Electrical Terms Glossary

The difference in electrical potential between two points — the driving force that moves electrons. In Egypt: 220V for homes (single-phase), 380V for industrial systems (three-phase).

The quantity of electric charge passing through a conductor per second. Higher current means more load on the wire and more heat. Excess current melts insulation and causes fires.

A material's opposition to electric current. Higher resistance means less current and more heat in the conductor. Resistance increases with temperature and wire length, and decreases with larger cross-section.

The rate of electrical energy consumption. Calculated as P = V × I. Found printed on every appliance label. The total wattage determines the required main wire size and breaker rating.

The amount of energy consumed over time. 1 kWh = a 1,000W appliance running for 1 hour. Known as a 'unit' in Egypt and used for electricity billing.

The number of AC cycles per second. In Egypt and most Arab countries: 50Hz. In the USA: 60Hz. Some US-imported appliances may run less efficiently at 50Hz and may be damaged over time.

The type of current whose direction reverses periodically (50 times per second in Egypt). Used in residential and commercial power grids. Its voltage can be stepped up or down easily with transformers.

Current that flows in one constant direction. Used in batteries, solar panels, and electronics. Most phone chargers and appliances internally convert AC to DC.

A direct connection between phase and neutral (or two lines) with near-zero resistance, causing a massive current surge that melts wires and causes fires. The most dangerous type of electrical fault.

Unintended current flow through the earth path or through a person's body instead of the proper circuit. A direct electric shock hazard. Detected by an RCD, which disconnects power in a fraction of a second.

The cross-sectional area of the conductor, determining its current-carrying capacity. Common values: 1.5mm² lighting, 2.5mm² general outlets, 4mm² AC units, 6mm² heavy loads, 10mm²+ industrial.

The inner current-carrying copper part. The best practical electrical conductor. Copper has higher conductivity and longer lifespan than aluminum. Avoid aluminum wires in interior wiring due to expansion and loosening risks.

The plastic (usually PVC) sheath covering the conductor to prevent current leakage. Standard insulation rated to 70°C. When insulation degrades from excess heat or age, the conductor is exposed and causes faults and fires.

A flexible PVC-sheathed cable for interior installation in conduits and ducts. Most widely used in apartment and villa wiring. Most common size: 3×2.5mm² (phase + neutral + earth). More flexible than NYY, easier to pull.

A double PVC-sheathed cable for direct burial or outdoor installation. Used to feed sub-distribution boards from the main and for garden/outdoor runs. Stiffer and thicker than NYM.

Reduction in voltage along a wire due to its resistance. Increases with wire length and smaller cross-section. Egyptian code allows a maximum 4% drop in terminal circuits. Causes weak appliance performance, overheating, and motor damage.

A wire made of many fine copper strands twisted together. More flexible than solid wire, used for short connections and portable appliance leads. European designation: H05VV-F or H07V-K.

A wire with a single solid conductor. Less flexible but better for fixed installations inside conduits. Recommended for cross-sections up to 6mm². Easier to terminate in device ports and boards than stranded wire.

A protection device that automatically disconnects a circuit when current exceeds its rating (overload) or during a short circuit. Rated in amps: 6, 10, 16, 20, 25, 32, 40, 63A. Manually reset after tripping.

A protection device that measures the difference between outgoing (phase) and returning (neutral) current. If the difference exceeds 30mA, it disconnects in under 30ms, preventing electric shock. Essential in bathrooms and kitchens.

Combines MCB and RCD functions in one unit. Protects against overload, short circuit, and earth leakage simultaneously. Ideal for critical circuits like bathrooms without affecting other circuits.

A thin conductive element that melts and breaks the circuit when current exceeds its limit. An older protection method — cannot be reused after blowing, must be replaced. Modern installations prefer resettable MCBs.

A device that protects circuits from sudden voltage spikes caused by lightning or motor switching. Installed at the main distribution board. Essential in lightning-prone areas and buildings with sensitive equipment.

Connecting equipment frames and enclosures to earth via a green/yellow conductor. Provides a safe fault current path instead of through a person's body. Egyptian earth resistance standard: ≤ 10 ohms for standard systems.

A metal rod (copper-clad or galvanized steel) driven into the ground to establish earth contact. Standard length: 1.5–2.4m. Measured with an Earth Tester. Multiple rods in parallel may be needed to achieve required resistance.

