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Statement 2016-2025 Minimising ener in power transm Minimising energy loss Minimising energy loss in power transmission in power transmission Saving energy Saving energy Today we are becoming aware of the need to need make moremore effieffi cient Todayincreasing we are becoming increasing aware of the to make cient use energy of non-renewable energyTraditional resources. Traditional fossilpower fuel power use of non-renewable resources. fossil fuel stations are less than 40% efficient. In other words, more than 60% of the stations are less thanenergy 40%ineffi cient. In other words, more than 60% of the the fuel is lost as heat to the environment. By combining district energy in the fuel is lost aswith heat to generation the environment. By combining heating power efficiencies of 60% to 80% can district be achieved. heating with power generation 60% 80% achieved. Before we caneffi useciencies it electricityof must get to to the endcan users.be This is done through the transmission and distribution systems. Metallic conductors, Before we can use itsuch electricity get to the end users. current This istodone as coppermust and aluminium, carry the electric our homes and places of work. However, some energy isMetallic lost along conductors, the way as heat through the transmission and distribution systems. even the best the conductors havecurrent some electrical resistance. such as copper and because aluminium, carry electric to our homes These losses have been reduced from about 13% in 1960 to about 7.5% and places of work. However, energy is lost along the way as heat in 2016. Can some we reduce these losses even further? because even the best conductors have some electrical resistance. Some background These losses have been reduced from about 13% in 1960 to about 7.5% in 2016. Can we reduce these losses even further? In a letter dated 20th March 1800 Alessandro Volta (1745–1827) described the construction of a battery. He demonstrated his invention in Paris and news of the device spread quickly. For the first time a continuous electric Some background current could be generated and scientists in Europe and America began experimenting with their own versions of the battery. In a letter dated 20th Before March 1800 Alessandro Volta (1745–1827) described long they had discovered two effects of electric current: the construction of a battery. He demonstrated his invention in Paris and • a heating effect and news of the device spread quickly. For the first time a continuous electric • a chemical effect. current could be generated and scientists in Europe and America began experimenting with their own(1800) versions of the battery. That year Nicholson and Carlisle decomposed water into hydrogen Before • • Power station Power station Distribution line Apar best copp gold 240 V silve its re were Step-up transformer Step-down transformer woul the r resp Step-down transformer Step-up transformer Electric power area of cross section of the alumin The power transferred over electric cables depends on the voltage the others because of its low density and the current. This can be written as follows: P = V × I , where P is would give it the lowest resistance the power (that is the energy per unit time), V is the electric potential (and best conductivity) per unit maso area (or voltage) and I is the electric current. Aluminium is also the best choice in The power transferred over electric cables depends on the voltage ot of cost. However, in practice the an allo In Ireland, in Europe generally, thewritten domestic as electricity supply and the and current. This can be follows: P = V × I , where is used inPtransmission lines towould operates at about 240 volts. On this system a jug kettle with a current it greater strength, although the thea energy perVunit is the electricgive potential (andit hb of 10 power amperes(that wouldis have power of: 240 × 10time), A = 2400Vwatts. about 10% more resistance. In words, itand wouldI transfer 2400 joules per second to the water in (orother voltage) is the electric current. Alumi the kettle. It would raise the temperature of a litre of water by more than of cos Other losses half a degree every second, since the specifi c heat capacity of water In Ireland, and in Europe generally, the domestic electricity supply used i is about 4200 J kg−1 K−1 (2400 /4200= 0.57) can be lost in transmission operates at about 240 volts. On this system a jug kettle withEnergy a current heating of the conducting cables. giveAlit of 10 amperes wouldvoltage have a power of: 240 V × 10 A = 2400alternating watts. magnetic fields which in Why we use high in transmission about inductive effect can be reduced by s In other words, it would transfer 2400 joules per second to the water in The main power transmission lines in Ireland operate at 110 kV to 400 kV reasonably possible. the kettle. current. It would