Electrical Safety and Hazards

These instructions cover basic safety principles applicable to persons working on, near or in the vicinity of electrical equipment and installations.  Most aspects apply to all trades.

How electrical current affects the human body

Of all the common utilities, electricity has the greatest potential and ability to cause serious injury and kill.  Electricity is invisible – this in itself makes it dangerous.  Even very short exposures to 240 volts can result in critical electric shock, arc flash burns and other serious injuries.

Three primary factors affect the severity of the shock a person receives when he or she becomes part of an electrical circuit:

• Amount of current flowing through the body (measured in milliamps).
• Path of the current through the body.
• Length of time the circuit flows through the body.

Other factors that may affect the severity of the shock are:

• The voltage of the conductor.
• The presence of moisture in the environment.
• The phase of the heart cycle when the shock occurs.
• The general health of the person prior to the shock.
• Conductivity or insulation resistance of the skin and body. Skin resistance is significantly reduced by dampness or sweat.

Effects can range from a barely perceptible tingle to severe burns and immediate cardiac arrest.  Although it is not known the exact injuries that result from any given current, the following table demonstrates this general relationship for a 50-cycle, hand-to-foot shock for a duration of one second:

The effect is worsened by the fact that the human body’s resistance to electrical current decreases with increasing current and/or duration of exposure.  High voltage electrical energy greatly reduces the body’s resistance by quickly breaking down human skin.  Once the skin is punctured, the lowered resistance results in massive current flow.

WARNING:      LOW VOLTAGE DOES NOT IMPLY LOW RISK!

When muscular contraction caused by stimulation does not allow the victim to free themselves from the circuit, even relatively low voltages can be extremely dangerous, because the degree of injury increases with the length of time the current flows through the body.  100mA for 3 seconds is the equivalent of 900mA for 30 milliseconds in causing fibrillation.

Note that a difference of less than 100 milliamps exists between a current that is barely perceptible and one that can kill.

Work de-energised (except for testing)

Undertaking electrical work on energised electrical equipment is only permitted in very limited and highly controlled circumstances.  No person is permitted to work on energised circuits and equipment except for the activities listed in that policy and then the work is governed by strict conditions – even for “live testing”.

Note: testing for de-energised is energised electrical work and shall only be performed by a suitably qualified person.

When working on or near live electrical equipment it is critical to ensure that you are not exposed to possible contact with live conductors.

• Conduct a Risk Assessment and use a SWMS when testing for de-energised.
• The equipment you work on must be de-energised and isolated.
• Follow full isolation procedures.
• Adjacent equipment should also be de-energised or separated by design or segregated and protected by use of insulated shrouding of any live conductors to prevent inadvertent contact.

Do not assume that electrical equipment is de-energised after isolation.

• Always regard conductors, switchgear and electrical equipment as being ENERGISED until YOU have proved them dead by means of approved and appropriate test equipment.

TEST EVERY TIME BEFORE YOU TOUCH

Remember Life Saving Rule #2

I will always ‘Test Before I Touch” and confirm DEAD before work

• Test equipment should be rated to the required class for the test being carried out and must be in good working order and checked for correct operation immediately before and after use.
• Testing must be undertaken prior to work commencing and before touching any bare conductor – this particularly applies where the electrical service is still connected.
• Use auto-sensing multimeters to reduce the risks of mixed voltages.
• Workers must be appropriately trained and competent in the isolation testing procedures and in the use of testing equipment.

This philosophy applies equally to other energy sources.

General electrical safety procedural guidelines

• Electrical installation work is to be carried out in accordance to relevant Australian Standards and in particular AS3000 Wiring Rules.
• Temporary wiring and electrical practices on construction & demolition sites is to AS3012.
• All exposed potentially live conductors within 500mm of your extended reach (including tools and objects you might be holding) from your work area should be shielded to prevent inadvertent contact unless they are proven to be effectively electrically isolated. This isolation and shielding includes the full depth of the drop zone.
• Do not work on live mains, switchgear or equipment unless you meet the rules for energised work detailed in the no live work policy.
• Ensure PPE utilised matches the electrical risks and equipment fault rating.
• Various forms of shielding can be used including perspex sheeting, insulated mats or plastic sheeting temporally fixed to preclude access and stop objects from falling or going into the space. Aim for IP2x as a minimum whilst working.
• Terminate any bare conductors that may potentially become energised.

Never assume an exposed conductor is dead –

TEST EVERY TIME BEFORE YOU TOUCH

Voltage

There have been and continue to be more electrical fatalities throughout Australia from low voltage electrocutions than from contact with high voltage conductors.

While not especially dangerous to the average healthy person, extra low voltages can also cause shocks and burns and be hazardous to a susceptible person.  No person can afford to be complacent about working on energised conductors at any voltage.

