Electrical Installation Flashcards
(23 cards)
Generation
- Electromagnetic Induction
- Ohm and Other laws
- AC/DC generators
Transmission
- Transporting voltage from a power station to the point of consumption
- High voltages used over longer transimission lines to avoid loss of energy (P)
- Transformers at the end of the line
6.6kV: 11kV: 22kV: 66kV: 132kV: 275kV: 400kV: 800kV
Distribution
- Brick built/ Mini substations
- Transformers at end of line steup-down the electricity for town standard reticulation systems [380/220V 3 phase 4 wire]
Domestic Distribution
- Single phase for domestic, supplied by nearest substation [P.V.C.A.S Underground]
8kVA-16kVA: 35A-70A: All at 230V
Supply and Meter Box
- Used by local authorities to moniter use of electricity by a consumer and charge them accordingly
- Contains main circuit breaker, earth, conduit for the user distribution board, conduit for imcoming main
Distribution/Sub-Distribution Board
- Neutral bar
- Circuit breakers
- Main circuit breaker (m.c.b)
- Earth leakage
- Earth leakage switch
- Conduit from meter box
- Conduits to lighting + sockets
Main Switch Disconnector/Isolator
- Double pole isolator (live and neutral)
- Mounted adjacent to the appliance it controls
- Switches installed to isolate/control the supply to sockets
- Isolates the appliances/entitre sdb from the mian supply when triggered
Earth Leakage Unit
- Earth all items of quipment
- Goal is to minimise the potential difference between the live wires and the earth
- The current flows thru eath wire because it is the path of least resistance
Circuit Breaker & Fuse
- Circuit breaker trips automatically when the current goes over the rating for an extended period of time
- Fuse melts when exposed to an overcurrent for an extended period of time, breaking the circuit
Both protect the systems from overcurrent
Wire Connection Variations
- Delta Connection
- 3 Star Connection
- 4 Star Connection
Single phase AC
- One alternating volatage between two conductors
- Standard of 50Hz
3 phase AC
- Is actually 4 pahse but the 4th phase connector/wire is neutral
- This Star Point is then earthed
Production of Alternating Current
- Water/Steam turbine
- Deisel for smaller ones
- Alternate energy sources available
- 50Hz standard
Production of Direct Current
- Non-Oscillating voltage
- Related to batteries and other stored energy sources
- Cannot be stepped up or down with a transformer
Design principles of domestic electrical installation
- Safe
- Economical
- Easy to maintain
Other aespects to consider when designing a domestic electrial system
- Volt drop [5%]
- Current Rating [I²R]
- Protection from overcurrent
- Earthing system
Linked to Authority’s earth cable,
Earth Rod,
Earth Mat [Copper,2m Deep]
Lighting Installation
- Cost
- Illumination Level and Lighting Type
- Origin
Usualy Radial type circuit; can be ring circuit
Code of Practice for the Wiring of Premises
Lighting Specifics
- Circuit breaker of 10Amps
- 1.5mm pvc insulated copper, in 20mm conduit
- New circuit for every 100m² of lighting
Sockets
- ** Living Area** – 3 sockets 150mm above f.f.l
- Bedrooms – Between beds and at diagonal corners of room
- Kitchen – 1 socket every 1.2m 150mm above worktops
- Bathroom – Supplied by double wound transformer only or not at all
- Stove – 10mm² insulated copper, 6mm² bare earth, 25mm pvc conduit
- Boilers – 2.5mm² insulated, 2.5mm² bare earth, 20mm pvc conduit
Main Wiring Systems
- Conduit
- PVC Sheathed Cables
- Mineral Insulated Sheathed Cables
Protect Conductor, Earth Cont: Bellow Plaster Finish: Surface Mounting
Cables
- Solid core vs Stranded core
- Armour
- Different materials for insulation
Calculating Estimated Load
[SUPP]
Electrical Installation Schedules
- Architecht and electrical contractor
- Does not require consulting engineer
- Certificate of installation once contractor is complete
SABS Code of Practice for the Wiring of Premises: SABS Code of Practice for Building Drawings Practice
