Power Different Essential

8/16/2019 Power Different Essential

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50kVA PMTx Substation Transformer

Name: 50kVA Pole Mounted Substation Transformer Rating: 50kVACooling: Oil Cooled

Application: Commercial, Heav !esidential, "arm #old.This type of transformer is mainly used for Step-Down purposes of voltages in the range of!"#$%&'$(".

$ffects of $xcess Current on t#e #uman bod

%elo& ' milli am(eres )*'mA+)enerally not percepti*le

' milliam(eres )'mA++aint tingle.

5 milliam(eres )5mA+Slight shoc! felt. Not painful *ut distur*ing. Average individual can let go. Strong involuntary reactions canlead to other in,uries.

-5 milliam(eres )-5mA+ainful shoc! loss of muscular control. The free/ing current or 0let-go0 range. 1ndividual cannot let go *ut

can *e thrown away from the circuit if e2terior muscles are e2ited *y the current.

.an/ers of $lectric S#ockShare

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The severity of in,ury from electrical shoc! depends on the amount of electrical current and the length oftime the current passes through the *ody. +or e2ample &( of an ampere 3amp4 of electricity goingthrough the *ody for ,ust ' seconds is enough to cause death. The amount of internal current a personcan withstand and still *e a*le to control the muscles of the arm and hand can *e less than (milliamperes 3milliamps or mA4. Currents a*ove ( mA can paraly/e or 5free/e6 muscles. 7hen this5free/ing6 happens a person is no longer a*le to release a tool wire or other o*,ect. 1n fact the

electrified o*,ect may *e held even more tightly resulting in longer e2posure to the shoc!ing current. +orthis reason hand-held tools that give a shoc! can *e very dangerous. 1f you can8t let go of the toolcurrent continues through your *ody for a longer time which can lead to respiratory paralysis 3themuscles that control *reathing cannot move4. 9ou stop *reathing for a period of time. eople havestopped *reathing when shoc!ed with currents from voltages as low as $ volts. ;sually it ta!es a*out eart paralysis occurs at $ amps which means the heart does not pump at all. Tissue is *urnedwith currents greater than % amps.

?onger e2posure times increase the danger to the shoc! victim. +or e2ample a current of (( mA appliedfor < seconds is as dangerous as a current of (( mA applied for a fraction of a second 3(.(< seconds4.The muscle structure of the person also ma!es a difference. eople with less muscle tissue are typicallyaffected at lower current levels. @ven low voltages can *e e2tremely dangerous *ecause the degree ofin,ury depends not only on the amount of current *ut also on the length of time the *ody is in contact withthe circuit.

Sometimes high voltages lead to additional in,uries. >igh voltages can cause violent muscularcontractions. 9ou may lose your *alance and fall which can cause in,ury or even death if you fall intomachinery that can crush you. >igh voltages can also cause severe *urns At (( volts the currentthrough the *ody may *e as great as $ amps causing damage to internal organs such as the heart. >ighvoltages also produce *urns. 1n addition internal *lood vessels may clot. Nerves in the area of thecontact point may *e damaged. Buscle contractions may cause *one fractures from either the con-tractions themselves or from falls. A domestic soc!et will produce a ma2imum lethal current of


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A severe shoc! can cause much more damage to the *ody than is visi*le. A person may suffer internal*leeding and destruction of tissues nerves and muscles. Sometimes the hidden in,uries caused *yelectrical shoc! result in a delayed death. Shoc! is often only the *eginning of a chain of events. @ven ifthe electrical current is too small to cause in,ury your reaction to the shoc! may cause you to fallresulting in *ruises *ro!en *ones or even death.

The length of time of the shoc! greatly affects the amount of in,ury. 1f the shoc! is short in duration it mayonly *e painful. A longer hoc! 3lasting a few seconds4 could *e fatal if the level of current is high enoughto cause the heart to go into ventricular fi*rillation. This is not much current when you reali/e that a small

power drill uses owever if the shoc! is short and the heart has not *een damaged a normalheart*eat may resume if contact with the electrical current is eliminated. 3This type of recovery is rare.4

Po&er Sstem et&orkShare

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A detailed e2planation of the conversion and distri*ution of electric energy from the power station toconsumer units.This post descri*es how electric energy moves from the power generating station throughconductors of various si/es to consumers premises.To minimi/e losses and for economical reasonselectrical energy has to *e converted into different magnitudes during transmission and distri*ution untilthe consumer load.

PO1$! STAT2O

1n most countries electrical energy is generated at!"

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ower )eneration Statistics:1ndia-!" P!2MA!3 .2ST!2%4T2O S4%STAT2OThe high voltage line terminates at a distri*ution su*station. The su*station receives voltage at $((!"

''(!"


