Heavy Electrical / Power Distribution
Transformers, contactors, busbars — the big stuff
Distribution Board / Panel
Switchgear
A metal or plastic enclosure that splits incoming mains power into multiple protected circuits. Each outgoing circuit has its own breaker or fuse, with a common neutral and earth busbar.
Contactor
Switchgear
An electromechanical switch rated for high current and frequent operation, used to switch motors, heaters, and lighting banks. Like a relay but built for industrial duty cycles and three-phase loads.
Isolator / Changeover Switch
Switchgear
The visible-break safety switch: an isolator disconnects a dead circuit so it can't come alive while someone works on it; a changeover switch selects between two sources — the classic mains/generator handle on Indian homes and shops.
HV Circuit Breakers (VCB / ACB / SF6)
Switchgear
Above the MCB/MCCB world live the big breakers: Air Circuit Breakers for large LT panels, Vacuum Circuit Breakers for 11/33 kV, and SF6 breakers for the highest voltages — machines built to interrupt tens of kiloamps of fault current on command.
Motor Starter (DOL / Star-Delta)
Control
Contactor + overload relay packaged to start and protect three-phase motors. DOL slams full voltage in (simple, big inrush); star-delta starts at 58% voltage then switches, cutting the inrush for larger motors.
Overload Relay
Protection
The motor's bodyguard: models motor heating and disconnects the contactor coil when sustained current says the windings are cooking. Trips on overload — deliberately slow, so it ignores normal starting inrush.
VFD / Variable Frequency Drive
Drive
A variable frequency drive rectifies mains to DC then synthesises variable-frequency AC, giving a three-phase motor smooth speed control, gentle starts, and big energy savings on fans and pumps.
Earthing / Grounding Components
Safety
The safety backbone of every installation: electrodes in soil, earthing conductors, and bonding that give fault current a low-impedance path so breakers trip fast and touchable metal stays at earth potential.
Lightning / Surge Arrester
Safety
Diverts lightning and switching surges on power lines to earth. Modern units are gapless metal-oxide (ZnO) stacks: insulators at normal voltage, conductors during a surge — protecting transformers and service entrances.
Protective Relay (Overcurrent / Differential / Distance)
Protection
The brains behind every big circuit breaker: relays watch CT/PT signals and decide within milliseconds whether a fault exists — then fire the breaker's trip coil. A full unit of every Switchgear & Protection syllabus, from induction-disc classics to numerical relays.
Busbar / Bus Duct
Distribution
Solid copper or aluminium bars that distribute heavy current inside panels — the motorways of a switchboard. Sized by cross-section, spaced for fault forces, and insulated by air, sleeves or enclosure design.
Line Insulators & Conductors (Pin / Disc / ACSR)
Transmission Hardware
The porcelain and aluminium of the power system: insulators hold live conductors off earthed towers, and ACSR conductors carry the power. String efficiency and the 'why do birds not get shocked' questions live here — a guaranteed exam unit in Power Systems.
Energy Meter
Metering
Measures real energy (kWh) by multiplying voltage and current over time. Utility revenue meters, DIN-rail submeters, and hobby modules (PZEM style) all do the same maths at different accuracy classes.
Capacitor Bank (PFC)
PFC
Banks of AC capacitors that supply the reactive current inductive loads (motors, transformers) would otherwise draw from the grid, correcting power factor and cutting utility penalties. Stored charge and resonance make them serious equipment.
Sockets, Plugs, Switches (wiring devices)
Accessory
The user-facing parts of an electrical installation — wall sockets, plugs, light switches, and dimmers. They connect appliances to mains power safely and let users control circuits manually.
Heating Element (Nichrome / Appliance Elements)
Utilization
Joule's law as a product: a resistance wire designed to run red-hot. Every iron, geyser, kettle, toaster and industrial furnace is a nichrome (or kanthal) element sized by P = V²/R — the Utilization of Electrical Energy chapter made tangible.