protection course - chapter 2

8/10/2019 protection course - chapter 2

1/57

22 TWOTWOPOWER SYSTEMPOWER SYSTEM

LAYOUT ANDLAYOUT ANDRELAYING PRINCIPLESRELAYING PRINCIPLES


2/57

Power system layout,

Review of short circuit calculation

Electrical engineering basic concepts

Three phase review and per unit. Voltage levels,

ne ne an ree ne agram, Generation system layout,

Transmission Layout,

Distribution layout,

Substation


3/57

Simplified generation system


4/57

Generation illustration (a) single phase

and (b) three phase


5/57

Typical

generating

plant one line

diagram


6/57

Electrical Power System LayoutElectrical Power System Layout


7/57

Operating Voltage Levels


8/57

Operating Voltage LevelsOperating Voltage Levels


9/57

ThreeThree--Line and OneLine and One--LineLine

DiagramsDiagrams


10/57

OneOne--line diagramline diagram


11/57


12/57

Interc.system

Advantages

Reliability

Economic

Disadvantages

Complex

Power loss

Voltage drop


13/57

diagram symbols


14/57

Impedance diagram for a power system


15/57

Bulk powertransmission system

transmit power

-

Change of power

Between utilities.

single line outageDoes not affect.


16/57

345 KV transmission

line to transmit bulk

power from remote

generating plants to

the system loadcenters.

Note, there are2conductor/phase


17/57

Subtransmission system. Note there is a set

of air break switches to isolate the line sec.


18/57

ApplicationApplication 22..22

Disconnect the system forfaults;

F2


19/57

Over all view of transmission

substation


20/57

Air break switch installation


21/57


22/57


23/57

Transfer bus

scheme

CB conn. TL to

main bus

disc. Sw. conn. TL

to transfer bus

Tr CB conn.

Buses 1,2


24/57

Application 2.3It is required to remove one of

the CBs


25/57

Radial distribution layout

Most economic

One CB for TL

Lowest Flexibility.


26/57


27/57

Distribution

substation one

line diagram


28/57


29/57

Overhead secondary dist. system

Radial manner

is used at each

user cables or

overhead mayused


30/57

S k


31/57

Spot network system

Similar to

net.system but

supply isolatedload centers in a

particular location-floors of high rise

building.


32/57

44thth Lec.Lec.CHCH 22


33/57

ChCh 22

PRINCIPLESPRINCIPLES


34/57

RELAY OPERATINGRELAY OPERATING


35/57

INTRODUCTIONINTRODUCTION InIn general,general, aa relayrelay cancan bebe designeddesigned toto

respondrespond toto anyany observableobservable parameterparameter ororeffecteffect.. TheThe fundamentalfundamental problemproblem inin powerpowersystemsystem protectionprotection isis toto definedefine thethe quantitiesquantities

abnormalabnormal conditionsconditions..ThisThis problemproblem ofof beingbeingableable toto distinguishdistinguish betweenbetween normalnormal andandabnormalabnormal conditionsconditions isis compoundedcompounded byby

thethe factfact thatthat 'normal''normal' inin thethe presentpresent sensesensemeansmeans thatthat thethe disturbancedisturbance isis outsideoutside thethezonezone ofof protectionprotection..


36/57

Problem of relay selectivity forProblem of relay selectivity for

faults at zone boundaryfaults at zone boundary


37/57

DETECTION OF FAULTSDETECTION OF FAULTS

InIn general,general, asas faultsfaults (short(short--circuits)circuits)occur,occur, currentscurrents increaseincrease inin magnitude,magnitude,

andand voltagesvoltages gogo downdown.. BesidesBesides thesethesemagnitudemagnitude changeschanges ofof thethe acac quantities,quantities,otherother chan eschan es mama occuroccur inin oneone oror moremore

ofof thethe followingfollowing parametersparameters:: phasephase anglesangles ofof currentcurrent andand voltagevoltage

phasors,phasors, harmonicharmonic componentscomponents,, activeactive

andand reactivereactive powerpower,, frequencyfrequency ofof thethepowerpower system,system, etcetc..


38/57

Level DetectionLevel DetectionThisThis isis thethe simplestsimplest ofof allall relayrelay

operatingoperating principlesprinciples.. AsAs reviewedreviewed ininSuctionSuction 22..11,, faultfault currentcurrent

greatergreater thanthan thethe normalnormal loadloadcurrentscurrents thatthat existexist inin aa powerpower

systemsystem.. ConsiderConsider thethe motormotorconnectionconnection toto aa 44 kVkV powerpower systemsystemshownshown inin FigureFigure 22..22..

O t t ti fO t t ti f


39/57

Overcurrent protection of aOvercurrent protection of a

motormotor


40/57

ExampleExample TheThe fullfull loadload currentcurrent forfor thethe motormotor isis245245

amperesamperes.. AllowingAllowing forfor anan emergencyemergencyoverloadoverload capabilitycapability ofof 2525%%,, aa currentcurrent ofof11..2525**245245==346346 amperesamperes oror lowerlower shouldshouldcorrespondcorrespond toto normalnormal operationoperation.. AnyAny

aboveabove346346 amperesamperesbyby aa safetysafety marginmargin ininthethe presentpresent example)example) maymay bebe takentaken totomoanmoan thatthat aa fault,fault, oror somesome otherother abnormalabnormal

condition,condition, existsexists insideinside thethe zonezone ofofprotectionprotection ofof thethe motormotor..


