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NERC Reliability Coordinator Exam Vocabulary 202 5. Terms have come
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Accelerating Power - ✔✔In a GENERATOR, the difference between the MECHANICAL INPUT POWER and the electrical output POWER (assuming no LOSSES). For a GENERATOR's TORQUE ANGLE to change, the GENERATOR must have accelerating POWER. Accumulated Inadvertent - ✔✔The accumulation over time of INADVERTENT ENERGY. The accumulated inadvertent account of a BALANCING AUTHORITY represents the amount of excess ENERGY a BALANCING AUTHORITY has either supplied to the INTERCONNECTION or absorbed from the INTERCONNECTION. BALANCING AUTHORITIES monitor their accumulated inadvertent to ensure the accounts do not grow too large Active Power - ✔✔The component of the COMPLEX POWER that performs the work. The common unit of active power is the MW and the symbol is "P". Active power is sometimes called REAL POWER. Actual Interchange - ✔✔The metered INTERCHANGE over a specific INTERCONNECTION between two PHYSICALLY ADJACENT BALANCING AUTHORITIES. Actual Load - ✔✔The actual MW drawn by a LOAD from the POWER SYSTEM. The actual load will be different from the rated or NOMINAL LOAD if the LOAD's VOLTAGE or FREQUENCY vary from their NOMINAL values Adequacy - ✔✔The ability of the electric SYSTEM to supply the aggregate electrical DEMAND and ENERGY requirements of the end-use customers at all times, taking into account SCHEDULED and reasonably expected unSCHEDULEd OUTAGEs of SYSTEM ELEMENTS.ua Adequate Regulating Margin - ✔✔The minimum on-line CAPACITY that can be increased or decreased to allow the SYSTEM to respond to all reasonable DEMAND changes in order to be incompliance with the CONTROL PERFORMANCE STANDARDS.
Adjacent Balancing Authorities - ✔✔A BALANCING AUTHORITY AREA that is interconnected to another BALANCING AUTHORITY AREA either directly or via a multi-party AGREEMENT or TRANSMISSION TARIFF. AGC Pulses - ✔✔The AGC SYSTEM sends signals to selected (regulating) GENERATORS to adjust their set- points. These signals are sent via telecommunication EQUIPMENT. The signals are often called AGC pulses. Air- Gap - ✔✔The air space between the ROTOR and STATOR of a motor or GENERATOR. Alternating Current (AC) - ✔✔In AC SYSTEM the CURRENT and VOLTAGE magnitudes constantly vary or alternate. CURRENT and VOLTAGE magnitudes do not alternate in a DC SYSTEM. Alternator - ✔✔A Rotating machine whose output is alternating VOLTAGE and CURRENT Aluminum Cable Steel Reinforced (ACSR) - ✔✔A common type of TRANSMISSION line CONDUCTOR that comes in many different sizes and designs. The aluminum is the CONDUCTOR and the steel provides strength. Amortisseur Winding - ✔✔A machine winding consisting of a number of conducting bars attached between the magnetic POLES of the machine's ROTOR. Amortisseur windings may be used as starter windings or to help dampen POWER OSCILLATIONS Ampere (amp) - ✔✔The unit of measurement for CURRENT flow, often stated as "amp". Amplitute - ✔✔The value or magnitude that a waveform has at a specific point in time. Analog Electronics - ✔✔Electronic circuitry in which the magnitudes of quantities are used in a continuous manner to perform functions. For example, input CURRENT values may be amplified and used to perform work in an analog CIRCUIT. Analog is different than digital in the sense that analog CIRCUITS use VOLTAGE and CURRENT magnitudes continuously while digital CIRCUITS use VOLTAGE and CURRENT to determine the state (on or off) of ELEMENTS.
