ELECTRICITY AND POWER DEFINITION

Supply
Supply has many meanings depending on the point of view of the organisation providing the data. The main definitions can be described by working back from the electricity end user to the power station:
Supply from the distribution system - this is equal to the end user consumption;
Supply from the transmission system - this is equal to the end user demand plus the demand from any large user being supplied directly from the transmission system plus the losses in the distribution system;
Supply sent out from the power stations - this is equal to the supply from the transmission system plus transmission system losses; and
Supply generated - this is the electricity generated by the power stations and is equal to the supply sent out from the power stations plus losses within the power stations that are associated with the generation of the electricity.
Note: For each of these, the "instantaneous" and "period" values of the electricity supply are required.

Switchyard
Fenced area containing electrical equipment used to control the transfer of power from one set of power lines to another set of power lines. It is usually associated with high voltage transmission lines, but is also used in association with lower voltage distribution lines.

Thermal efficiency (Cogen) (overall)
[Cogen gross elec output] + [imported electricity] + [site steam] divided by:
[fuel to cogen unit] + [fuel used for imported electricity] + [fuel to aux boiler]
Where [site steam] includes hot water as applicable.

Topping cycle
High-pressure steam is raised in an auxiliary boiler and expanded through a backpressure steam turbine to the required site steam conditions.

Total installed capacity
Sum of the capacity of each unit making up the power plant.

Transmission
Electrical cabling system which transfers large amounts of power, usually over long distances. Transmission systems are usually operated at extra high voltages (eg 132kV, 275kV & 330kV).

TUOS
Transmission use of system charge. In the National Electricity Code, the charge for using the electricity network above 66 kV voltage level

Turnkey
Installation to the point of readiness for operation, generally a single design and construct contract. Some owner's costs, such as owner's engineering, spares, owner's start up labour and fuel, may be excluded and need to be considered in the indirect costs or elsewhere.

Waste
Waste products used in power generation include cane residue (bagasse) in the sugar industry; sludge gas from sewerage treatment plants; and methane from landfill sites.

Waste heat boiler
A boiler that uses waste heat (such as gas turbine or reciprocating engine exhaust gas) to produce steam or hot water.