PROTECTIVE RELAYSUNIT-03 PROTECTIVE RELAYS SPaNauore l(a DT oeas eC aero eee k iota Peer rekon ne nt kre acc cd Soe ECR OC RO cotati erent Cae omer nea CRcomnent Bic wnes ace cc rt ec eMamt cert t ket faulty element. Oe eer R en O Reet inte cake at cn ear ee entities teen eictcn yt PSE MC Rre ent estre ne cernbr mimes Cer cee nn ees Chl ee au nen eens aM eens i eM ertartm ia reece CO SRST TET CeRy Nom T Nae ent cant COSC ent scree tsk ra et smmett erste Pee aR a en Ce Treen en Tenant rar) OE eS eee CRS enolOPN ESR acta s ee ene ocsiacem one eet C CU entry tented oa ee vam nT aoe Role mere ag OM MR NOB eRe coc S est STOR CSCa Ch eater coe keke CUCM rk Rem MCC RCO CNAY Corn ecole Third part is the tripping circuit which may be either a.c and d.c. It cosists of a source of suply, PCattnen Roa Ceeraote omens Ce onaee tnt meer etm@ In normal (healthy) working condition circuit breaker contact is close and a Oe Roe neat tte eee esta et ea teeta cere © Due to this normal current the C.T (current transformer) is not receiving to PON e cet cch Ces Caen mCi tee mter ware Meat tre So in normal working condition trip coil is not energies and contact of circuit Ker) ous Ske Censcon @ When a short circuit occurs at point F on the transmission line, the current SiO arem ROM Br OueecmCO meter Ry escors Cena cce ICL ae ttattl es CeCOP RCo mCOENaesTe tertThg Pirereieb em Awnn nm Om mon mee CPC neni Caer Ceen Cart colnet Cee nCanty sttae Cretan yore Comme) es @ In this way transmission line is isolated in faulty condition.Fundamental Quality Requirements For the better performance of protective relay, it should have following qualities SRC hae TEES name BICCUST name Site oth Op neotnng 1) Selectivity ‘It is the ability of the protective system to select correctly that RPS a RETR TCT nec nerat Cecile erm otc reatra tts Pam ACCRA ZT CeT Tt should be able to detect the point at which the fault occurs and cause the Qeniea rea ere ete ner iem ct eet ittt i Ramen Ete tck a Tore PRS eRe VEC APSA eae Ton G ne ence eee cnaet Coreen eae possible. Electrical apparatus may be damaged if they carry the fault currents for Terence8) Sensitivity :- It is the ability of the relay system to operate with low value of actuating quantity. PO hes SEO CSO a CRNA ONE CROC CRT Com ts eM CCOmnCRCO Cee CRAs OC nC ORR or emcees tT EOI ew OCMC MEU mrs Cama etme me eel Ng PRIETO ST hae Ge ace Con Gaeta te haces TT eRe ST rr CTT Re CMe cartes aTee eet ore sti na UDO OR SUCCES ENN ae son y(n ete BUC CM SUH CeCe seers COE not cost more than 5% of total cost.Basic Relay Terminology 1) Protective Relay ‘ Protective relay is a sensing device which sences the fault and gives fone GR CRS tanta Nx) comC Res ee TCR SO ETCRS Rattan (a aes CR CRC a com CUR cana roe etme eet Coase Seem eee Sn CEA ca co Re Cenc Tee Ta cee Cece e CRs ene a Cee RR Cee terre niet Ce aac occa 4) Fault Clearing Time * It is the sum of the relay time and circuit breaking time. 5) Pickup * A relay is said to be picked up when it moves from the off position to ON position. Thus when relay operates it is said that relay has picked up. 6) Pickup value *- It is the minimum valve of an actuating quantity at which relay starts oct senate encncUntantent hsccte ene teeta ent ent tnt” Siena eC ecriorckar kr teatsEURO me SLOCNBEE CR CRS CMON O eC mdI een ere. a Cd PECTIN ER RT rec eN meen eter mitre ene Cer bier tem MCC Cae nw et Mace ei oe a eee eres Cer ee called time delay of relay. Some relays are instantaneous while in some other relay intentionally time delay is provided. ROM or asco aes Sto a mC y CRO Me UCM CEU MCA CUCM CAKE PaO Ra vO eeecaCe note ies aea Teta N an eee tern ate tapping on the relay coil. TREN IGr tsetse RnR on enya totien steam C rt errs tmatcrsrtg Phere