Towers and Lines
A transmission line is a circuit to deliver power between two locations.
The transmission line consists of a series of conductors supported by structures to maintain a safe electrical clearance to the ground. The support structures are either steel towers or poles made of steel, concrete or wood. Each structure requires a series of insulators to suspend the conductors in the air away from the structure.
The majority of TransGrid’s transmission occurs using above ground lines. However in certain circumstances underground cabling has also been installed. Underground cables are generally buried under roadways in major urban areas such as Sydney.
When interconnected, these transmission lines are called a high voltage transmission network.
Substations and Switching Stations
Our substations operate at 132 kV, 220 kV, 330 kV or 500 kV.
Electricity is transmitted at high voltages when required to travel over large distances as this reduces electrical losses. At substations, high voltage transmission can be reduced in voltage for local needs or for further transmission.
Switchyards can generally be divided into substations and switching stations.
Transmission lines enter the switchyard and are connected to electrical equipment on their way to the power transformer. A power transformer is used to change the voltages from one level to another. Different voltages are used for generation, high voltage transmission and local distribution The power transformer steps the voltage up or down before attaching to similar equipment and exiting the substation.
In switching stations, there are no power transformers and all connected transmission lines enter and leave at the same voltage. Switching stations provide greater control of the outgoing energy where a change in voltage is not required.