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Depending on the type of load of the consumer Single phase&


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Nominal "oltage $((!"Cicuits per phase Su*-conductors per phase 'Span $((mConductor Name and Si/e Boose%$&


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>eight : m7idth 3at *ase4:G( m *ase $( m crestBaintained *y : Buay!ensan

Reservoir informationCreates : ?a!e Nasser Capacity : !m<

ower )eneration 1nformationTur*ines : '1nstalled capacity: '.)7

1ntroductionDesigned and *uilt *y the ;SSRJs Ku! >ydropro,ect 1nstitute which is a state organi/ation that designedthe countryJs river-control schema including =( hydro-electric power stations the Aswan Dam is Africa8stallest dam standing at a massive %$' feet from the river *ottom to a a!im *i-Amr Allah to regulate the flooding of the Nile a tas! reuiring an early attempt at an AswanDam.LM After his field wor! made him aware of the impracticality of this schemeL'M and fearing thecaliphJs anger he feigned madness. >e was !ept under house arrest from ( until al->a!imJs death in(' during which time he wrote his influential Eoo! of Fptics.The Aswan >igh Dam was constructed in %$ when the actual planning *egun. 1n %G the Soviet;nion stepped in and funded the dam pro,ect. The Soviets also provided technicians and heavymachinery. The enormous roc! and clay dam was designed *y the Soviet >ydropro,ect 1nstitute alongwith some @gyptian engineers. '% thousands @gyptian engineers and wor!ers formed the *ac!*one ofthe wor!force reuired to complete this tremendous pro,ect which deeply changed many aspects [email protected] *egan in (. The >igh Dam as-Sad al-JAali an em*an!ment dam was completed on '

uly =(. 1t too! ( years to *uild with the first stage completed *y $. The reservoir *egan filling in$ while the dam was still under construction and first reached capacity in =. 1n the late %(Js thereservoir raised concern with archaeologists *ecause ma,or historical sites were a*out to *e under water.

A rescue operation *egan in ( under ;N@SCF. Sites were to *e surveyed and e2cavated and '$ma,or monuments were moved to safer locations or granted to countries that helped with the wor!s 3suchas the De*od temple in Badrid and the Temple of Dendur in New 9or!4.Fn the @gyptian side the pro,ectwas led *y Fsman Ahmed FsmanJs Ara* Contractors. The relatively young Fsman under*id his onlycompetitor *y one-half.


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Construction Statistics: At ma2imum ((( cu*ic metres of water can pass through the dam every second. There are furtheremergency spillways for an e2tra %((( cu*ic metres per second and the Tosh!a Canal lin!s the reservoirto the Tosh!a Depression. The reservoir named ?a!e Nasser is %%( !m long and


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the story and humans continue to learn to predict the outcomes of their actions and the effects these newconditions create.

/on/ 1ind Po&er - enaShare

2nstalled Ca(acit8 59' Me/a 1attsCommisionin/ 3ear8 :00;1ind Turbines8 Out(ut of eac# turbine8


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turn the line on again if the noise is not present then it is pro*a*ly arcing caused *y capacitor switchingor transients if the noise is there when the line is turned *ac! on then it is pro*a*ly arcing and this can*e visi*le a mile away with a daytime corona camera.9 1#at is a /ood readil available !"2BTV2 noise detector@The AB radio in your car or truc! tuned where there is no radio station and ad,usts the volume forcomfort then drive into the radio interference complaint area and listen for the loudest pole. Some noisescan *e outside the radio reception and will reuire other detectors.79 1#at can cause !"2BTV2@@lectrical arcing micro-arcing and for a utility items such as loose tie wires at insulators loose washersor hardware spar! gaps *etween pieces sometimes rattled *y heavy vehicle traffic in industry or thehome causes can range from T" sets microwaves transformers electric motors vehicles spar! plugwiring over the road diesel truc!s with inverters etc. places where an arc can flash-over momentarily *ut*e limited in current flow so it doesnJt result in a continuous flash-over.59 1#at is electrical corona@Corona is the ioni/ation of the nitrogen in the air caused *y an intense electrical field. @lectrical coronacan *e distinguished from arcing in that corona starts and stops at essentially the same voltage and isinvisi*le during the day and reuires dar!ness to see at night. Arcing starts at a voltage and stops at avoltage a*out %( lower and is visi*le to the na!ed eye day or night if the gap is large enough 3a*out %&G0at


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Corona on a conductor can *e due to conductor configuration 3design4 such as diameter too small for theapplied voltage will have corona year-around and e2treme losses during wet weather the opposite occursduring dry weather as the corona produces nitric acid which accumulates and destroys the steelreinforcing ca*le 3ACSR4 resulting in the line dropping. Road salts and contaminants can also contri*uteto starting this deterioration.'9 1# s#ould 2 care@1nsulating materials that are failing can cause flash-overs and outages.'79 1# &ill m boss )and #is boss+ care@

