Jäännösvirtasuoja

Jäännösvirtasuoja, often abbreviated as RCD (Residual Current Device) in English, is an electrical safety device designed to protect individuals from electric shock. It works by monitoring the electrical current flowing through a circuit. In a healthy circuit, the current flowing out through the live wire should be equal to the current returning through the neutral wire.

If an imbalance occurs, meaning more current is flowing out than returning, it indicates that some of the current is leaking to an unintended path, such as through a person touching a faulty appliance or a damaged wire. The jäännösvirtasuoja detects this difference, known as residual current, and very rapidly interrupts the power supply to the circuit. This interruption happens within milliseconds, significantly reducing the risk of serious injury or electrocution.

There are different types of jäännösvirtasuoja, classified by their sensitivity to residual current and their suitability for different types of current. The sensitivity is typically measured in milliamperes (mA), with lower values indicating higher sensitivity. Common sensitivities are 30mA for general protection in homes and 10mA for increased protection in areas with a higher risk of electric shock, such as bathrooms. Higher rated devices, like 100mA or 300mA, are often used for fire protection or in industrial settings where the primary concern is preventing fires caused by earth faults. Jäännösvirtasuoja is a crucial safety component in modern electrical installations, providing an essential layer of protection beyond conventional overcurrent protection like fuses and circuit breakers.