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The following terms and definitions are for your reference for the language used in this document and for use in any correspondence with EDTI.

This term … Is defined as …
active power The time average of the instantaneous power over one period of the wave, expressed in watts. For sinusoidal quantities in a single-phase circuit, it is the product of the voltage, the current and the cosine of the phase angle between them.
AECUC Alberta Electrical and Communication Utility Code. Refer to website:
AIES Alberta Interconnected Electric System. This system encompasses all transmission facilities and all electric distribution systems in Alberta that are interconnected, as defined in the Alberta Electric Utilities Act.
alternating current (AC) An electric current that reverses direction at regularly recurring time intervals and has alternating positive and negative values. In North America, the standard for alternating current is 60 complete cycles each second. Such electricity is said to have a frequency of 60 Hz.
ampere (amp) The unit of current flow of electricity.
ANSI American National Standards Institute. Refer to website:
anti-islanding Designed to detect and disconnect from a stable unintended "island" with matched load and generation. Reliance solely on undervoltage/overvoltage and frequency trip is not considered sufficient to qualify as anti-islanding.
apparent power The product of the root-mean-square current and the root-mean-square voltage, expressed in volt-amperes (VA). This term is used for alternating-current circuits because current flow is not always in phase with voltage, so multiplying volts by amperes does not necessarily give watts. Apparent power is made up of two components, active and reactive power.
automatic circuit recloser (ACR) A self-controlled device for automatically interrupting and reclosing an alternating-current circuit with a predetermined sequence of opening and reclosing. EDTI uses these devices for overcurrent protection on some distribution circuits.
capacity In the electric power industry, capacity has two meanings: 1) system capacity: the maximum power capability of a system. For example, a utility system might have a rated capacity of 5,000 megawatts. 2) equipment capacity: the rated load-carrying capability of generating equipment or other electrical apparatus, expressed in kilovolt-amperes (kVA) or kilowatts (kW).
CEC The Canadian Standards Association's C22.1 Safety Standard for Electrical Installations Part 1, also known as the Canadian Electrical Code.
certification test A test adopted by EDTI that verifies conformance of certain equipment with commission-approved performance standards in order to be classified as certified equipment. Certification tests are normally performed by a nationally recognized testing laboratory such as the CSA or Underwriter's Laboratory.
certified equipment Equipment used in a DER facility that has passed the certification test.
closed transition A mode of operation in which the DER is operated in parallel with EDTI's distribution system for a brief period of time, to ensure that the load is maintained while transferring from the utility to the DER or vice versa.
commissioning test A test performed during the commissioning of all or part of a DER facility system to achieve one or more of the following: verify specific aspects of its performance, calibrate its instrumentation, or establish instrument or protective function set points.
CSA Canadian Standards Association. Refer to website:
current The flow of electricity in a conductor. Current is measured in amperes.
direct current (DC) A unidirectional electric current in which the changes in value are either zero or so small that they may be neglected. The current supplied from a battery is direct current.
distributed generation (DG) Electric generation facilities connected to a distribution system through the point of common coupling. Distributed generation is a subset of distributed energy resources.
distributed energy resources (DER) Sources of real electric power that are not directly connected to the bulk power transmission system. These include both generators and energy storage technology.
distribution system Any facilities that operate at a nominal voltage of 25,000 V or lower and that allow electric power to be delivered to a load, regardless of ownership.
EDTI EPCOR Distribution and Transmission Inc., the company that operates the electric distribution system in the city of Edmonton. Refer to website:
electrical energy The quantity of electricity delivered over a period of time. The commonly used unit of electrical energy is the kilowatt hour (kWh).
electrical power The rate of delivery of electrical energy and the most frequently used measure of capacity. The commonly used unit of electrical power is the kilowatt (kW).
electromagnetic interference (EMI) Any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of a device, equipment or system.
export limiting Designed to prevent the transfer of electrical energy above a certain value (the export limit), from the generating facility to EDTI's distribution system.
ferroresonance An oscillatory phenomenon caused by the interaction of system capacitance with the non-linear inductance of a transformer, usually resulting in a high transient or sustained overvoltage.
frequency The number of cycles through which an alternating current passes in a second. The North American standard is 60 cycles per second, known as 60 Hz.
generation The process of converting solar, thermal, mechanical, chemical or nuclear energy into electric energy.
grid A network of electric power lines and connections.
harmonics Sinusoidal currents and voltages with frequencies that are integral multiples of the fundamental power line frequency.
hertz (Hz) The unit of frequency for alternating current. Formerly called cycles per second. The standard frequency for power supply in North America is 60 Hz.
IEC International Electrotechnical Commission. Refer to website:
IEEE Institute of Electrical and Electronics Engineers, Inc. Refer to website:
independent distributed energy resource provider (IDERP) A privately owned power generating facility, which may be connected to a utility system to supply electricity for domestic or export markets. Referred to as simply a "distributed energy resource provider (DERP)" in this document.
induction generator An induction machine that is driven above its synchronous or zero-slip speed by an external source of mechanical power in order to produce electric power. It does not have a separate excitation system and therefore requires its output terminals to be energized with alternating-current voltage and supplied with reactive power to develop the magnetic flux.
in-rush current The maximum current drawn from EDTI by the generator during the start-up process.
installed capacity The capacity measured at the output terminals of all the generating units in a station, without deducting station service requirements.
interconnected system A system consisting of two or more individual power systems connected together by tie lines.
interconnection The physical connection of distributed generation to EDTI's distribution system so that parallel operation can occur.
interconnection point See point of common coupling.
