NERC Reliability Coordinator Exam Vocabulary 2022

Accelerating Power - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-The metered INTERCHANGE over a specific INTERCONNECTION between two PHYSICALLY ADJACENT BALANCING AUTHORITIES. Actual Load - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-The air space between the ROTOR and STATOR of a motor or GENERATOR. Alternating Current (AC) - ANSWER-In AC SYSTEM the CURRENT and VOLTAGE magnitudes constantly vary or alternate. CURRENT and VOLTAGE magnitudes do not alternate in a DC SYSTEM. Alternator - ANSWER-A Rotating machine whose output is alternating VOLTAGE and CURRENT Aluminum Cable Steel Reinforced (ACSR) - ANSWER-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 - ANSWER-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) - ANSWER-The unit of measurement for CURRENT flow, often stated as "amp". Amplitute - ANSWER-The value or magnitude that a waveform has at a specific point in time. Analog Electronics - ANSWER-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. Ancillary Services (FERC Definition) - ANSWER-Those services that are necessary to support the TRANSMISSION of CAPACITY and ENERGY from RESOURCES to LOADS while maintaining reliable operation of the TRANSMISSION SERVICE PROVIDER's TRANSMISSION SYSTEM in accordance with GOOD UTILITY PRACTICE. Angle Instability - ANSWER-The opposite of ANGLE STABILITY. When a POWER SYSTEM loses ANGLE STABILITY it enters a PERIOD of angle instability. An angle unstable SYSTEM has lost some portion of the magnetic bound that holds sections of the POWER SYSTEM in synchronism with one another. Angle Stability - ANSWER-An angle stable POWER SYSTEM is one in which all ELEMENTS of the POWER SYSTEM are bound together via magnetic forces. For example, an angle stable GENERATOR's internal MAGNETIC FIELD rotates in synchronism (in-step) with the MAGNETIC FIELD of the 3Φ POWER SYSTEM to which it connects. Apparent Power - ANSWER-The product of VOLTAGE and CURRENT PHASORS. Apparent power comprises both active and REACTIVE POWER, usually expressed in KILOVOLTAMPEREs (kVA) or megavoltamperes (MVA). Another term for apparent power is COMPLEX POWER. ARC - ANSWER-The discharge of CURRENT through the air or in a gas. Arcing Horns - ANSWER-An enhancement to a DISCONNECT SWITCH to increase the switch's CURRENT interrupting capability. Area Control Area (ACE) - ANSWER-The instantaneous difference between net actual and SCHEDULED INTERCHANGE, taking into account the effects of FREQUENCY bias including a correction for meter error. Armature - ANSWER-The component of a machine in which the VOLTAGE is induced. In a SYNCHRONOUS GENERATOR the armature is usually the STATOR. The armature winding is wrapped about the armature. Asynchronous - ANSWER-To be OUT-OF-STEP with a reference. An induction GENERATOR is an asynchronous GENERATOR as its ROTOR does not rotate in synchronism with the POWER SYSTEM. Auto-Load - ANSWER-A feature on some GENERATORS that automatically moves the GENERATOR to a TARGET LOAD (MW) level. Automatic Generation Control (AGC) - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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) - ANSWER-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) - ANSWER-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 - ANSWER-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) - ANSWER-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 - ANSWER-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 - ANSWER-POWER provided by contract to a customer when that customer's normal SOURCE of POWER is not available. Balancing Authority - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-ENERGY delivered or received by a utility with the intent that it will be returned in kind (as ENERGY) in the future. Base Load - ANSWER-The minimum amount of electric POWER delivered or required over a given period at a constant rate. Base Load Capacity - ANSWER-CAPACITY used to serve an essentially constant level of customer DEMAND. Base load generating units typically operate whenever they are available, and