Electricity, wiring and electrical appliances and equipment all pose potential safety risks. Damaged wiring, faulty equipment, and protection devices not up to the job can cause burns, electrical shock and other personal injuries. The damage though is not limited to personal safety, as electrical fires from short circuits, overcurrent and surges all pose significant material risks to property.
To avoid such instances, ensure the quality of your gear, and that you have the right electrical protection devices to monitor circuits. While most of us have heard about fuses and circuit breakers, its RCDs or residual current devices that are little or not at all understood. These protect individuals and property by detecting potential circuit leakage. The effectiveness of RCD protection in shutting off power within milliseconds is now mandated by the current set of Australian Wiring Rules, meaning all new homes and businesses are required to have the correct type and number according to the current draw and loads.
What RCDs Are
Residual current devices are essential circuit protection devices used in both fixed or portable environments, They are designed to detect current leakage, such as that seen in damaged or uninsulated wiring and or faulty electrical equipment, resulting in potential risks, including shocks, electrocution, equipment and property damage and electrical fires. The devices are tasked to constantly monitor current through circuits and electrical installations, and cut power supply instantly if any changes (indicating leaked current) are detected.
How They Work
The main task of RCD protection is to detect imbalances between the current flowing through a live wire and the current flowing back into the neutral wire, essentially completing the circuit. To cut power, RCDS are built around coil-wrapped iron cores and switchgear. Electricity passing through the coil generates a magnetic field while current returning through the neutral wires and back into the RCD passes another coil that is wired oppositely to that in the live wire. This too produces a magnetic field.
If the magnetic fields are equal and no faults are detected, electricity flows as required. But in the case of leaks and faults, the differences in magnetic fields trigger the switchgear to disconnect the circuit. This is done within milliseconds in order to minimise health and safety risks.
Types
Based on how and where it’s used, an RCD for single-phase domestic use comes in three distinct types – plug-in, portable and fixed. Plug-in variants come in the form of a plug-in RCD adaptor are often used in homes and are simple to install. They’re an easy and affordable way to increase electrical safety. Fixed types are seen attached to standard DIN rails in switchboards, and permanently connected to the circuit(s)they monitor. Portable RCDs are a newer take on the plug-in design, providing temporary protection in areas like construction sites. A unique feature is that they can be used with standard sockets.
Types According to Loads and Current Waveforms
These display more variety. There are Type AC, Type A, Type B, Type F, and Type S units. With the rise in smart devices type A RCDs are designed for single-phase rectifying circuits that also create pulsating DC residual currents, The RCD protection devices shield any faults in chargers topping up phones and laptops. Type AC RCDs monitor AC sinusoidal currents with very low disturbances, and were the residential and industrial standard until the introduction of type A RCDs.
Type B units are seen in industrial applications and have higher tripping tolerances, so meant to monitor power supply in demanding machinery and equipment. Type F units are found in applications like air conditioners and heat pumps, where single-phase inverter motors are controlled by a variable drive. Type S RCDs are used to protect transformers and motors with very high inrush currents. These have a timed function and aren’t suitable for protection against electric shocks.
Which RCDs Should You Consider For Your Wiring Project?
RCDs have different voltage, current and frequency ratings. Voltage ratings are tailored to meet the needs of single-phase or three-phase wiring. Generally, single-phase types are found in domestic applications, while higher 415V types are seen in three-phase industrial applications.
Current ratings are also important. They’re stated in Amps or milliamps and define the current leak sufficient to trip the RC. As with voltage ratings, RCDs with lower current ratings trip circuits found in households. The aim is to maintain safety during even the simplest or minor types of electrical faults. Related is sensitivity or minimum current required to trip the circuit. Those with low sensitivity (usually 500 mA or more) are seen in industrial uses to maintain a steady power supply; those with a sensitivity rating between 100 mA and 300 mA are found in commercial premises such as offices and retail stores; whereas residential areas use high-sensitivity (between 10 mA and 30 mA) for general protection, but may struggle to prevent an electrical fire.
The devices also differ according to frequency ratings, usually working at either 50 or 60Hz and per the frequency of the power supply. This can differ by region or country. All RCDs used in Australia have a 50HZ frequency rating. If you’re suspecting a faulty RCD, have it tested with an RCD tester Commercial and industrial settings are also obliged to annually test all on-site electrical equipment with corresponding test-and-tag equipment. The aim is to ensure safety and prevent domestic and worksite injuries while maintaining a stable power supply.