theassume temperature of aoperate litre ofatwater by more than of alternating For raise simplicity that these lines Anyof pair of conductors that are near direct current. In that case, second, if a 220 kV since line canthe safely carry a c current 1000 half a degree every specifi heatofcapacity water storing energy in an electric field. In amperes then the maximum that can be transmitted on it is 220 MW. −1 power −1 is about 4200 J kg K (2400 /4200= 0.57) Energ effects are unavoidable but they red P = (220,000 V ) × (1000 A ) = 220,000,000 W = 220 MW user. These effects can be largely o heatin transmission. However, stepping D To transmit the same power at 110,000 volts would require a current of altern DC transmission is economical only 2000 amperes; this would exceed the limit of that conductor. Power can induc the sub-sea East–West Interconnec be transmitted much more efficiently by using high voltage. 110 kV – 400110 kV kV – transmission line 400 kV transmission line e.g. 10 k V Electric power Minimising energy loss in power transmission and oxygen ― a process known as electrolysis. Around 1808 Humphry long they hadDavy discovered effects of electric current: potassium, discovered two several new elements using electrolysis: sodium, barium, calcium and magnesium. It is somewhat surprising that the a heating effect and effect of electric current was not discovered until 1820. magnetic Although the heating effect of electric current is more obvious it was not a chemical effect. studied in detail until the 1840s. Part of the reason for this was the rather poor understanding at that time of the concepts of heat and energy — concepts that take for granted today. Nicholson andweCarlisle decomposed water into hydrogen That year (1800) and oxygen ― a process known as electrolysis. Around 1808 Humphry Joule’s Law Davy discovered several new elements using electrolysis: potassium, Jamesand Joulemagnesium. (1818–1889) spent of his life studying these two sodium, barium, calcium It ismuch somewhat surprising that the concepts. In 1840 he replaced steam engines in his brewery with magnetic effect of electric current wasmotors. not discovered untilthe 1820. recently developed electric He began to study heat loss from conductors. Even the best conductors (silver and copper) show some Although the heatingresistance effect oftoelectric current more obvious not a large electric current and is may become quite hotitifwas they carry current. Part of the reason for this was the rather studied in detail untilelectric the 1840s. poor understanding at thatJoule timediscovered of the concepts and energy — was In 1841 that the rateof of heat heat loss from a conductor proportional to its resistance concepts that we take for granted today. multiplied by the square of the electric current. 2 Joule’s Law Today we express this relationship mathematically as follows: P = R × I where P is the power (that is the energy produced per unit time), R is the resistance and I is the electric current. This was an important discovery. An example James Joule (1818–1889) spent much of his life studying these two concepts. In 1840 heThe replaced steam engines his brewery electrical resistance of a piece in of copper wire 100 with metres long and 0.7 millimetre in diameter is approximately onethe ohmheat (R = 1loss Ω ). Iffrom this wire recently developed electric motors. He began to study carries a current of 2 amperes then the heat loss per second is given by: (P) conductors. Even the best conductors copper) some (i.e. 1 2 ) J/s = 4 J/s. If the (silver length ofand the wire were tenshow times greater = (1)(2 resistance to electric current may would become if they a large km), then theand resistance be tenquite ohms hot and the rate ofcarry heat loss would be (10)(22) or 40 J/s. electric current. However, if the electric current were now made ten times greater the rate 2 In 1841 Joule discovered the rate of heattimes lossgreater: from (10)(20 a conductor wasSo, ) = 4000 J/s. of heat that loss would be a hundred energy lossmultiplied can be minimised by keeping theof electric current low. proportional to its resistance by the square the electric current. Today we express this relationship mathematically as follows: P = R × I 2 where P is the power (that is the energy produced per unit time), R is the resistance and I is the electric current. This was an important discovery. An example The electrical resistance of a piece of copper wire 100 metres long and 0.7 millimetre in diameter is approximately one ohm (R = 1 Ω ). If this wire carries a current of 2 amperes then the heat loss per second is given by: (P) = (1)(22) J/s = 4 J/s. If the length of the wire were ten times greater (i.e. 1 km), then the resistance would be ten ohms and the rate of heat loss would be (10)(22) or 40 J/s. However, if the electric current were now made ten times greater the rate of heat loss would be a hundred times