Auto-Load - ✔✔A feature on some GENERATORS that automatically moves the GENERATOR to a TARGET LOAD (MW) level. Automatic Generation Control (AGC) - ✔✔EQUIPMENT that automatically adjusts GENERATION in a BALANCING AUTHORITY AREA from a central location to maintain the BALANCING AUTHORITY's INTERCHANGE SCHEDULE plus FREQUENCY BIAS. AGC may also accommodate automatic INADVERTENT payback and TIME ERROR CORRECTION. Automatic Operations Systems - ✔✔SPECIAL PROTECTION SYSTEMS, REMEDIAL ACTION SCHEMEs, or other operating SYSTEMs installed on the electric SYSTEMs that require no intervention on the part of SYSTEM OPERATORS. Auto-Transformer - ✔✔A POWER TRANSFORMER with a single coil. The entire coil acts as the PRIMARY WINDING while a portion of the same coil acts as the SECONDARY WINDING. Auxiliary Relay - ✔✔A RELAY whose function is to supplement the actions of other types of RELAYS. For example, a LOCKOUT RELAY is an auxiliary relay with numerous contacts that each can perform an action. The IEEE has numbers assigned to two types of auxiliary relays; 86 (lock-out) and 94 (tripping). Availability - ✔✔A measure of time a generating unit, TRANSMISSION line, or other FACILITY is capable of providing service, whether or not it actually is in service. Typically, this measure is expressed as a percent available for the PERIOD under consideration. Available Flowgate Capability (AFC) - ✔✔The available CAPACITY in MW or MVA on a FLOWGATE, which a TRANSMISSION SERVICE PROVIDER has determined, is available for sale. The available CAPACITY determined will be dependent on the GENERATION, LOADS and TRANSMISSION configuration assumed for the time period studied and therefore is referred to as a capability. The AFC will account for all thermal, VOLTAGE and STABILITY LIMITS under both pre and post CONTINGENCY conditions, along with any TRM or CBM. There is no one set of SOURCE and SINK points associated with an AFC. The AFC can be used to determine the amount of MW that can be transferred between a specific set of SOURCE and SINK points with respect to the FLOWGATE, by dividing the AFC by its corresponding PTDF. Available Transfer Capability (ATC) - ✔✔A measure of the TRANSFER CAPABILITY remaining in the physical TRANSMISSION network for further commercial activity over and above already committed uses. It is defined as TOTAL TRANSFER CAPABILITY less existing TRANSMISSION commitments (including retail customer service), less a CAPACITY BENEFIT MARGIN, less a TRANSMISSION RELIABILITY MARGIN.
Avoided Cost - ✔✔The cost the utility would incur but for the existence of an independent GENERATOR or other ENERGY service option. Avoided cost rates have been used as the POWER purchase price utilities offer independent suppliers. Back EMF (Conductors Back EMF) - ✔✔When AC CURRENT flows through a CONDUCTOR an alternating MAGNETIC FIELD is created. This alternating MAGNETIC FIELD induces a VOLTAGE in the CONDUCTOR. The induced VOLTAGE is called the CONDUCTOR'S back EMF. Back-To-Back HVDC - ✔✔An HVDC SYSTEM in which AC is converted to DC and then immediately back to AC. The HVDC TRANSMISSION path is very short, normally consisting of a short section of buswork. Backup Power - ✔✔POWER provided by contract to a customer when that customer's normal SOURCE of POWER is not available. Balancing Authority - ✔✔The responsible ENTITY that integrates resource plans ahead of time, maintains LOADINTERCHANGE-GENERATION balance within a BALANCING AUTHORITY AREA, and supports INTERCONNECTION FREQUENCY in real time. Balancing Authority Area - ✔✔The collection of GENERATION, TRANSMISSION, and LOADS within the metered boundaries of the BALANCING AUTHORITY. The BALANCING AUTHORITY maintains LOAD- RESOURCE balance within this area Bandwidth - ✔✔The acceptable range of a quantity. For example, if it is desired to hold the VOLTAGE at a 345 kV BUS between 355 and 360 kV then the bandwidth is 355 - 360 kV or 5 kV. Banking - ✔✔ENERGY delivered or received by a utility with the intent that it will be returned in kind (as ENERGY) in the future. Base Load - ✔✔The minimum amount of electric POWER delivered or required over a given period at a constant rate.
