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Managing Electrical Risks

Electrical Hazards​

Electricity is essential on construction sites but presents serious hazards:

Electric Shock:

  • Current passes through body
  • Can cause death, severe burns, falls from height
  • Low voltages (< 50V AC/120V DC) generally safe, but not always
  • 230V AC (standard power) can kill

Arc Flash and Burns:

  • Electrical faults create intense heat and light
  • Severe burns, eye damage, ignition of materials

Fire and Explosion:

  • Faulty wiring, overloaded circuits
  • Ignition of flammable materials/atmospheres

Secondary Injuries:

  • Falls from height after shock
  • Injuries from muscle contractions

[!warning] Fatal Risk Electricity kills quickly. Even brief contact with live parts can cause cardiac arrest.

Who Has Duties?​

PCBUs​

Must:

  • Ensure electrical equipment safe
  • Maintain electrical installations
  • Use licensed electrical workers for electrical work
  • Provide RCDs (residual current devices)
  • Test and tag equipment
  • Manage risks from overhead/underground electrical services

Licensed Electrical Workers​

Only licensed electricians may perform electrical work (installation, alteration, maintenance, repair of electrical equipment).

Exceptions (general workers may perform):

  • Replacing lamps, fuses
  • Plugging/unplugging equipment
  • Resetting RCDs or circuit breakers

Risk Management Process​

1. Identify Hazards​

Construction Site Electrical Hazards:

  • Overhead powerlines
  • Underground cables
  • Temporary site wiring
  • Damaged cables and equipment
  • Wet conditions
  • Metal scaffolding near electrical sources
  • Inadequate RCD protection

2. Assess Risks​

Higher Risk Situations:

  • Contact with overhead powerlines (cranes, EWPs, scaffolding, long materials)
  • Excavation near underground cables
  • Wet/damp environments
  • Use of metal ladders or scaffolding
  • Damaged or poorly maintained equipment

3. Control Risks: Hierarchy of Control​

Level 1: Elimination

  • Eliminate need for electrical equipment (use battery/pneumatic tools)
  • De-energize powerlines before work near them

Example: Request electrical utility to isolate and earth overhead lines before crane operation.

Level 2: Substitution/Engineering

Isolation and Earthing:

  • De-energize electrical equipment before work
  • Lockout/tagout procedures
  • Earthing of de-energized systems

Insulation:

  • Insulated cables and equipment
  • Insulation barriers around live parts
  • Insulated tools for electrical work

Residual Current Devices (RCDs):

  • Detects leakage current, disconnects power instantly
  • Mandatory for construction sites (WHS Reg 164)
  • 30 mA maximum for socket outlets supplying equipment

Double Insulation:

  • Equipment with extra layer of insulation
  • Marked with double square symbol
  • Reduces shock risk

Extra-Low Voltage (ELV):

  • Systems ≤50V AC or ≤120V DC
  • Reduced risk of electric shock
  • Example: 12V or 24V power tools

Physical Barriers:

  • Guards around switchboards, junction boxes
  • Fencing/barricades around substations
  • Covers over floor boxes

Level 3: Administrative/PPE

  • Safe work procedures
  • Electrical safety training
  • Permit systems for work near live parts
  • Exclusion zones around overhead powerlines
  • PPE (insulated gloves, dielectric footwear) - for electrical workers only
  • Safety Observers: Must be competent to rescue and resuscitate (assessed in previous 12 months) for energized work.

4. Maintain and Review​

  • Regular testing and inspection
  • Test and tag portable equipment
  • RCD testing (push test button monthly, full test every 6 months)
  • Replace damaged cables immediately

RCDs (Safety Switches)​

How RCDs Work: Monitors current flow. If imbalance detected (leakage to ground through person), disconnects power within 30 milliseconds.

Types of RCDs​

Switchboard RCD unit Figure: Switchboard RCD unit

Fixed socket outlet RCD unit Figure: Fixed socket outlet RCD unit

Portable RCD fitted directly to power cable Figure: Portable RCD fitted directly to power cable

Portable RCD protected power board Figure: Portable RCD protected power board

Requirements for Construction:

  • RCD protection for all socket outlets supplying portable equipment
  • Portable RCDs if fixed RCDs not available
  • Test before each day's use (push test button)

[!important] RCDs Save Lives RCDs are the primary protection against electric shock on construction sites. Never bypass or disable.

Overhead Powerlines​

Extreme Risk: Contact with overhead powerlines causes many construction fatalities.

Affected Activities:

  • Crane operations
  • Elevated work platforms
  • Scaffolding erection
  • Carrying long materials (pipes, ladders, formwork)
  • Tipping trucks (raised bodies)
  • Tree work

Safe Approach Distances​

For voltages ≤132,000V:

  • Non-electrical workers: Maintain safe approach distances as determined by the electricity supply authority (typically 3 meters, check local regulations)
  • Licensed electrical workers: Refer to AS/NZS 4836

For voltages >132,000V:

  • Greater distances apply - check with electrical authority

[!warning] Increased Distances for Equipment When operating plant, increase distance to 6 meters or more. Account for boom swing, load sway, vehicle movement.

