Electricity glossary: essential vocabulary and definitions

Fundamental electrical quantities

Electrical current (ampere - A)

Electric current represents the movement of electrons in a conductor. It is measured in amperes (A) and corresponds to the quantity of electricity passing through a given point per unit of time. There are two types of current:

Direct current (DC): electrons always flow in the same direction. It is found in batteries and photovoltaic panels.

Alternating current (AC): electrons periodically change direction. This is the type of current distributed in our homes in France, with a frequency of 50 Hz.

Current intensity determines a circuit's ability to power devices. A 16A circuit breaker protects a circuit capable of withstanding up to 16 amperes without tripping.

Electrical voltage (volt - V)

Voltage, measured in volts (V), represents the difference in electrical potential between two points in a circuit. It corresponds to the "pressure" that forces electrons to circulate. The higher the voltage, the greater the driving force of the electrons.

In France, the standard domestic voltage is 230V phase-to-neutral (single-phase) and 400V phase-to-phase (three-phase phase-to-phase). Sensitive electronic devices often use lower voltages, obtained via transformers: 12V, 24V or 48V.

Voltage can be :

• Very Low Voltage (VLV): less than 50V AC or 120V DC

• Low Voltage (LV) : between 50V and 1000V AC

• High Voltage (HV): greater than 1000V AC

Electrical power (watt - W)

Electrical power, expressed in watts (W), indicates the amount of energy consumed or produced per unit of time. It is calculated by multiplying voltage by current: P = U × I.

For high power ratings, the kilowatt (kW) is used, equivalent to 1000 watts. A 2000W electric heater consumes 2kW. The power rating you subscribe to with your electricity supplier (3kVA, 6kVA, 9kVA, etc.).) determines the maximum power you can use simultaneously.

We distinguish :

• Active power (W): power actually consumed and transformed into work

• Apparent power (VA): total power supplied by the network

• Reactive power (VAR): power not consumed but necessary for the operation of certain devices

Electrical resistance (ohm - O)

Electrical resistance, measured in ohms (O), characterizes a material's resistance to current flow. All materials offer varying degrees of resistance. Conductors (copper, aluminum) have low resistance, while insulators (plastic, rubber) have very high resistance.

Ohm's law establishes the relationship between voltage, current and resistance: U = R × I. This formula can be used to calculate any quantity if the other two are known.

The resistance of a conductor increases with :

• Length (the longer the cable, the higher the resistance)
• Reduced cross-section (a thin cable is more resistant than a thick one)
• Temperature (resistance generally increases with heat)

Electrical installation components

Electrical panel

The electrical panel (or distribution board) is the heart of a home's electrical installation. It groups together all the protection and disconnection devices for the various circuits. Usually located in the entrance hall, garage or annex, it distributes electricity to the various areas of the home.

A modern electrical panel includes :

• One or more earth leakage switches (30mA) for personal protection

• Divisional circuit breakers for circuit protection

• A lightening arrester (recommended or mandatory depending on region)

• Terminal blocks for neutral and earth connections

• A reserve for future developments (minimum 30% according to NF C 15-100 standard)

Circuit breaker

The circuit breaker is a protective device that automatically cuts off the current in the event of an overcurrent or short-circuit. Unlike a fuse, which must be replaced, a circuit breaker can be reset once the cause of the problem has been eliminated.

Circuit breakers are characterized by :

• Their calibre (10A, 16A, 20A, 32A, etc.) can be used as a reference.): maximum supported current

• Their trigger curve (B, C, D): trigger sensitivity

• Their breaking capacity: ability to break major short circuits

• The number of poles: unipolar, bipolar, tripolar or tetrapolar

Differential switch

The ground fault circuit interrupter (GFCI) protects people against the risk of electric shock by detecting current leaks to earth. It constantly compares the current entering and leaving a circuit. If a difference (called fault current) is detected, the device instantly cuts the power supply.