they generally have a CAPACITY FACTOR that is above 60%. Base Load Generating Units - ANSWER-GENERATORs that normally run continuously to serve a BALANCING AUTHORITY'S LOAD. Bilateral Payback - ANSWER-INADVERTENT INTERCHANGE accumulations paid back via an INTERCHANGE SCHEDULE with another BALANCING AUTHORITY. Bipolar HVDC - ANSWER-An HVDC SYSTEM that uses two CONDUCTORS. One CONDUCTOR is energized with a positive VOLTAGE and the other a negative VOLTAGE. Black-Start Unit (BSU) - ANSWER-A generating unit that has the ability to go from a shutdown condition to an operating condition and start delivering POWER without assistance from the POWER SYSTEM the GENERATOR normally connects to. Blackstart Capability Plan - ANSWER-A documented procedure for a generating unit or STATION to go from a shutdown condition to an operating condition delivering electric POWER without assistance from the ELECTRIC SYSTEM. This procedure is only a portion of an overall SYSTEM RESTORATION plan. Blade (Steam) - ANSWER-The component of a steam TURBINE upon which the steam impacts. Blades are also called "buckets". Blocked Governor - ANSWER-A GOVERNOR CONTROL SYSTEM that has somehow been blocked or prevented from responding to a FREQUENCY DEVIATION. There are many ways to block a governor. Boiler - ANSWER-The component of a steam POWER plant in which the steam is created. Boiler Follow - ANSWER-A MODE of operation of a fossil unit's TURBINE/BOILER CONTROL SYSTEM in which the unit's TURBINE is allowed to immediately respond to a LOAD (MW) change request while the BOILER response "follows" with the resulting temperature and pressure swings. Braking Resistor - ANSWER-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 - ANSWER-A third party who establishes a TRANSACTION between a seller and a purchaser. A Broker does not take title to CAPACITY or ENERGY. Brush - ANSWER-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) - ANSWER-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 - ANSWER-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 - ANSWER-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) - ANSWER-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) - ANSWER-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 - ANSWER-A LOAD that supplies LAGGING REACTIVE POWER to the SYSTEM. Capacitive Reactance (Xc) - ANSWER-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) - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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) - ANSWER-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 - ANSWER-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 - ANSWER-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. Cascading - ANSWER-The uncontrolled successive loss of SYSTEM ELEMENTS triggered by an incident at any location. Cascading results in widespread electric service INTERRUPTION that cannot be restrained from sequentially spreading beyond an area predetermined by studies. Cascading Outages - ANSWER-The uncontrolled successive LOSS of BULK ELECTRIC SYSTEM FACILITIES triggered by an incident (or condition) at any location resulting in the INTERRUPTION of ELECTRIC SERVICE that cannot be restrained from spreading beyond a pre-determined area. Cavitation - ANSWER-Noise or vibration causing damage to a hydro unit's TURBINE BLADEs as a result of bubbles that form in the water as it goes through the TURBINE which causes a loss in CAPACITY, HEAD loss, efficiency loss, and the cavity or bubble collapses when they pass into higher regions of pressure. Centrifugal Ballhead governor - ANSWER-A mechanical governor that uses rotating FLYWEIGHTS to sense shaft speed. A very common governor due to its durability and accuracy. Charge - ANSWER-An atomic force. An electron has a negative charge. A proton has a positive charge. Like charges repel one another while opposite charges attract one another. CURRENT is the flow of charge. Charging - ANSWER-The Mvar production of a TRANSMISSION line. For example, a 100 mile long 345 kV line has approximately 75 Mvar of charging. Charging Current - ANSWER-The