Capitulo-13-Glosario.pdf

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CAPITULO XIII 1

Glossary

Absolute Zero The point at which molecular motion stops, objects contain no heat, andtemperature is at its lowest possible measurement. Absolute zero is -273.16°C or - 459.69°F.

AC Exciter An AC generator that supplies power for a main generator field winding.It consists of a stationary field and a rotating armature.

Acceleration The rate of change of velocity with respect to time.

Accumulator A device used to store fluid under pressure. Normally consists of twochambers (fluid and gas) separated by a piston, diaphragm, or bladder.Normally, used to smooth out pressure surges in a hydraulic system.

Air Ejector A steam-motivated converging/diverging nozzle used to suck air andother non-condensable gases from the main condenser.

Alarm A device (bell, chime, or horn) that provides an audible indication of an

event (problem or condition change).

Algorithm A set of rules, procedures, and mathematical formulas that define adesired control strategy.

Alkali A solution called a "BASE" that contains hydroxyl ions and has a pHmore than 7.00.

AlternatingCurrent (AC)

Electric current that reverses direction periodically. The number of cycles (two reverses) per second is referred to as Frequency.

Ammeter An instrument that measures current flow.

Ampere (Amp) The unit of measurement for the flow of electricity (current).Proportional to the number of electrons passing a point in a unit of time.

Analog A condition or value that continuously varies across a range. NormallyBase 10. Contrast with Digital.

And Gate A logic device that produces a true output signal when all of therequired input signals are true.

Anion A negatively charged ion.

Anneal The process of heating and cooling a metal to make it softer and moreductile.

Annunciator A light indicator that energizes when an alarm sounds (may be a localpanel or a diagram on the WDPF).

Apparent Power

The amount of power that a generator would produce if inductivereactance or capacitive reactance were not present.

Arc The flow of current across a gap in a circuit.



CAPITULO XIII 2

Arc Chute A device that provides insulating barriers to confine an arc and preventit from causing damage in high current switching devices.

Arc Of Admission

That portion of the first row of stationary vanes through which steam isflowing. Related terms are partial arc and full arc.

Armature The part of a generator from which the output is taken or the part of amotor which is energized from the line voltage; also the moving part of a relay. Generally the moving part.

AtmosphericPressure

Pressure exerted by the atmosphere; standard atmospheric pressure atsea level is 14.7 psi (29.92 inches of Mercury).

Atom The smallest division of an element that still retains the chemicalproperties of the element.

Atomic Number The number of protons in one atom of an element.

Atomic Weight The weight of an element with respect to the weight of carbon.

Atomization The breaking up of a substance, such as fuel oil, into tiny droplets. Allows more complete combustion by increasing the surface area.

Attemperator A component that sprays a fine mist of water into steam pipes to controlsteam temperature, called a Desuperheater.

Auto-IgnitionTemperature

The temperature at which the vapors of a material spontaneously ignite.

Auxiliaries Equipment external to the turbine generator necessary for itssatisfactory operation, (hydrogen gas system, sea¡ oil system, etc.).

Auxiliary Steam Steam used for purposes other than driving a main turbine.

Axial FlowCompressor

A compressor that accelerates fluid along the compressor shaft,causing the fluid to be compressed.

Axial Movement

Movement parallel to the axis. End-to-end movement along a shaft or axis.

Axial Thrust A force created along a shaft that tries to push the shaft in the directionof lower force.

Babbitt Metal alloy lining for a sleeve bearing. Generally composed of Tin,Copper and Antimony.

Back Pressure The difference between atmospheric pressure and turbine exhaust.Normally measured in inches absolute of mercury ("HgA).

Backwashing A process of reversing the flow through a component (filter or ionexchanger) to remove trapped material.

BalanceDynamic

The distribution of weight so that rotating parts will rotate with the leastvibration.



CAPITULO XIII 3

Balance Static The distribution of weight so that a rotor will remain stationary in anyposition when placed on a level plane.

BalancingPiston

A device that helps to compensate for axial thrust by creating another force that opposes the axial thrust; also called a Dummy Piston.

Barometer An instrument used to measure atmospheric pressure.

Base LoadStation

A generating station which is normally operated at a constant maximumoutput.

Bearing A component that supports a shaft, carries a load, and aligns movingparts. Classified as: sleeve bearings, roller bearings, or thrust bearings.

BearingBracket/Housing

Structural component that houses and supports a bearing.

Bearing FlowIndicator

A device that provides a means of visually checking the oil flow leavinga bearing.

Bearing OilSeal

A device that inhibits oil flow axially along the shaft.

Bearing,Journal

A bearing that radially supports the rotor.

Bearing, Thrust A bearing that sustains axial loads produced by flow through the turbineblades. It also locates the axial position of the turbine rotor.

Bernoulli'sPrinciple

If a fluid flowing through a tube reaches a constriction, or narrowing of the tube, the velocity of the fluid flowing through the constrictionincreases and the pressure decreases.

BimetallicThermometer

A temperature measuring device that operates on the principle thatdifferent metals expand and contract at different rates in response tochanges in temperature.

Biocide A chemical, such as chlorine, used to prevent biological organisms inwater from growing.

BiologicalFouling

Restriction of flow due to the accumulation of biological organisms.

Blade A rotating part of a turbine. Converts flow energy into rotatingmechanical energy.

Blade Group A number of blades interconnected by a shroud band. The number inthe group is a function of the natural frequency of the individual blades,the group, and the blade row.

Blanketing A process of filling a component with steam or an inert gas such asnitrogen to displace air from the component. Used to minimizecorrosion.