outa COd DRT RULE NBEO rim Pick up current = current setting x Rated secondary current of CT. TOM CEs LO arctan nla cott erm ism ne cee ta Non mc Ont eC PSO wey So when relay coil current is greater than pickup current, relay operates.190 125 150 20 TOMES ncoea Ton ee EN CEC ORC crust ent Ena RCed ts PO at eeecen ee Peake Deere Se ~~ Pick-up current ~ Rated secondary current CTx Current settingFor example, suppose that a relay is connected to a 400/5 transformer and set at UM Oe recta toey Oren Catach tat nrc be calculated as under : Pick up value = Rated secondary current of CT xCurrent setting Sse awN oC StS Races ae ee Bre eee11) Time-setting multiplier :- A relay is generally provided with control to adjust ECO Re COUNT eEU oon eee Ce ensmteec treet tsa MMCache coerce ice Bike OR om elec Ske mR t { muttpnerClassification Of Protective Relays POSE Gc aa aot CEST nM een Scie eet Be EG) the following types SUS GRRE Test Coron oe NTS eeerer eas A aes tenn Lan CB Cae ccm hy 2Induction Type Relays OB nrnere ema Cpa tccntert nats BRO ecsenW Mpe cn Ce everett ngs Ce arses ara ay ts 4.Relays based on Timing @ Instantaneous Type © Definite Time Lag Type CB Noe n ee ng ERE coe CN © Impedance Type @ Reactance Type een en ny 6 Differential Type Relays © Current Differential Type Cotes rrcresrii hatsecccecee OSS OE ene eae Ng hearse nan once tg Thermal Relay eran coe Permanent Magnet Moving Coil Relay Strep cota epee netcrecs rgELECTROMAGNETIC RELAY Electromagnetic relays are those relay which operates on the principle of electromagnetic Elion nae Itis a type of a magnetic switch which uses the magnet for creating a magnetic field. eR ece Ge meron rnc ices tet Coe eomsrcrtnta ty mechanical operation. types of an Electromagnetic Relay cco ng On Toe en egos en tke Contact rot nsee ong ces nr ett nag oe een SO enone ee CUTe rr oeNae TT 2. Electromagnetic Induction Relay1.Electromagnetic Attraction Relay Ce nn a Cnn seer n taro ckoeeot tts Riemer tree tte Cntr cto tiacn Crt easas ts current flow through the coil. © This relay responds to both the alternating and direct current. PB oow ern nme eo eon Cs Oe ks RCE Co nS KI? = K(Imaxs cos2ut] DUS coone ence ccsCret a een CST Ce man COSC EM Nt ene Ces EYP Coons en itt Rng RK oUt ange etg Oe en eenn Steen et enga) Attraction armature type relay VOCE aaa eRe erence ir Cc cme tent antce ny a Coe mone Tis Bsn Teta aAg CT Mp Done ence cee ny ty Nene ntinckay ORC r tn Caer an earn e cys Sabie tttin ect sce er errnrta hs cenantent mate mettecer teal Cee Dna eee nee Cnn cic Resscoter cnt varnn teste mn tet ted cen CSCO enue eee cnet air er Onee etter man ete rer tents Crete Ce rece Otc Ree to or OT TRCEN Caer TCR Omen eee m totem ol recone ta tsi Croc tere Relays can be used for a.c. as well as d.c. Cou easoent senor Renner tccectnrtttts (ores CR ek Crrnairt Nesertete tee ce CanCSriniatnt Geckos Greece tnt ect Ere CTS Om Renee ee eo ROCCO ER Tei Poet os Ran mT Cr ntsc e nrc RC kick terest eet cr) poco ateatatasMoving Contacts Fixed Contacts ToTrip Cireuit UR CECE See nace nent gsra eS Ce Rao aD aR Ronen od Sorento rte © It consists of a solenoid which is nothing but an electromagnet. It also consists a UNE ee tne eatnt eae Se neat renee eee ens er td SHRM mO CR SO MOMS etme etela PE ener eCemis a Meut Ret cati men ee Centos isenemry eres tneton ta Pata sae sneer ene eTtT Ce ee area one eek eee ne ener teat an eres rcatttg Onna No eeen snes nT ey circuit breaker. Vor Input wezdzaza2. Electromagnetic Induction Relay Centro t seta coroner array koe yen” electromagnetic induction. © The operating force developed will be due to the interactions of fluxes displaced in time and SC eh eo CR menlar Ceca oe CO eee eo nat Ce Cea Cee es © Induction relays are classified