Braking Resistor - ✔✔A device used to enhance the angle stability of a power system that uses hydro- electric generation. A Braking Resistor is a large resistive load that is inserted to absorb excess energy when an accelerating condition is detected in the power system. Broker - ✔✔A third party who establishes a TRANSACTION between a seller and a purchaser. A Broker does not take title to CAPACITY or ENERGY. Brush - ✔✔A sliding contact, usually made of carbon, located between the excitation CURRENT SOURCE and the ROTOR FIELD WINDING leads of a SYNCHRONOUS GENERATOR. Bulk Electric System (BES) - ✔✔As defined by the REGIONAL RELIABILITY ORGANIZATION, the electrical GENERATION RESOURCES, TRANSMISSION LINES, INTERCONNECTIONS with neighboring SYSTEMS, and associated EQUIPMENT, generally operated at VOLTAGES of 100 kV or higher. Radial TRANSMISSION facilities serving only LOAD with one TRANSMISSION SOURCE are generally not included in this definition. Bulk Transmission - ✔✔A functional or VOLTAGE classification relating to the higher VOLTAGE portion of the TRANSMISSION SYSTEM, specifically, lines at or above a VOLTAGE level of 115 kV. Burden - ✔✔Operation of the BULK ELECTRIC SYSTEM that violates or is expected to violate a SYSTEM OPERATING LIMIT or INTERCONNECTION RELIABILITY OPERATING LIMIT in the INTERCONNECTION, or that violates any other NERC, REGIONAL RELIABILITY ORGANIZATION, or local operating RELIABILITY standards or criteria. Bus (Busbar) - ✔✔An abbreviation of the word busbar. A bus is a location in an electrical network where one or more ELEMENTS are connected together. Capacitance (C) - ✔✔The property of an ELECTRICAL CIRCUIT that opposes VOLTAGE changes by storing ENERGY in its ELECTRIC FIELD. The symbol for capacitance is "C" and the unit is the FARAD. All energized EQUIPMENT has a natural capacitance. Capacitive Load - ✔✔A LOAD that supplies LAGGING REACTIVE POWER to the SYSTEM.
Capacitive Reactance (Xc) - ✔✔The opposition that CAPACITANCE provides to AC CURRENT. The capacitive reactance (XC) in a 60 HZ CIRCUIT is: XC = 1 / 2π fC Capacitively Coupled Voltage Transformer (CCVT) - ✔✔An instrument TRANSFORMER that is similar in function to a potential TRANSFORMER (PT). A capacitive VOLTAGE divider CIRCUIT is used in a CCVT to reduce POWER SYSTEM VOLTAGE magnitudes to usable (≈120 Volt) levels. Capacitive VOLTAGE TRANSFORMERS (CVTs), Coupling CAPACITOR Potential Devices (CCPDs), and Bushing Potential Devices (BPDs) are similar in design and function to a CCVT. Capacitor - ✔✔A device intentionally designed to act as a capacitor and store ENERGY in its ELECTRIC FIELD. A shunt capacitor acts as a SOURCE of REACTIVE POWER to the SYSTEM. Series capacitors are seldom seen devices that are used to reduce the INDUCTIVE REACTANCE of a TRANSMISSION path. Capacitor Bank - ✔✔A CAPACITOR is an electrical device that provides REACTIVE POWER to the SYSTEM and is often used to compensate for reactive LOAD and help support SYSTEM VOLTAGE. A bank is a collection of one or more CAPACITORS at a single location. Capacity - ✔✔The rated continuous LOAD-carrying ability, expressed in megawatts (MW) or megavolt- amperes (MVA) of GENERATION, TRANSMISSION, or other electrical EQUIPMENT. Capacity Benefit Margin (CBM) - ✔✔That amount of firm TRANSMISSION TRANSFER CAPABILITY preserved by the TRANSMISSION PROVIDER for LOAD SERVING ENTITIES (LSEs), whose LOADs are located on that TRANSMISSION SERVICE PROVIDER's system, to enable ACCESS by the LSEs to GENERATION from INTERCONNECTED SYSTEMS to meet GENERATION RELIABILITY requirements. Preservation of CBM for an LSE allows that entity to reduce its installed generating CAPACITY below that which may otherwise have been necessary without INTERCONNECTIONS to meet its GENERATION RELIABILITY requirements. The TRANSMISSION TRANSFER CAPABILITY preserved as CBM is intended to be used by the LSE only in times of EMERGENCY GENERATION deficiencies. Capacity Emergency - ✔✔A capacity emergency exists when a BALANCING AUTHORITY AREA's operating CAPACITY, plus firm purchases from other systems to the extent available or limited by TRANSFER CAPABILITY, is inadequate to meet its DEMAND plus its regulating requirements. Capacity Factor - ✔✔The ratio of the total ENERGY generated by a generating unit for a specified period to the maximum possible ENERGY it could have generated if operated at the maximum CAPACITY RATING for the same specified period, expressed as a percent.