CAPITULO XIII 4

Block Diagram A simplified drawing that uses squares or rectangles to represent major systems or components.

Blowdown A type of drain that is opened during system operation to removecontamination that has built up in the system (steam drum). Maybecontinuous or intermittent.

Bourdon Tube A curved tube used to sense pressure and convert changes in pressureto mechanical motion.

Boyle's Law A theory explaining the relationship between the volume and pressureof gases during compression or expansion: As the temperature remainsconstant P1V1=P2V2.

Breakthrough A condition that occurs when ion exchange resin is exhausted andwater flows through the ion exchanger without being treated.

British Thermal(Btu)

The standard unit of heat energy. Defined as the amount of heat energyrequired to Unit raise the temperature of 1 pound of water 1 ºF under standard atmospheric pressure.

Broadcast The process of sending information across the Data Highway.Broadcasts may be periodic (every second or 100 ms) or non-periodic(broadcast on demand).

BrushlessExcitationSystem

A system that supplies DC power to the rotating field winding of thegenerator without the use of brushes and slip rings. It consists of apermanent magnet generator, a solid-state regulator, an AC exciter,and rotating rectifier circuitry.

Buck, BoostSignal

The "buck" signal is subtracted from the base excitation signal toreduce the excitation to the generator. The "boost" signal is added tothe base excitation signal to increase the excitation to the generator.

Bus A conductor that receives electric current and distributes it toequipment.

Bus AllocationList

A file in the WDPF system that describes the order in which DropsBroadcast messages on the Data Highway.

Bushing (Elect.) A device that connects electrical equipment to electrical lines.

Bushing (Mech.) A type of sleeve bearing.

Calibration The process of comparing an instrument with a device (instrument) of greater and known accuracy.

Capability The maximum load which an electrical apparatus can carry under specified conditions for a given period of time, without exceedingapproved limits of temperature and stress.

Capacitance A physical property of AC circuits that opposes changes in voltage.

CapacitiveReactance

The effect of capacitance on an AC circuit.



CAPITULO XIII 5

Capacity The load for which an electrical apparatus is rated, usually stated bymanufacturer's name plate ratings.

Carbon Dioxide(CO2)

A colorless, odorless, incombustible gas commonly used in fireextinguishers.

Carbon Filter A filter containing activated carbon; typically used as a pre-filter in ionexchange systems. Removes suspended solids, chlorine, and organicmaterial.

Carryover The process by which impurities (water) is entrained in steam as itleaves the boiler.

CascadingBlowdown

The process where the continuous blowdown line is connectedbetween the high pressure and low pressure steam drums.

Casing The turbine shell that confines the pressurized fluid.

CasingExpansion

Growth of the turbine casings as a result of heating.

Channeling The result of improper diffusion of water entering an ion exchanger;water flows through only part of the resin bed and the overall efficiencyof the ion exchanger is reduced.

Characteristic Set of 8 alphanumeric characters associated with a Point, representuser-defined aspects of the controlled process. Used in Alarmprocessing and point review functions at the Operator Station.

ChemicalCleaning

Cleaning method that uses chemicals to breakdown deposits for removal.

Clarification A water treatment process. Uses chemicals to group together particles

into heavier clumps so they will settle to the bottom.

Clarifier Water Treatment Equipment. Used to remove suspended solids.

Closed ControlLoop

A control loop that has a sensing element, a measuring element, and afinal control element.

Coagulant A chemical added to raw water to cause particles suspended in thewater to group together into heavier clumps.

Coil A Ladder Diagram element that usually controls a real-world output fielddevice (e.g., a motor starter, solenoid, etc.).

CombustionChemical reaction between a combustible material (fuel) and oxygenthat produces heat.

Commutator Component of a DC exciter that changes alternating current to directcurrent.

Concentric The relationship between two circular, cylindrical, or spherical shapesof different sizes when the smaller one is exactly within the larger one.



CAPITULO XIII 6

CondensateDepression

The difference between the temperature of condensate in thecondenser hotwell and the saturation temperature that corresponds tothe vacuum maintained in the condenser.

Condensing The process of changing water from a vapor state to a liquid state.

CondensingTurbine

A turbine that operates with an exhaust pressure below atmosphericpressure.

Conduction The process by which heat is transferred from a hotter object to acolder one through physical contact.

Conductivity The ability of a solution to transmit electrical current. The opposite of Resistance.

ConductivityCell

Instrument used to measure the conductivity of a solution.

Contact A Ladder Diagram element that represents a real-world input device(e.g., a pushbutton, switch, etc.).

Control Stage Normally the first stage of blading of a turbine. The inlet nozzle blocksare usually made in segments of the nozzle arc connected toindividually operated control valves.

Control Air Air specifically used to control a physical plant device.

Convection The process by which heat is transferred to or from a moving fluid.

Coupling The mechanical device that provides a means of joining one rotatingdevice to another.

Creep The deformation of a material occurring with time and due to an

externally applied constant stress.

Critical Point Conditions of 705.47 °F and 3208.2 psia, where there is nodistinguishable difference between water and steam.

Critical Speed A rotor speed at which the rotor is in it's resonance (excessivevibration).

Cycle A course that recurs regularly and leads back to the starting point. Inpower plants, a cycle is the course of the thermodynamic fluid throughthe various equipment.

Data Highway The communication link between Drops; also called a local areanetwork (LAN).

DeaeratingHeater

A mixing-type heat exchanger in which the heating steam is condensedand combined with the heated condensate. It boils off any oxygen or other non-condensable that might be carried in the condensate.

