RCD’s & managing electrical risks in the workplace
A residual current device, or safety switch, protects you from the most frequent cause of electrocution. Which is a shock from electricity passing through the body to the earth. It can also provide some protection against electrical fires.
RCDs are electrical safety devices designed to immediately switch off the supply of electricity when electricity leaking to earth is detected at harmful levels. They offer high levels of personal protection from electric shock.
According to Safework Australia workplace injuries and fatalities can be prevented. This is by the use of properly installed and maintained residual current devices.
You may need to seek technical advice from a competent business such as Spark Safety Solutions about the kinds of RCDs that are right for your workplace.
What are electrical risks?
Electrical risks are risks of death, electric shock or other injury caused directly or indirectly by electricity.
The most common electrical risks and causes of injury are:
- electric shock causing injury or death. The electric shock may be received by direct or indirect contact. And then tracking through or across a medium, or by arcing. For example, electric shock may result from indirect contact where a conductive part that is not normally energised becomes energised due to a fault (eg metal toaster body, fence).
- arcing, explosion or fire causing burns. Injuries are often suffered because arcing or explosion or both occur when high fault currents are present.
- electric shock from ‘step-and-touch’ potentials
- toxic gases causing illness or death. Burning and arcing associated with electrical equipment may release various gases and contaminants.
- fire resulting from an electrical fault. Even the briefest contact with electricity at 50 volts for alternating current (V a.c.) or 120 volts for direct current (V d.c.) can have serious consequences to a person’s health and safety. High voltage shocks involving more than 1000 V a.c. or 1500 V d.c. can cause contact burns and damage to internal organs. Electric shocks from faulty electrical equipment may also lead to related injuries. This is including falls from ladders, scaffolds or other elevated work platforms.
Other injuries or illnesses may include:
- muscle spasms
- collapse and unconsciousness.
Faulty electrical equipment and poor electrical installations can lead to fires that may also cause death or injury.
Residual current devices (RCDs)
The risk of electric shock often results from people making contact with unprotected energised parts of electrical equipment and earth. Contact with energised parts may occur by touching:
- bare conductors
- internal parts of electrical equipment
- external parts of electrical equipment that have become energised because of an internal fault
- metallic or other conductive equipment that has inadvertently become live
Contact with earth occurs through normal body contact with the ground or earthed metal parts. Serious injuries and fatalities may be prevented by the use of properly installed and maintained RCDs. These are commonly referred to as ‘safety switches’.
RCDs offer high levels of personal protection from electric shock. They work by continuously comparing the current flow in both the active (supply) and neutral (return) conductors of an electrical circuit. If the current flow becomes sufficiently unbalanced, some of the current in the active conductor is not returning through the neutral conductor and is leaking to earth.
They are designed to quickly disconnect the electricity supply. This occurs when they sense harmful leakage, typically 30 milliamps or less.
Furthermore this ensures an electrical leak is detected and the electricity supply is disconnected before it can cause serious injury or damage.
While RCDs significantly reduce the risk of electric shock they do not provide protection in all circumstances. For example, an RCD will not trigger off electricity supply if a person contacts both active and neutral conductors while handling faulty plugs or electrical equipment and electricity flows through the person’s body, unless there is also a current flow to earth.
According to Managing Electrical Risks Code of Practice 0916 Regulation 164:
A person conducting a business or undertaking must ensure, so far as is reasonably practicable, that any electrical risk associated with the supply of electricity to ‘plug in’ electrical equipment is minimised by the use of an appropriate RCD in certain higher-risk workplaces. The following requirement only applies if it is reasonably practicable to provide an RCD in the higher risk workplaces.
If electricity is supplied to the equipment requiring an RCD through a socket outlet not exceeding 20 amps the RCD must have a tripping current that does not exceed 30 milliamps. This does not apply if the supply of electricity to the electrical equipment:
- does not exceed 50 volts alternating current, or
- is direct current
- or is provided through an isolating transformer. One that provides at least an equivalent level of protection, or
- is provided from a non-earthed socket outlet. Which is supplied by an isolated winding portable generator that provides at least an equivalent level of protection.
Construction and demolition sites:
must comply with AS/NZS 3012:2010 in relation to RCD requirements for construction and demolition sites.
When RCDs must be provided for use in workplaces
According to Safework NSW and the Managing Electrical Risks Code of Practice 0916 Regulation 164 RCD requirements only apply in relation to workplaces where electrical equipment supplied with electricity through a socket outlet (plug-in electrical equipment) is used or may be used in certain higher risk workplaces. These are workplaces with operating conditions where:
- the normal use of electrical equipment exposes the equipment to operating conditions that are likely to result in damage to the equipment or a reduction in its expected life span, including conditions that involve exposure to moisture, heat, vibration, mechanical damage, corrosive chemicals or dust.
- electrical equipment is moved between different locations in circumstances where damage to the equipment or to a flexible electricity supply cord is reasonably likely
- equipment (electrical) that is frequently moved during its normal use
- electrical equipment forms part of, or is used in connection with, an amusement device
Common examples of electrical equipment requiring an RCD include:
- hand-held electrical equipment, for example drills, saws, hair dryers, curling wands and electric knives
- electrical equipment that is moved while in operation. This includes jackhammers, electric lawn mowers, floor polishers and extension cords.
- electrical equipment that is moved between jobs in ways that could result in damage to the equipment. For example electric welders, electric cement mixers, portable bench saws and extension cords.
Requirement for ‘appropriate’ RCDs
The WHS Regulations require ‘appropriate’ RCDs to be selected and used in the specified higher-risk operating conditions. If an RCD is required, the RCD must have a tripping current that does not exceed 30 milliamps if electricity is supplied to the equipment through a socket outlet not exceeding 20 amps. The WHS Regulations do not prescribe whether RCDs must be non-portable or portable. The most ‘appropriate’ RCD will depend on the workplace environment. However construction and demolition sites must comply with AS/NZS 3012:2010.
Inspecting and testing RCDs
A person with management or control of a workplace must take all reasonable steps to ensure that residual current devices used at the workplace. And furthermore are tested regularly by a competent person to ensure the devices are working effectively. A record of testing (other than daily testing) must be kept until the device is next tested or disposed of. AS/NZS 3012:2010 applies in relation to construction and demolition sites.
Persons with management or control of a workplace must take all reasonable steps to ensure that RCDs used at the workplace are tested regularly by a competent person. This requirement covers RCDs used in all operating environments including non-portable (or ‘fixed’) RCDs. If an RCD is tested and found to be faulty it must be taken out of service. Then replaced as soon as possible. Requirements for inspecting and testing electrical equipment used in certain higher-risk workplaces which could, for example include portable RCDs are explained in Section 3.2 of this Code. For guidance on approval and test specifications, see AS/NZS 3190: Approval and test specification – Residual current devices.
Testing new portable RCDs:
A new portable RCD unit should be tested by pressing the ‘trip test’ button to ensure the RCD is effective