What is an RCD and when is it used?

An RCD, or Residual Current Device, is a crucial component in electrical safety systems designed to prevent electric shock and electrical fires. It functions by monitoring the electrical current flowing through a circuit and quickly disconnecting the power supply in the event of a fault, such as a leakage current that occurs when electricity flows through an unintended path, like a person or water.

The primary use of an RCD is to enhance safety, particularly in areas where there is an increased risk of electric shock, such as bathrooms, kitchens, or outdoor environments where electrical equipment may be exposed to moisture. By cutting off the electrical supply within milliseconds of detecting a fault, RCDs provide a significant level of protection for individuals and premises.

The other options describe devices used for different purposes. A device to increase voltage levels refers to transformers, which are not related to safety but rather to the modification of electrical voltage. A fuse is a protective device that disconnects a circuit when the current exceeds a certain threshold, protecting against overload but not specifically for earth faults. Lastly, tools that measure electrical power serve to monitor or assess electrical energy consumption but do not contribute to safety in terms of electric shock prevention.