LEADING CURRENT that flows into the natural CAPACITANCE of a TRANSMISSION line when it is first energized. Checkout Process - ANSWER-The method by which any two ENTITIES in the utility industry routinely perform a confirmation of SCHEDULES for a period of time. Circuit - ANSWER-A CONDUCTOR or a SYSTEM of CONDUCTORS through which electric CURRENT flows. Circuit Switcher (CS) - ANSWER-A piece of POWER SYSTEM EQUIPMENT that is used to disconnect other EQUIPMENT from the POWER SYSTEM. Circuit breakers are grouped according to their insulating medium. For example, Air Circuit Breaker (ACB), Gas Circuit Breakers (GCB), Oil Circuit Breakers (OCB), etc. Circuit Switcher (CS) - ANSWER-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 - ANSWER-The 60-min PERIOD ending at :00. All surveys, measurements, and reports are based on clock hour PERIODS unless specifically noted. Cogeneration - ANSWER-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 - ANSWER-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) - ANSWER-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) - ANSWER-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) - ANSWER-These terms may be used INTERCHANGEably to refer to a unit in which two or more GENERATION OWNERS share. Commutation - ANSWER-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) - ANSWER-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 - ANSWER-The entity that monitors, reviews, and ensures compliance of responsible entities with RELIABILITY standards. Complimentary Currents - ANSWER-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 - ANSWER-A machine that increases the pressure of a gas (typically air) or vapor. Condenser - ANSWER-The component of a steam POWER plant in which the steam is cooled to water after exiting the TURBINE. Conductor - ANSWER-A material with a low RESISTANCE to CURRENT flow. A conductor is the opposite of an INSULATOR. Congestion - ANSWER-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) - ANSWER-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 - ANSWER-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. Constrained Facility - ANSWER-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. Constraint - ANSWER-A limitation placed on INTERCHANGE TRANSACTIONS that flow over a CONSTRAINED FACILITY. Contiguous - ANSWER-To belong to a common area. Adjoining. A contiguous BALANCING AUTHORITY is selfcontained. A non-contiguous BALANCING AUTHORITY may have pieces spread over an entire INTERCONNECTION. Contingency - ANSWER-The unexpected failure or OUTAGE of a system component, such as a GENERATOR, TRANSMISSION LINE, CIRCUIT BREAKER, SWITCH or other electrical ELEMENT. Contingency Analysis - ANSWER-The process by which the effects of contingencies are identified. CA SOFTWARE is used to identify N-1 violations. Contingency Reserve - ANSWER-The provision of CAPACITY deployed by the BALANCING AUTHORITY to meet the DISTURBANCE CONTROL STANDARD (DCS) and other NERC and REGIONAL RELIABILITY ORGANIZATION contingency requirements. Continuous Rating - ANSWER-The RATING as defined by the EQUIPMENT owner that specifies the level of electrical loading, usually expressed in megawatts (MW) or other appropriate units that a SYSTEM, FACILITY, or ELEMENT can support or withstand indefinitely without loss of EQUIPMENT life. Contract Path - ANSWER-An agreed upon electrical path for the continuous FLOW of ELECTRICAL POWER between the parties of an INTERCHANGE TRANSACTION. Contractually Adjacent Balancing Authorities - ANSWER-Two BALANCING AUTHORITIES that are part of the same Regional Transmission Organization Control Center - ANSWER-The physical location from which an operating entity operates. Control Performance Standard (CPS) - ANSWER-The reliability standard that sets the limits of a BALANCING AUTHORITY'S AREA CONTROL ERROR over a specified time period. Control System - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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) - ANSWER-The rate of flow of electrons in an electrical CONDUCTOR. Symbol is "I" and unit is the