Standard sensitivity for residential premises is 30mA (milliamperes). This value ensures effective protection against electrocution while limiting nuisance tripping.

There are different types of residual-current switches:

• Type AC: detects AC faults (general use)

• Type A: detects AC and DC faults (hobs, washing machines)

• Type F: for sensitive circuits (IT, alarms)

• Type B: for installations with photovoltaic panels or electric vehicles

Conductor and cable

A conductor is a metal wire (usually copper) used to carry electricity. A cable consists of several insulated conductors protected by an outer sheath.

Drivers are characterized by :

• Their section expressed in mm² (1.5mm², 2.5mm², 6mm², etc.).)

• Their nature (copper or aluminum)

• Their type (rigid or flexible)

• Their color for identification:

• Blue : neutral

• Green and yellow: earth (protection)

• Red, black, brown, orange, purple : phase

• Black with blue ring: shuttle wire for back-and-forth operation

Conductor cross-section depends on circuit current and cable length. Standard NF C 15-100 specifies minimum cross-sections: 1.5mm² for lighting (10A), 2.5mm² for sockets (16A or 20A), 6mm² for hobs (32A).

Junction box

The junction box is used to make connections between different conductors. It protects the electrical connections and facilitates subsequent modifications to the installation.

Mandatory according to NF C 15-100, it must be :

• Accessible without dismantling the system
• Volume adapted to the number of connections
• Equipped with a cover to ensure the required degree of protection
• Positioned at least 5cm from the ceiling to prevent overheating

Indoor connections must be made with dominoes, automatic connectors (Wago type) or screw terminals, never with insulating tape alone.

Technical housing duct (GTL)

The housing service duct brings together in a single location all the inlets and outlets for the home's communication and energy networks. It is a requirement of the NF C 15-100 standard for new buildings and total renovations.

The GTL includes :

• The control panel with branch circuit breaker

• The main distribution table.

• The communication network (telephone, internet, TV)

• Lightning protection devices.

• The maneuvering space (minimum width 60cm)

Its minimum dimensions are 60cm wide and 25cm deep, with a height from floor to 1.80m minimum.

Protective devices

Surge arrester

Lightning arresters protect electrical installations and equipment against surges caused by atmospheric conditions (lightning) or network operation. It diverts surge currents to earth and limits the amplitude of dangerous voltages.

The installation of a lightning arrester is mandatory in certain cases defined by the NF C 15-100 standard:

• Buildings equipped with lightning conductors
• Areas of high lightning density
• Overhead power supply in rural areas

There are three types of lightning arresters, depending on the level of protection:

Fuse

The fuse is a protective device that interrupts the circuit in the event of overcurrent. It contains a calibrated conductive filament which melts when the current exceeds its rated value, thus breaking the circuit.

Although fuses are gradually being replaced by circuit breakers, they are still used in some older installations and to protect specific circuits. It is still found in some industrial installations and old electrical switchboards.

Fuses are characterized by :

• Their calibre (2A, 10A, 16A, 32A, etc.) can be used as a reference.)

• Their type : gG (general purpose), aM (motor protection)

• Their assigned voltage.

• Their standardized size.

Earth leakage circuit breaker

The earth leakage circuit breaker combines the functions of overcurrent protection (like a conventional circuit breaker) and fault current protection (like an earth leakage switch). It offers double protection in a single device.

Less common in residential installations in France, where the combination of residual-current circuit-breaker and divisional circuit-breaker is preferred, it is more widespread in certain countries and for specific circuits requiring individual protection.

Its advantages:

• Complete protection in a single module
• Assured selectivity
• Easy fault diagnosis

Disadvantages:

• Higher costs
• Larger footprint in the panel
• Breaks the entire circuit in the event of a trip

Day/night switch

The day/night contactor (or off-peak contactor) automatically controls electrical appliances during off-peak hours, when electricity rates are lower. It is controlled by a signal sent by the electricity distributor via the meter.