Demand The rate at which electric energy is delivered to or by a system.



CAPITULO XIII 7

Demister A device to remove liquid particles from air or vapor. A demister is usedin conjunction with the oil vapor extractor on the oil reservoir.

Diagram A graphic depiction of a plant process displayed on the Operator Station.

Differential A term used to specify the comparison between "Blade Path Setpoint"and "Average Blade Path Temperature". Contrast with Spread andVariance.

DifferentialExpansion

A measure of the difference in expansion between rotating andstationary parts of the turbine.

Digital A signal or value that is either on or off. Contrast with Analog.

Digital Electro-HydraulicControl System

An electronic-hydraulic turbine control system that has a digitalcomputer capable of controlling the turbine and generator during allphases of operation.

Dispatching The operating control of an integrated electric system.

Distribution A functional classification of that portion of utility plant used for thepurpose of delivering electric energy to the consumers.

DoubleAmplitudeVibration

A vibration that is both above and below an imaginary centerline. Singleamplitude is that from the centerline to either of the peaks. Doubleamplitude is that from the high peak to the low peak.

DoubleFrequencyVibration

A vibration with a cyclic rate twice that of the rotational speed of therotor.

Dowel A pin in mating parts to provide precise alignment of the parts.

Downcomer The large pipes in drum-type boilers that recirculate water from thesteam drum to the lower drum (mud drum).

DPU Distributed Processing Unit, a Drop in the WDPF system thatprocesses sequential logic (Ladder Diagrams) and continuous control(Loops).

Drain Pot A sump or reservoir mounted on a steam pipe to collect water in theline and minimize the possibility of large accumulations of water in thepipe.

Drip Leg A small pipe attached to a steam line for the purpose of collecting andremoving dirt from the line.

Drop A station on the WDPF Data Highway.

Dry Steam Steam containing no moisture or water droplets.

Ductility The property of a metal that allows permanent deformation by stress or tension without fracture.



CAPITULO XIII 8

Duplex Strainer A two basket strainer that allows one strainer element to remain inoperation while the other strainer element is removed from service for maintenance.

Eccentricity A condition normally associated with a bowed turbine shaft. The degreeof deviation from absolute roundness; the amount that the rotor deviates from its normal center of rotation.

Economizer A component that transfers heat from the exhaust gas leaving the heatrecovery steam generator to feedwater flowing into the boiler.

Efficiency A measure of the amount of energy going into a process compared withthe amount of energy coming out of the process.

Effluent The fluid leaving any process (water leaving an ion exchanger).

Electro-HydraulicSystem

A turbine control system that uses an electronic governor andpressurized hydraulic fluid to monitor and control turbine speed andload.

Emergency Trip

A system that provides automatic shutdown of the turbine for certainabnormal System operating conditions.

Enable A command for a circuit, function, or device to be activated or tooperate.

Enclosure A structure that usually covers the turbine. Although designed from anaesthetic viewpoint, the enclosure affords practical benefits, such asreducing the noise level and protecting equipment and personnel.

End Shield,Generator

An assembly of laminated magnetic steel punching on each end of thegenerator core designed to prevent axial magnetic flux from excessivelyheating the core.

EnergizedSystem

A system at rated voltage and frequency that may or may not be under load.

Engineer Station

A Drop in the WDPF system used for configuration and entry of systemprograms. It also incorporates the capabilities of the Operator Station.

Enthalpy A measure of the total heat content of the working fluid. In steamturbines, enthalpy is expressed in units of Btu/Ib.

Excess Air An amount of air in excess of the air theoretically required to producecomplete combustion under Stoichiometric Condition.

ExcitationSystem A generator's source of field current and its associated supply andcontrol mechanisms.

Excitation,Generator

The electrical power needed to provide the magnetic field in agenerator.

Exciter-Regulation

Control of the exciter field voltage that determines the magnetic field inthe exciter and, consequently, its output.



CAPITULO XIII 9

Exciter Stability The capability of the exciter to maintain a constant output to thegenerator field winding when supplied with a constant input.

Exhaust Hood That portion of the LP steam turbine outer cylinder that contains thesteam leaving the last row of blades and directs it into the condenser.

Exhaust Loss Energy losses that occur between the last turbine stage and thecondenser.

ExhaustPressure

The pressure at the exit of a turbine section.

Expansion Line

A line plotted on a Mollier Chart showing the properties of steam as itexpands through the turbine.

External GlandLeakages

Steam leakage through the turbine gland seals that is directed toexternal receivers such as the gland steam condenser and feedwater heaters.

Extraction Non-

Return Valve

A valve located in an extraction pipe, which should prevent a backflow

of vapors to the turbine.

ExtractionStage

A turbine stage that has steam extracted at its exit conditions for feedwater heating or process steam.

Fail Position The physical position to which a device will go upon loss of its actuatingelectrical, electronic, pneumatic or hydraulic control signal.

Fatigue Failure of material by cracking caused by repeated cyclic stressing.

Feedback Information about a process output which is communicated to theprocess input. (ie. Valve Position).

Feedwater The water supplied to a boiler.

Feedwater Heater

A heat exchanger used to heat feedwater before it is supplied to theboiler.

Flash Point The lowest temperature at which vapors above a volatile combustiblesubstance ignite in air when exposed to flame.

Flashing The process of liquid rapidly changing to vapor when the pressure of the liquid is decreased below its saturation pressure.

Force Value To set the value of a WDPF point to a desired state, regardless of theother input values.

Fuel A combustible material used to produce heat.

GeneratingStation

The location where the equipment that converts mechanical energy intoelectrical energy is located.

