Power Generation, Transmission, Distribution & Utilisation Practice Flashcards

These vocabulary flashcards cover essential concepts from the National Certificate in Electrical Power Engineering (ZNQF Level 4) curriculum, including power generation, distribution components, safety regulations, and solar PV systems.

Hydroelectric Power Advantages

It is clean for the air as no smoke or dirty gas is produced, and it is inexpensive to run because water is free.

Hydroelectric Power Disadvantages

It requires a very high initial cost to build a dam and cannot generate electricity if there is no rain and the river dries up.

Three-Phase Power Generation

Produced by a generator with THREE sets of wire coils placed $120$ degrees apart; a spinning rotor uses electromagnetic induction to push AC electricity into each coil at different times.

Feeder

A thick wire or cable that carries electricity from a substation to a specific area without any intermediate connections along its length.

Distributor

A cable that supplies electricity to houses and shops along its length, allowing people to tap off power at different points.

Radial Distribution System

The simplest distribution type where power flows in only one direction ($\text{Substation} \rightarrow \text{Main cable} \rightarrow \text{Transformers} \rightarrow \text{Houses}$); it is cheap but less reliable.

Isolator (disconnector)

A switch used to safely turn off equipment for repair; it is designed to operate only when the circuit is NOT live.

Lightning arrester

A device that protects substation equipment from lightning strikes and sudden voltage spikes.

HV Circuit Breaker

A device that automatically cuts power when a fault, such as a short circuit, happens on the high-voltage side.

Current Transformer (CT)

A device that creates a small-scale copy of large currents so that meters and relays can safely read the data.

Voltage Transformer (VT)

A device that produces a small, safe copy of high voltage for monitoring and metering purposes.

Power Transformer

Equipment used to step the high voltage down to low voltage, such as from $11111111111111111111111111111,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,00111111111111111111111111111,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,00111111111111111111111111111,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,00111111111111111111111111111,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,00111111111111111111111111111,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,00111111111111111111111111111,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,000100010010,00111 kV$ to $415 V$.

Cartridge Fuse (HBC)

A safety device sealed in a tube filled with sand that is very accurate and cannot be tampered with.

HRC Fuse (High Rupturing Capacity)

A type of fuse designed to handle very large fault currents without blowing apart dangerously.

Vacuum Circuit Breaker (VCB)

A breaker that uses a vacuum bottle to extinguish arcs quickly when contacts separate; it is faster than oil or air breakers because arcs disappear at the first moment current reaches zero.

Metallic Bellows

A flexible metal seal in a Vacuum Circuit Breaker that allows the moving contact to travel while maintaining the vacuum seal.

Tariff

A list of prices charged by an electricity company, including costs per unit ($kWh$), maximum demand charges, and standing charges.

Static Capacitor Banks

Devices connected next to large motors to supply reactive power locally, reducing the burden on the main supply.

Synchronous Condenser

A large motor running empty at high excitation that acts like a capacitor to supply reactive power to the system.

Phase Advancers

Equipment connected to a motor's rotor to feed in leading reactive current directly at the source.

Stroboscopic Effect

An optical illusion where spinning machinery appears still or moving backwards due to fluorescent lights flickering at the same speed as the rotation.

Exposed Conductive Parts

Metal parts of equipment like kettle casings that do not normally carry electricity but could become live during a fault.

Extraneous Conductive Parts

Metal objects NOT part of the electrical system, such as water pipes or gas pipes, that could accidentally carry electricity.

Circuit Protective Conductor (CPC)

The specific earth wire inside a circuit cable that connects exposed metal to the main earth point to trip protective devices during a fault.

Earth Electrode

A copper rod driven into the soil that connects the building's earth system to the ground.

Hazardous Zones (0, 1, 2)

Zone 0 has explosive gas always present; Zone 1 has gas present sometimes during normal work; Zone 2 rarely has gas present except during a failure.

Micro-shock

A dangerous condition in hospitals where a tiny leakage current as small as $10 \text{ microamps}$ can stop a patient's heart if they have internal wires like catheters.