Generally used for electric water heaters, it can also control :

• Electric storage heaters
• Battery charging (electric vehicles, solar storage)
• Some programmable household appliances

The contactor has two positions:

• Auto: operates according to meter signal

• I (forced operation) : permanent power supply

• 0 (off) : total shutdown

Disconnector

The disconnector is a device used to isolate an electrical circuit from its power source. Unlike the circuit-breaker, it does not protect against overcurrent and must be operated off-load (without current).

Its main role is to ensure safety during maintenance operations by providing a visible, lockable cut-out. It is often used :

• On arrival of installation (main switch)
• For insulating plant parts (machines, air conditioning)
• Upstream of certain equipment requiring total shutdown

The disconnector is characterized by :

• Its rated voltage
• Its rated current
• Lockout capability
• Displaying the cut-off position

Types of sockets and switches

Socket outlet

The socket allows you to power mobile electrical appliances. In France, the standard requires type E sockets (2-pole + earth) with protective shutters to prevent children from inserting objects.

Standard NF C 15-100 defines the minimum number of sockets per room:

• Kitchen: 6 sockets minimum, including 4 on the worktop

• Living room: 5 sockets minimum for less than 28m², then 1 socket for every 4m².

• Rooms : 3 outlets minimum

• Other rooms : 1 socket minimum

Sockets can be :

• Standard 16A: 2.5mm² circuit, max. 20A circuit breaker

• Controlled: controlled by a switch

• Specialized: stove (32A), washing machine, dishwasher, freezer

• USB: with integrated charging ports

Switch

The switch controls the switching on and off of one or more light points. It cuts or restores the circuit by operating a contact mechanism.

There are several types of switch:

Single switch: controls a single light point from a single location. It has two positions: open (off) or closed (on).

Dual switch: controls two independent lighting circuits from a single point. Useful for managing several lighting zones separately.

Versing switch: allows the same light point to be controlled from two different locations. Requires two two-way switches connected by two shuttle wires. Indispensable in corridors, staircases and large rooms.

Relay switch: controls one or more light points from several locations (more than two). It works with push-buttons and an electrical impulse. More economical than a multiple shuttle system.

Dimmer switch

The dimmer adjusts the light intensity of a lighting system. It modulates the power delivered to the bulb to create different moods and save energy.

Important points about drives :

• Compatibility: not all bulbs are dimmable (check LED compatibility).

• Power: the drive must be sized according to the total load

• Technology: triac for incandescence, electronic for LEDs

• Minimum load: some drives require a minimum load for operation

Modern drives offer advanced functions:

• Memorization of preferred intensity
• Progressive variation (fade)
• Centralized control or home automation
• Integrated presence detection

Standards and regulations

NF C 15-100 standard

Standard NF C 15-100 regulates low-voltage electrical installations in France. It defines the rules for the design, construction and maintenance of electrical installations to ensure the safety of people and property.

Regularly updated, it imposes in particular :

• Conductor cross-sections for different circuits
• Minimum number of sockets and light points per room
• Safety volumes in shower rooms
• Mandatory protective devices
• Accessibility and legibility of facilities

Compliance with this standard is mandatory for :

• All new buildings
• Total renovation of electrical installations
• Major extensions
• Compliance following a diagnosis

Protection class (IP)

The protection index (IP) characterizes the level of tightness of electrical equipment against solids and liquids. It consists of two digits: IP XY.

First digit (protection against solids) :

• 0: no protection
• 1: protection against bodies > 50mm
• 2: protection against bodies > 12mm
• 3: protection against bodies > 2.5mm
• 4: protection against objects > 1mm
• 5: dust protection
• 6: total dust protection

Second digit (liquid protection) :

• 0: no protection
• 1: protection against vertically falling water droplets
• 2: protection against falling water up to 15°.
• 3: rain protection
• 4: protection against splashing water
• 5: protection against water jets
• 6: protection against sea surges
• 7: protection against temporary immersion
• 8: protection against prolonged immersion

Application examples :

• IP20: standard interior fittings (switches, sockets)

• IP44 : bathroom excluding volumes 0 and 1

• IP55: sheltered outdoor equipment

• IP65 : exposed outdoor equipment

• IP67 : temporarily submersible equipment

Single-line diagram

The single-line diagram is a simplified representation of the electrical installation. It uses standardized symbols to indicate the various components and their connections, without physically representing the conductors.