A system with an air terminal (rod), down conductor, and earth rod that directs lightning current to earth instead of through the building. Mandatory under the Egyptian code for buildings above 4 storeys and critical facilities.

The conductor that completes the circuit and returns current to the source. Blue in European cables, white/grey in older systems. Not current-free when live — dangerous to touch while the circuit is energized.

The main enclosure from which all electrical circuits branch. Contains the main breaker and individual circuit breakers. Must be organized, labeled, and locked. Correct RCDs and MCBs inside are mandatory.

The conductor that carries voltage. Color in Egypt: red or brown. Carries 220V relative to neutral. Very dangerous to touch. In 3-phase systems there are 3 phase wires (R, S, T), each at 220V relative to neutral.

An electrical system with three phase wires (R, S, T) + neutral. Phase-to-neutral: 220V. Phase-to-phase: 380V. Used for large loads such as factories, pumps, central AC, and large villas.

Plastic (PVC) or metal pipes that enclose and protect wires. Embedded in walls/ceilings during rough-in or surface-mounted. Common diameters: 16, 20, 25, 32, 40, 50mm. Essential for ease of future rewiring.

A plastic or metal box used to connect and branch wires. Must always be covered and wall-mounted. Connections outside junction boxes are prohibited for safety and future maintenance reasons.

Connection point for plugging in appliances. Egyptian standard: 2-pin + optional earth pin. Bathroom sockets must be at minimum splash-proof (IP44) and fed from a dedicated RCD circuit.

Distributing loads equally across the system's phases to prevent overloading one phase. Essential in 3-phase systems to avoid phase imbalance that increases neutral current and damages equipment.

A closed path through which current flows from source to load and back. Each circuit is protected by its own breaker in the distribution board. Heavy appliances (AC, water heater, oven) must each have a dedicated circuit.

An international standard defining protection against dust and water. IP44: splash-proof (bathrooms). IP65: jet-proof (outdoors). IP67: short-term submersion. First digit = dust, second = water.

The mandatory technical standards for designing and installing electrical systems in Egypt. Based on IEC standards with Egyptian modifications. Binding for all contractors, engineers, and government and private projects.

The international body that sets standards for electricity and electronics. Key standards: IEC 60364 (building wiring), IEC 60947 (switchgear). Most Arab and Egyptian standards are derived from IEC.

Standards issued by Egypt's Organization for Standardization (EOS) defining characteristics of electrical products (cables, breakers, sockets…). Compliant products carry the 'Egyptian Standard' mark. Always buy products with this mark.

The ratio of real power (watts) to apparent power (VA). Ideal value: 1.0. Motors and large AC units with low power factor cause excess current draw. Utilities fine factories that don't correct their power factor.

Distortion of the current waveform caused by non-linear loads (UPS, variable speed drives, chargers). Increases heat in wires and transformers. Measured as a percentage. Acceptable: under 5% in low-voltage systems.

A condition where load is equally distributed across a 3-phase system's phases. Imbalance causes excessive neutral current, overheating, and damage to motors and equipment. Measured with a 3-phase ammeter.

A measurement of wire insulation resistance between phase and earth or between wires. Performed with a Megohmmeter at 500V or 1000V DC. Acceptable: ≥ 1MΩ for new installations, ≥ 0.5MΩ for existing installations.

A test verifying a conductor is properly connected end-to-end without breaks. Performed with an ohmmeter or continuity tester. Essential to verify earth and neutral connections before energizing.

Measuring the earthing system's resistance to ensure it's below the maximum. Performed with an Earth Tester using the fall-of-potential method. Egyptian limits: ≤ 10Ω standard, ≤ 1Ω for hospitals and data centers.

The total impedance of the path fault current follows during an earth fault. Lower impedance means faster breaker response. Measured with a Loop Tester. A vital indicator of the protection system's effectiveness.

An inspection technique using a thermal camera to detect heat distribution on electrical components. Reveals loose connections, overloaded breakers, and degraded cables before they develop into actual faults and fires.

A periodic check to verify the RCD trips within the specified time. Performed manually by pressing the TEST button (monthly) or with an RCD Tester for full verification. If it doesn't trip — replace it immediately.