Any outage costs repair time and lac! of customer service in this age we are all some*odys customer.'59 Ho& does t#is cost our com(an@?ost opportunity revenue you canJt sell electricity or ma!e products if you donJt have power. Anine2pensive part 3cotter pin devoured *y corona acid4 can fail and cost a transformer *y the time thespar!s uit flying. Customers with continuous process applications critical care facilities computingsystems typically have uninterrupti*le power and *ac!-up generating capacity for part of there load for alimited time.'9 Ho& does t#is affect t#e reliabilit of our electrical sstem@Corona is a symptom it may *e present for years *efore the component finally fails. Corona can *e anindication or the catalyst of the chemical soup that permeates insulator *onding cements preparing themfor internal flash-over. >ow can you detect this as! me.'9 1#at tools are available to identif t#e (resence of corona@

Corona produces sound nitric acid 3in the presence of moisture4 o/one and ultraviolet light. No R+1&T"1here as this is a chemical reaction.'


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The enya @lectricity )enerating Company en)en: enyaJs largest power producer is ready to switchoff @mergency ower )enerators. These power generators were commissioned last year 3'((4 duringthe period of acute shortage in power caused *y low rainfall and low water levels in the hydroelectricdams.

The @mergency ower )enerators which produce %(B7into the grid produce power from Diesel fuelresulting in the high electricity costs for enyans. The ower Relief cost the government .=Eillion sh

and have *een running since the commissioning.

The e2pected switch off of these fuel gu//lers will ta!e place on th anuary '((.This will mean lesspower *ills in the coming future as the government calls investors to e2plore the rich energy potential ofenya. Fn the other hand The enya ower ?ighting Company ?C - The ?argest distri*utor ofpower said consumers have *een pointing a finger on them *laming them of huge power *ills. ?C hasreassured its customers that they have to charge a higher +uel ?evy *ecause of the @mergency owergenerators.

A recent survey of the power in enya shows that the countries over-reliance of >ydro ower has seenmassive shortage of power once the rains falls. 1t is *ecause of this that en )en has em*ar!ed of ane2pansion of its )eothermal ower at Fl!aria Naivasha.

Stadium Po&er Su((lies - "2"A 1orld Cu( :0'0Share

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)iven the national and international e2posure that each stadium in the +1+A 7orld Cup '(( receives itis imperative that all efforts are made to ensure that electrical power supply in the venues is as relia*le aspossi*le. 1n this post according to 5''nd AB@; Technical Convention( AB@; roceedings '((

Stadium electricity supplies an assessment of the specification and readiness6 document 1 have outlinedthe various power aspects involved in Stadium ower Supplies.

The stadia and surrounding areas are fundamentally *ro!en down into threeBain focus areas include:. Domestic&stadium power 3stadium itself4'. Technical ower 3Bedia Eroadcasting4aving a ;Swould also ensure that the potential impact on pitch lighting during switching *etween electrical supplieswill *e mitigated. AB@; roceedings '(( - )enerators or alternate power supply capa*le of sustaining the pitch lighting for a minimum of three

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hours.- Baintenance and refueling are the responsi*ility of the host city.- Configuration of the power supply is at the discretion of the host city *ut must have a minimum n-redundancy.Stadium *uilding power: Stadium *uilding power is the reuired supply within the stadium to powerappliances facilities and lighting within the stadium i.e. general stand lighting administration offices andsuites.- Eac!up power reuirement in the event of a power failure is limited to that of the Fccupational >ealthand Safety Act 3F>SACT4- This power e2cludes any *roadcast or media provisioning.- Configuration of the B" power supply is at the discretion of the host city and is recommended to haveminimum n- redundancy.

Tec#nical (o&er This is power for the *roadcasting and television reuirements.No host city involvement. This is the responsi*ility of the ?FC.No grid supply. 1slanded from the grid power supply. Supply is provided via diesel generators supplied *ythe ?FC. Covers all *roadcasting mediums.Total of three %(( !"A generators each capa*le of ta!ing the full load. Two generators run in parallel withthe third *eing a *ac!up. A fourth generator will *e reuired for the venue hosting the final game.

Kero supply switching tolerance this means no time interval in the changing from diesel power to au2iliarypower in case of a pro*lem with generators.

OverlaBPrecinct (o&er This is Area immediately surrounding the stadium including tic!eting offices hospitality accreditation etc.>ost city is responsi*le to supply a medium voltage 3 !"4 point&s of supply. +or '(( there may *e asmany as four reuired per stadium and the num*er and location of these *ul! supply points will *estadium dependent.