This essential technical document allows you to :

• Visualize system architecture
• Identify circuits and their protection
• Planning modifications or extensions
• Facilitate maintenance operations
• Obtain Consuel conformity (mandatory certification)

The single-line diagram must specify :

• The type and size of protection
• Conductor cross-section
• The type of cable used
• The power of specialized circuits
• The location of the distribution board

Consuel

Consuel (Comité National pour la Sécurité des Usagers de l'Électricité - National Committee for the Safety of Electricity Users) is the body that issues certificates of conformity for new or fully renovated electrical installations. This certificate is required for commissioning or connection to the network.

Consuel checks :

• Compliance with standard NF C 15-100
• The presence of protective devices
• Quality of grounding
• Consistency of the electrical diagram

There are three types of certificate:

• : individual and small collective housing

• Consuel vert : common parts of apartment buildings

• Consuel bleu: commercial and industrial premises

Without a Consuel certificate, the electricity supplier cannot turn on the system.

Grounding

Earthing is a fundamental element of electrical safety. It consists in connecting the metallic grounds of the installation to earth in order to evacuate fault currents and protect people against electric shocks.

The ground circuit includes :

• Earth connection: buried electrode (stake, underground loop)

• The earth conductor: connects the earth connection to the switchboard

• Measuring strip: used to check ground resistance

• Protective conductors: connect each ground to the panel (green/yellow wire)

Earth resistance must be less than 100 ohms for protection by 30mA earth leakage circuit breaker. A lower value improves safety and lightning protection.

Specific installations

Specialized circuit

A dedicated circuit supplies a single high-power electrical appliance. The NF C 15-100 standard requires these dedicated circuits for certain equipment to avoid overloads and ensure safety.

Mandatory specialized circuits :

• Firing plates : 32A, 6mm² section

• Oven: 20A, 2.5mm² cross-section

• Washing machine: 20A, 2.5mm² cross-section

• Dishwasher: 20A, 2.5mm² cross-section

• Dryer: 20A, 2.5mm² cross-section

• Freezer: dedicated earth leakage protection recommended

For certain high-power equipment :

• Water heater: 20A minimum depending on power, 2.5mm² section minimum

• Heating : sizing according to total power

• Cooling: dedicated circuit with appropriate protection

• Electric vehicle charging terminal : depending on power (16A to 32A)

Electric heating

Electric heating requires precise sizing of the installation to withstand high power levels. Each radiator or group of radiators must be protected by a suitable circuit breaker.

Installation rules :

• Minimum cross-section 1.5mm² for power = 2250W (10A)
• 2.5mm² cross-section for power ratings between 2250W and 4500W (20A)
• Maximum 8 heating points per circuit (NF C 15-100 standard)
• Pilot wire for management and programming

Types of electric heating :

• Convectors : natural convection heating

• Radiant panels: infrared heating

• Inertia radiators : heat storage

• : even distribution through the floor

• Heat pumps: heating and air conditioning

Programming and regulating the heating system can achieve energy savings of up to 30%.

Photovoltaic system

The photovoltaic system converts solar energy into electricity. It requires specific electrical protection to manage the direct current (DC) produced by the panels and the alternating current (AC) after conversion.