greater: (10)(202) = 4000 J/s. So, energy loss can be minimised by keeping the electric current low. ChD Oth Why we use high voltage in transmission The main power transmission lines in Ireland operate at 110 kV to 400 kV reaso As saw earlier, current. the energy For loss is proportionalassume to the square the of we alternating simplicity thatof these lines operate at Skin effect and corona current, by halving current the if energy losskV would reduced Any p direct so current. Inthe that case, a 220 linebecan safely carry a current of 1000 to 25% of it previous value. Distribution lines operate at lower voltage When large conductors carrystorin large a amperes then theinmaximum be transmitted on it is 220 MW. and so the total current them is muchpower greater that than incan transmission lines. of the current is confined to the oute Also, distribution lines are shorter but there are more of them. or ‘skin’ of the conductor. Theeffect skin d P = distribution (220,000losses V ) ×are(1000 A3) to=6220,000,000 W = 220depends MW on the material anduser. For this reason typically times greater than on the transmission losses. At 50 Hz the skin depth is around 8 trans To transmit the same power at 110,000 volts would require acopper current of and around 10 mm for alumi DC tra net effect is an increase in the a 2000 amperes; this would exceed the limit of that conductor.The Power can Quantitymuch more effi Unitciently by using high voltage. resistance of the conductor. The the effe su be transmitted Quantity Unit Meaning Symbol Symbol reduced by the use of multicore cab cable is also more flexible and durab As we saw earlier, the energy losstheisrate proportional to the square of the of flow of electric Electric I = Q/t ampere A = C/s At very high potentials (e.g. 500 kV) in coulombs second be reduced current so by halving the current charge current, the energy lossperwould near the cable may become ionised toElectric 25% of it previous value. Distribution lines operate at lower voltage the electric charge transferred When capable of conducting electric curre = I t current coulomb in Cthem = A s isbymuch one ampere in one second and so theQtotal greater than in transmission lines. Apart from cables or to pylons. los charge of athe the resulting ‘arcing’ or ‘corona dis Also, distribution lines are shorterthe but there are more of them. or ‘ski energy carrier by each Electric creates noise and electromagnetic For this reason losses are typically to 6 times greater than cables anddepen one volt is3one joule potential V = E/Q distribution volt V= J/C coulomb; and may damage insula per coulomb (voltage) transmission losses. larger the diameter of the cable At the 50 effect. The corona effect is also redu energy is the capacity to do coppe joule use of multiple smaller cables (typic J = N m work, so work and energy have Energy E instead of one large cable. Their Thelarg n the same unit (the joule); kilowattkW h area keeps them cooler and resist they ar 1 kWUnit h = 3,600,000 J or 3.6 MJ hour Quantity used today in transmission lines (rig Quantity Unit Meaning Skin Symbol Symbol Electric current I = Q/t ampere A = C/s the rate of flow of electric charge in coulombs per second Electric charge Q=It coulomb C=As the electric charge transferred by one ampere in one second Electric potential (voltage) V = E/Q volt V = J/C the energy carrier by each coulomb; one volt is one joule per coulomb joule Energy E kilowatthour J=Nm kW h energy is the capacity to do work, so work and energy have the same unit (the joule); 1 kW h = 3,600,000 J or 3.6 MJ reduc cable At ver near t capab cable the re create and m larger effect use o instea area k used All-Island Generation Capacity ng energy loss Statement transmission 2016-2025 Minimising energy loss in power transmission Choice of conductorChoice of conductor Distribution line Apart from superconductors, silver the superconductors, best conductor of electricity, Apartisfrom silver is the followed by copper (95% of the best conductivity gold followed (69%) by conductorofofsilver), electricity, 10 kIfV1 kg of copper and aluminiume.g. (60%). silver were a wire 1 kmofinsilver), length (95%made of theinto conductivity its resistance would be 168 Ω. Ifgold the (69%) same were done with (60%). 