Ot#er Stadium loadsThe following other stadium loads reuire an automated switched firm supply 3to either an independentgrid supply or local *ac!up generation4:. @mergency lighting 3Stadium and par!ing4

'. +irst aid&medical facility


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maintenance or refur*ishment plans.$. Detailed emergency planning and simulation of these plans prior to the event.%. lans for o*taining and storing of strategic spares as well as logistic constraints such ascommunications and transport are in place.. 1nspection of networ!s will ta!e place earlier than normal practice for those networ!s identified ascritical for relia*ility and uality of supply.

.istributionThe esta*lishment of regional tas! teams 3RTT4 in all the host cities has ena*led the preparation to *etrac!ed and understood. The suggested actions that are *eing carried out 3many have *een completed4*y the relevant host cities include:. 1dentify and assess the condition of the electrical infrastructure that could directly or indirectly influencethe supply to the stadium3s4 training venues and !ey loads in their area of responsi*ility.'. Replacement refur*ishment or maintenance of these networ!s to *e scheduled to *e completed well*efore the commencement of the tournament.


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$. ?oftus "ersveld 3retoria4 rimary power generators G 2


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=. Soccer City 3ohannes*urg4 rimary power generators Eac!up power grid 3n-4 ;ninterrupta*lepower supply 3;S4.

G. B*om*ela Stadium 3Nelspruit4 rimary power generators Eac!up power grid 3n-4 ;ninterrupta*lepower supply 3;S4.

. eter Bo!a*a Stadium 3olo!wane4 rimary power generators Eac!up power grid 3n-4;ninterrupta*le power supply 3;S4.

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(. Nelson Bandela Stadium 3ort @li/a*eth4 rimary supply grid supply 3Bount R su*station U &''!"4 Eac!up power gas tur*ine

There are rotary ;Ss which are installed in each of the $ stadium su*stations which will *e dedicated for pitch lighting and emergency supplies.

T#e Fian/Giaba - S#an/#ai igh "oltage transmission and distri*ution systems have shown a gradualincrease in DC transmission systems at very high voltage levels. >igh "oltage Direct Current 3>." D.C4has *ecome common in developed countries due to reduced costs at high voltages as compared to

Alternating Current 3A.C4 transmission. 1t is *ecause of such reasons that the recently completedViang,ia*a-Shanghai G((!" ;>"DC transmission line was *uilt.

ProGect .etailsFperating "oltage: WG((!" DCNo. of oles: 'Connection oint Viang,ia*a: +ulong Su*stationConnection oint Shanghai: +engViang Su*stationFwnership: State )rid Corporation of ChinaStart of ro,ect: Decem*er '((=Commissioning 9ear: ole and Ei-pole '((

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Transmission Technology: ;>"DC 3;ltra >igh "oltage Direct Current4Transmission Capacity: $((B7 3.$)74?ength of Fverhead DC ?ine: '(=!m

AC "oltage: %'%!" 3*oth ends4Bain Reason for Choosing >"DC: ?ong Distance and ?ow ?osses>"DC converter stations: Convert AC to DC and DC to ACDesign Supply and 1nstallation: AEE

This new lin! is a*le to meet the electricity needs of a*out '$ Billion people and sets a new *enchmar! interms of voltage levels and transmission capacity superseding the ((!" 1taipu transmission line inEra/il also *y AEE

.C Transmission and .istribution1n DC transmission technology the following terminologies are used: X."4 igh "oltage 3@.>."4 Y=%!": ;ltra >igh "oltage 3;.>."4DC technology is used for large transmission and distri*ution of power at high voltages *ecause at suchlarge uantities the systems are less e2pensive and suffer lower power losses. >"DC has found its placedue to economic reasons of transmission.

Eeneration of .C ).irect Current+)enerally there are two methods of producing DC power:. Standard DC )enerators'. Converting AC to DC ;sing: Botor )enerator Sets phase Bercury Arc Rectifiers Rotary Converters

Standard .C Eenerators A standard DC )enerator is an electrical machine that consists of a magnetic coil provided *y permanentor electromagnets and a coil of wire of a significant num*er of turns rotating in the magnetic flu2.

According to +aradays8 ?aw of @lectromagnetism induction a DC current shall *e produced when the coilis rotated.

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Convertin/ AC to .CThe conversion of AC to DC is nowadays used in parallel to AC for specific loads that use strict DC.>owever this is done at a large scale in >" and @>".. A motor )enSet is simply a motor driven *y AC to provide mechanical power to a generatorproducing DC.'. A rotary converter is a type of electrical machine where a motor-generator machine shares a singlerotating armature and set of field coils."DC is less relia*le and lower availa*ility than AC systems"DC circuit *rea!ers are difficult to *uild *ecause some mechanism must *e included in the circuit*rea!er to force the current *ac! to /ero. Ftherwise arcing and contact wear would *e too great to allowrelia*le arching.

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$. Fperating a >"DC reuires many spare parts to *e !ept often e2clusively for one system since>"DC systems are less standardi/ed.