into two types as PAV Clas ec mAy en ast etch b) Shaded pole type induction relay, a) Watt-hour Meter Type Induction Relay : @ It consists of two electromagnets and a disc that is free to rotate in between two Dlcaroneta tes Certo e coroners es core Cel CSC emoecnc eee chun tre Oe retteteds cooetenteter Cena Ratt thtkiorintramnt ecco cram sett Roars Sere STL CRN ene C eee knee aot ee aodWatt Hour Meter Type Induction Relay © The two windings produce an alternating flux when they are energized. Let the fluxes be ®1 Prinses rcniey Cee ene neon Cet n cet econ mtn seen Cena neyIO RT Cy secondary winding. Ceiscenenar tc tc Een CeM ctr e t s a goCnan eee en yO mr Cr Cy currents of the other in the disc is proportional to @1 ®2 sin0.Advantages of Induction Dise Relay : Oe eer een ee Reena OURO c Roms tent tro Reno teen a ce acoso renee arrears pea oaeuenitay eccco cragcoil ae ICO eee een Cnet nner Rene © Induction disc type relays are reliable and accurate. mena tenOm ena ecco Applications of Induction Disc Relay : CB in traroNteng ro Orne Ra cece hag een enn tcc Oey eset Rac rene erences i nore in) © Induction disc type relays are employed where adjustable operating time and time-delay eer ce CRI ORS R Cee eC mC Sn ee ce nseTHERMAL RELAYS SSC ce ROMS ene CMa Cente Comes ccnvcanac ae The bimetallic strips, heating coils and the current transformers are the important parts of the fiers Suerte arenes Cone enero Na ce CRON eR as CS to Pee emerson eens eter ea steel csr The bimetallic strips are made of the alloy of nickel and steel. The alloy of the nickel and steel has high steel resistivity, and also they are free from thermal cnt SUCSN ON Cee eos erCOn Ce Cece) coil along with the spring and the bimetallie Errotns SUMO ROM ents Re Tec rn aU Co a eee rey etsBiiforerctiteg @ When the system is in normal operating condition, the spring remains straight. Rear eccene tn tran ea titer caches tere ie nt mte tht rsa en ROR CR rena scents CoRR TO Nr ec eNmSCTATCCe Du reIeemONl ac meer cea ta teneraria comer mc Tema reer Cree aT Ta circuit breaker close. Thus, the system remains safe. © The thermal selay is mainly used in the low voltage Squirrel Cage induction motor and in low output rating DC motor. © The thermal relay has low overloading capability. It is designed to operate under 6 to 7 times more than the full load current. © Such type of relay is not used under short-circuit condition. The short circuit current increases the temperature of the bimetallic strips due to which the contacts of the Poenae eteSchematic Arrangement of Thermal RelaySTATIC RELAYSTATIC RELAY Riera UNO MC eon RCT ne Nan un ys Cees son eee Cece Cac ne © Insuch type of relays, the output is obtained by the static components like magnetic and eereenete retro © The relay which consists static and electromagnetic relay is also called static relay because the Seen ee ee Cn ecient een ate omen ont Sesto © Static relay operates quickly and it has Jong life and high accuracy. SeUG esc sere © The static relay block diagram is shown below. © The components of static relays are a rectifier, amplifier, o/p unit & relay measuring circuit. Here, the measuring circuit of the relay includes the level detectors, logic gate & the Cone oes ce myn Cr sorte Ceo SCR hme acc Roni Renaomor neem eso m rcoo ce transformer (PT) so that the transmission line provides the input to the CT/PT.Oe on Oe eh eee nem Nec ey input AC signal into the DC signal. This DC signal is given to the measuring unit of a relay. CRA ne nr anccsitat Fone TCMe ROUn ITT ater than predefined value of relay circuit then relay circuitConnie sts ent ent a eka cogs Vet soa tee tts Cents and amplified signal goes as input of output device. CRM rere TR Sas ne een ne ame Ronco