see also:

• camping off-grid - power, batteries, solar, fridges
• solar power for camping
• solar regulator / controllers for solar panels for camping
• 12V batteries and battery boxes
• basic electronics
• voltage droop
• troubleshooting electrical faults
• https://www.youtube.com/watch?v=sBRvXBf7DCo how transmission lines work

• Australia has an inter-state distributed electrical grid which supplies households with single phase 50Hz 230-240V AC electricity (WA and Qld use 240V, the other states now use 230V)
  • Australia is similar to UK, India, Indonesia and most of Europe and Middle East albeit with different plug standards
  • many other countries including UAE, China, most of SE Asia use 50Hz 220V
  • 20% of countries (including USA, Canada) use 60Hz 120V
  • Japan uses 100V 50/60Hz
• this is derived from a mix of sources:
  • brown coal fired power stations
  • gas fired power stations
  • hydroelectric (Snowy Mountains, NSW and in Tasmania)
  • solar
  • wind
  • minimal geothermal
• DC power
  • this provides linear voltage with a constant polarity
  • electric motors will run in the direction of a given polarity, reversing it will make the motor rotate the opposite way
  • many electronics require the correct polarity to work including LED torches
  • simple light globes will run in either polarity
  • the problem with DC power is the voltage drops rapidly over distances in proportion to the distance and the resistance of the wires and this is not efficient for transmission more than a few meters.
  • DC can be converted to AC via an AC inverter
• AC “mains” power
  • overcomes the loss in voltage issue of DC and can be transmitted long distances but this comes at a cost - alternating sine wave voltages which means at a point of the cycle the voltage becomes zero and then reverses polarity - this is problematic for electric motors which will not “know” which way to start unless a capacitor is used to drive it the correct direction.
  • the cycle frequency also causes flickering of many light sources at this frequency which is not detectable by human eyes but is picked up in videos and photographs
  • AC voltage can be changed via an AC transformer (eg. transformer substations on power transmission lines)
  • AC can be converted to DC via a AC-DC power transformer or “AC-DC power adapter” which use a transformer to lower the voltage and then use diodes and capacitors to convert AC to DC
• standard single phase AC power
  • the common Australian standard is 50Hz 230V 10A which can supply a maximum 2300W.
  • Australian household AC plugs generally are earthed and thus have 3 points - active, neutral and earth and are usually rated to 10A 2300W limit (lighting circuits are generally rated lower, and some households may have a 15A circuit to the garage or for special appliance needs - a 15A three-pin plug will have a slightly larger ground pin and will not fit into a 10A outlet, however a 10A appliance plug will fit into a 15A outlet)
  • there are also variants for 20A, 25A and 32A single phase outlets, but only found in industrial settings and these appliances are usually hard-wired into the power supply rather than use a plug.
• 3 phase AC power
  • higher appliance power needs can be supplied via a 3-phase supply which has 3 active wires instead of one and each active power cycle is staggered one-third of a cycle apart to provide more consistent voltages (makes electric motors able to start without a capacitor system hence are cheaper and more efficient to run), higher power outputs, and can supply power at both 230/240V and 400/415V.
  • the higher voltage helps to deliver more power to appliances
  • 3 phase machines requiring a 400/415V electricity connection are generally hardwired to the power supply.
  • look at the main switch in your switchboard, if it is 1 pole wide (about 1 finger width), then your electricity supply is single phase, if it is 3-pole wide (about 3 finger widths), then its likely 3 phase power.
  • upgrading to three phase power supply:
    • need to check with power company to ensure three phase is available
    • an electrician will need to:
      • upgrade the power cable from the street to your meter box
      • replace the meter box with a new tariff meter and special 3 phase circuit breakers
      • if the existing switchboard is small it may need replacement and re-wiring
    • you may get charged an extra daily connection fee for having three phase
  • alternatively, buy a 3 phase power converter which converts single phase 230V into three phase 400V output

• in Melbourne, most households with more than 1 person and without swimming pools use an average 14-18kWh/day (slightly more in winter)
• a reverse cycle central heating system for a standard single story house might pump out hot air at a rate of 4-5kW although some of these systems can go to 25kW on a 3 phase power supply
• swimming pool pump 1000W and if ran for 8hrs a day = 8kWh per day!
• microwave ovens are generally 1200 or 2400W

• power in Watts = voltage x current in amps
• energy used in Watt-hours 1 Wh = 3600 Watt-seconds = 3600 Joules
• energy used in a 12V battery 12Wh = 1Ah (ie multiply the amp hours used by the voltage)
• car cigarette lighter outputs are usually 10A max at 12V = 120W max.