Costs of HV.CNormally manufactures such as Alstom Siemens and AEEdo not state specific costs of information of aparticular pro,ect since this is a commercial matter *etween the manufacturer and client. Costs are widedepending on the specifics of the pro,ect such as ower rating Circuit ?ength Fverhead vs. ;nderwaterroute ?and Costs and AC Networ! improvements reuired at terminal.

+or an G)7 $(!m lin! laid under the @nglish Channel an appro2imate rimary euipment costs for a'(((B7 %((!" *ipolar convectional >"DC lin! 3e2cluding way-leaving onshore-reinforcement wor!sconsenting engineering insurance etc4 is as follows: Converter StationsI J''0Million Subsea Cable K 2nstallation IJ'MillionBkm

TH$ F2AEL2A%A - SHAEHA2 ydro plant in S.7 China to Shanghai. This new lin! will meet theelectricity need if '$Billion people and set a new record in terms of voltage levels and transmissioncapacity superseding the ((!" 1taipu transmission line in Era/il.Transmission line losses on the new line are well under =. AEE *eing the main technology supplier isresponsi*le for the overall system design. The scope of delivery of euipment to Viang,ia*a included 'G

>igh and ;ltra >igh "oltage converter transformers. ( of which were delivered from Sweden and the restmanufactured with AEE components and technology in local partnership. Fther products deliveredinclude: Thyristor "alves DC and AC Switchyard euipment and the newly developed.CC


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line.'. The ower rating $((B7 3.$)74 is more than dou*le the power rating of the most powerfultransmission line in operation today."DC line in Congo-Era/il was the longesttransmission line.

An ;>"DC lin! '((( !m long is


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1t is usual practice to attach the word Z lagging8 or Zleading8 with the numerical value of power factor tosignify whether the current lags or leads the voltage. Thus if a circuit has p.f. of (. and the current lagsthe voltage we generally write p.f. as (. lagging.ower factor can also *e e2pressed as a percentage i.e. ( lagging.

Po&er "actor :Share

Po&er factor in !elation to Po&er

ower is consumed only in resistance since neither pure inductor nor the capacitor consumes anypower. The power consumed 3True ower4 in 1nductor 3?4 and Capacitor 3C4 is /ero. There is a circulatingpower that moves from the source to the load *ac! and forth and does not do any useful wor! in thecircuit. Current and voltage are in phase in a Resistance while they are ( Degrees out of phase in 3?4and 3C4.7hen current is in phase with voltage it produces active or True ower while it produces Reactiveower when ( Degrees out of phase with voltage.

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Po&er Trian/leNote:Due to formating limitations all suared values shall *e indicated *y 3suared4

FA3suared4 [ AE3suared4 OFE3suared43Active ower43suared4[3Reactive ower43suared4 O Apparent ower43suared4The lagging rective power is responsi*le for low power factor.The smaller the reactive power componentthe higher the power factor.

!"AR O !"1Sin\ !"AR O !"ASin\ *ut Cos\ O!7&!"A therefore !"A O !7&Cos\ !"AR O!7&Cos\HSin\ !"AR O !7tan\

+or ?eading currents the power factor triangle *ecomes reverse *iased and this provides a !ey factor inpower factor improvement.1f a device ta!ing leading currents or reactive power a capacitor is connected

with this device in parrarell and the power factor is improved.Capacitors ta!e in a leading power factorand thus are used in power factor correction.

@2ample:1f a circuit draws a current of (A at a voltage of '((" and its pf is (.G lagging determine the ActiveReactive and Apparent ower.

+or apparent power] O 1" O(H'(( '((("A

+or active power]

O 1"Cos\ O (H'(((HCos\ 3Cos\ Oower +actorO(.G4 O ((7

+or reactive power]

O 1"Sin\ O (H'((HSin\ O '(("AR

+rom the a*ove calculations we can see that the circuit receives an apparent power of '((("A and it iscapa*le of converting only ((7 into useful active power. The reactive power is '(("AR and it doesno useful wor!. 1n fact it is a lia*ility on the source *ecause it has to supply an additional current of 1Sin\.

.isadvanta/es of 6o& Po&er "actor9. ?arge !"A rating of euipment 3switchgear alternators transformers4 7e !now that !"A O!7&Cos\ Therefore Cos\ O!7&!"A 7hen \ is increasing Cos\ is decreasing and when \ is decreasing Cos\ is increasing. 1t is from thissimple fact that we can conclude that when the power factor is decreasing the !"A is increasing thesmaller the power factor the larger the !"A rating of the euipment.'.)reater Conductor Si/eTo transmit and distri*ute a fi2ed amount of power at a constant voltage the conductor will have to carry a


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current at low power factor. This will necessitate the use of a greater conductor si/e.


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completely on the positive side of the a2is it shows that the power in the system is traveling only in onedirection toward the load.