mec Ra mn cyte rc POs ERs ny ecome CRC encase acts a) eeorccn a ONCE SUT ng ‘The following are the benefits of static relays. eee eet ans rod © The static relay gives the quick response, long life, high reliability and accuracy and it is Boson © The reset time of the relay is very less. OS eerie nena er rnmcer te rons © The relay amplifies the input signal which increases their sensitivity.SFr RUS ceCe ce © The relay is easily affected by the high voltage surges. Thus, precaution should be taken for OCCT Rn Ren ces ‘The working of the relay depends on the electrical components. PCr ENS CeCe secur gc a crag Peer u Ceo acre Me Sto nC ac nas oneness Pier enatcceOat CS ENaC ae cece nes Cees nst ect ccoOVERCURRENT RELAY OCs eee Ean teat cere cama na Moston eee CS cet Ranctataestt Procr centr ke tce Cece Nase Cen tr screen mes Orme ee nt Racscet intact snes © [t automatically disconnect the circuit or sending a signal to another device that will take action to protect the circuit. © Ideally, this type of current relay consists of two main components’ a sensing device and a control device. The sensing device is used to detect the current flowing through the circuit, ‘le the control element determines the tripping current, usually based on user settings. Zeya cetera soubette) cy © Ina typical application, the over current relay is connected to a current transformer. © Overcurrent relay has a current coil when current flows through that coil then due to magnetic Piedra et cette © In normal condition current coil do not produce sufficient electromagnet so that it will pull the moving element of relay, in this condition restraining force is greater than deflection force.Oe ena Oe ean Reon ee comune rTt cys onal cnn-s Ove Ceara sen MCec Tv sO cce Uimelocs ac meen c Torey tes RMR ERG Rote Tom t nC ner ar keke terete re co Cy So Pen Crd et) et as Cur ET pe Pein Seed Cr Cee aaAdvantages of Overcurrent Relay eC TE Reena eS emer exeo eaten ee eet yt Its price is low. Cen i ts esc a cine This can help to prevent damage to equipment and reduce the risk of fire. een One ee ee oer nCe nT e ota tos PRorerc tesco nace RCNA ieee estat DECOR Og Tene eS ee ae TOT CU Ream Oa Ere Oo aa siutcrC eh ertC roe nen crs arc t Tn PUTYPES OF OVERCURRENT RELAY Depending on the time of operation of relays, they are categorized as follows a) Instantaneous Over-current Relay eS Cacao CN OMe eects a ark CRE None RECOV ence OMA Cap rors cg me enone oe Lg RBG C MUO cea LN Cece MnO een OCR Cen OnE Onn en Oe CSU ra etre ero eet te© A dofinite time over-current (DTOC) relay is a relay that operates after a definite period of PO eee kes c hence © When input current is greater than predetermined value of relay then relay will not operate TEOMA ROUSE Ceo a CORoTICRCnnT Ts © Hence, this relay has current setting range as well as time setting range. nite Time Delayo) Inverse time over current Relay: CB ieee nCE Comat Ro Ce ROT RNS UCR Re Meo ROM ong Cece Ta fault current increases. SE ee Rk cu Roa aCe Inverse Timed) Inverse definite minimum time (IDMT) Over-current Relay OSC SRA O ROC manna Ce CSR OMT Roce nace is approximately inversely proportional to the fault current near pick-up value and then Pee ace enc ate Rom teeORR Cm UN er SCN © In this type of relay more inverse characteristics compared to inverse definite minimum rinetecctce ec oeTe IY UDR tg Rona ener mrss eee CECE Stans acne nes tne trite cote Sy eoronCN MON ort ew ENg OU Ror eee cnr heat to chee ner ka etre icon stant tea UM MTT Rat Roa Paton CI acne CRO monica ee mre ort a te CeO re Cc nMa nen Cat at nr tCtOm: Ckonn nace toc et Cnn Ces Chg Capra ats CVE eu Cee Chom oct com nce CEC marae a CeCe earn an ttre tern aoa ea tte tiitees SVC oe enn Cro een eens CR UCC ECs