AMPERE, or amp. Current Transformer (CT) - ANSWER-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 - ANSWER-A reduction in the SCHEDULED CAPACITY or ENERGY delivery. Cut-Out - ANSWER-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 - ANSWER-Programmable electronic devices and communication networks including hardware, software, and data. Cycle - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-The entity supplying the CAPACITY and ENERGY to be transmitted at the POINT OF RECEIPT. Delta Connection - ANSWER-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. Demand - ANSWER-1. The rate at which electric ENERGY is delivered to or by a SYSTEM or part of a SYSTEM, generally expressed in kilowatts or megawatts, at a given instant or averaged over any designated interval of time. 2. The rate at which ENERGY is being used by the customer. Demand Interval - ANSWER-The time period during which a DEMAND is measured, usually in 15-, 30-, or 60-minute increments. Demand-Side Management (DSN) - ANSWER-The term for all activities or programs undertaken by LOAD-SERVING ENTITY or its customers to influence the amount or timing of electricity they use. Derating (Generator) - ANSWER-A reduction in a generating unit's NET DEPENDABLE CAPACITY. Deviation - ANSWER-The variance from the SCHEDULED value. For example, if the SCHEDULED value of VOLTAGE is 142 kV and the actual value is 138 kV then the VOLTAGE deviation is -4 kV. Dielectric - ANSWER-Insulating material used to separate and insulate. CAPACITORs use a dielectric between its two conducting plates. Differential Relay - ANSWER-A PROTECTIVE RELAY that responds to the difference between the CURRENTS entering and leaving the protected zone of the RELAY. Differential relays are typically applied to TRANSFORMERS, SUBSTATION BUSes, and GENERATORS. Digital Electronics - ANSWER-Electronic circuitry that operates on data in the form of digits. Most digital CIRCUITS use the binary SYSTEM in which digital components are either turned on (a data value of "1") or off (a data value of "0") based on CIRCUIT VOLTAGE magnitudes. Digital electronics have replaced ANALOG ELECTRONICS in most, but not all, applications. Direct Control Load Management (DCLM) - ANSWER-DEMAND-SIDE MANAGEMENT that is under the direct control of the SYSTEM OPERATOR. DCLM may control the electric supply to individual appliances or EQUIPMENT on customer premises. DCLM as defined here does not include INTERRUPTIBLE DEMAND. Direct Current (DC) - ANSWER-In DC SYSTEM the CURRENT and VOLTAGE magnitudes are constant. CURRENT and VOLTAGE magnitudes alternate in an AC SYSTEM. Disconnect Switch - ANSWER-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 - ANSWER-GENERATION available physically or contractually to respond to changes in SYSTEM DEMAND or to respond to TRANSMISSION security CONSTRAINTS. Distance Relay - ANSWER-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 - ANSWER-For electricity, the function of distributing electric POWER using low VOLTAGE lines to retail customers. These lines are typically 60hz Distribution Facilities - ANSWER-The facilities owned or controlled by a TRANSMISSION Owner and used to provide Wholesale DISTRIBUTION Service. Distribution Factor (DF) - ANSWER-The portion of an INTERCHANGE TRANSACTION, typically expressed in PER-UNIT, that flows across a TRANSMISSION FACILITY (FLOWGATE). Distribution Lines - ANSWER-CONDUCTORS used to distribute POWER to the utility's customers. Distribution lines may be 3Φ or 1Φ. Distribution Network - ANSWER-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 - ANSWER-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 - ANSWER-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) - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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. Transient Droop - ANSWER-A feature implemented in some GOVERNOR CONTROL SYSTEMS to ensure GENERATORS do not enter into POWER OSCILLATIONS following LOAD changes. POWER OSCILLATIONS may occur due to the inherent time delay between a request for a LOAD change by the governor and