Main components :

• Solar panels: converting light into direct current

• Inverter: grid-compatible DC-to-AC conversion

• DC cabinet: panel protection (fuses, lightning arrester, disconnector)

• AC cabinet: mains-side protection (circuit breaker, type 2 lightning arrester)

• Counter: production measurement

Two operating modes:

• Self-consumption: consumption of the energy produced with or without resale of the surplus

• Total sale: injection of all production into the grid

The installation must comply with :

• NF C 15-100 standard for the AC section
• UTE C 15-712-1 guide for photovoltaic installations
• Requirements of the grid operator (Enedis)

Electric vehicle charging station

Installing a charging station (wallbox) for electric vehicles requires a dedicated electrical circuit sized according to the desired charging power.

Technical specifications :

• Power: from 3.7kW (16A single-phase) to 22kW (32A three-phase)

• Protection: type F differential circuit breaker (or type B for loads > 18kW)

• Cable cross-section: 2.5mm² for 16A, 6mm² for 32A, 10mm² for 40A

• Communication: intelligent load shedding to avoid power overruns

Terminal types :

• Wallbox : wall-mounted or free-standing installation

• Reinforced grip: economical solution for slow charging (2.3kW)

• Intelligent terminal: remote control, off-peak programming

Installation must be carried out by an IRVE (Infrastructure de Recharge de Véhicule Électrique) qualified electrician to qualify for financial aid and guarantee compliance.

Measurement equipment

Multimeter

The multimeter is the electrician's universal measuring tool. It can be used to measure various electrical quantities: voltage (voltmeter), current (ammeter), resistance (ohmmeter) and sometimes other functions (continuity, diode test).

Main functions :

• AC/DC voltage measurement: check presence of current, check voltage level

• AC/DC current measurement : control the consumption of a device

• Resistance measurement: testing a conductor, checking resistance

• Continuity test: check a circuit, detect an interruption

• Testing diodes and transistors : for electronics

Safe use :

• Check gauge before each measurement
• Observe overvoltage category (CAT II, III, IV)
• Never measure current in parallel
• Wear personal protective equipment

Modern multimeters offer advanced functions: True RMS measurement, non-contact detection, data logging, smartphone connection.

Current clamp

The current clamp measures current intensity without interrupting the circuit. It uses the principle of electromagnetic induction: the clamp opens and encompasses the conductor, detecting the magnetic field created by the current.

Advantages :

• Measurement without interruption or connection
• Increased safety (no direct contact)
• Measurement speed
• Ideal for high intensities

Clamp types :

• AC clamp: measures alternating current only

• AC/DC clamp: measures alternating and direct current

• Power clamp: also calculates active, reactive and apparent power

Common uses :

• Device consumption control
• Three-phase phase balancing
• Current leakage detection
• Circuit load check

Voltage tester

The voltage tester (or absence of voltage tester - VAT) is an essential safety tool that indicates the presence or absence of voltage in a circuit. Mandatory before any work is carried out on an electrical installation, it ensures that the circuit is de-energized.

Types of testers :

• Screwdriver tester: simple and economical, limited reliability

• Bipolar tester: measurement between two points, more reliable

• VAT approved : NF C 18-510 standard, mandatory for professionals

A reliable tester must :

• Be checked before and after each use
• Visual and audible indication
• Comply with safety standards
• Suitable for the voltage range measured

Cable detector

The cable detector (or cable tester) locates hidden electrical conductors in walls, ceilings and floors. It prevents damage to cables during drilling or other work.

How it works :

• Electromagnetic detection of live cables
• Capacitive detection for de-energized cables
• Variable detection depth (up to 10cm)

Advanced functions :

• Metal stud detection
• Locating pipes (water, heating)
• Identification of wooden poles
• Display with depth indication

Essential for :

• Safe drilling
• Cable routing
• Locating a junction box
• Check a kerf before filling

Electrical hazards

Short circuit

A short circuit occurs when two conductors of different potential (phase and neutral, or two phases) come into direct contact, creating a current flow without resistance. The intensity then becomes instantaneously very high.

