Dividing up the Power
Until 1998 the Tasmanian electricity system was wholly owned by the Hydro Electric Corporation. As a result of disaggregating the system three businesses were formed to operate Tasmania's power system.
Hydro Tasmania generates electricity, owns the generation assets (dams and power stations) and since 2005 has traded energy in the NEM.
Transend Networks Pty Ltd owns and operates the electricity transmission system in Tasmania - the highways of power between power stations and the local distribution network.
Aurora Energy Pty Ltd has a licence to retail electricity and gas in Tasmania and owns the distribution network. Until November 2006 it was the only electricity retailer licensed in Tasmania. Since 2005 Aurora buys electricity from the NEM and holds a vesting contract with Hydro Tasmania to supply electricity for those Tasmanian customers not subject to retail contestability.
Some large customers buy their electricity in bulk from Aurora. They receive it at 220,000 or 110,000 volts and transform it in their own substations.
Major substations serving other large industries, business and domestic customers use transformers to step down the voltage. A network of feeder lines divide up the power and carry it away from the substations at 33,000, 22,000 or 11,000 volts. These feeder lines are connected to distribution substations (some of which are mounted on poles) and the voltage is stepped down to 240 volts for supply to individual customers.
Four lines lead away from distribution substations - one for each phase and a neutral wire. Each house is connected to one phase wire and the neutral wire. Power is drawn from the phase wire, and the circuit back to the distribution substation is completed using the neutral wire.
A pole-mounted transformer
(distribution substation)
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 110 000 volt single circuit transmission tower |
 22 000 and 240 volt distribution lines |
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