1. The voltages generally encountered at a workplace are as described in AS3000 and will fall into one of the following categories:

• Extra low voltage, ELV – Not exceeding 50 Volts AC or 120 Volts ripple-free DC
• Low voltage – Exceeding ELV but not exceeding 1000 Volts AC or 1500 Volts DC
• High voltage – Exceeding low voltage.

2. Before commencing work on any electrical apparatus at any of these voltages, ensure that a properly planned and safe approach can be adopted, preferably in accordance with an approved SWMS and any Compliance Code.

High voltage work

Access regarding work on or near their high voltage electrical installations is subject to relevant State Legislation, Codes and/or Australian Standards.  Any works associated with High Voltage installations must be conducted in accordance with those requirements and specific information and guidelines for working on high voltage equipment and installations are available from the applicable electricity network operator.

When you are working in the vicinity of live exposed conductors you must not come within the minimum safe working distances for nominal network voltages.  Also be aware of induced currents and voltages such as when removing earths and breaking bonds.

Persons who intend to or are required to work on high voltage equipment after switching, isolation, short circuiting (bonding) and earthing must be appropriately instructed and provided with an access permit issued by an appropriately trained and authorised person (High Voltage Switching Operator).  Care must be taken to ensure that equipment is isolated on both the high and low voltage sides.  For more information please contact  NECA or your local electricity network operator.

Electric shock

In the case of electric shock, it is a priority that the casualty be disconnected from the electrical source, preferably by removing the cause from the casualty, rather than the casualty from the cause.  It is essential to check for danger, before commencing treatment.

Call 000 or 112 (mobile only) for an ambulance as soon as possible and follow emergency plan procedures.

Although there are several possible causes for persons being unconscious at work, electric shock is among the more common causes, and Cardio-Pulmonary Resuscitation (CPR) is the usual first treatment.  A casualty may also receive significant burns and these may be internal and greater than they appear on the surface.  Cool the surface burns with clean water for an extended period (typically up to 30 minutes) and cover burns with non-stick dressing.

Electric shocks received in the workplace are reportable to the safety regulator in your jurisdiction and it is important to seek immediate medical attention.  An electrical shock may cause serious burning and damage of internal organs as well as on the skin and will likely require hospitalisation.

Conductive materials

Regarded all materials, including liquids and gases as conductive unless there is definite knowledge to the contrary.  It should be noted that:

• Earth, concrete and wet or damp timber is conductive.
• Flame conducts electricity and care must be taken when using flame producing tools and equipment.
• Metallic products, such as portable radios and telephone units with telescopic aerials, rulers, tapes, torches and the like must be handled with care to avoid contact when working near live circuits.
• Certain apparel, such as metallic belts and zippers, metallic threads, studs, and jewelry such as rings, ear rings, facial rings/studs, neck chains and bracelets, are hazardous when working near live circuits and equipment.
• The liquid contained in some types of fire extinguishers are conductors.

Working on neutral and earth conductors

Always treat the neutral as an active conductor.  To energise and de-energise mains and apparatus involving a neutral conductor, when connecting and disconnecting mains and apparatus, the neutral conductor must be connected first and disconnected last.

There are fault situations where the neutral and/or earth conductors can carry a dangerous voltage.  In particular, if you cut the neutral and it has been used (incorrectly) as the return path for a second sub-circuit then it may rise to 240 volts.  Also, the voltage coil on the electricity meter provides a connection from active to neutral which remains even when the main circuit breaker is switched off.  If the neutral is disconnected from the network due to a fault and the earth is disconnected from ground there may well be 240 volts on the neutral and earth side.

Whenever equipment is energised, an earth conductor or bond should not be disconnected as under fault conditions the earth cable and equipment could become live.  There can also be induced voltages.

Cutting conduits or cables

When cutting existing conduits or cables, the cable must be treated as energised and the procedures for working on energised electrical equipment adhered to, until positive tests can be made to prove that the cable is de-energised at the cutting point.  For conduits, use insulating gloves and a screw-feed tubing cutter: set the depth so as not to cut the cable insulation inside.  Always check physically that no other cable exists within the same conduit.  If not sure: then don’t cut it – it could be live.

Working near live conductors

For licensed low voltage electrical work, “Near” is effectively 500mm within the reach of movement of body plus objects or tools you might be holding, and in the full drop zone.  Try to have equipment to IP2x standard, as a minimum.  Isolate as much as possible and use the appropriate PPE:

• Approved type Insulating Gloves should be worn when working near exposed live circuits and equipment. Test before use.
• Approved Insulating Mats, Shrouds and Hose (Tiger Tails – warning only) must also be used when working adjacent to exposed live circuits and equipment in order to insulate or separate the worker’s body from Earth and Electrical Energy. When used, these items shall be securely fixed to prevent their displacement.
• If potential for high fault currents, refer to the section on Arc Flash Protection.

Where there is an opening (e.g. to or within a cabinet) to where there are exposed energised conductors, the opening should be covered or shielded, e.g. by temporarily fixing plastic sheeting to stop inadvertent entry.