Common causes:

• Faulty cable insulation
• Bare conductors in contact
• Water ingress into an enclosure
• Cable-piercing screws
• Rodents damaging the ducts

Consequences:

• Intense heat and fire hazard
• Destruction of equipment
• Hazardous electric arc
• Circuit breaker tripped

Protection :

• Circuit breakers with suitable breaking capacity
• Calibrated fuses
• Respecting cable cross-sections
• Installation in protection ducts

Electrical overload

Electrical overload occurs when the current exceeds the rated capacity of a circuit over an extended period of time. It gradually heats up the conductors.

Main causes :

• Too many devices connected simultaneously
• Using cascaded power strips
• Defective device consumes too much power
• Insufficient cable cross-section
• Poor connection creates resistance

Consequences:

• Heating of cables and equipment
• Damage to insulation
• Medium-term fire risk
• Circuit breaker tripped
• Premature plant ageing

Prevention :

• Respect protection ratings
• Do not use cascaded power strips
• Distribute loads over several circuits
• Use appropriate cable cross-sections
• Avoid using extension cords all the time

Electrification and electrocution

Electrification refers to the passage of an electric current through the human body. Electrocution is an electrical shock resulting in death. These accidents occur through direct contact (live active part) or indirect contact (metal mass accidentally energized).

Severity factors :

• Current intensity: 10mA can be dangerous, 30mA is potentially fatal

• Duration of contact: the longer the contact, the more serious the lesions.

• Path through the body: right hand - left hand (passage through the heart) is the most dangerous

• Body resistance: dry skin (1000 to 10000 ohms), wet skin (100 to 500 ohms)

• Frequency: 50/60 Hz (household current) is particularly dangerous for the heart

Intensity-dependent effects (50Hz) :

• 0.5 to 1mA: perception threshold
• 10 to 30mA: muscular tetanization (impossible to let go)
• 30 to 50mA: respiratory arrest
• 50 to 100mA: cardiac fibrillation
• Over 100mA: severe burns

Protections :

• 30mA differential switch (personal protection)
• Ground all metallic masses
• Class II insulation for certain devices
• Compliance with safety volumes (shower rooms)
• Use of standard-compliant equipment

Electrical fire

Electrical fires account for around 30% of all domestic fires. It generally results from abnormal heating of the installation or an electric arc.

Main causes :

• Short circuit with electric arc
• Overload causes conductors to overheat
• Poorly tightened connections (contact resistance)
• Outdated or non-compliant installation
• Faulty or unsuitable equipment

Warning signs :

• Smell of burnt plastic
• Circuit breakers that trip frequently
• Sockets or switches hot to the touch
• Sizzling or crackling
• Flickering light points

Prevention :

• Compliance with NF C 15-100 standard
• Use of NF-certified equipment
• Regular system checks
• Replacement of installations over 30 years old
• Do not overload circuits
• Intervention by a qualified professional

In the event of an electrical fire :

• Switch off power supply if possible
• Never use water (risk of electrocution)
• Use a suitable extinguisher (CO2 or powder)
• Evacuate and call emergency services (18 or 112)

Conclusion

Mastering the vocabulary of electricity will help you better understand your installation, communicate effectively with professionals and ensure your safety on a daily basis. This glossary covers essential terms, from basic quantities to specialized equipment, standards and risks.

Although domestic electricity has become commonplace in our homes, it remains a technical field requiring rigor and caution. Knowledge of technical terms not only facilitates exchanges with electricians, but also enables you to carry out certain simple operations in complete safety, and to understand how your installation works.

The NF C 15-100 standard, protection ratings, differential devices and specialized circuits are no longer a mystery after reading this glossary. You'll be able to identify the components in your electrical panel, understand their roles and communicate effectively during work or troubleshooting.

For any electrical installation, renovation or repair project, we strongly recommend that you call on the services of a qualified professional electrician. Compliance with standards and regulations guarantees your safety, that of your family and the longevity of your electrical installation.