medium. For example, Air Circuit Breaker (ACB), Gas Circuit Breakers (GCB), Oil Circuit Breakers (OCB), etc. Circuit Switcher (CS) - ✔✔An enhanced DISCONNECT SWITCH that is similar in function to a CIRCUIT BREAKER. A circuit switcher will contain an interrupting device (typically gas based) to enhance its CURRENT interrupting ability. Clock Hour - ✔✔The 60 - min PERIOD ending at :00. All surveys, measurements, and reports are based on clock hour PERIODS unless specifically noted. Cogeneration - ✔✔Production of ELECTRICITY from steam, heat, or other forms of ENERGY produced as a by-product of another process. Example: recycled steam from a (CC) COMBINED CYCLE Natural Gas unit. Uses exhaust heat from the Simple Cycle (CT) generator and run a secondary Steam Turbin (ST) Cold Load Pick-Up - ✔✔The increase in a LOAD's magnitude during the initial PERIOD after it is energized. The cold load pick-up consists of a short-term (possibly several seconds) in-rush component and a longer term (possibly many minutes) LOSS OF LOAD DIVERSITY component. Combined Cycle (CC) - ✔✔An electric generating technology in which electricity and process steam are produced from otherwise lost waste heat exiting from one or more combustion TURBINES. The exiting heat is routed to a conventional BOILER or to a heat recovery steam GENERATOR for use by a steam TURBINE in the production of electricity. This process increases the overall efficiency of the electric generating unit. Combustion Turbine Generator (CT) - ✔✔A type of GENERATOR in which a fuel (oil, gas, etc.) is ignited and the combustion products are used to drive a TURBINE. Commonly or Jointly owned units (COU/JOU) - ✔✔These terms may be used INTERCHANGEably to refer to a unit in which two or more GENERATION OWNERS share. Commutation - ✔✔The process of turning off one VALVE and turning on another in an HVDC CONVERTER. In a twelve-pulse converter there are twelve commutations per CYCLE of the AC supply VOLTAGE.
Complex Power (S) - ✔✔The vector sum of the active (MW) and reactive (Mvar) POWER. The common unit for complex POWER is MVA and the symbol is "S". Complex Power is sometimes called APPARENT POWER. Compliance Monitor - ✔✔The entity that monitors, reviews, and ensures compliance of responsible entities with RELIABILITY standards. Complimentary Currents - ✔✔When a SUBSYNCHRONOUS CURRENT flows in the STATOR winding of a SYNCHRONOUS MACHINE it will induce two complimentary currents in the ROTOR of the machine. These complimentary currents will have frequencies of 60 ± the FREQUENCY of the SUBSYNCHRONOUS STATOR CURRENT. Compressor - ✔✔A machine that increases the pressure of a gas (typically air) or vapor. Condenser - ✔✔The component of a steam POWER plant in which the steam is cooled to water after exiting the TURBINE. Conductor - ✔✔A material with a low RESISTANCE to CURRENT flow. A conductor is the opposite of an INSULATOR. Congestion - ✔✔The condition that exists when MARKET PARTICIPANTS seek to dispatch GENERATION in a pattern which would result in POWER flows that cannot be physically accommodated by the TRANSMISSION SYSTEM. Although the TRANSMISSION SYSTEM will not normally be operated in an overload condition, it may be described as congested based on requested/desired SCHEDULES. Constant Frequency Control (CFC) - ✔✔An operating MODE of an AGC SYSTEM. While in constant FREQUENCY control an AGC SYSTEM will determine the ACE value by considering only the FREQUENCY ERROR. Constant Net Interchange (CNI) Control - ✔✔An operating MODE of an AGC SYSTEM. While in constant net interchange control an AGC SYSTEM will determine the ACE value by considering only the INTERCHANGE error.