the ability of a GENERATOR to actually deliver the LOAD change. This natural time delay could lead to excessive control action by the governor. A condition of oscillation called "hunting" could result. If a GENERATOR is on isochronous control, TRANSIENT droop is a necessity. The TRANSIENT droop function or "compensation" dampens a governor's initial response following a speed change. The effect is temporary as opposed to a permanent droop function which is permanent. Droop Curve - ANSWER-A graphical method of representing the performance of a governor. The horizontal axis is typically GENERATOR output while the vertical axis is SYSTEM FREQUENCY. When a governor with a % DROOP is plotted on such a curve the plot DROOPS from left to right with increasing GENERATOR output. Dynamic Rating - ANSWER-The process that allows a SYSTEM ELEMENT RATING to vary with the changing environmental conditions in which the ELEMENT is located. Dynamic Reactive Reserve - ANSWER-REACTIVE POWER held in reserve in fast responding SOURCEs. GENERATORS and STATIC VAR COMPENSATORS are possible SOURCEs of dynamic reactive reserve. Dynamic Schedule or Dynamic Interchange Schedule - ANSWER-A telemetered reading or value that is updated in real time and used as a SCHEDULE in the AGC/ACE equation and the integrated value of which is treated as a SCHEDULE for INTERCHANGE accounting purposes. Commonly used for scheduling jointly owned GENERATION to or from another BALANCING AUTHORITY AREA. Dynamic Transfer - ANSWER-The provision of the real-time monitoring, TELEMETERING, computer SOFTWARE, hardware, communications, engineering, ENERGY accounting (including INADVERTENT INTERCHANGE), and administration required to electronically move all or a portion of the real ENERGY services associated with a GENERATOR or LOAD out of one BALANCING AUTHORITY AREA into another. Earth Surface Potentials (ESP) - ANSWER-VOLTAGES induced in the surface of the earth by the ELECTROJETS (CURRENT) that flow above the earth's surface. ESPs cause geomagnetically induced CURRENTS (GICs) to flow in the earth's surface. Economic Dispatch - ANSWER-The allocation of DEMAND to individual generating units on line to effect the most economical production of electricity. Economy Energy - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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) - ANSWER-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 - ANSWER-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 - ANSWER-Temporary magnet created by passing electric CURRENT through a coil. The coil is typically wound about a magnetic CORE. Electromotive Induction - ANSWER-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) - ANSWER-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) - ANSWER-ENERGY and/or CAPACITY provided to a utility to assist that utility during a CAPACITY EMERGENCY. Emergency Energy - ANSWER-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 - ANSWER-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 - ANSWER-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. Emergency Voltage Limits - ANSWER-The operating VOLTAGE range on the INTERCONNECTED SYSTEMS that is acceptable for the time, sufficient for SYSTEM adjustments to be made following a FACILITY OUTAGE or SYSTEM DISTURBANCE. Energy - ANSWER-The POWER used over a period of time. Electrical energy is measured in watt-hours, kilowatt-hours (kWh), or Megawatt-hours (MWh) Energy Conversion - ANSWER-The conversion of ENERGY from one form to another. For example, a coal fired steam TURBINE/GENERATOR converts the coal's chemical ENERGY to thermal ENERGY by burning the coal. The thermal ENERGY is then converted to MECHANICAL ENERGY by heating water and turning the TURBINE with steam. The MECHANICAL ENERGY of the TURBINE is then converted to ELECTRICAL ENERGY via ELECTROMAGNETIC INDUCTION. Energy Emergency - ANSWER-A condition when a LOAD Serving Entity has exhausted all other options and can no longer provide its customers' expected ENERGY requirements. Energy "In-Kind" Payback - ANSWER-INADVERTENT INTERCHANGE accumulated