The area under this power sine wave curve represents the amount of energy delivered to the load. 1f thepower sine wave is shifted the difference in area *etween the positive and the negative sides representsthe power delivered to the load. The negative side of the power sine wave represents the reflected powerfrom a reactive load.

A lagging power factor is one in which the current is lagging *ehind the voltage and is characteristic of aninductive load.

A leading power factor is one in which the current is leading the voltage and is characteristic of acapacitive load. 1f the phase angle were to *e shifted to *e greater than ( degrees in either direction theload would effectively *ecome the source.

Po&er "actor Correction A power factor of one 34 or 0unity power factor0 is the goal of any electric utility company since if thepower factor is less than one 3X4 they have to supply more current to the user for a given amount ofpower use. 1n so doing they incur more line losses. They also must have larger capacity euipment inplace than would *e otherwise necessary. As a result an industrial facility will *e charged a penalty if its

power factor is much different from .

1ndustrial facilities tend to have a 0lagging power factor0 where the current lags the voltage 3li!e aninductor4. This is primarily the result of having a lot of electric induction motors - the windings of motorsact as inductors as seen *y the power supply. Capacitors have the opposite effect and can compensatefor the inductive motor windings. Some industrial sites will have large *an!s of capacitors strictly for thepurpose of correcting the power factor *ac! toward one to save on utility company charges.

Hdroelectric Po&er StationShare

This is a generating station which utili/es the potential energy of water at a high

level for the generation of electrical energy. 1t uses the gravitational force of falling or flowing water. They are located in hilly areas where dams can *e *uiltand large water reservoirs can *e o*tained. >ydroelectricity is the most widelyused form of renewa*le energy. 7orldwide an installed capacity of ==)7esupplied a total of 'GT7e of hydroelectricity in '((. This was appro2imately'( of the worldJs electricity and accounted for a*out GG of electricity fromrenewa*le sources...

Bost hydroelectrity comes from the potential energy of dammed water driving awater tur*ine coupled to a generator. Therefore the energy e2tracted from thewater much depends on the difference in height *etween the source and thewaters outflow. This height difference is called the head. To o*tain a very highhead water for a hydraulic tur*ine may *e run through a large pipe called a

penstoc!.

7hile most of the power stations are *uilt for pu*lic utility networ!s there arethose dedicated to supply large electricity needed for aluminum electrolyticplants and other industrial esta*lishments. @2amples include: 1n the Scottish>ighlands of ;nited ingdom inlochleven and ?ocha*er were constructedduring the early years of the '(th century. 1n Suriname the Ero!opondoReservoir was constructed to provide electricity for the Alcoa aluminumindustry. New KealandJs Banapouri ower Station was constructed to supplyelectricity to the aluminum smelter at Tiwai oint

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E$$!AT2O O" PO1$! AT A H9$9P STAT2O

The dam is constructed across a river or a la!eand water collects *ehind the dam to form a reservoir. A pressure tunnel ista!en off the reservoir and water is *rought to the valve house at the start of thepenstoc!. The valve house contains the main sluce valve which controls thewater flow to the power house and automatic isolating valves which cuts off supply of water when the penstoc! *ursts. +rom the valve house water is ta!ento the tur*ine through the penstoc!s. The tur*ine converts hydraulic energy intomechanical energy. The surge tan! protects the penstoc! from *ursting in casethe tur*ine gates close due to electrical load *eing thrown off. 7hen the gatesclose there is a sudden stopping water at the lower ends of the penstoc!. The

surge tan! a*sor*s this pressure swing *y increase in its level of water. Thewater tur*ines are of ' types namely: 1mpulse and Reaction tur*ines.

Advanta/es of Hdroelectric Po&er • Reuires no fuel since it uses water as a source of energy.

• ?ess or no greenhouse gas emissions in modern plants.

• Can *e used for many purposes i.e. Control floods 1rrigation.

• ?onger operational life i.e.


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0The 1taipu power plant on the araguay River on the Era/il-araguay *order currently produces second most hydroelectricityin the world. 7ith '( generator units and $((( B7 of installed capacity in'((G the 1taipu power plant reached a new historic record for electricityproduction *y generating $.G terawatt-hours 3


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1#ic# one is more dan/erous, AC or .C@Share5

This question has been asked by many people who have experienced an

electric shock before.I recently received an electric shock from thedomestic household current of 10A.The feeling was ecstatic. any will come

across large A! currents" but have you ever thought of #! $lectrification%This would sound weird because #! current available in domestic premises

is in the order of mA &milliamperes'. In industrial environments #! current

is available in large quantities and is very lethal when handled improperly.The severity of a shock largely depends on(

---Amount of current---Amount of time on the exposure

---Resistance of the body.AC:Alternating Current

A! in theory would allow your muscles time to be able to move so that you

could pull your hand ) limbaway from whatever it was that was giving you the shock. This is so because

A! alternates from *eroto maximum &amplitude' in a specified time frame &frequency'.It is during

this timeframe that muscle

signals may retract you hand)limb...The time frame we are talking about here is only a few milliseconds+which

means that for largercurrents" there is no time for reflex action. ,owever as I said above"

this largely depends on the amount of current flowing.

