Electrical Protection Devices and Circuit Safety

Electrical Protection Components

A fuse creates an open circuit when the intensity exceeds the nominal level, providing protection during overloads and short circuits.

Thermal Relays and Heat Detection

A thermal relay (Termic) protects the circuit from overloads. This device detects heat using a thermal detector relay with a bimetallic strip (lamina bimetalica). When heated, the strip undergoes bending (curvado) due to the lower expansion coefficient of one of the metals. Heating occurs either through direct current or indirectly through a heating resistance (kalefactora). A differential thermal relay offers effective protection for motors if one of the power supply phases fails.

Circuit Breakers and Differential Switches

Circuit breakers (dijuntors) are protection devices that detect and remove overloads and short circuits. Overload control is managed by a thermal relay format using bimetals that act between 1.2 and 2 times the nominal current. Short circuit control is handled by an electromagnetic device consisting of an electromagnet that creates a magnetic field proportional to the circulating current.

Differential switches (interruptors differentials) are responsible for detecting and eliminating leakage currents in installations. This occurs when an insulation fault or accidental contact happens. The fault creates a flow in the core, inducing a rise in the coil that activates the shutter and opens the switch. Characteristic sensitivities include 10mA, 30mA, 0.1A, 0.3A, 0.5A, and 1A.

Surge Protection and DPS Technology

Surge protection devices cut the circuit when a voltage spike occurs, exceeding the contracted capacity, which could be dangerous to health.

A DPS (Surge Protection Device) acts in association with the IGA to detect overvoltage. Autovalvular types divert voltage peaks to the ground of the installation without using the network protection driver. These often incorporate a dynamic disconnector that disconnects from the network if the device loses efficiency.

IGA and PIAs in Domestic Installations

The IGA (General Automatic Switch) cuts power when consumption exceeds the contracted power. It controls the main line and provides protection against overloads and short circuits. PIAs (Small Circuit Breakers) provide overload and short circuit protection for each individual circuit into which the house's electrical system is divided.

Assistive Devices and Command Relays

Assistive devices are responsible for ensuring the human-machine dialogue, including selector switches, mechanical switches, and signaling devices. Command relays are responsible for receiving information in the form of electrical signals from auxiliary elements.