41/57

Pickup Setting of the RelayPickup Setting of the Relay TheThe levellevel aboveabove whichwhich thethe relayrelay operatesoperates isis

knownknown asas thethepickuppickup settingsetting ofof thethe relayrelay.. ForForallall currentscurrents aboveabove thethe pickup,pickup, thethe relayrelay

operates,operates, andand forfor currentscurrents smallersmaller thanthan thethe

pickuppickup valuevalue,,thethe relayrelay takestakes nono actionaction.. ItIt isisofof coursecourse possiblepossible toto arrangearrange thethe relayrelay toto

operateoperate forfor valuesvalues smallersmaller thanthan thethe pickuppickup

valuevalue,, andand taketake nono actionaction forfor valuesvalues aboveabove

thethe pickuppickup.. AnAn underunder voltagevoltage relayrelay isis ananexampleexample ofof suchsuch aa relayrelay..

Characteristic of a level detectorCharacteristic of a level detector


42/57

Characteristic of a level detectorCharacteristic of a level detector

relayrelay


43/57

Magnitude comparison relayingMagnitude comparison relaying

for two parallel transmission linesfor two parallel transmission lines


44/57

Magnitude comparisonMagnitude comparisonOneOne couldcould useuse aa magnitudemagnitude

comparisoncomparison relayrelay whichwhich comparescomparesthethe magnitudesmagnitudes ofof thethe twotwo lineline

currentscurrents anan .. ssgreatergreater thanthan || IBIB || ++ ,, andand lineline BB isisnotnot open,open, thethe relayrelay wouldwould declaredeclare aa

faultfault onon lineline AA andand triptrip it,it, wherewhere isisaa suitablesuitable tolerancetolerance..


45/57

Differential ComparisonDifferential ComparisonDifferentialDifferential comparisoncomparison isis oneone ofof

thethe mostmost sensitivesensitive andand effectiveeffectivemethodsmethods ofof providingproviding protectionprotection..

differentialdifferential comparisoncomparison isis quitequitesimple,simple, andand cancan bebe bestbest understoodunderstood

byby referringreferring toto thethe generatorgeneratorwindingwinding shownshown inin FigureFigure 22..55..


46/57


47/57

Phase Angle ComparisonPhase Angle Comparison


48/57

Pilot RelayingPilot Relaying CertainCertain relayingrelaying principlesprinciples areare basedbased

uponupon informationinformation obtainedobtained byby thethe relayrelayfromfrom aa remoteremote locationlocation.. TheThe informationinformationisis usuallusuall --althou halthou h notnot alwa salwa s -- inin thethe

formform ofof contactcontact statusstatus (open(open oror closed)closed)..TheThe informationinformation isis sentsent overover aacommunicationcommunication channelchannel usingusing powerpower

lineline carrier,carrier, microwave,microwave, oror telephonetelephonecircuitscircuits..


49/57

Harmonic ContentHarmonic Content

TheseThese abnormalabnormal conditionsconditions cancan bebe

detecteddetected byby sensingsensing thethe harmonicharmoniccontentcontent throughthrough filtersfilters inin

-- ,,

oror byby calculationcalculation inin digitaldigital relaysrelays.. OnceOnceitit isis determineddetermined thatthat anan abnormalabnormalconditioncondition exists,exists, aa decisiondecision cancan bebemademade whetherwhether somesome controlcontrol actionaction isisrequiredrequired..


50/57

Frequency SensingFrequency Sensing

NormalNormal powerpower systemsystem operationoperation isis atat 5050 oror 6060Hz,Hz, dependingdepending uponupon thethe countrycountry.. AnyAnydeviationdeviation fromfrom thesethese valuesvalues indicatesindicates thatthat aaproblemproblem existsexists oror isis imminentimminent.. FrequencyFrequency

,,

countingcounting ofof zerozero crossingscrossings ofof waveformswaveforms inin aaunitunit ofof time,time, oror byby specialspecial samplingsampling andanddigitaldigital computercomputer techniquestechniques.. FrequencyFrequencysensingsensing relaysrelays maymay bebe usedused toto taketakecorrectivecorrective actionsactions whichwhich willwill bringbring thethesystemsystem frequencyfrequency backback toto normalnormal..


51/57

RelaysRelays

SomeSome relaysrelays areare alsoalso designeddesigned toto respondrespond totomechanicalmechanical devicesdevices suchsuch asas fluidfluid levelleveldetectors,detectors, pressurepressure oror temperaturetemperature sensors,sensors,etcetc.. RelaysRelays maymay bebe constructedconstructed fromfrom

solenoids,solenoids, hingedhinged armatures,armatures, inductioninductiondiscs,discs, solidsolid statestate elementselements suchsuch asas diodes,diodes,SCRs,SCRs, transistorstransistors oror magneticmagnetic oror operationaloperationalamplifiers,amplifiers, oror digitaldigital computerscomputers usingusinganaloganalog--toto--digitaldigital convertersconverters andandmicroprocessorsmicroprocessors

THERMAL RELAYSTHERMAL RELAYS


52/57

THERMAL RELAYSTHERMAL RELAYS

Electromagnetic relay, HingedElectromagnetic relay, Hinged


53/57

armature relaysarmature relays

SOLIDSOLID--STATE RELAYSSTATE RELAYS


54/57

SOLIDSOLID--STATE RELAYSSTATE RELAYS

SolidSolid--state Instantaneous Overstate Instantaneous Over--


55/57

SolidSolid state Instantaneous Overstate Instantaneous Over

current Relaycurrent Relay


56/57

WaveformWaveform

of theof thesolidsolid--statestate

ns an anens an aneousous

overcurreovercurrent relaynt relay

COMPUTER RELAYSCOMPUTER RELAYS


57/57

COMPUTER RELAYSCOMPUTER RELAYS

Documents

protection course - chapter 2