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-tarting current of motors &1/A' would never give you a chance of eventhinking

A! current will allow you to move your hand for the muscles which are not inthe path of the electric

current.In A! &Alternate !urrent' the muscles will contract and extend and

through the spasms youmight eventually free yourself &that is why people say that the current threw

them while" in fact"it was their own muscles'.

DC: Direct Current#efinitely #!. The passing of current through the muscles make them

contract.

In #! irect !urrent0,*' it will make your hand clamp the live wire2 that

is why" when in doubt"

you should touch wires with the back of the hand. In A! &Alternate !urrent'

the muscles will contract

and extend and through the spasms you might eventually free yourself &that

is why people say that the

current threw them while" in fact" it was their own muscles'. 3o time forconscious efforts when under

current. #o not be fooled" 34 43$ can sense the *ero voltage 5in between5

the 60,* &cycles per second'.

7eople tend to underestimate #! because in normal life one encounters verylow dc voltages while the

mains ac is everywhere. 8iven the proper voltage #! will kill you. 9y the

way" it is not as much the voltage

as it is the current. A potentially lethal &depending on the health condition'value starts from a 0mA current

through your body. The better the contact &e.g. wet hands" bare feet' the

lower the lethal voltage.


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:ou better stay away of voltages over ;< &A! or #!' if you have no specialqualification. +++$lectrical $ngineer

If #! was used at ;0v in household appliances then somebody would die

every day. A! is very safe then #!

at high voltages because it alters its charges. #! can be safely and easilystored in low voltage in batteries

and that=s why people have these wrong assumptions that #! is safe.

After the above arguments I have come to a conclusion that #! !urrent is

far more lethal than A! because(#! will not release you at the point of contact with live conductor

#! will cause fibrillations in the heart leading it to stop due to over+contracted muscles.This is caused by

A! also but #! is more severe.#! causes a clench in hand muscles that>s

why when not sure" use the back of your hand. The clenching causes the victim to grip the conductor and won>t let go.

E929S - Eas 2nsulated Substations 'Share

A gas-insulated su*station 3)1S4 uses a superior dielectric gas sulfur he2afluoride 3S+4 at a moderatepressure for phase to phase and phase to ground insulation. The high-voltage conductors circuit *rea!erinterrupters switches current transformers and voltage transformers are encapsulated in S+ gas insidegrounded metal enclosures. The atmospheric air insulation used in a conventional air-insulatedsu*station 3A1S4 reuires meters of air insulation to do what S+ can do in centimeters. )1S can therefore*e smaller than A1S *y up to a factor of ten. A )1S is mostly used where space is e2pensive or notavaila*le. 1n a )1S the active parts are protected from deterioration from e2posure to atmospheric air

moisture contamination etc. As a result )1S is more relia*le reuires less maintenance and will have alonger service life 3more than %( years4 than A1S. )1S was first developed in various countries *etweenG and ='. After a*out % years of e2perience the user rate increased to a*out '( of newsu*stations in countries where space was limited. 1n other countries with space easily availa*le thehigher cost of )1S relative to A1S has limited its use to special cases. The 1@@@ L$ %M and the 1@C LM havestandards covering all aspects of the design testing and use of )1S. +or the new user there is a C1)R@application guide. 1@@@ has a guide for specifications for )1S.

7hat is Sulphur >e2afluoride S+Q

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Sulfur he2afluoride is an inert nonto2ic colorless odorless tasteless and nonflamma*le gas consistingof a sulfur atom surrounded *y and tightly *onded to si2 fluorine atoms. 1t is a*out five times as dense asair. S+ is used in )1S at pressures from $(( to (( !a a*solute. The pressure is chosen so that theS+ will not condense into a liuid at the lowest temperatures the euipment e2periences. S+ has two tothree times the insulating a*ility of air at the same pressure. S+ is a*out (( times *etter than air forinterrupting arcs. 1t is the universally used interrupting medium for high-voltage circuit *rea!ers replacingthe older mediums of oil and air. S+ decomposes in the high temperature of an electric arc or spar! *utthe decomposed gas recom*ines *ac! into S+ so well that it is not necessary to replenish the S+ in)1S. There are some reactive decomposition *yproducts formed *ecause of the interaction of sulfur andfluorine ions with trace amounts of moisture air and other contaminants. The uantities formed are verysmall. Bolecular sieve a*sor*ents inside the )1S enclosure eliminate these reactive *y products overtime. S+ is supplied in %( !g gas cylinders in a liuid state at a pressure of a*out (((!A forconvenient storage and transport.