during "ON-PEAK" hours shall only be paid back during "ON-PEAK" hours. INADVERTENT INTERCHANGE accumulated during "OFF-PEAK" hours shall only be paid back during "OFF-PEAK" hours. Energy Management System (EMS) - ANSWER-An EMS SYSTEM is a computer SYSTEM used by an ENERGY company. The EMS includes the subfunctions of SCADA and AGC. Envelope - ANSWER-The imaginary boundary that surrounds the FUNDAMENTAL FREQUENCY OSCILLATIONS waveshape. The FREQUENCY of lower FREQUENCY OSCILLATIONS can be determined by noting the FREQUENCY of the oscillation envelope. Equal Area Criterion - ANSWER-A method of determining the ANGLE STABILITY or instability of a simple POWER SYSTEM. The Equal Area Criterion states that the decelerating area of a POWER-ANGLE CURVE must be at least as large as the accelerating area for the POWER SYSTEM to be angle stable. Equipment Rating - ANSWER-The maximum and minimum permissible VOLTAGE, CURRENT, FREQUENCY, or active and REACTIVE POWER flows on individual EQUIPMENT under steady state, short-circuit, and TRANSIENT conditions, as specified by the EQUIPMENT owner. ERCOT - ANSWER-Acronym for the Electrical Reliability Council of Texas. Excitation System - ANSWER-A GENERATOR CONTROL SYSTEM used to control the production of REACTIVE POWER. The excitation system's main components are the VOLTAGE REGULATOR and the EXCITER. Exciter - ANSWER-The DC POWER SOURCE for an EXCITATION SYSTEM. Exciting Current - ANSWER-The CURRENT drawn by a TRANSFORMER to magnetize its CORE and supply the CORE LOSSES. The exciting current is typically 1-2% of the TRANSFORMER'S full LOAD CURRENT. Extinction Advance Angle (γ) - ANSWER-In an HVDC CONVERTER operating as an INVERTER, the angle by which the VALVE firing is advanced from its normal VOLTAGE based COMMUTATION point. The Greek lower case letter gamma (γ ) is the symbol for the extinction advance angle. The extinction advance angle is used to control the magnitude of the converter's (when operated as a INVERTER) output VOLTAGE. Facility - ANSWER-A set of electrical EQUIPMENT that operate as a single bulk electrical SYSTEM ELEMENT (for example, a line, a generating unit, a shunt CAPACITOR). Facility Rating - ANSWER-The maximum or minimum VOLTAGE, CURRENT, FREQUENCY, or active and REACTIVE POWER flows through a FACILITY that would not violate the applicable RATINGs of any EQUIPMENT comprising the FACILITY. Facility ratings are based upon EQUIPMENT RATINGS and other limits as applicable to the EQUIPMENT. FARAD (F) - ANSWER-The unit of CAPACITANCE. Symbol is "F". Fast Valving - ANSWER-A method of reducing the accelerating ENERGY in a steam TURBINE/GENERATOR. Fast valving involves the rapid adjustment of TURBINE VALVES when a GENERATOR starts to accelerate. Fast valving may assist in maintaining the ANGLE STABILITY of a POWER SYSTEM. Fault - ANSWER-An event occurring on an ELECTRIC SYSTEM such as a SHORT CIRCUIT, a broken wire, or an intermittent connection. Federal Energy Regulatory Commission (FERC) - ANSWER-Independent Federal agency that, among other responsibilities, regulates the TRANSMISSION and wholesale sales of electricity in interstate commerce. Feedback Loop - ANSWER-A control loop in which CURRENT control actions are influenced by the responses to previous control actions. In a feedback loop (such as in a GENERATOR's EXCITATION SYSTEM) the response of the controlled variable is constantly monitored to determine what new control actions should be taken. Ferranti Rise Effect - ANSWER-A phenomena in which a TRANSMISSION line, with one end closed and one end open, is exposed to its highest VOLTAGE magnitude at the open-end of the line. The Ferranti Rise Effect is due to the absorption of a LEADING CHARGING CURRENT when a TRANSMISSION line is energized but open ended. Ferroresonance - ANSWER-A RESONANCE condition in which a portion of the INDUCTANCE is provided by an iron-core INDUCTANCE (Ferro is Latin for iron.). Iron-core INDUCTANCES change magnitude when the iron is saturated. Ferroresonance is possible in the TRANSMISSION or DISTRIBUTION SYSTEM but is much more common in the DISTRIBUTION