inverter A machine, device or system that changes direct-current power to alternating-current power.
inverter-type voltage- following Generating equipment that uses power electronic devices to produce a waveform, using the external voltage of the distribution system to control the electronic devices, in such a way that if the external voltage ceases, the electronic devices instantaneously stop producing the waveform.
island(ing) A condition where a portion of EDTI's distribution system is solely energized by one or more DERs, while electrically separated from the rest of the distribution system.
isolated A condition where a normally parallel generator becomes disconnected from EDTI's distribution system, but continues to supply only its own load. Only generators with stand-alone capability are able to operate isolated.
kilovar (kvar) 1,000 vars. See reactive power.
kilovolt (kV) 1,000 volts.
kilovolt-ampere (kVA) 1,000 volt-amperes. See apparent power.
kilowatt (kW) The commercial unit of electric power; 1,000 watts. A kilowatt can best be visualized as the total amount of power needed to light 10 100-watt light bulbs.
kilowatt hour (kWh) The commercial unit of electric energy; 1,000 watt hours. A kilowatt hour can best be visualized as the amount of electricity consumed by 10 100-watt light bulbs burning for an hour.
load The amount of electric power delivered or required at any specified location.
load factor The ratio of the average load during a designated period to the peak or maximum load in that same period. Usually expressed as a percentage.
load forecast The anticipated amount of electricity required by customers in the future.
megavar (Mvar) 1,000 kvars.
megavolt-ampere (MVA) 1,000 kVA.
megawatt (MW) A unit of bulk power; 1,000 kilowatts.
megawatt hour (MWh) A unit of bulk energy; 1,000 kilowatt hours.
nationally recognized testing laboratory (NRTL) A laboratory approved to perform the certification testing requirements for generating facilities.
NEMA National Electrical Manufacturers Association. Refer to website:
non-exporting Designed to prevent any transfer of electrical energy from the generating facility to EDTI's distribution system.
overfrequency The abnormal operating state or system condition that results in a system frequency above the normal 60 Hz.
parallel (operation) The operation of a generating unit, while connected to either the Alberta Interconnected Electric System or a smaller separate electric power grid, in parallel with other sources of electric power generation.
point of common coupling (PCC) The point where EDTI's electrical facilities or conductors are connected to the DERP's facilities or conductors, and where any transfer of electric power between the DERP and EDTI takes place.
power The rate of doing work. Electric power is measured in watts.
power factor The ratio of active power to apparent power. It is the cosine of the phase angle difference between the current and voltage of a given phase.
distributed energy resource provider (DERP) A person or an organization interconnected to EDTI's distribution system for the purpose of producing electric power from an unregulated generating facility.
power system The interconnected facilities of an electrical utility. A power system includes the generation, transmission, distribution, transformation and protective components necessary to provide service.
reactive power The square root of the square of the apparent power, minus the square of the active power. Reactive power is developed when there are inductive, capacitive or non-linear elements in the system. It is measured in vars.
resonance The enhancement of a circuit's or system's response to a periodic excitation, usually resulting in very high currents and voltages.
root-mean-square (RMS) The equivalent heating value of a current or voltage waveshape. It is defined mathematically as the square root of the average of the square of the value of the function taken throughout one period. For a sinusoidal waveshape, the RMS value is equal to the peak value divided by 1.414.
secondary injection testing A method in which low-level signals obtained from current and voltage signal generators are injected into a power system protective device to test device response.
simulated utility An assembly of variable frequency and variable voltage test equipment used to simulate a normal utility source.
stabilized Will be used to refer to EDTI's distribution system, returning to the normal range of voltage and frequency following a disturbance.
stand-alone (capability) Distributed generation that can operate by controlling the frequency and voltage of its facility while in islanded or isolated mode.
synchronous generator An alternating-current machine in which the rotational speed of normal operation is constant, and when interconnected, is in synchronism with the frequency and in step with the voltage of the electric utility system.
system controller (SC) A provincially appointed authority responsible for dispatching load and generation on the Alberta Interconnected Electric System, in real time.
target (operation indicator) A supplementary device operated either mechanically or electrically, to indicate visibly that the relay or device has operated or completed its function.
telemetering Transmission of measurable quantities using telecommunications techniques.
total harmonic distortion (THD) The ratio of the root-mean-square of the harmonic content to the root-mean-square value of the fundamental quantity, expressed as a percentage of the fundamental.
transformer An electromagnetic device for changing the voltage of alternating electricity.
trip time The time between the start of the abnormal condition and the interconnection device ceasing to energize the distribution system.
type test A test performed on a sample of a particular model of a device to verify specific aspects of its design, construction and performance.
UL Underwriters Laboratories. Refer to website:
underfrequency The abnormal operating state or system condition that results in a system frequency below the normal 60 Hz.
visible-break disconnect A disconnect switch or withdrawable circuit breaker that can simultaneously disconnect under full load the generator and all protective devices and control apparatus from the circuits supplied by the generator. The switch or breaker shall be provided with the means for adequate visible inspection of all contacts in the open position, and the blades or moving contacts shall be connected to the generator side.
voltage The electrical force or potential that causes a current to flow in a circuit (just as pressure causes water to flow in a pipe). Voltage is measured in volts (V) or kilovolts (kV). 1 kV = 1,000 V.
voltage flicker A condition of fluctuating voltage on a power system that can lead to noticeable fluctuations in the output of lighting systems.
watt The scientific unit of electric power. A typical light bulb is rated 25, 40, 60 or 100 watts. One horsepower is 746 watts.