Current transformer circuits

The secondary circuit of a current transformer (CT) shall not be opened whilst the primary circuit is live unless the secondary winding has been short-circuited.  Failure to do this can product a dangerous voltage at the secondary terminals.  CT secondary windings must be short-circuited and earthed before test voltages are applied to the primary circuit.

Warning – auxiliary circuits and alternate sources of supply

• Care must be taken to properly identify circuitry before isolating to ensure satisfactory precautions are made regarding all potential sources of power. Auxiliary circuits or functions such as UPSs, automatic sequence starting, fail-safe start-up systems, remote control systems, emergency power supply systems, and other technologies such as Wind or Solar may override a single isolation. Remember that the point of supply shown on the circuit diagram and labelling may be in error.  Check and test thoroughly for potential secondary sources of supply.
• Solar power systems should be isolated and it should be recognised that a photovoltaic / solar panel array has a voltage output at all times when exposed to sunlight. Inverters and power factor correction units will need to be discharged even after they have been isolated as they may have a charge stored in any internal capacitors.

Installation and refurbishment of electrical services/equipment

• Coordinate with Builder/Client in regard to services that are to be disconnected or rearranged to ensure a minimum shutdown.
• Submit a request for interruption of services to the appropriate person or persons, if required.
• Proceed with works only after approval has been given.
• Carry out effective isolation, lockout, tag-out and test.

WARNING:  Failure to carry out effective isolation as described in the section on Isolation, or to remove any isolation, lock or tag without authority may result in termination of employment.

Remember Life Saving Rule #1

I will always Lock and Tag out all energy sources

Remember Life Saving Rule #3

I will never remove another person’s Danger tag without written authorisation

Removing out-of-service electrical equipment

When removal of out-of-service or decommissioned electrical equipment is required, the equipment must the isolated from supply and appropriate tests made to ensure the equipment is de-energised.  Further tests must be made at any point that a cable is to be cut.  Terminate the cable if it is not to be removed.

Restricted electrical workers (REW) licence

Trades persons that have a REW licence to work on low voltage equipment are permitted to fault find on the equipment and perform a disconnect-reconnect at or near to the equipment for which they are licenced for the disconnection and reconnection of ‘like for like’ equipment, for the purposes of repair, replacement or maintenance.  It is the role of a fully licenced electrician to provide the wiring from the switchboard and to do the initial connection, test and certification.

Other electrical safety issues

Other electrical safety issues for all workers/trades include:

• Dangers of unearthed split metal conduits in ceiling and underfloor spaces, particularly when disturbed. It is strongly recommended that you isolate the power off on such old installations, prior to entering the particular space.
• Another problem with these older installations is the aging of Vulcanized India-Rubber (VIR) insulation. It can be perished and crumbles when moved during repair or renovation. Such installations should be rewired, and at least be protected by an RCD.
• Dangers of cutting metal water pipes where the neutral/earthing has failed. Serious problem for Plumbers – use a solid jumper lead across the cut to retain electrical continuity. If there are indications of electrical voltage, then stop work and call an Electrical Contractor.

Re-energising the circuit after lockout and tag-out

The lock preventing operation of the fuse-switch or circuit breaker will only be removed as follows:

• When the cabling and connected equipment is inspected and tested as safe to be energised.
• When all locks and danger tags have been appropriately removed (in line with processes and policies on danger tag removal) from the isolation point, fuse-switch or circuit breaker.

Complete and submit any electrical installation Certificate of Compliance as required for your jurisdiction.

REMEMBER – PROVE IT DEAD.

• Planning, preparation and risk assessment.
• Identify all relevant circuits and energy sources.
• Record phase rotation if required, prior to de-energising.
• Ensure the relevant equipment has been shut-down.
• Isolation switches are to be tagged and locked “OFF”.
• All electrical equipment/circuits are to be inspected and tested to ensure they are “DE-ENERGISED” (OFF).
• Shield exposed conductors prior to commencing work – maintain a clearance of 500mm from any exposed conductors at all times and protect all drop zones that may have exposed conductors.
• Various forms of shielding can be used including Perspex sheeting, insulated mats or plastic sheeting temporally fixed to preclude access and stop objects from falling into the space.
• Prior to energisation and on completion of the works, a visual check of work area is to be done to ensure that all tools and waste has been removed from switchboards, electrical enclosures, etc.
• All new electrical works are to be inspected and tested to the requirements of AS3000 prior to energisation – refer to AS3017. All existing electrical works shall be checked for correct phase rotation prior to energisation.
• All new electrical works are to be tested upon energisation to ensure correct polarity, phase rotation and operation.
• Update circuit schedules in electrical distribution boards and control panels and provide appropriate labels.
• Complete, sign-off the relevant safety certificate for your jurisdiction for – electrical work.
• Make sure that any unfinished work is made safe before leaving the job, eg check for exposed conductors and terminate all prior to energising.

Never assume an exposed conductor is dead

– TEST EVERY TIME BEFORE YOU TOUCH.