10Verify termination torque, clearances and can condition before energisation, provide extinguishers appropriate to electrical fire outside the switchroom, and thermographically survey the bank under load at commissioning.
11. 11Confirm egress from the switchroom is clear and known before opening any board, work with a second person present, and never work alone in a switchroom with live equipment.
12. 12Handle leaking or ruptured cans with chemical-resistant gloves and eye protection over containment, keep dielectric fluid out of drains, and treat any release as a reportable environmental incident.
13. 13Assess noise exposure against the exposure standard by a competent person, limit and rotate occupancy of the switchroom during runs, and select hearing protection to the measured level to AS/NZS 1270.
14. 14Use mechanical aids and two-person handling for cans, reactors and enclosure sections, stage material at the point of use, and rotate tasks in restricted switchroom space.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

A commissioning electrician is fault-finding a PFC bank that has been tripping a step. He isolates the board, waits, opens the bank's door and discharges the step he is interested in through his discharge stick. He proves it at zero at the terminals — correctly, with a proving unit checked before and after. He begins work. Eleven minutes later he reaches back into the same step to reseat a fuse and receives a fatal shock from the capacitor he personally proved dead. The investigation identifies dielectric absorption. The discharge stick drained the surface charge and the meter read zero, truthfully. Over the following minutes, charge trapped within the dielectric migrated back to the plates and re-established a hazardous voltage on a capacitor with nothing connected to it. The can had no discharge resistor across it — the step's resistor had failed open, which is why the step was tripping, and which is why nothing was bleeding the recovered charge away. Two mechanisms, both published, both invisible from the outside, and both defeated by the same control: **earths applied and left applied for the duration of the work**. The contractor's SWMS said 'isolate, discharge, prove dead'. Every one of those steps was performed. SafeWork NSW's position was that the SWMS described a sequence for a moment in time and the hazard was continuous — and that a document written for capacitor work that does not name voltage recovery has not addressed the equipment it is written for. This SWMS names it, requires earths for the duration, and requires the discharge to be proved to have occurred rather than assumed from the clock.

Related legislation

• Work Health and Safety Act 2011 (NSW) — primary duty of care (s19), consultation (s47), notifiable incidents (ss35–38), industrial manslaughter (s26A)
• Work Health and Safety Regulation 2025 (NSW) — HRCW (s291), SWMS content and requirement (s299), SWMS review (s302)
• Work Health and Safety Regulation 2025 (NSW) — Part 4.7 Division 4, sections 154 and 157 — prohibition on energised electrical work
• Protection of the Environment Operations Act 1997 (NSW) — PCB dielectric fluid as scheduled waste; offences for discharge to land or waters
• Electricity Supply Act 1995 (NSW) and the licensing framework administered by NSW Fair Trading — electrical work licensing

Frequently asked questions