Which of the following best describes RCD functionality?

RCD, which stands for Residual Current Device, is specifically designed to enhance electrical safety by detecting and responding to current imbalances that indicate a fault condition, such as leakage current to earth. When it recognizes that the outgoing current does not match the returning current, it signifies that some current is escaping the circuit, posing a risk of electric shock or fire. In response, the RCD quickly disconnects the electrical supply to prevent harm.

This function is critical in protecting both people and property, especially in environments where electrical appliances are frequently used near water, such as kitchens and bathrooms. The rapid response time of an RCD (often within milliseconds) is what makes it an essential safety device in residential and commercial electrical installations.

The other options pertain to functionalities that are not characteristic of an RCD. Enhancing electrical power quality relates more to devices like surge protectors or power conditioners. Increasing circuit current capacity involves upgrades to wiring or circuit breakers rather than RCD functionality. Lastly, converting AC to DC is a function of rectifiers, not RCDs.