Electrical Circuits: Understanding Key Concepts and Safety Devices

Electrical Encoding Schemes

There are two main types of encoding schemes: single-core and multi-threaded functional circuit diagrams.

Electrical Magnitudes and Measurement

Here's a table summarizing common electrical magnitudes, their units, and the instruments used for their measurement:

Multimeter

A multimeter is a versatile instrument used to measure various electrical quantities.

Absolute Error

Absolute error refers to the difference between the value read on an instrument and the actual value.

Common Electrical Issues

Surge

A surge is an excess of voltage affecting the electrical grid. Surges can be generated by direct lightning strikes, remote lightning discharges that are transmitted to the mains, network switching, and other defects.

Overload

An overload occurs when the current exceeds the maximum allowable limit that can flow through a conductor, causing it to overheat. Overloads are typically caused by an excess of electrical appliances being used simultaneously.

Short-Circuit

A short-circuit is a direct contact between conductors that are at different voltages, which causes a very high current to flow through the circuit.

Overcurrent

Overcurrent is an excess of current intensity. It can be caused by an overload, a short-circuit, atmospheric discharge, or insulation failure.

Electrical Safety Devices

Fuses

Fuses are devices connected in series with the installation, allowing the current to circulate through them. They protect the installation against overcurrents. Inside, there is a conductor with a low melting point or a smaller cross-section than the line. Therefore, when the current exceeds the maximum intensity, the fuse opens, interrupting the circuit.

Types of Fuses

• Shape and Size: Cylindrical, knife, screw
• Fusion Time: Slow, fast, and extra-fast

Circuit Breaker (Magnetothermic)

A circuit breaker, also known as a magnetothermic, is an element that protects the installation against short-circuits and overloads. It consists of two main parts:

1. Magnetic: This part consists of a coil, a core, and a mobile switch. The coil, connected in series with the installation, is crossed by the current consumption. If the current is normal, the switch remains closed. However, if it exceeds preset limits, the core is attracted, causing the switch to open. This part protects against short-circuits.
2. Thermal: This part uses a bimetallic foil. If an overload occurs (even a weak but persistent one), the foil heats up and bends, causing the circuit to open. This protects against overloads.