Generator A machine that converts a rotational mechanical energy into electricalenergy.



CAPITULO XIII 10

Generator Saturation

The point at which no further flux can be induced into a material byincreasing the current in the circuit is referred to as "saturation."

Gland Seal Device used to minimize the leakage along a shaft. Labyrinth seals andcarbon ring seals are two types of gland seals.

Gland SteamCondenser

Shell-and-tube heat exchanger that condenses leakoff from the turbineglands. Condensed steam (condensate) is returned to the steam cycle,air and non-condensable gases are vented to atmosphere. Coolingmedium is normally condensate.

Gland SteamRegulator

A valve that maintains a given pressure in the sea¡ steam header byadmission of steam from a higher-pressure source or by bleeding off steam to a lower-pressure zone.

Governor Valve

The valve(s) that controls the flow of steam to the nozzles of the firststage.

Grout A Portland cement mixture poured or packed around foundation bolts,leveling wedges, between the foundation and sole and/or seating plates

to support the plates and the loads on the plates.

Heat Balance A diagrammatic representation of a thermal cycle with pressures,temperatures, enthalpies, and flows listed. It represents the anticipatedperformance of the unit for the designated conditions.

Heat Exchanqer Any device that transfers heat from one fluid to another.

Heat Rate A measure of thermal efficiency, generally expressed in Btu per kilowatthour. It is computed by dividing the total Btu content of fuel burned bythe resulting kilowatt hour generation.

Heating Value Amount of usable energy available in fuel that can be released by

combustion.

High-PressureSection

That part of a high pressure steam turbine into which steam is firstadmitted. In some turbine designs there is a combined high-pressureplus intermediate-pressure zone within one casing. The high-pressurezone of the HP-IP turbine is sometimes referred to as the high-pressuresection.

Hogger Device used to remove large quantities of air from a condenser. Can bean air removal pump, an air-driven air ejector, or a steam-driven air ejector. Usually a one stage operation used to pull vacuums up to 21 "HgA.

HotwellTank at the bottom of the condenser where condensate is collected.

House Load The electrical power necessary to maintain al¡ station auxiliaryequipment in operation.

Hydrogen A colorless, odorless gas. Used as a cooling medium for some types of generators. It has excellent heat transfer characteristics and lowaerodynamic drag.



CAPITULO XIII 11

HydrogenCooler

Heat exchanger in which the heat absorbed by the hydrogen gas istransferred to station cooling water.

Hydrogen Inner-Cooled

A generator in which cooling of the stator and rotor windings isaccomplished by circulating hydrogen gas through hollow conductors of the coils. Generator

Ignition Application of sufficient heat to start the combustion process.

Impulse Blading Blading in which the space between blades at the inlet is the same asat the outlet. Energy transfer in impulse blading results in a decrease invelocity. Generally refers to the moving blades. (Contrast with ReactionBlading)

Inductance A physical property of AC circuits that opposes change in current flow.

InductiveReactance

The effect of inductance on an AC circuit.

Inner Cylinder A pressure vessel located inside the outer turbine cylinder. Used to

contain the high-pressure and high-temperature steam, thus reducingthe stress on the outer cylinder.

Interceptor Valve(s)

The steam valves that control the Intermediate pressure steam flow intothe turbine.

Interfacing The place at which independent systems meet.

Interference Fit

A shrunk-on fit between cylindrical parts. Interference is the amount of deformation necessary to force an internal member into a smaller external member.

Intermediate-

PressureSection

A turbine section that receives steam from a higher-pressure section

and exhausts it to a lower-pressure section. It is usually the section thatreceives steam from the reheater.

KiloVar (Kvar) 1000 reactive volt-amperes.

Labyrinth Seal A seal composed of grooves and ridges that form a tortuous path torestrict the passage of fluid flow.

Ladder A Diagram representing sequential (relay-type) control logic. (ContrastLoop)

Latch, Latched A turbine is latched pressurizing hydraulic control fluid lines andactuation of the turbine main steam inlet valves. Latch is the opposite of TRIP.

Latent Heat Of The heat that must be added to water to transform it into steam.Vaporization

Leveling Wedge

A device fitted between the foundation and the seating plates to alignthe turbine generator.



CAPITULO XIII 12

Line Loss Power lost due to the impedance of transmission and distribution linesunder specified conditions.

Load The amount of electric power delivered or required at any specifiedpoint on a system.

Locus Of ValvePoints

In sequential valve operation, as load is increased, there are a number of points at which some governor valves are fully open and al¡ othersare fully closed. At these points, there are minimal governor valvethrottling losses, resulting in more efficient operation of the turbine. Alocus of valve points is a heat rate curve drawn through these points.

Loop A Diagram representing a modulating or continuous process control.(Contrast Ladder)

Loop Seal Tank

A tank that receives oil returned from the generator journal bearing andair side of the hydrogen gland seals. It prevents hydrogen from enteringthe main oil reservoir.

Loss (Losses) The general term applied to energy and power lost in the operation of

an electric system.

Low-PressureExhaust Blades

Blading used as the final stage in LP turbines.

Low-PressureSection

The section of the turbine casing containing the lowest-pressure steam.

MAC Multi-Application Controller, the terms MAC and DPU areinterchangeable.

MagneticParticle

Inspection

A nondestructive method for detecting cracks and other discontinuitiesat or near the surface in ferromagnetic materials.

Magnetite An iron oxide (Fe304) corrosion layer that occurs under low oxygenconditions; the iron oxide layer prevents further corrosion.

MechanicalLoss

Bearing losses, oil pump losses, and any other similar losses in aturbine generator.