Control Measures​

Preferred (Level 1):

  • De-energize and earth powerlines for duration of work

If De-Energization Not Practicable:

  • Install physical barriers (goal posts, height markers)
  • Appoint spotter to watch clearances
  • Use insulated/non-conductive equipment
  • Establish exclusion zones
  • Continuous communication between spotter and operator

Example: Crane work near powerlines - Request utility to de-energize lines, or install goal post barriers and appoint dedicated spotter.

Underground Cables​

Risk: Striking underground cables during excavation causes electrocution, burns, explosions.

Before Excavating:

  1. Dial Before You Dig (1100) - Obtain service location plans
  2. Locate services on ground (use plans, cable locators)
  3. Mark services clearly (paint, pegs)
  4. Expose services carefully (hand dig within 500mm)
  5. Inspect services (confirm type, depth, condition)
  6. Support and protect services during work

[!important] Always Dial Before You Dig Free service provides plans showing underground services. Call 1100 at least 2 business days before excavating.

Safe Excavation Procedure​

  • No mechanical excavation within 500mm of marked services
  • Hand tools only (spades, shovels - not picks or mattocks)
  • Assume unidentified cables are live
  • Locate all services even if only one type expected
  • Support services crossing trenches
  • Restore covers before backfilling

Temporary Site Wiring​

Installation:

  • Licensed electrician only
  • Adequate capacity for loads
  • Protected from damage (elevated or buried)
  • RCD protection on all socket outlets

Cables:

  • Heavy-duty flexible cables (not domestic cable)
  • Supported off ground where practical
  • Protected from traffic, plant, sharp edges
  • No joins in cables (use correct length)

Switchboards:

  • Weather-protected enclosures
  • Secured to prevent movement
  • RCDs installed and labeled
  • Accessible for testing/maintenance

Test and Tag​

Portable electrical equipment must be regularly tested and tagged:

Visual Inspection:

  • Damage to cables, plugs, casing
  • Strain relief intact
  • Correct rating for use

Electrical Testing:

  • Earth continuity
  • Insulation resistance
  • RCD function (if built-in)
  • Conducted by competent person

Testing Frequency:

  • Construction sites: Every 3 months (high-risk environment)
  • Other workplaces: 6-12 months depending on environment

Tagging:

  • Tag shows test date, next test due, tester details
  • Do not use untagged equipment

Wet Conditions​

Increased Risk: Water conducts electricity - wet conditions greatly increase shock risk.

Controls:

  • Keep equipment dry (covers, shelters)
  • Use waterproof equipment rated for wet use (IP rating)
  • Use 10mA portable RCDs
  • Extra-low voltage tools (12V/24V)
  • Delay work until conditions dry where possible

Damaged Equipment​

Never use damaged electrical equipment:

  • Frayed or cut cables
  • Broken plugs or sockets
  • Cracked casings
  • Damaged switches

Action:

  • Tag as defective ("DO NOT USE")
  • Remove from service
  • Arrange repair by electrician or disposal

Practical Construction Example​

Scenario: Installing steel formwork near 11kV overhead powerlines

Hazards Identified​

  • Formwork panels 3.6m long (unwieldy)
  • Overhead powerlines 5m above ground
  • Risk of contact during lifting/placing
  • Metal formwork conducts electricity

Risk Assessment​

  • Extreme risk: Powerline contact = electrocution, arc flash

Controls Implemented​

Engineering (Level 1):

  • Powerlines de-energized by electrical utility for 4-hour work period
  • Isolation confirmed and earthed

Administrative:

  • Permit to work issued by utility
  • Work scheduled within de-energized period
  • All workers briefed on powerline location
  • Spotter assigned to monitor work area

If De-energization Not Available: Would implement:

  • Goal post barriers at 6m from powerlines
  • Spotter with authority to stop work
  • Pre-assembled formwork on ground to minimize lifting near lines
  • Exclusion zone barricaded

Result​

Work completed safely with powerlines de-energized. Zero risk of electrical contact.

Information and Training​

Workers must know:

  • Risks of electricity
  • How to identify electrical hazards
  • Importance of RCDs and how to test
  • Not to use damaged equipment
  • Overhead and underground powerline risks
  • Who to contact if electrical issues arise
  • Emergency response to electric shock

Emergency Response - Electric Shock​

If someone receives electric shock:

  1. Do not touch the person if still in contact with electricity
  2. Turn off power at switchboard if safe to do so
  3. Call 000 immediately
  4. If power cannot be turned off, use non-conductive material (dry wood) to separate person from source
  5. Begin CPR if trained and person not breathing
  6. Continue until ambulance arrives

[!warning] Do Not Touch Do not become a second victim. Never touch someone in contact with electricity until power disconnected.