SYSTEM. Field Winding - ANSWER-The winding wrapped about the ROTOR of a SYNCHRONOUS MACHINE. DC excitation CURRENT is fed to the field winding to produce the ROTOR's MAGNETIC FIELD. Filter - ANSWER-A combination of CAPACITORS, inductors, and resistors used to encourage or block the flow of a specific FREQUENCY or band of frequencies of ENERGY. Firm Capacity - ANSWER-CAPACITY that is as firm as the seller's NATIVE LOAD unless modified by contract. Associated ENERGY may or may not be taken at option of purchaser. Supporting reserve is carried by the seller. Firm Demand - ANSWER-That portion of the DEMAND that a POWER supplier is obligated to provide except when SYSTEM RELIABILITY is threatened or during EMERGENCY conditions. Firm Transmission Service - ANSWER-The highest quality (priority) service offered to customers under a filed rate SCHEDULE that anticipates no planned INTERRUPTION. Flare - ANSWER-A sudden eruption of ENERGY on the solar disk lasting minutes to hours, from which radiation and particles are emitted. Flashover - ANSWER-An ELECTRICAL discharge through air around or over the surface of insulation, between objects of different potential, caused by placing a VOLTAGE across the air space that results in the ionization of the air space. Flat Frequency Control - ANSWER-An alternative name for CONSTANT FREQUENCY CONTROL. Flat Tie-Line Control - ANSWER-An alternative name for CONSTANT NET INTERCHANGE CONTROL. Flowgate - ANSWER-A designated point on the TRANSMISSION SYSTEM through which the INTERCHANGE DISTRIBUTION CALCULATOR calculates the POWER flow from INTERCHANGE TRANSACTIONS. Flyweights - ANSWER-The portion of a CENTRIFUGAL BALLHEAD GOVERNOR that rotates. Forced Outage - ANSWER-1. The removal from service AVAILABILITY of a GENERATING UNIT, TRANSMISSION LINE, or other FACILITY for EMERGENCY reasons. 2. The condition in which the EQUIPMENT is unavailable due to unanticipated failure. Forced Outage Rate - ANSWER-An indication of the percentage of time a generating unit, TRANSMISSION line or other ENERGY FACILITY is forced out of service for EMERGENCY reasons. This percentage excludes the time during which the unit experiences a planned service shutdown (for example, SCHEDULED maintenance). This number can be used to describe a FACILITY's RELIABILITY. A weighted average of forced outage rates for all generating facilities in a utility's SYSTEM may be used to describe SYSTEM RELIABILITY. Forced Outage Hours + In-Service Hours x 100 = Forced Outage Rate. Forecast - ANSWER-Predicted DEMAND for electric POWER. A forecast may be short term (for example, 15 minutes) for SYSTEM operation purposes, long-term (five to 20 years) for GENERATION PLANNING purposes, or for any range in between. A forecast may include PEAK DEMAND, ENERGY, REACTIVE POWER, or DEMAND profile. A forecast may be made for total SYSTEM DEMAND, TRANSMISSION LOADING, SUBSTATION/feeder LOADING, individual customer DEMAND, or appliance DEMAND. Forecast Uncertainty - ANSWER-Probable DEVIATIONS from the expected values of factors considered in a FORECAST. Fourier Analysis - ANSWER-A scientific process in which the various FREQUENCY components (HARMONICS) of a waveform are identified. For example, a waveform may have a FUNDAMENTAL FREQUENCY of 60 HZ but also contain 3rd and 5th harmonic components. Fourier Analysis is used to identify the order of the harmonic components. FRCC - ANSWER-Acronym for the Florida Reliability Coordinating Council. FRCC is one of the eight NERC REGIONAL RELIABILITY ORGANIZATIONS. Frequency (F) - ANSWER-The rate at which a repeating waveform repeats itself. Frequency is measured in CYCLES per second or in HERTZ (HZ). The symbol if "F". Frequency Bias - ANSWER-A value, usually expressed in megawatts per 0.1 HERTZ (MW/0.1 HZ), associated with a BALANCING AUTHORITY AREA that approximates the BALANCING AUTHORITY AREA's response to INTERCONNECTION FREQUENCY ERROR. Frequency Bias Settings (B) - ANSWER-A value, usually expressed in MW/0.1 HZ, set into a BALANCING AUTHORITY ACE algorithm that allows the BALANCING AUTHORITY to contribute its