1 kg of Ifcopper and aluminium 1 kg of 240 V be 150 Ω. silver the resistance would For gold and aluminium the resistances were made into a wire 1 km in length would be 440 Ω and 72 Ω respectively. The reason thesame its resistance would for be this 168isΩ.that If the area of cross section of the aluminium wire would much greater than were done with 1 kg be of copper the resistance wn transformer all the others because of its lowwould density; the lowest bethis 150would Ω. Forgive goldit and aluminium resistance (and best conductivity) unit theper resistances would be 440 Ω and 72 Ω mass. Aluminium is also the best choice respectively. The reason for this is that the in terms ofcost.section However, an wire would be much greater than all area of cross of inpractice the aluminium alloy of aluminium in transmission the others becauseisofused its low density; this lines giveititthe greater strength, although wouldtogive lowest resistance l it(and hasbest about 10% more resistance. conductivity) per unit mass. Relative of size of silver, copper, gold Aluminium is also the best choice in terms and aluminium conductors of equal of cost. However, in practice an alloy of aluminium length and weight. is Other losses used in transmission lines to Relative of size of silver, copper, gold t give it greater strength, although it has and aluminium conductors of equal Energy can be lost in transmission in other ways, apart from resistive length and weight. about 10% more resistance. n heating of the conducting cables. Alternating currents in power lines produce an alternating magnetic fields which induce currents in nearby lines. These Other losses er inductive effect can be reduced by separating the conductors as much as is reasonably Energy canpossible. be lost in transmission in other ways, apart from resistive heating conducting Alternating currents in power lines produce Any pairof ofthe conductors thatcables. are near one another can act as a capacitor, alternating magnetic fields field. whichIninduce currents in nearby These storing energy in an electric AC systems inductive andlines. capacitive inductive effect can be reduced by separating the conductors as much as is effects are unavoidable but they reduce the power delivered to the end 0 kV reasonably user. These possible. effects can be largely overcome by using direct current at transmission. However, stepping DCone up another or downcan is more costly and so Any pair of conductors that are near act as a capacitor, of 1000 DC transmission only uninterrupted cables such as storing energy in is aneconomical electric field. In for AC long, systems inductive and capacitive 0 MW. the sub-sea East–West Interconnector Ireland and the U.K. effects are unavoidable but they reducebetween the power delivered to the end user. These effects can be largely overcome by using direct current transmission. stepping DCdischarge up or down is more costly and so of Skin effectHowever, and corona DC transmission is economical only for long, uninterrupted cables such as an When large conductors large alternating currents A) much of the sub-sea East–West carry Interconnector between Ireland(e.g. and 2000 the U.K. the current is confined to the outer layer or ‘skin’ of the conductor. The skin depth depends on the material and on the frequency. At 50 Hz the skin depth Skin effect and corona discharge is around 8 mm for copper and around 10 mm for aluminium. The net effect is an increase the apparent resistance of the currents (e.g. 2000 A) much When large in conductors carry large alternating ines. conductor. Theiseffect is reduced by the use of the current confined to the outer layer of cable; such cable is also more or multicore ‘skin’ of the conductor. The skin depth an flexible and depends ondurable. the material and on the frequency. At 50 Hz the skin depth is around 8 mm for At very high potentials (e.g. 500 kV) the air copper and around 10 mm for aluminium. near the cable may become ionised and The net effect is an increase in the apparent capable of conducting electric current to resistance of the conductor. The effect is other cables or to pylons. Apart from a loss reduced by the use of multicore cable; such of power the resulting ‘arcing’ or ‘corona cable is also more flexible and durable. Steel reinforcedand andcomposite composite Steel reinforced discharge’ creates noise and electromagnetic core aluminium core aluminiumconductors conductors interference may damage cables andair At very high and potentials (e.g. 500 kV) the econd insulation. The may largerbecome the diameter of and the near the cable ionised erred cable theofless the effect. The corona is capable conducting electric currenteffect to other cond also reduced by the Apart use offrom multiple smaller cables or to pylons. a loss of power cables (typically four) or instead of one large the resulting ‘arcing’ ‘corona discharge’ h cable. larger surface area keeps them createsTheir noise and electromagnetic interference joule cooler anddamage they arecables commonly used today in and may and insulation. The transmission lines (right). larger the diameter of the cable the less the effect. The corona effect is also reduced by the do use of multiple smaller cables (typically four) y have instead of one large cable. Their larger surface area keeps them cooler and they are commonly 3.6 MJ used today in transmission lines (right). EirGrid is responsible for a safe, secure and reliable supply of electricity: Now and in the future. We develop, manage and operate the electricity transmission grid. This brings power