Control Performance Standard (CPS) - ✔✔The reliability standard that sets the limits of a BALANCING AUTHORITY'S AREA CONTROL ERROR over a specified time period. Control System - ✔✔A collection of electrical and mechanical components designed to produce a series of outputs based on a series of measured inputs. Common control systems related to POWER are excitation control and GOVERNOR CONTROL SYSTEMS. Coordinated Control - ✔✔A MODE of operation of a fossil unit's TURBINE/BOILER CONTROL SYSTEM in which the operation of the BOILER and the TURBINE SYSTEMS are coordinated. The coordination balances the pressure and temperature limits of the BOILER SYSTEM with the desire for a TURBINE to immediately respond to LOAD (MW) change requests. Core - ✔✔The material used within a TRANSFORMER. A TRANSFORMER's core is formed of a magnetic material such as iron. The purpose of the core is to confine the MAGNETIC FIELD to a TARGET area. Corona - ✔✔A condition that occurs on energized EQUIPMENT when the surface potential (VOLTAGE) is so large that the DIELECTRIC strength of the surrounding air breaks down (IONIZATION occurs). Symptoms of corona are a visible ring of light and a hissing sound. Corona is undesirable as ENERGY LOSSES and electrical interference are a consequence. Corona rings are used to reduce the gradient of the ELECTRIC FIELD and reduce the likelihood of corona occurring. Cosine - ✔✔The cosine of either of the unknown angles of a RIGHT TRIANGLE is the ratio of the side adjacent to the unknown angle to the HYPOTENUSE. Cracking Path - ✔✔A portion of the electric SYSTEM that can be ISOLATED and then energized to deliver ELECTRIC POWER from a GENERATION SOURCE to enable the startup of one or more other GENERATING UNITS. Current (I) - ✔✔The rate of flow of electrons in an electrical CONDUCTOR. Symbol is "I" and unit is the AMPERE, or amp. Current Transformer (CT) - ✔✔A low POWER TRANSFORMER (an instrument TRANSFORMER) used to reduce normally high POWER SYSTEM CURRENT magnitudes to lower values (≈ 5 amps). A CT has a low number of turns on the PRIMARY WINDING and a high number of turns on the SECONDARY WINDING. The low magnitude secondary CURRENTS of a CT are typically input to PROTECTIVE RELAYS, meters, etc.
Curtailment - ✔✔A reduction in the SCHEDULED CAPACITY or ENERGY delivery. Cut-Out - ✔✔A switching device typically found in the DISTRIBUTION SYSTEM. Cut-outs often include a fuse so the device serves the dual purpose of providing electrical isolation and protection. Cyber Assets - ✔✔Programmable electronic devices and communication networks including hardware, software, and data. Cycle - ✔✔A complete sequence of a repeating waveform. For example, the magnitude of a SINE wave changes as the degrees progress from 0° to 360°. After 360° the SINE wave begins to repeat itself. One cycle of a SINEWAVE is therefore 360°. Damping - ✔✔Forces or CONTROL SYSTEM actions that reduce the magnitude of OSCILLATIONS. Damping is provided by various natural phenomena and by various electrical EQUIPMENT. Damping can either be positive (reduce OSCILLATIONS) or negative (amplify OSCILLATIONS). Deadband - ✔✔The distance about a TARGET value within which a CONTROL SYSTEM will not respond. For example, a GOVERNOR CONTROL SYSTEM may have a deadband of ±0.036 HZ. Unless the FREQUENCY DEVIATION exceeds 0.036 HZ, the governor will not respond. Delayed Fault Clearing - ✔✔FAULT clearing consistent with correct operation of a breaker failure PROTECTION SYSTEM and its associated breakers, or of a backup PROTECTION SYSTEM with an intentional time delay. Delivering Party - ✔✔The entity supplying the CAPACITY and ENERGY to be transmitted at the POINT OF RECEIPT. Delta Connection - ✔✔A 3Φ electrical connection in which the three PHASES are connected in series with one another. The three PHASES form a closed triangle. TRANSFORMER windings are often connected in a Delta configuration.