Megavar (MVAR)

A unit of measurement for reactive power; equal to 1,000 KiloVars.

MegavoltAmpere (MVA)

A unit of measurement for apparent power; equal to 1,000 kilovoltamperes.

Megawatt (MW) A unit of measurement for true power; equal to 1,000 kilowatts.

Micromho(μmho)

An electrical unit used for measuring the conductivity of water,equivalent to the quantity of one divided by the resistance of the water to electrical conductivity.



CAPITULO XIII 13

Micron One millionth of a meter. The term identifies particle size in fluidsystems and identifies the smallest particle a filter is capable of removing from a fluid.

MoistureContent

The percentage of water in a steam/water mixture.

Moisture Region The area of a steam properties chart at which both the liquid and vapor phases exist.

Molecular Weight

The weight of one molecule of a compound; can be determined byadding the atomic weights of the elements that make up the compound.

Molecule The smallest division of a compound that still retains the chemicalproperties of the compound.

Mollier Diagram A graph of entropy versus enthalpy that indicates most of the propertiesof saturated and superheated steam.

Motoring A system condition in which the generator acts as a motor and drives

the turbine.

NameplateRating

A full load continuous rating of a generator, prime mover, or other electrical equipment under specified conditions as designed by themanufacturer.

Network A system of distribution lines operated as to permit multiple power supply to any principal point on it.

Neutral Bus,Generator

The electrical connection device between the three neutral terminalbushings.

Nitrogen Oxides(NOx)

Pollutant gases that are produced during combustion when nitrogenand excess oxygen combine at a very high temperature.

Non-ReturnValves

Valves that operate like swing check valves. Protects the turbine frompossible back-flow if the flow of steam to the turbine stops.

Not Gate A logic gate that produces a true output only when its input signal is nottrue.

Nozzle Block(NozzleChamber)

A machined stationary vaned section at the first stage of a turbine thatcontains the first stage nozzles.

Nozzle FlowThe rate of steam flow through the Nozzle to the first-stage blades.(Throttle flow minus valve stem and cylinder inlet sleeve leakage.)

Off-StoichiometricCombustion

Conditions of combustion such that after burning is complete, a smallamount of fuel or air is left over. Contrast with StoichiometricCombustion.

Oil Cooler Heat exchanger used to cool turbine lubricating oil.



CAPITULO XIII 14

Oil Filter A device used in an oil system to remove solids above a specific size.

OilNeutralizatonNumber

The weight in milligrams of potassium hydroxide required to neutralizethe acid in 1 gram of oil.

Oil Pump,Emergency

A DC motor-driven pump that supplies lubricating oil during emergencyshutdown. This pump helps protect the turbine generator in the event of

AC power loss.

Oil Pump, SealOil Backup

A high-pressure pump (normally DC motor-driven) that provides asource of backup oil to the seal oil system. Operates during startup,shutdown, turning gear operation, main oil pump malfunction, andemergency shutdown.

Oil Reservoir A large tank in which the lube oil is contained.

Oil Vapor Extractor

A motor-driven centrifugal fan that creates a slight vacuum in the oilreservoir, interconnecting oil drain piping and turbine bearing housings.

Oil Whip A vibration of the rotor and journal caused by instability of thehydrodynamic forces in the oil film.

Oil, Lubricating Oil supplied, under pressure, to the bearings of the turbine generator for lubrication.

Open Circuit The electrical isolation of two or more circuits. Also refers to a type of fault where connecting elements have become physically separated.

Operator Station

A Drop in the WDPF system, used to control and monitor plantoperation.

Or Gate A logic gate that produces a true output if one or more of the input

signals is true.

Overexcited A generator operating condition that exists during operation at laggingpower factor due to inductive reactive loads on the system.

OverspeedProtection

A protective system that detects a sudden loss of load or an overspeedof 103% and limits overspeed to a safe value by closing thegovernor valves. Controller

Packing A dynamic seal material, it is flexible and is used to provide a sealalong a shaft.

Pawl A hinged piece that engages teeth in a gear or ratchet. Used to effect or prevent movement.

Pedestal A separate housing that supports the rotor bearings.

PermanentMagnetGenerator (PMG)

A generator in which the magnetic field is produced by permanentmagnets. In the brushless excitation system, a set of rotating magnetsprovides the field for a stationary armature winding to form a generator that is the source of power for the regulator and exciter field.



CAPITULO XIII 15

Permeability The ability of material to become magnetized. A generic term used toexpress various dynamic relationships between magnetic induction andmagnetizing force, for magnetic material subjected to a cyclic excitationby alternating or pulsating current.

pH A measure of the acidity or alkalinity of a solution on a scale from 0.00(most acidic) to 14.00 (most alkaline).

Phase Lead The connection between a stator winding coil end and a parallel ring.

PhosphateEster

The synthetic base from which a hydraulic or lubricating fluid is made.

Pickling To clean a metal part by dipping it into an acid solution.

Pilot Exciter That portion of the brushless excitation system that contains thepermanent magnet generator. It is the source of all field current for the

AC exciter.

Pilot Valve A small primary valve whose output is used to control or activate a

larger valve.

Plant Master Control System

An integrated control system used to coordinate the control of all of power plant systems.

Point A record in the WDPF global database containing a value (such as aninput or output) and related data.

Point Name Alphanumeric identifier associated with a point on the Data Highway.

Pole The unslotted portions of the generator rotor encircled by the fieldwinding. The areas of greatest magnetic flux in a device.

Pour Point The lowest temperature at which a ¡¡quid will flow.