ent esos Cram CEng PR eo CU Ee Cre et nce ee keat Gene Care eo ete tacticInverse Relay Very Inverse RelayMICROPROCESSOR BASED OVERCURRENT RELAY © Microprocessor base overcurrent relay is a type of overcurrent relay which is Pee yi ert Se en See ete er eNcr nce ences © This relay consist of a microprocessor(Intel 8085) which take the decision and STE entice rr Teor mete ACV © The current setting and delay time of relay is set through the programming. L Bis CET COn Ream nen co nme NMOL MEO ROCo Ue n teeta nce Re ee EO ere rh ar Tt men reliable and fast.Cena ey nO ROM ME ORONO RCN ra coe Sen aS Cccnnreee ne Rete h Oe erneOm ecco © The A.C. voltage is converted into D.C. voltage by using rectifier. Cee Romo etee ener vnce cet Raters tereaera enn Cities The Multiplexer gives output to A/D Converter where Analog DC voltage is converted to Pts oon oo Eee eve Rhee Coa) Niece Center nt enone BSE oc orc U Ray ea On Ce umO mene ON RS Tm eY Rey oe Cm) OT mc) CMON eee entered man cee re non Oni ment nT t10) SN eiconaernt ait nint lorena Te eee into Ry ere Vi Reatcenremeeat CeO ene tt nr dEUS OOOReeDU Ro Concorso When work of A/D is over then up compare the magnitude of this incoming current with er Renna Cocotte kes Satin RCT CSOR OC Mere CRcatcr nt et meet ner Ti bCee CR CRel Seren a ya crmcoli ee Renee Oc RC ecko ec TRC eTe See One eee temo CSCC nant CS Tonos cme esa Cera ern Cem orca tenets teen Tec cnoctgoy FeetWorking Principle of Distance or Impedance Relay © ‘The working principle of distance relay or impedance relay is very simple. Oe eno CanoScan croc Ck Rats na crn iay Cero mee sents mone CENT Cero tnt cs srt Mh aeccc eee keene RCC TCS SoCo DRO eer © In normal operating condition, restoring torque is more than deflecting torque. Hence relay STB ma oem SU eR ket CEE eC i RoR ec coe oe Centric eet ete Ct Cnn cena Teen Manne ets Te Meee arr anon ee aces eGR ROmD Ae © Hence clearly operation or working principle of distance relay depends upon the ratio of USOT RO LET Cnn ncn ores CC er komo eect SR aT ee eens Oe acy cee Cocco aot mone Ce ccc aCe Cem naeca@c te Piterrct err tert atns tee ake ck CRO ec Ronn coe) predetermined value.CR Cem enc anes mTOR CS CCM Roan sea cots less than predetermined impedance (voltage/current). © As the impedance of a transmission line is directly proportional to its length, it can easily be Ponotcen ne Mee ern nt Mao n Ene Css cn serene Rot Nhe Soca nt creeenrs cnt tesrite DRO a DS E Cone Preec ences iottg Pe SNE aang RO MOC each Perna Pn ete neDefinite distance relay. Pree nner Ota Gch Terie TORO ORES etn r ance Manse cna Tako eGo ORR runes ter uci e een me Rene Teint oe eects one ee Coke RL CSC Other end of the beam is pulled downward by the magnetic force of current coil fed from Creer oem Ee nent ST PRs eed OO cece Pests Moving, SMCR CeCe Roe cacaTs Cee TRO CROCE cicero CU omeke eter eer eras magnet Cliente taste lot omoene vee tertntd Conner TTR crt greater than deflecting torque.Hence contacts of this Creenieec hearer e tite Definite Distance Relay ToT: eam f—— GPPea incision C are ECR nace em Car horn etd CeCe ee DOO me et ROR a RO nee eee the pre-determined value. In this situation, current coil pulls the beam more strongly than Oo Caan eh re Geena eetaete ier tt kectteranmeceerecttta ste ed Pree er hau near entre cea TkcttsDIFFERENTIAL RELAY The differential relay is one that operates when there is a difference between two or more Prien Renan Cee cee ccc msestaet cyte Ce oe eee Ce ccoe snes eee cerry POO e See RCN ne one mee Rc © According to Kirchhoff Current Law, the resultant current flowing through the relay coil is Pere tiers ean ate estes A a enon tot CRO oe Ro can toot rs CMS ani ern Rent Reece eran cat Mra near eee eT BTR MD iCoN EISEN © There