from where it is generated to where it is needed – throughout Ireland. We use our grid to supply power to industry and businesses that use large amounts of electricity. Our grid also powers the distribution network. This supplies the electricity you use everyday in your homes, businesses, schools, hospitals, and farms. Minimising energy loss in power transmission Image Image source: source: Wikipedia Wikipedia We develop new electricity infrastructure only when required. EirGrid is a state-owned company, but we answer to government and to regulators. We work for the benefit and safety of every citizen in Ireland; we abide by strict laws and safety standards. You can find out more about the work of EirGrid at www.eirgrid.com Find this and other lessons on www.sta.ie Minimising Minimisingenerg ener in inpower powertransm transm Minimising energy loss in power transmission Exa Ex Syllabus SyllabusReferences References Student StudentActivities Activities The Themain mainsyllabus syllabusreferences referencesforforthe thelesson lessonare: are: 1.1. The Theresistivity resistivity(ρ), (ρ),oror 1m 1m 1m 1m specifi specifi c cresistance, resistance,ofofa a material materialisisthe theresistance resistance ofofa auniform uniformsample sampleofof the thematerial materialofofunit unitlength length 1m 1 2m2 1m 1 2m2 and andunit unitcross crosssection. section. (In(Inpractice practicethis thiswould wouldbebe virtually virtuallyimpossible impossibletotomeasure measuredirectly.) directly.) −8 −8 ΩΩm.m. The Theresistivity resistivityofofcopper copperisis1.68 1.68× ×1010 Show Showthat thatif ifa acubic cubicmetre metreofofcopper copperwere wereformed formedinto intoa auniform uniform 2 2 it itwould wouldbebe1000 1000km kmininlength length wire wirewith witha across crosssection sectionofof1 1mm mm 4 4 ΩΩoror16.8 16.8kΩ. kΩ. and anditsitsresistance resistancewould wouldbebe1.68 1.68× ×1010 Leaving LeavingCertifi Certifi cate catePhysics Physics(pp. (pp.36–38) 36–38) • • Resistance: Resistance: Defi Defi nition nitionofofresistance, resistance,unit. unit.Ohm’s Ohm’slaw. law. Resistance Resistancevaries varieswith withlength, length,cross-sectional cross-sectionalarea, area,and and temperature. temperature.Resistivity. Resistivity.Resistors Resistorsininseries seriesand andparallel. parallel. Thermistor. Thermistor. • • Potential: Potential:Potential Potentialdivider. divider. • • Heating: Heating:WW= =I 2IR2 Rt. t. Chemical: Chemical:ananelectric electriccurrent currentcan cancause causea achemical chemicalreaction. reaction. Magnetic Magneticeffect effectofofananelectric electriccurrent. current. • • Magnetic Magneticfields: fields:Magnetic Magneticfield fielddue duetotomagnets, magnets,current currentinina along, long, a aloop looporora asolenoid. solenoid. • • Alternating Alternatingcurrent: current:Peak Peakand andr m rm s svalues. values. Science Scienceand andTechnology Technologyinin Action Actionisisalso alsowidely widelyused usedbyby Transition TransitionYear Yearclasses. classes. Learning LearningOutcomes Outcomes Minimising energy loss in power transmission On Oncompletion completionofofthis thislesson, lesson,students studentsshould shouldbebeable ableto:to: • • • • • • • • • • • • • • 2.2. The Thetable tableshows showsthe the 3 3 –3 –3 Silver Silver 10.49 10.49 ×× 1010 kgkg mm densities densitiesofofsilver, silver,copper copper and andaluminium. aluminium.Show Showthat that 3 3 –3 –3 Copper Copper 8.96 8.96 ×× 1010kgkg mm the thevolume volumeofofone onekilogram kilogram 3 3 –3 –3 Aluminium 2.65 2.65 ×× 1010 kgkg mm ofofthese thesemetals metalswould wouldbebe95, 95, Aluminium 3 3 respectively. respectively. 112 112and and377 377cm cm outline outlinethe thegeneral generalstructure structureand andfunction functionofofthe thenational nationalgrid grid calculate calculatepower powergiven giventhe thevoltage voltageand andcurrent current explain explainwhat whatisismeant meantbybyresistive resistiveheating heating calculate calculateenergy energyloss lossgiven giventhe theresistance resistanceand andcurrent current describe describethe thefunction functionofofa atransformer transformer explain explainwhy whyhigh highvoltages voltagesare areused usedinintransmission transmissionlines lines give givereasons reasonswhy whyaluminium aluminiumisisthe thebest bestchoice choiceofofconductor conductorforfor transmission transmissionlines. lines. General GeneralLearning LearningPoints Points These Theseare areadditional additionalrelevant relevantpoints pointswhich whichare are used usedtotoextend extendknowledge knowledgeand andfacilitate facilitatediscussion. discussion. • • Under Underordinary ordinaryconditions conditionsallallmetals metalshave havesome someelectrical electrical resistance. resistance. AsAsa aresult resultthey theybecome becomehot hotwhen whencarrying carryinglarge large currents. currents.The Theheating heatingeffect effectisisproportional proportionaltotothe