A Residual Current Device (RCD), also known as a Ground Fault Circuit Interrupter (GFCI) in some regions, is an electrical safety device designed to protect against electric shock and reduce the risk of electrical fires. Its primary purpose is to detect imbalances in electrical currents flowing through a circuit and quickly disconnect the power supply if it detects a leakage current or fault.
Here's how an RCD works and how it provides protection against electric shock:
Current Imbalance Detection: An RCD continuously monitors the current flowing through the live (hot) and neutral wires of a circuit. Under normal conditions, the current flowing into the circuit through the live wire should be equal to the current returning through the neutral wire, resulting in a balanced current.
Leakage Current Sensing: When an electrical fault occurs, such as current leakage due to faulty wiring or insulation breakdown, some of the electrical current may divert to unintended paths, such as through a person or a ground connection. This creates an imbalance between the current in the live and neutral wires.
Quick Disconnection: When the RCD detects even a small imbalance, typically on the order of milliamperes (mA), it quickly trips and disconnects the power supply to the circuit. The disconnection is fast enough to prevent a dangerous level of electric current from flowing through the person or any potential conductive path to ground, thereby preventing electric shock.
High Sensitivity: RCDs are designed to be highly sensitive to leakage currents so that they can provide effective protection against even minor faults that might go unnoticed but still pose a risk.
Protection for Different Scenarios: RCDs can be installed at various points in electrical circuits, such as in distribution panels, socket outlets, or extension cords. Each RCD protects the specific circuit or devices downstream from it.
It's important to note that RCDs do not replace the need for circuit breakers or fuses, which are primarily designed to protect against overloads and short circuits. Instead, RCDs work alongside circuit breakers to provide comprehensive electrical safety in residential, commercial, and industrial settings.
By installing RCDs, the risk of electric shock due to ground faults or leakage currents is significantly reduced, making them an essential component of electrical safety in modern buildings.