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Glossary


Base load plant	Usually a coal-fired and nuclear plant used to maintain the base load.
Combined cycle	An electric generating technology in which electricity is produced from otherwise lost waste heat exiting from one or more gas (combustion) turbines.
Conductive fog	The unusual combination of fog and dust or ash particles, possibly from recent fires.This fog is instant and unpredictable (as far as Eskom is aware). Some glass insulators used in substations and lines cannot withstand the phenomenon, causing widespread flashovers which initiate tripping of lines and plant.
Daily peak	The maximum amount of energy demanded in one day from a company or utility service.
Decommissioning	Removing a facility (eg reactor) from service, and subsequent actions of safe storage, dismantling and making site available for unrestricted use.
Demand-side management (DSM)	Planning, implementing and monitoring activities to encourage consumers to modify patterns of electricity use, including timing and level of electricity demand.
Disabling injury incident rate (DIIR)	The number of disabling injuries suffered in proportion to manhours worked.
Embedded derivative	An embedded derivative causes some or all cash flows that otherwise would be required by a contract to be modified according to a specified variable such as a currency.
Energy availability factor (EAF)	Measures plant availability and takes into account energy losses not under the control of plant management, as well as internal non-engineering constraints.
Energy efficiency	Programmes aimed at reducing energy used by specific end-use devices and systems, typically without affecting services provided.
Eskom sustainability performance index (ESPI)	Index using technical, economic, environmental and social measures to measure sustainable performance over the short and long term.
Flashover	Electrical breakdown of insulation.
Forced outage	Shutdown of a generating unit, transmission line or other facility, for emergency reasons or a condition in which generating equipment is unavailable for load due to unanticipated breakdown.
Free basic electricity (FBE)	Amount of electricity deemed sufficient to provide basic electricity services to a poor household.
Human resources sustainability index	A measure of Eskom’s ability to achieve its human resources objectives.
International Financial Reporting Standards (IFRS)	A set of global accounting standards issued by the International Accounting Standards Board that require transparent and comparable information in general purpose financial statements.
Independent power producer (IPP)	Any entity that owns or operates, in whole or in part, one or more new independent power production facilities.
Interruptible load	Load that can be interrupted in the event of capacity or energy deficiencies on the supplying system.
Interruptible power	Power whose delivery can be curtailed by the supplier, usually under some sort of agreement by the parties involved.
Kilowatt-hour (kWh)	Basic unit of electric energy equal to one kilowatt of power supplied to or taken from an electric circuit steadily for one hour. One kilowatt-hour equals 1 000 watt-hours.
Load	Amount of electric power delivered or required at any specific point on a system.
Load management	Influencing the level and shape of demand for electrical energy so that demand conforms to present supply situations and long-run objectives and constraints.
Load profile	Information on a customer’s electricity use over time, sometimes shown as a graph.
Load shifting	A load shape objective that involves moving loads from peak periods to off-peak periods. If a utility does not expect to meet its demand during peak periods but has excess capacity in off-peak periods, this strategy might be considered.
Load shedding	Scheduled and controlled power cuts by rotating available capacity between all customers when demand is greater than supply to avoid total blackouts in the supply area.
Maximum demand	Highest demand of load within a specified period.
Megawatt	One million watts.
Megawatt-hour (MWh)	One thousand kilowatt-hours or one million-watt hours.
Mid-merit power generation	Those installations which generate electricity during the daily periods when electricity demand is higher than average.
Mothball	Plant (ie power stations) placed in long-term storage.
Operational sustainability index	Reflects overall technical performance, while balancing low-cost production of electricity with sustainable long-term reliability.
Outage	The period in which a generating unit, transmission line, or other facility is out of service.
Off-peak	Period of relatively low system demand.
Peak demand	Maximum power used in a given period.
Peaking capacity	Generating equipment normally operated only during hours of highest daily, weekly or seasonal loads.
Peak load plant	Usually a gas turbine or pumped storage scheme used during peak-load periods.
Unit capability factor (UCF)	Measures plant availability and indicates how well plant is operated and maintained.
Power pool	An association of two or more interconnected electric systems with an agreement to coordinate operations and plan for improved reliability and efficiencies.
Primary energy	Energy embodied in natural resources (eg coal, liquid fuels, sunlight, wind, uranium, water).
Pump storage scheme	A plant that usually generates electric energy during peak-load periods by using water previously pumped into an elevated storage reservoir during off-peak periods when excess generating capacity is available.
Reserve margin	Difference between net system capability and system maximum load requirements (peak load or peak demand).
Spent fuel	Fuel assemblies removed from a reactor after several years of use.
Supply-side management (SSM)	Planning, implementing and monitoring supply-side activities to create opportunities for cost-effective purchase, management, generation, transmission and distribution of electricity and all other associated activities.
System minutes	The international benchmark for measuring the severity of interruptions to customers. One system minute is equivalent to time loss of the entire system for one minute at annual peak.
Unplanned automatic grid separations (UAGS)	A measure of the reliability of the service provided to the electrical grid that measures the number of supply interruption per operating period.

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