PWM (Pulse Width Modulation)

A simple and cheap solar charge controller that slows down charging as the battery approaches full capacity.

MPPT (Maximum Power Point Tracking)

An efficient charge controller that finds the best power level from solar panels, potentially gaining up to $30\%$ more power.

National Grid System

A network connecting power stations (e.g., $11 kV$ generation stepped up to $330 kV$) to move electricity across the country and improve reliability.

Draw-in Duct System

A method of laying underground cables where pipes are buried in concrete, allowing cables to be pulled through later for easy replacement.

PILSWA Cable Lead Sheath

A lead tube layer that keeps water out of the cable and acts as an earth screen.

Steel Wire Armour

A strong layer of steel wires wrapped around a cable for mechanical protection against damage such as digging.

Coal-Fired Power Station Pollution

Air pollution ($SO_2, NO_x, CO_2$), water pollution (thermal discharge), and solid waste (ash).

Nuclear Power Station Pollution

Radioactive waste that stays dangerous for thousands of years, thermal pollution of water, and risk of radiation accidents.

IEE Wiring Regulations (BS 7671)

The primary rulebook for electrical design, equipment, and safety in all electrical work.

Generation Voltages in Zimbabwe

Standard levels include $6.6 kV, 11 kV, 13.8 kV, 15 kV,$ and $22 kV$ (at Kariba).

Transmission Voltages in Zimbabwe

Main national levels include $330 kV, 132 kV, 88 kV, 33 kV,$ and $11 kV$ for local distribution.

First Aid for Electric Shock

Switch off the supply, use dry wood/rubber to move the casualty, call for an ambulance, and perform CPR if the victim is not breathing.

Three-Phase Four-Wire System

A system using three line conductors ($415 V$ between lines) and one neutral ($230 V$ to any line), commonly used in mixed commercial buildings.

Off-Peak Tariff

A pricing system where electricity is cheaper at night or weekends to encourage use when the grid is less busy.

PME (TN-C-S) Earthing

A system where the neutral and earth are one wire ($PEN$) in the street but split at the house; carries a risk if the street $PEN$ wire breaks.

TN-S Earthing

A safe earthing system where the neutral and earth are two completely separate wires from the transformer to the house.

Buchholtz Relay

A transformer protection device that triggers an alarm for slow gas-forming faults and trips the breaker for sudden oil surges.

Silica Gel Breather

A container of crystals that removes moisture from air entering a transformer; the crystals turn pink when they need replacement.

Star-Delta Motor Starter

A device that reduces starting current to $1/3$ by starting a motor in Star connection ($58\%$ voltage) before switching to Delta connection for full power.

Iron Losses

Heat generated in a transformer core by eddy currents and hysteresis; reduced by using thin laminated silicon steel sheets.

Lap Winding

A type of armature winding where coil ends connect to neighboring commutator segments; used for LOW VOLTAGE, HIGH CURRENT machines.

Wave Winding

A type of armature winding with only $2$ parallel paths; used for HIGH VOLTAGE, LOW CURRENT machines.

No-Volt Release (NVR) coil

A safety component in starters that prevents an automatic restart after a power failure by snapping the arm to the OFF position.

Rotary UPS System

A system using a motor, heavy flywheel, and generator to provide clean power and bridge the gap ($10$ to $30$ seconds) during a power failure using kinetic energy.

Days of Autonomy

The number of consecutive cloudy days a solar battery bank can supply power without receiving any sunlight (typically $2$ to $5$ days).

Insulation Resistance Test

An IEE inspection test carried out to ensure electricity is not leaking between wires or to the ground.

Closed Circuit (Series) Fire Alarm

A fail-safe fire alarm system where a continuous monitoring current sounds the alarm if any wire is cut or broken.

Totally Enclosed Motor Enclosure

A completely sealed motor housing with no ventilation openings; suitable for outdoor, dusty, or hazardous environments.