are two types of differential relay 1) Current Relay Da otescrngSROor a ONG Cn ann Pets TS Re eton cnet Mann eoa Metco mene Cet Both current transformer must be of same current rating. ee ener es Oona ee tease ReaD acct nmene cna Co es eT Brericcstny Under normal working the current flow through the relay coil is zero. But when fault occur in protected device, the value of current in the coil will be exceed the predefined value then operating coil is operated. Sees nec eae eeAon snare © Under normal operating conditions, the protected equipment (either power transformer or Vout Counc een een E ote In this situation, say the secondary current of CT1 is [1 and secondary current of CT2 is 12. ee ke One Rena ene CO eet eo eC Amcor CRC alta sbR ba © [£11 =12, hence there will be no current flowing through the relay coil. NOUR RCC Re cect tet ocala ene De SCM e iran CeceeNmen ens Eat encPA ol recom Ce EN © In this arrangement the current transformer are connected in both side of equipment in such a oa nso NCE nent nasa esterase em an necro Cd too © The EMFs induced in both of the CT secondary are equal and opposite hence there would be no Circe onstrates eNaco © Ifany internal fault occurs in the equipment under protection, these EMEs are no longer Pee Ceres nea hate eee crn ae ete Alternator cl Relay Operating 1 Voltage Balance Differential Relay ProtectionaSCOUa 4 Ce eRe sn eco Ce eR ene ce Cama ROM ee Ree nM OURS nea Co ESR re Ce Onn Can tC ecole orth OOS Enc tC eco ed ene Od USER nm: Cee Ee Sentence ome CSE meo GRC ae etcDirectional relay is a type of relay which senses the direction of current flowing. In other word, the directional relay is a type of overcurrent relay which have directional Tarim SNES NE SCR ne CoS Nera eee CS NAT R CST TT For example, consider a three phase synchronous motor. Assume fault on the system. Power supply to motor is not available. But 3-phase armature is rotating in magnetic field due to inertia. So motor starts generating power. Which feeds fault. To avoid this, Directional Relay is ree NORMAL LOAD FLOW FAULT CONDITION 1 % = coneensFAULT CONDITION 2 SOLUTION tre SSS 36- = =» ‘curRENT Principle Of Operation A directional overcurrent relay operates on the same principle as that of an SRM cet ea Lan U Eee nr Me nT ace eeSt Che Oe UCR CR Utara ey produced by the operating current of the cireuit given through a current transformer. While in the case of directional overcurrent relay the driving torque is developed due to the magnetic fields produced by both the operating current and voltage of the cireuit in which it Pelee cere m uccecrtaneCROC RC nt ee cc mn aC SER crite crrearey OMB Ventre Ran inca C heroes ens toa) evry Ceo seman rea rent! erecsnier © The secondary winding of P.T is connected with voltage coil and secondary winding of Cuerretnctns tenets! © The current coil is provided with a number of tapping connected to the plug bridge, so as este er conec mane nmetn ts Ce ence ee innate eek te Sess OPEC RM Nees RTO RAC electromagnets. Rovorso Power RelayOperation ROCCO at eater C ce Lon ana ence see scnotC Tn Rae © When the power flows in the normal direction, the torque developed on the disc tend to turn PCa ae tence a teice ner Rete acr et aa MI Cen Eee eiora CR et eIC en ETA Cen nt cscs rere emer meester eet nt scr cy a vit disc rotates in the reverse direction and the moving contact closes the trip circuit @ This causes the operation of the circuit breaker to disconnect the faulty section. ache R meter cc kengent ce Ryser Operating Characteristics The active power flowing through clectrical circuit is a aerrt) Se cee SOPOT eee aE SCM Toca geen tte Pr ere Bred ee© Therefore, the power flow can be senced by sensing the magnitude and sign of V.I cos @