Disconnect Switch - ✔✔A mechanical device that is used to isolate EQUIPMENT from energized parts of the POWER SYSTEM. Disconnect switches are not rated for interrupting CURRENT unless additional ARC interrupting components are added to the disconnect. Dispatchable Generation - ✔✔GENERATION available physically or contractually to respond to changes in SYSTEM DEMAND or to respond to TRANSMISSION security CONSTRAINTS. Distance Relay - ✔✔A PROTECTIVE RELAY that activates if the ratio of the measured VOLTAGE divided by the CURRENT (the IMPEDANCE) falls below a pickup point. A Distance relay is also commonly called an IMPEDANCE RELAY. Distribution - ✔✔For electricity, the function of distributing electric POWER using low VOLTAGE lines to retail customers. These lines are typically 60hz Distribution Facilities - ✔✔The facilities owned or controlled by a TRANSMISSION Owner and used to provide Wholesale DISTRIBUTION Service. Distribution Factor (DF) - ✔✔The portion of an INTERCHANGE TRANSACTION, typically expressed in PER- UNIT, that flows across a TRANSMISSION FACILITY (FLOWGATE). Distribution Lines - ✔✔CONDUCTORS used to distribute POWER to the utility's customers. Distribution lines may be 3Φ or 1Φ. Distribution Network - ✔✔The portion of an electric SYSTEM that is dedicated to delivering electric ENERGY to an end user. The distribution network consists primarily of low VOLTAGE lines and TRANSFORMERS that "transport" electricity from the bulk POWER SYSTEM to retail customers. Distribution Provider - ✔✔Provides and operates the "wires" between the TRANSMISSION system and the end-use customer. For those end-use customers who are served at TRANSMISSION VOLTAGEs, the TRANSMISSION OWNER also serves as the Distribution Provider. Thus, the Distribution Provider is not defined by a specific VOLTAGE, but rather as performing the DISTRIBUTION function at any VOLTAGE.
Disturbance - ✔✔1. An unplanned event that produces an abnormal SYSTEM condition. 2. Any perturbation to the electric system. 3. The unexpected change in ACE that is caused by the sudden failure of GENERATION or INTERRUPTION of LOAD. Disturbance Control Standard (DCS) - ✔✔The RELIABILITY standard that sets the time limit following a DISTURBANCE within which a BA or RSG must return its AREA CONTROL ERROR to within a specified range. Disturbance Monitoring Equipment - ✔✔Devices capable of monitoring and recording SYSTEM data pertaining to a DISTURBANCE. Such devices include the following categories of recorders: •Sequence of event recorders which record EQUIPMENT response to the event.
- FAULT recorders, which record actual waveform data replicating the SYSTEM primary VOLTAGES and CURRENTS. This may include PROTECTIVE RELAYS.
- DYNAMIC DISTURBANCE RECORDERS (DDRs), which record incidents that portray POWER SYSTEM behavior during dynamic events such as low-FREQUENCY (0.1 Hz - 3 Hz) OSCILLATIONS and abnormal FREQUENCY or VOLTAGE excursions. Diversity Factor - ✔✔The ratio of the sum of the coincident maximum DEMANDS of two or more LOADS to their noncoincident maximum DEMAND for the same period. Droop - ✔✔A characteristic of a GOVERNOR CONTROL SYSTEM that requires a decrease in GENERATOR shaft speed to produce an increase in the GENERATOR's MW output. There are two types of droop; permanent and TRANSIENT: Permanent Droop - ✔✔Permanent droop is the droop used to enable all GENERATORs (with active governors) to share in FREQUENCY REGULATION and to ensure a MW response in proportion to unit size. Desired values of permanent droop are in the neighborhood of 5%. The 5% droop means that a 5% FREQUENCY change will result in the unit's governor moving the fuel (steam, water, gas, etc.) VALVES across their full range.