thesquare squareofofthe the electric electriccurrent. current. • • Transmitted Transmittedpower powerisiscalculated calculatedbybymultiplying multiplyingthe thevoltage voltagebybythe the current. current.The Thesame samepower powercan canbebetransmitted transmittedbybyincreasing increasingthe the voltage voltageand andlowering loweringthe thecurrent currentbybythe thesame samefactor. factor.Less Lessenergy energy isislost lostbybyusing usinghigher highervoltage. voltage. • • The Thetransmission transmissionlines linesininthe theNational NationalGrid Gridoperate operateatat400,000 400,000V.V. • • Transformers Transformersare areused usedtotostep stepthe thevoltage voltageupuporordown down asasrequired. required. • • Energy Energyisislost lostthrough throughresistive resistiveheating heatingmainly mainlyininthe thedistribution distribution lines lineswhich whichoperate operateatatlower lowervoltages voltagesand andcorresponding correspondinghigher higher overall overallcurrent. current. • • Although Althoughaluminium aluminiumisisnot notthe thebest bestconductor conductorofofelectricity electricitywhen when compared comparedwith withother otherconductors conductorsofofthe thesame samelength lengthand andweight weightit it isisabout abouttwice twiceasasgood goodasassilver silverand andcopper. copper. 3.3. The Thetable tableshows showsthe theresistivities resistivitiesofofsilver, silver,copper copperand andaluminium. aluminium. If Ifone onekilogram kilogramofofeach eachofofthe themetals metalsabove above(Q. (Q.3)3)were weremade made into intoa aone onekilometre kilometrewire wireshow showthat: that: a)a)their theircross crosssections sectionswould would −8 −8 2 2 Silver Silver 10.49 10.49 ×× 1010 ΩΩ mm bebe9.5, 9.5,11.2 11.2and and37.7 37.7mm mm −8 −8 respectively respectively Copper Copper 1.68 1.68 ×× 1010 ΩΩ mm b)b)their theirresistances resistanceswould would −8 −8 Aluminium Aluminium 2.65 2.65 ×× 1010 ΩΩ mm bebe1.67, 1.67,1.50, 1.50,0.703 0.703ΩΩ respectively. respectively.(R(R= =ρ ρl /l A/ A ) ) How Howdoes doesthis thisillustrate illustratethe theadvantage advantageofofusing usingaluminium aluminiumasasa a conductor conductorforforelectricity electricitytransmission? transmission? Leav Le R “ The Th cons con lines line Irela Ire lowe low The Th unde und whic wh dista dis Pow Po varie var elect ele land lan AtAtth into into 2.1 2.1m ( ( ( ( True/False True/FalseQuestions Questions ( a)a)Transmission Transmissionlines linesbring bringelectricity electricitydirectly directlytotopeoples’ peoples’ homes. homes. T TF F ( b)b)Transformers Transformersare areused usedtotochange change AC ACtotoDC. DC. T TF F c)c) The Theelectric electricbattery batterywas wasinvented inventedbybyVolta Voltainin1800. 1800. T TF F d)d)The Theunit unitofofenergy energyisisnamed namedafter afterJames JamesJoule. Joule. T TF F ( e)e)Resistive Resistiveheating heatingisisproportional proportionaltotothe theelectric electriccurrent. current. T TF F ( 9. 9. What What is is electromagnetic electromagnetic induction? inductio f) f) Electric Electricpower powercan canbebecalculated calculatedbybymultiplying multiplyingthe thevoltage voltage Describe Describe anan to to demonst demon bybythe thecurrent. current. Texperiment Texperiment FF Leav Le g)g)Gold Goldisisthe thebest bestelectrical electricalconductor. conductor. h)h)Thinner Thinnerwires wireshave havegreater greaterresistance. resistance. T TF F Nam Nao The The transformer transformer is is a device a device based based Tdevices T F Fthat Name Name two two devices that useuse transfor transf The Th supp sup T TF F conn con j) j) Direct Directcurrent currentisisnot notused usedforfortransmission transmissionofofelectricity. electricity. T T F F Name Name thethe parts parts ofof thethe transformer transformer la 400 400 k)k) The Themagnetic magneticeffect effectofofelectric electriccurrent currentwas wasdiscovered discovered Wha Wh inin1810. 1810. Telectricity T F F supply voltm volV The The mains mains electricity supply (230 (230 i) i) Even Eventhe thebest bestconductors conductorsshow showsome someresistance. resistance. turns. turns.C C hashas 100 100 turns. turns.What What is is thet l) l) Aluminium Aluminiumconductors conductorsare arewidely widelyused usedinintransmission transmission lines. lines. T TF F Check Checkyour youranswers answerstotothese thesequestions questionsononwww.sta.ie. www.sta.ie. How How is is thethe part part labelled labelled BB designed design The The efficiency efficiency ofof a transformer a transformer is is 9 ViVi NpNp VoVo NsNs ( ( == ) ) ng g energy energyloss loss transmission ransmission orm m ngth th m –3 –3 –3 m 3 –3 m. um. e m m Minimising energy loss in power transmission Examination ExaminationQuestions Questions Did DidYou YouKnow? Know? Leaving LeavingCertifi Certifi cate catePhysics Physics(OL) (OL)2013, 2013,Q.Q.1111 • • The The demand demand forfor electricity electricity varies varies with with the the time time ofof day, day, the the seasons, seasons, the the weather weather and and even even with with patterns patterns ofof TVTV viewing. viewing.The The graph graph shows shows the the varying varying All-Island All-Island demand demand (and (and anticipated anticipated st st Aug. Aug. 2016. 