Power (Electric) The time rate of generating, transferring, or using electric energy,usually expressed in kilowatts.

Power (Electric),Reactive

That portion of apparent power that does no work. Measured inKiloVars.

Power Factor (Pf)

The ratio of real power (kW) to apparent power (kVA) for any given loadand time. Generally expressed as a percentage ratio.

Pressure A force per unit area. Normally measured in units of pounds of force per square inch of area.

PressureRegulator SetPoint

The pressure that the regulator tries to maintain. For example, if the setpoint is 1000 psig, the controls move the regulating valves to maintaina pressure of 1000 psig.

Pressure Switch A device that changes the position of an electrical contact based onsensed pressure.



CAPITULO XIII 16

PressureTransducer

A device with an electrical signal output determined by a sensedpressure input, the output is usually proportional to the input.

Pressure,Absolute

A term used to indicate pressure above a perfect vacuum. Measured inunits of pounds per square inch or inches of mercury.

Pressure,Atmospheric

The pressure due to the weight of the atmosphere. Measure in units of pounds per square inch or inches of mercury.

Pressure,Exhaust

The pressure at the exit of a turbine section.

Pressure,Extraction

The pressure of the steam extracted from the turbine. It is measured atthe extraction connection of the turbine.

Pressure,Gauge

A term used to indicate the difference between the absolute pressureand atmospheric pressure.

Pressure, Initial

The pressure of the steam supplied to the turbine. Measured at theturbine throttle Steam valve inlet.

PressurizedDrain

A drain line in a fluid system that is sealed from the atmosphere. Maycontain devices to control pressure in the line.

Pre-stress The internal stress that remains in a bolting member after tightening.

Primary Voltage The voltage of the circuit supplying power to a transformer. Generallythe high voltage side of a transformer.

Prime Mover The engine, turbine or similar machine which drives an electricgenerator, a pump, etc.

Protective Trip

Devices

Devices that detect a condition that could damage a machine and take

actions to protect the machine.

Proximitor An electronic device that is used to measure the distance between todevices, provides an signal proportional to the closeness (proximity).

Psia Pound per square inch absolute; pressure measurement includingatmospheric pressure.

Psig Pound per square inch gauge; pressure measurement not includingatmospheric pressure.

Punchings,Generator

A keystone-shaped magnetic steel sheet insulated on both sides. Usedto form the generator core. The term "punchings" is derived from themethod of manufacture.

Purging The act or process of cleaning, such as removing hydrogen from thegenerator, removing foreign matter from oil systems, and removingmoisture from compressed air systems. Purging may involve the use of an intermediate fluid.

Radial Side - to - side movement. Movement



CAPITULO XIII 17

Rated Capability The capability of a turbine operating at rated inlet and reheatconditions, and assigned site exhaust and makeup conditions.

Rated Flow The throttle flow necessary to produce the rated capability.

Rated Load The maximum guaranteed capability of a turbine generator at ratedsteam conditions.

Rated SteamConditions

The normal initial steam pressure, initial steam temperature, andexhaust steam pressure.

Rated ThrottleFlow

The inlet flow necessary to produce the rated capability at nameplateconditions.

Reactance,Inductive

Resistance to current flow due to an electromotive force produced bythe change in current flow. Opposes the change of current flow andcauses the change of current to lag the change of voltage across thedevice by 90 electrical degrees.

Reaction

Blading

Blading in which the space between the blades is smaller at the

exhaust than at the inlet. Energy transfer in moving reaction bladingresults in a decrease in steam pressure and an increase in velocity.(Contrast with Impulse Blading)

Reactive Power

Power that must be supplied to a load to compensate for the effects of inductive reactance or capacitive reactance.

Real Power The actual power (in kilowatts) being produced by the generator.

Regeneration The process of returning an ion exchanger's capability for exchangingions.

Regulator A device that controls its output or the output of another device to a

preset value.

Reheat The practice of removing partially expanded steam from a turbine,increasing its temperature, and then returning it to the turbine tocomplete its expansion.

Reheat StopValve(s)

Valves located between the boiler reheater and the turbineintermediate-pressure section. Used to isolate the intermediate andlow-pressure sections of the turbine from the reheater.

Reheater A section of the boiler that receives high-pressure turbine exhauststeam and increases its temperature to increase its energy level beforeit is admitted to the lower-pressure sections of the turbine.

ResinExhaustion

A condition in which the exchangeable ions on the resin bead siteshave become depleted. Sufficient ion exchange can no longer takeplace. See Breakthrough.

ResistanceTemperatureDetector (RTD)

An instrument that measures temperature, based on the principle thatthe resistance of certain metals change when they are heated or cooled. (Contrast with Thermocouple)



CAPITULO XIII 18

Root-MeanSquare (Rms)Current

The value of alternating current that will provide the same power as thecorresponding value of direct current. Root mean square refers to themethod of computing this value.

Root-Mean-Square (Rms)Voltage

The effective value of a varying or alternating voltage. That which wouldproduce the same power loss as if a continuous voltage were applied toa pure resistance.

Rotor The rotating components in a machine.

Rotor End-TurnVentilation

Design methods adopted to provide cooling ventilation to the rotor endturns, that portion of the winding which lies outside the body of therotor.

Rotor Position The relative axial position of the rotor thrust collar with respect to thethrust bearing support, due to the magnitude of axial thrust on the rotor system.

Rotor-Long A condition in which a rotor expands faster than the casing.

Rotor-Short A condition in which a rotor contracts faster than the casing.

Runback(lubrication Oil)

The oil that drains back into the reservoir when the lubrication oilsystem is shut down.