Economy Energy - ✔✔ELECTRICAL ENERGY produced and supplied from a more economical SOURCE in one SYSTEM and substituted for that being produced or capable of being produced by a less economical SOURCE in another SYSTEM. Electric Field - ✔✔The invisible lines of force that surround an energized piece of EQUIPMENT. An electric field is created when a CONDUCTOR is energized by a VOLTAGE. ENERGY is stored in an electric field. Electric System Losses - ✔✔Total electric ENERGY LOSSES in the electric SYSTEM. The LOSSES consist of TRANSMISSION, transformation, and DISTRIBUTION LOSSES between supply SOURCEs and delivery points. Electric ENERGY is lost primarily due to heating of TRANSMISSION and DISTRIBUTION ELEMENTS. Electric Utility - ✔✔Person, agency, authority, or other legal entity that owns or operates facilities for the GENERATION, TRANSMISSION, DISTRIBUTION, or sale of electric ENERGY primarily for use by the public, and is defined as a utility under the statutes and rules by which it is regulated. An electric utility can be investor owned, cooperatively owned, or government owned (by a federal agency, crown corporation, state, provincial government, municipal government, and public POWER district). Electrical Distance - ✔✔An electrical circuit consists of a VOLTAGE SOURCE, a conducting path to a LOAD, a LOAD, and a return path from the LOAD to the VOLTAGE SOURCE. All four of these ingredients are necessary for CURRENT to flow in the electrical circuit. Electrical Distance - ✔✔The IMPEDANCE of a TRANSMISSION line is a measure of the electrical distance. For example, if a line has a 100 Ω IMPEDANCE then 50 Ω is ½ the line's electrical length. IMPEDANCE RELAYS are often called DISTANCE RELAYS in reference to the use of IMPEDANCE as a measure of electrical distance. Electrical Energy - ✔✔The GENERATION or use of electric POWER by a device over a period of time, expressed in KILOWATTHOURs (kWh), or MEGAWATTHOURs (MWh), or gigaWATTHOURs (GWh). Electrodes - ✔✔The connection to GROUND of an HVDC CONVERTER. The grounding electrode provides a VOLTAGE reference and may be part of the CURRENT return path.
Electro-Hydraulic Control (EHC) - ✔✔A form of a CONTROL SYSTEM in which electrical devices are typically used to measure a quantity magnitude and HYDRAULICS used to perform a control action. For example, a GOVERNOR CONTROL SYSTEM may consist of a simple electrical machine that measures the shaft's speed of rotation (FREQUENCY) and a hydraulic SYSTEM that changes the positions of fuel VALVES. Electrojet - ✔✔A CURRENT flow path in the shape of a donut that situates itself above the north and south magnetic POLES of the earth. Electrojets are the result of solar DISTURBANCES. Electromagnet - ✔✔Temporary magnet created by passing electric CURRENT through a coil. The coil is typically wound about a magnetic CORE. Electromotive Induction - ✔✔The creation of a VOLTAGE in a CONDUCTOR due to a relative movement between the CONDUCTOR and a MAGNETIC FIELD. Electromagnetic induction is the basic principle of operation of TRANSFORMERS and GENERATORS. Electromotive Force (EMF) - ✔✔The VOLTAGE produced by a GENERATOR is called an electromotive force or EMF. The symbol "E" is often used to indicate an EMF. Emergency Assistance (EA) - ✔✔ENERGY and/or CAPACITY provided to a utility to assist that utility during a CAPACITY EMERGENCY. Emergency Energy - ✔✔ELECTRICAL ENERGY purchased by a member SYSTEM whenever an event on that SYSTEM causes insufficient Operating Capability to cover its own DEMAND requirement. Emergency Rating - ✔✔The RATING as defined by the EQUIPMENT owner that specifies the level of electrical loading or output, usually expressed in megawatts (MW) or Mvar or other appropriate units, that a SYSTEM, FACILITY, or ELEMENT can support, produce, or withstand for a finite PERIOD. The RATING assumes acceptable loss of EQUIPMENT life or other physical or safety limitations for the EQUIPMENT involved. Emergency Response Rate - ✔✔The rate of LOAD change that a generating unit can achieve under EMERGENCY conditions, such as loss of a unit, expressed in megawatts per minute.