2016. demand) demand) onon Sunday Sunday 2121 • • The The supply supply ofof electricity electricity must must match match the the demand. demand. Renewable Renewable energy energy sources sources make make aa signifi signifi cant cant contribution contribution inin windy windy weather weather but but other other forms forms ofof energy energy are are also also necessary necessary toto meet meet the the demand. demand. Read Read this this passage passage and and answer answer the the questions questions below. below. “The “The National National Grid Grid - Ireland’s - Ireland’s Transmission Transmission System System The The national national grid grid system system supplies supplies electricity electricity toto customers. customers. The The grid grid consists consists ofof aa network network ofof high high voltage voltage transmission transmission stations, stations, power power lines lines and and cables cables delivering delivering power power toto over over 100 100 sub-stations sub-stations allall over over Ireland. Ireland. From From these these sub-stations sub-stations power power can can bebe taken taken onwards onwards onon lower lower voltage voltage lines lines toto individual individual customers’ customers’ premises. premises. The The network network includes includes about about 6,000 6,000 km km ofof overhead overhead lines lines and and underground underground cables. cables. High High voltages voltages are are used used toto avoid avoid power power losses losses which which would would otherwise otherwise occur occur when when transferring transferring power power over over long long distances. distances. AtAt the the sub-stations sub-stations power power is is transferred transferred from from the the grid, grid, transformed transformed into into medium medium and and low low voltage voltage electricity electricity and and is is delivered delivered toto Ireland’s Ireland’s 2.1 2.1 million million domestic, domestic, commercial commercial and and industrial industrial customers.” customers.” (Adapted (Adapted from from EIRGRID EIRGRID ATAT A GLANCE, A GLANCE, Eirgrid Eirgrid information information publication.) publication.) m a sa (b)(b)Why Why are are high high voltages voltages used used toto transmit transmit power power over over the the national national grid? grid? TF F TF F 4000 4000 2000 2000 anticipated anticipated demand demand 0 0 The The data data below below show show the the mix mix ofof st st August August 2016. 2016. sources sources atat 21:38 21:38 onon 2121 Note Note the the net net import import shows shows aa negative negative number; number; this this means means that that some some electricity electricity was was exported exported viavia the the Interconnector. Interconnector. Minimising energy loss in power transmission Power Power is is generated generated byby power power plants plants throughout throughout the the country, country, using using aa variety variety ofof fuel fuel oror energy energy sources, sources, including including gas, gas, oil,oil, coal, coal, peat, peat, hydrohydroelectricity, electricity, wind wind turbines turbines and and other other sources sources such such asas biomass biomass and and landfi landfi ll gas. ll gas. AllAll ofof the the major major power power plants plants feed feed into into the the national national grid. grid. (a)(a) What What are are the the key key components components ofof the the national national grid? grid? TF F MWMW (d)(d)Name Name two two renewable renewable and and two two non-renewable non-renewable energy energy sources sources used used toto generate generate electricity. electricity. (e)(e)The The national national grid grid uses uses alternating alternating current current (a.c.) (a.c.) rather rather than than direct direct current current (d.c.). (d.c.). What What is is the the difference difference between between them? them? (f)(f)Name Name the the device device used used toto convert convert high high voltages voltages toto lower lower voltages. voltages. TF F (g)(g)Give Give the the principle principle ofof operation operation ofof the the device device named named inin part part (f).(f). TF F (h)(h)Name Name the the unit unit ofof electrical electrical energy energy that that is is used used inin the the delivery delivery (9)(9) periment demonstrate demonstrate electromagnetic electromagnetic induction. induction. Texperiment F F to to Leaving Leaving Certifi Certifi cate cate Physics Physics(OL) (OL)2002, 2002,Q.Q.9 9 (6)(6) supply supply (230 (230 V)V) is is connected connected toto A,A, which which has has Trts F F of of thethe transformer transformer labelled labelled A, B and B and C100 in C in theturns. the diagram. diagram. 