Runout (Shaft) When expressed in inches alone, or accompanied by abbreviation"TIR" (total indicator reading), it refers to twice the radial distancebetween shaft axis and axis of rotation.

Rupture Disc A device used for protection against over pressure. Releases largevolumes of fluid to protect a system or component.

Salt An ionically bonded compound that is composed of a metal and a non-

metal.

SaturatedLiquid

A liquid that is at it's boiling point for a given pressure.

SaturatedSteam

Steam at the saturation temperature that has no water present.

SaturationTemperature

The temperature at which water will boil for a given pressure.

Scale A hard deposit that collects on the surfaces of heat exchangers.

ScanThe processor module's sequential and ongoing examination of eachcontact circuit, control relay, special function and process control loopin the application program. During the scan, the processor accessesdata stored in memory and the current states of the field I/O. Thedetermination of Analog/Digital output information.

Scrubbing The removal of non-condensable gases from water. Example, as steamraises in a deareator, it contacts the water removing the dissolvedoxygen and carbon dioxide.



CAPITULO XIII 19

Seal Any device used to prevent the passage of a fluid.

Seal Oil System A of system used to help prevent the loss of hydrogen from, and theintroduction of air into, the generator.

Set Point A value at which process variables within a system are maintained.

Shaft Reciprocating or rotating member usually within a cylinder; not incontact with walls.

Shim A thin piece of material placed between two surfaces to obtain a proper fit, adjustment, or alignment.

Shrink In a boiler, a short-term decrease in drum water level which results froma change in the boiler pressure (pressure decrease). Contrast to Swell.

Shroud Flat metal strips riveted to the tips of blades. Shrouds provide surfacesfor sealing and are used to stabilize blade groups by controlling theresonant frequency of the blades.

Sight FlowIndicator

A glass window through which the flow or presence of a liquid can beobserved.

Slots Slots in the stator or rotor into which coils are assembled to obtain thegenerator stator winding or rotor winding.

Sludge A soft deposit of impurities with a consistency similar to mud. Sludgebaked onto a hot boiler tube forms a hard deposit similar to Scale.

Specific Gravity

The ratio of the density of a substance to the density of water.

Specific Heat The amount of heat, in BTU's, required to raise the temperature of onepound of a substance one degree Fahrenheit.

Specific Volume

The measurement of the amount of space occupied by a specific massof a substance.

Speed Pickup A magnetic device that senses a toothed wheel mounted on the turbinerotor. An AC signal output is generated whose frequency is proportionalto turbine rotational speed.

Speed,Synchronous

The speed of rotation of the magnetic flux produced by the primarywinding.

Spread A term used to specify the comparison between "Lowest Blade PathTemperature" and "Average Blade Path Temperature". Contrast withDifferential and Variance.

Stage The combination of a row of stationary blades and rotating bladesthrough which the steam expands to produce work.

Stage, Curtis A velocity-compounded turbine stage. Consists of a row of fixednozzles, a row of moving impulse blades, a row of fixed reversingblades, and a second row of moving impulse blades.



CAPITULO XIII 20

Stage, Reaction A turbine stage consisting of a row of fixed nozzles, and a row of moving reaction blades.

Static Head Pressure resulting from the height of fluid in a tank or container.

Station Use(Generating)

The kilowatt-hours used at an electric generating station. (Excitation,operation of auxiliary and other facilities essential to the operating of the station, etc.)

Stator The stationary element of a motor or generator and its associatedelectrical windings and leads.

Steam Chest A collection area designed to reduce the turbulence of steam before thesteam enters the turbine control valves.

Steam Cycle The complete loop from the boiler, through the steam turbine, throughthe condenser, and back to the boiler.

Steam Drum A closed vessel used to hold a large quantity of water for the productionof steam, also used to separate water from steam.

Steam Rate The quantity of steam needed by the turbine per unit of power output,measured at the output terminals of the generator (Pounds of steamper kilowatt-hour).

Step Down To change electricity from a higher to a lower voltage.

Step Up To change electricity from a lower to a higher voltage.

StoichiometricCombustion

Conditions of combustion such that fuel constituents and oxygen arematched atom for atom so that no combustibles are left over after burning. Contrast with Off-Stoichiometric Combustion.

Stop Valve A valve used to shut off the flow in a line.

Strain Deflection due to a force.

Stress Force per unit of original cross section area.

Stress-CorrosionCracking

A mechanical-environmental fatigue process in which sustained tensilestress and chemical attack combine to initiate and propagate fracture ina metal part.

Stroking Operating valves and other linear mechanical devices from one limit tothe other (full closed to full open to full closed).

SubcooledWater Water at a temperature below the saturation temperature.

SubcriticalConditions

Steam conditions below the Critical Point of 705.47°F and 3208.2 psia.

Substation An assemblage of equipment for the purpose of switching and/or regulating the voltage of electricity.



CAPITULO XIII 21

Sudden A relay designed to detect a rapid buildup of pressure inside atransformer. Pressure Relay

Sulfur Oxides Pollutant gases produced in a Combustion Turbine when Fuel Oilcontaining sulfur is burned.

Supercritical Steam conditions above the Critical Point of 705.47°F and 3208.2 psia.

SuperheatedSteam

Steam that is heated above it's saturation temperature.

Swell In a boiler, a short-term increase in boiler drum water level whichresults from a change in the boiler pressure (Pressure increase).Contrast to Shrink.

System, Electric The physically connected generation, transmission, and distributionequipment, and other facilities operated as an integral unit under onecontrol, or operating supervision.