• see https://www.youtube.com/watch?v=sBRvXBf7DCo for an explanation of how they work and the various components
• you can estimate the voltage by how many porcelain insulator discs are used at each tower as ~ 1 disc per 11kV is used:
  • 1 disc is used for 11kV
  • 3 discs is used for 33kV
  • 12 discs is used for 132kV
• power station generators usually produce 11kV and this is transformed to generally output at 765kV
  • substation converts 765kV to 440kV output
    • substation converts 440kV to 220kV output
      • substation converts 220kV to 132kV output
        • main local substation converts 132kV to 33kV output
          • local substation feeder converts 33kV to 11kV
            • local distribution transformer generally converts the 11kV to output 3 phase 433V
              • feeders sent to houses as single phase 220-240V (110V in US)
• issues
  • sagging
    • power lines stretch and sag in hot weather hence towers are placed at spans of 300-400m apart
    • to strengthen the cable, Aluminium Conductor Steel Reinforced (ACSR) design is generally used - made up of a many conducting aluminium cables surrounding a core of steel cables (for strength)
    • sag distance = (weight x length²)/(8 x tension) - tension falls as it gets hotter and the metal expands
  • vibrations from wind turbulence
    • wind passing a cable develops turbulence which induces vibration in the cable
    • this vibration is reduced by heavy dumbbell shaped dampeners placed near the towers and this helps reduce transmission of the vibrations down the line
  • cable termination at each tower
    • cables end at each tower and are connected to the tower by insulator “strings”
      • but this leaves sharp edges at the end which concentrates electric fields there making them glow faintly which loses power hence corona rings are placed to reduce this by spreading the electric field and also help reduce corona discharge when it is raining
    • the power transmission bypasses the tower via separate connector cables “jumper wires”
    • this allows easier replacement of cable in the event of damage - only one span needs replacing
  • skin effects
    • high frequency AC voltage generally is mainly at the outer rim of each cable which may only be 1% of its diameter - skinning effect
    • this results in heating of the surface of the cable resulting in power losses, especially at very high voltages such as 765kV
    • hence cables are made up of many smaller diameter cables to reduce this skinny effect
  • corona loss
    • the voltage in the cables produces an intense electric field emanating out from the cable which causes power losses “corona losses”
    • this ionises air creating a crackling hum
    • for this reason, the cables are also located at a distance from humans to ensure the electric field is at a safe intensity level
    • corona losses are reduced by using bundle conductors - each phase carried by 2 or more conductors (joined to each other by space damper bars) which increases the effective radius
    • corona power loss = (244/delta)(f+25)(E_n-E₀)²(sqrt(radius) / sqrt(D) ) x 10^-5 kW/km/phase
  • capacitative interference
    • as the transmission lines are +ve compared to the ground and are separated from ground by air which acts as a dielectric medium similar to that of a capacitor, in very high voltage lines, the voltage actually INCREASES along the line
    • this also results in current leading the voltage called leading reactive power
    • this is mitigated by attaching a shunt reactor in parallel to the line which has no output but reduces the voltage back to what is required
  • high inductance device usage causes a current lag effect
    • these devices are typically motors and result in lagging reactive power
    • this is mitigated by attaching a shunt capacitor in parallel to the line (not at the same time as a shunt reactor is attached though?), although in smaller substations, capacitor banks are used instead
  • tower damage in extreme winds
    • mini-tornados and other very strong winds can severely damage towers resulting in regional break to power transmission and prolonged outages
  • bushfire risk
    • especially in very strong winds on extreme weather days when located near flammable forests etc.