FREQUENCY RESPONSE to the INTERCONNECTION. Frequency Deviation - ANSWER-A change in INTERCONNECTION FREQUENCY. Frequency Error (DeltaF) - ANSWER-The difference between the actual and SCHEDULED FREQUENCY. (FA - FS) Frequency Regulation - ANSWER-The ability of a BALANCING AUTHORITY to help the INTERCONNECTION maintain SCHEDULED FREQUENCY. This assistance can include both TURBINE governor response and AUTOMATIC GENERATION CONTROL. Frequency Response (Equipment) - ANSWER-The ability of a SYSTEM or ELEMENTS of the SYSTEM to react or respond to a change in SYSTEM FREQUENCY. Frequency Response (System) - ANSWER-The sum of the change in DEMAND, plus the change in GENERATION, divided by the change in FREQUENCY, expressed in megawatts per 0.1 HERTZ (MW/0.1 HZ). Frequency Response Characteristic (FRC or Beta) - ANSWER-The MW response of the POWER SYSTEM (or a section of the POWER SYSTEM) to a FREQUENCY DEVIATION. The FRC is typically stated in terms of MW per 0.1 HZ. For example, a BALANCING AUTHORITY may have an FRC of 200 MW/0.1 HZ. This value of FRC indicates that for a FREQUENCY DEVIATION of 0.1 HZ this BALANCING AUTHORITY would respond with 200 MW. The FRC of a SYSTEM varies with changing SYSTEM conditions. Frequency Swings - ANSWER-Constant changes in FREQUENCY from its NOMINAL or steady-state value. Fundamental Frequency - ANSWER-The base FREQUENCY for a SYSTEM. For example, the fundamental frequency of North American POWER SYSTEMS is 60 HZ while a large portion of the world uses 50 HZ as the fundamental frequency. Gallery - ANSWER-A passageway within a water dam created to allow inspection of the dam's structure. Gate/Grid Control - ANSWER-The means of controlling a MERCURY ARC VALVE (MAV) or a THYRISTER VALVE. A pulse of CURRENT or VOLTAGE is applied to the GRID of a MAV or the gate of a THYRISTER. The pulse will turn the VALVE on if it is forward biased. Gate/grid control is typically only used to turn a VALVE on. Generation - ANSWER-The process of producing ELECTRICAL ENERGY from other forms of ENERGY; also, the amount of electric POWER produced, usually expressed in kilowatt hours (kW) or megawatt hours (MW). Generation Control - ANSWER-The process by which the GENERATION supply is adjusted to both maintain SYSTEM FREQUENCY and keep a close match between the actual TIE-LINE flows and the SCHEDULED TIE-LINE flows. Generator - ANSWER-Generally, an electromechanical device used to convert mechanical POWER to electrical POWER. Generator-to-load Distribution Factor (GLDF) - ANSWER-The algebraic sum of a GENERATOR SHIFT FACTOR and a LOAD SHIFT FACTOR to determine the total impact of an INTERCHANGE TRANSACTION on an identified TRANSMISSION FACILITY or FLOWGATE. Generator Operator - ANSWER-The entity that operates GENERATING unit(s) and performs the functions of supplying ENERGY and INTERCONNECTED OPERATIONS SERVICES. Generator Owner - ANSWER-Entity that owns and maintains GENERATING units. Generator Shift Factor (GSF) - ANSWER-A factor to be applied to a GENERATOR's expected change in output to determine the amount of flow contribution that change in output will impose on an identified TRANSMISSION FACILITY or FLOWGATE. Geomagnetic Disturbance (GMD) - ANSWER-Solar (sun) induced DISTURBANCES to the earth's MAGNETIC FIELD. GMDs may result in large low FREQUENCY CURRENTS flowing in the earth's surface. These CURRENTS (called GICs) may enter the POWER SYSTEM and damage TRANSFORMERS. GMDs are also called SOLAR MAGNETIC DISTURBANCES, or SMDs. Geomagnetic Induced Currents - ANSWER-Low FREQUENCY CURRENTS induced in the surface of the earth by EARTH SURFACE POTENTIALS (ESPs). ESPs are created by the ELECTROJETS that form above the earth's magnetic POLES following solar DISTURBANCES. Geomagnetic Storm - ANSWER-A worldwide disturbance of the earth's magnetic field, distinct from regular diurnal variations. Good Utility Practice - ANSWER-Any of the practices, methods and acts engaged in or approved by a significant portion of the ELECTRIC UTILITY industry during the relevant time period, or any of the practices, methods and acts which, in the exercise of