Tandem-

CompoundTurbineGenerator

Tandem-compound turbine generators are made up of a group of two

or more turbine elements, plus a generator, arranged in line along acommon axis.

Temperature A measure of the heat level of an object or medium.

Thermal Stress

The stress in a material as it is heated or cooled due to the difference intemperature of various parts of the material.

Thermal StressCycle

The change of stress in a material as it is heated and cooled from onestable temperature to another and back to the original temperature.

Thermocouple An instrument for measuring temperature that uses voltage created by

the heating of two dissimilar metals.

Three-ElementFeedwater Control

An automatic feedwater flow control system which senses steam flow,feedwater flow and drum water level, and acts to maintain boiler drumwater level at a constant setpoint.

Throttle To expand fluid from one pressure to a lower pressure, usually at aconstant enthalpy. Valves are widely used for variable throttling.

ThrottlePressure

The steam pressure supplied to the steam turbine throttle valves; alsocalled "Above Seat Pressure".

Throttle

PressureRegulator

A part of a steam turbine control system that monitors steam inletpressure to help protect the turbine against sudden reduction of steaminlet pressure and possible resultant water carryover from the boiler.

Throttle Valves Large plug-type valves that admit steam to an HP-IP turbine. Used toshut off the flow of steam to the turbine in the event of a system trip.

Also used for controlling steam flow to the turbine when the unit isbrought up to speed.



CAPITULO XIII 22

Through-Bolt A bolt that passes axially through several components to keep thecomponents together. For example, through the laminated core of agenerator stator to keep the laminations together.

Thrust A force created when moving fluid strikes an immovable object, i.e.,steam striking the blades in a steam turbine. Thrust is in the direction of the fluid flow.

Thrust Bearing A bearing designed to absorb axial thrust.

Thyristor A controlled rectifier device that provides high-speed turn-on.

Timestarter An electromechanical device that controls the startup of large DCmotors.

Top Heater The highest-pressure heater through which the feedwater flows beforeentering the boiler.

Transformer A static electric device consisting of one or more windings and amagnetic core. Transformers are used in electric power systems to

transfer power by electromagnetic induction between circuits, usuallywith changed values of voltage and current.

Trip A rapid shutdown of the turbine generator, generally in response toabnormal conditions.

True Power The amount of power that is actually doing work in an AC circuit.

Tube Bundle A group of tubes, mechanically held together as a unit, through whichone of the fluids in a heat exchanger passes.

Turbine Deck A reinforced concrete foundation that supports the turbine, generator,and exciter.

TurbineGenerator Unit

The combination of a generator coupled directly to a driving turbine.

Turbine InletConditions

The pressure and temperature of the steam at the turbine throttlevalves and after reheating in the boiler, if applicable.

TurbineSupervisoryInstruments(TSI)

Solid-state electronic systems that monitor conditions of casingexpansion, speed, governor valve position, differential expansion, rotor position, vibration, and eccentricity of the rotor.

Underexcited A generator operating condition that exists during operation at loadingpower factor due to capacitive loading on the system.

Unity Power Factor

An operating condition in which True Power and Apparent Power areequal.

Unloader Valve A valve used to regulate pressure in an electro-hydraulic fluid system.

Valve StemLeakage

Fluid leakage along a valve stem, normally from the inside of the valvethrough a seal system to atmosphere.



CAPITULO XIII 23

Valves WideOpen (VWO)

All turbine governor valves at the full-open position, passing amaximum flow of steam.

Vane A none rotating part of a turbine, vanes direct the steam or hot gas intothe rotating blades. Contrast with Blade.

Vaporization A process in which a liquid reaches its boiling point and changes to agas.

VAR (VoltAmpereReactive)

The basic unit of measurement for Reactive Power.

Variance A term used to specify the comparison between "Highest Blade PathTemperature" and "Average Blade Path Temperature". Contrast withSpread and Differential.

Vented Drain A drain line in a fluid system that is open to atmospheric pressure.

Vibration A continuing periodic change of displacement. In a turbine generator,

rotor vibration is often caused by unbalance of the rotating parts.Rotational forces acting on this unbalance produce the vibration.

VibrationPickups

Proximity pickups measure the vertical displacement of the rotor withrespect to the casing, while seismic pickups measure casing vibration.The two values are summed to provide total vibration.

Vibration,Absolute

The sum of the relative and seismic vibration levels. Displayed by theWDPF control system and used for alarm and trip functions. Contrast toVibration, Relative and Seismic.

Vibration,Relative

Motion of the rotor relative to the bearing housing. Contrast to Vibration, Absolute and Seismic.

Vibration,Seismic

Motion of the bearing housing relative to the ground. Contrast toVibration, Absolute and Relative.

Viscosity The measure of a fluid's resistance to flow. Viscosity varies withtemperature

VolatileChemical

A chemical that vaporizes when heated to its boiling point.

Volt A unit of electrical potential difference and electromotive force.

Volt Ampere A unit of electrical measurement equal to the product of a volt and anampere that for direct current constitutes a measure of power equivalent to a watt. (See Apparent Power.)

VoltageAdjuster

Part of the regulator, A potentiometer that enables the operator tomanually set the AC generator regulated voltage at any value within aband of ±10 percent of the rated generator voltage.

Volumetric Flow

A volume of fluid at a given temperature flowing past a point in a giventime interval.



Water Induction

The entrance of water into a steam turbine.

Watt A basic unit of power; equal to the amount of work performed by acurrent of 1 ampere at a voltage of 1 volt.

WDPF Westinghouse Distributed Processing Family of products.

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