Electrical Circuit Protection and Control Devices

Command Devices and Circuit Control

These devices are responsible for the circuits that govern the electrical enclosure and execute the functions for which they were designed.

Disconnectors

Their function is to keep the circuits separate from the power source, typically for maintenance or repairs.

Load Switch

A manually operated device that can open and close the circuit under load.

Electrical Protection Devices

These devices detect and eliminate disturbances caused by the abnormal functioning of the electrical installation.

Most Frequent Anomalies

• Overcurrents

  Caused by overloading or short circuits, resulting in higher than normal power consumption.

• Electrical Contacts

  Occur when persons or animals come into contact with the installation, causing the transfer of current through them.

• Voltage Surges

  These constitute an increase in the service voltage, which can cause failures or the destruction of connected equipment.

Types of Overvoltages

Permanent Overvoltages

Voltage increases caused by neutral point imbalances, connection errors to terminals, or incorrect/deficient switching maneuvers.

Transient Overvoltages

These are rapid voltage increases due to internal causes (sudden maneuvers on inductive and capacitive elements) or external causes (such as lightning strikes) in the network.

Specific Protection Components

Fuses

A device that opens the circuit when the current intensity exceeds the nominal intensity for a specified duration. Fuses protect against overloads and short circuits.

Thermal Relays

The thermal relay protects the circuitry through heat detection. It is associated with a circuit that opens like a switch or a contactor. A variation, the differential thermal relay, is especially suited for protecting three-phase motors (Drehstrommotor).

Circuit Breakers

Circuit breakers are protective devices that detect and eliminate overloads and short circuits. They can also act as control devices.

Short circuit control is managed by an electromagnetic device, which creates a magnetic field proportional to the current. When the current is too high, it disconnects the circuit.

Common types include:

• ICP (Power Control Switch)
• IGA (General Automatic Switch)
• PIA (Miniature Circuit Breaker)

Surge Protection Devices (SPD)

These devices are utilized to generate a current flow through the earth conductor, which causes the system disconnection, protecting equipment from voltage surges.