T#e Stockbrid/e .am(er Share

A Stoc!*ridge damper is a tuned mass damper used to suppress wind-induced vi*rations on taut ca*lessuch as overhead power lines. The dum**ell-shaped device consists of two masses at the ends of ashort length of ca*le or fle2i*le rod which is clamped at its middle to the main ca*le.1t is placed a*outmidway *etween the nodes of the vi*rations i.e. where amplitude of the vi*rations would *e more. Thevi*ration causes movement of the damper and energy is a*sor*ed *y the inter stand friction in the steelca*le. The vi*rations have low amplitude up to %mm and high freuency of %(>/-((>/. A typical damper for use on a


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C#aracteristic "eatures of Snc#ronous Motors9. They run at synchronous speed. This machine will run at a constant speed which can *e changed*y varying the supply freuency.'. They are not self starting.-The rotor and stator fields have to *e e2cited *y a separate D.C e2citationvoltage.


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1n Star connection the hase Current is always eual to ?ine Current.

i.e. 1?1N@ O 1>AS@ ">AS@ O _


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The !" line is connected to the Step-Down Transformer 3!"&$%"4 though a gang isolator and fuses.The lighting arrestors are installed on the H.T side to protect the Sub-Station from lightening strokes.The transformer steps down the 11kV to 415V, phase, 4-wire suppl!. The "oltage between an! twolines is 415V, and between an! line and a phase is #4$V. The %il &ircuit 'reaker (%.&.'), installed onthe *.T side automaticall! isolates the transformer from the consumers in case of an! fault. The +ole

ounted Sub-stations are generall! used fortransformer capacit! up to #$$kVThe! should be periodicall! checked for dielectric strength of oil in the transformer and (%&')n case of repair the transformer or (%.&.') both the /ang solators and (%.&.') should be shut off.This e0uipment is "er! epensi"e leading to the reason wh! people "andali2e them. The Step-3ownTransformer is oil cooled and its this oil that people steal. This costs the distribution compan! millionsofShillings annuall!. +lease be warned that the current flowing through the transformer is deadl!, itwould kill !ou in seconds. Stealing that oil means that the transformer will o"erheat, reduce itsefficienc! andpossible eplode under normal circumstances. n case !ou spot an! one"andali2ing the e0uipment please call The en!a +ower and *ighting &o. *imited www.kplc.co.ke.See the image below of a +ole ounted Sub-Station.

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Electric Supply System

The con"e!ance of electric power from a power station to consumers6 premises is known aselectric supply

system. n electric suppl! s!stem consists of three principal components viz ., the power station, the

transmission lines and the distribution s!stem.

The electric supply system can be broadly classified into

1. d.c. or a.c. system

#. overhead or underground system.

7ow-ada!s -phase, -wire a.c. s!stem is uni"ersall! adopted for generation and transmission of electric

power as an economical proposition.

T!pical a.c. Power Supply Scheme

8lectric Suppl! Schematic

http://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Power_supply


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The network can be broadl! di"ided into two parts viz.,

1. transmission system and

#. distribution system.

8ach part can be further sub-di"ided into two9primary transmission and secondary transmission and

primary distribution and secondary distribution.

t ma! be noted that it is not necessar! that all power schemes include all the stages.

(i)Generating station : n :ig, /.S. represents the generating station where electric power is produced b! -

phase alternators operating in parallel. The usual generation "oltage is 11 kV. :or econom! in the

transmission of electric power, the generation "oltage (i.e., 11 kV) is stepped upto 1# kV (or more) at the

generating station with the help of -phase transformers.

The transmission of electric power at high "oltages has se"eral ad"antages including the sa"ing of conductor

material and high transmission efficienc!.

/enerall! the primar! transmission is carried at ;; kV, 1# kV, ##$ kV or 4$$ kV.

(ii) Primary transmission. The electric power at 1# kV is transmitted b! -phase, -wire o"erhead s!stem

to the outskirts of the cit!. This forms the primar! transmission.

(iii) Secondary transmission. The primar! transmission line terminates at the recei"ing station (RS) which

usuall! lies at the outskirts of the cit!. t the recei"ing station, the "oltage is reduced to kV b! step-down

transformers. :rom this station, electric power is transmitted at kV b! -phase, -wire o"erhead s!stem to

"arious sub-stations (SS) located at the strategic points in the cit!. This forms the secondar! transmission.

(iv ) Primary distribution. The secondar! transmission line terminates at the sub-station (SS) where "oltage

is reduced from kV to 11kV, -phase, -wire. The 11 kV lines run along the important road sides of the

cit!. This forms the primar! distribution. t ma! be noted that big consumers (ha"ing demand more than

5$ k

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