400 400 turns. turns. CA, C has has 100 turns. What What is is the the reading reading onon the the (9)(9) Ttricity F F supply voltmeter? voltmeter? ectricity supply (230 (230 V)V) is connected is connected to to A,A, which which hashas 400 400 TF F V V 100 0 turns. turns.What What is the is the reading reading onon thethe voltmeter? voltmeter? (9)(9) TF F AA BB InIn December December 1922 1922 bebe began began working workingforfor Siemens Siemens in in Germany. Germany. AtAt the the time time the the company company was was developing developing hydroelectric hydroelectric power power plants. plants. McMc Loughlin Loughlin was was familiar familiar with with the the many many previous previous proposals proposals toto use use the the Shannon Shannon asas aa source source ofof hydro hydro power. power. With With the the backing backing ofof Siemens Siemens hehe went went toto Ireland Ireland in in 1923 1923 and and met met with with members members ofof the the new new Free Free State State Government. Government. His His proposals proposals were were initially initially turned turned down down but but in in January January 1924 1924 hehe returned, returned, accompanied accompanied byby a senior a senior director director ofof Siemens. Siemens. This This time time the the proposal proposal st May 1925 1925 was was accepted. accepted. Detailed Detailed plans plans were were drawn drawn upup and and onon 1st1May the the Shannon Shannon Electricity Electricity BillBill was was introduced introduced in in the the Dáil. Dáil. Despite Despite further further opposition opposition from from vested vested interests interests (e.g. (e.g. local local electricity electricity suppliers suppliers in in Dublin Dublin and and elsewhere) elsewhere) the the contract contract was was signed signed and and work work began began later later that that year. year. The The Electricity Electricity Supply Supply Board Board (ESB) (ESB) was was setset upup in in 1927, 1927, with with McMc Loughlin Loughlin asas executive executive director. director. HeHe was was just just 3131 years years ofof age. age. Wikipedia: Wikipedia: Thomas_McLaughlin_(engineer) Thomas_McLaughlin_(engineer) Wikipedia: Wikipedia: Shannon_hydroelectric_scheme Shannon_hydroelectric_scheme (12) (12) T F F a device Name Name the the parts parts of the the transformer transformer labelled labelled A,A, BB and and CC inin the the diagram. diagram. mer r is aisdevice based based onon the the principle principle ofof of electromagnetic electromagnetic induction. induction. Tces F Fthatthat vices useuse transformers. transformers. The The mains mains electricity electricity DrDr Thomas Thomas A.A. Mc Mc Laughlin Laughlin (1896 (1896 −− 1971) 1971) Although Although Thomas Thomas McMc Laughlin Laughlin was was born born in in Drogheda Droghedahehe was was educated educated in in Dublin, Dublin, obtaining obtaining a BSc a BSc and and MSc MSc atat UCD. UCD. HeHe completed completed a BE a BE and and PhD PhD while while working working asas anan assistant assistant physics physics lecturer lecturer in in UCG. UCG. (c)(c)Why Why is is the the power power supplied supplied toto domestic domestic customers customers atat lower lower voltages? voltages? magnetic romagnetic induction? induction? ofof electricity electricity toto homes homes and and businesses. businesses. Biographical BiographicalNotes Notes CC art labelled labelled B designed B designed to to make make thethe transformer transformer more more efficient? efficient? (6)(6) of y of a transformer a transformer is 90%. is 90%.What What does does this this mean? mean? (5)(5) Revise ReviseThe TheTerms Terms Can Can you you recall recall the the meaning meaning ofof the the following following terms? terms? Revising Revising terminology terminology is is aa powerful powerful aid aid toto recall recall and and retention. retention. alloy, alloy, ampere, ampere, arcing, arcing, area area ofof cross cross section, section, battery, battery, capacitor, capacitor, conductivity, conductivity, conductor, conductor, corona corona discharge, discharge, direct direct current current transmission, transmission, distribution, distribution, electric electric current, current, electric electric potential, potential, electrical electrical resistance, resistance, electrolysis, electrolysis, energy, energy, heat, heat, ionised, ionised, kV, kV, magnetic magnetic effect effect ofof electric electric current, current, magnetic magnetic field, field, MW, MW, non-renewable, non-renewable, power, power, resistance, resistance, specifi specifi c heat c heat capacity, capacity, superconductor, superconductor, transmission, transmission, volt, volt, watt. watt. Check Check the the Glossary Glossary ofof terms terms for for this this lesson lesson onon www.sta.ie www.sta.ie