ELECTRICITY AND POWER DEFINITION

Renewable Generation
Produces no net greenhouse emissions. Includes power generated from non-hydrocarbon, natural resources such as biomass, hydro, wind, solar (photovoltaic) and tidal. It also includes power generated using waste products. Tend to be distributed and connected to local distribution networks.

Reserve Plant Margin
Reserve Plant Margin is a well used (but generally misunderstood) simplistic measure which, in theory, is meant to give an indication of the ability of the electricity system's generation plant to cope with the estimated peak (instantaneous) demands on the system.
It is measured by:
1. Summing the supply capacities of all the power stations able to operate at any time during a particular interval of time(usually the three winter months or the three summer months);
2. Dividing by the total power station sent out supply required to meet the maximum peak (instantaneous) demand estimated for that interval of time;
3. Taking away 1.
A value of (say) 0.3 means that there is a 30% "excess" in sent out supply capacity available to meet the maximum peak demand (i.e. the Reserve Plant Margin - 30%).
Note: The reserve plant margin calculation may not take into account:
The generating capacity kept in reserve for system stability reasons;
The unavailability of power stations due to scheduled and unscheduled outages;
The short term overload capabilities of some of the power stations;
The energy limits of the northern hydros and some peaking plants, such as Wivenhoe pumped storage hydro power station;
The ability of demand side management techniques (such as hot water switching and short term reduction in industrial loads) to reduce peak loads;
The interconnectors being able to supply some of the required capacity; or
The load limits on the interconnectors and inter-zonal transmission lines.
For these, and other, reasons, the reserve plant is compared to a "guesstimated" optimum value that is supposed to take some account of these factors. Historically, values between about 20% to 25% have been used in Queensland. A reserve plant margin less than this meant that there was a risk of not having sufficient plant to meet the demand peaks, while more than this indicated an over-capacity in generating plant to meet the peak demands and that some plant would be under-utilised.
The main problem with using the reserve plant measure is that most people are not be aware of the way in which it is calculated and so would assume that there was always a large excess in generating capacity and that all peak loads would be met. With the advent of the NEM, the importance of the Reserve Plant Margin measure has, thankfully, declined in importance, usefulness and usage.

Retrofit
Any improvement activity on an existing power plant that generally involves fitting new equipment to an existing plant.

Sent Out Energy
Electrical energy leaving the power plant. This is the generated energy minus the auxiliary energy used in the plant.
Energy generated (MWh) minus auxiliary energy (MWh).

Shallow Connection
Transmission assets and services provided for one participant where the assets will never be part of the shared network.

Steam turbine
An engine in which a vaned wheel is made to revolve by the impingement of steam. Converts steam energy to mechanical energy.

Substation
Similar to a "switchyard" but is usually associated with lower voltage distribution lines. Most of the equipment is enclosed within a building.

Superheater
A heat exchanger part of a boiler for increasing the temperature of saturated steam to superheated steam. Generally steam admitted into a steam turbine must be superheated (that is, above the saturation temperature at that pressure).

Supplementary fired
Additional gas firing into a waste heat boiler when the unfired exhaust gas is not sufficiently hot for raising the site steam requirements (temperature or steam mass flow). Can generally be done on gas turbine exhausts because sufficient oxygen remains in the exhaust. Not generally done on reciprocating engine exhausts due to lower excess oxygen in exhaust.