ee 104 assignment.doc

8/17/2019 ee 104 assignment.doc

1/25

Jan Benedict T. BullecerBSEE – V / EE 104 – C3

Fuses

History

The oldest and simplest of all protectie deices! it is a leel detector

and is "oth the sensor and interruptin# deice. $t is installed in series %ith

the e&uipment that is to "e protected and operates "' meltin# a fusi"leelement in response to the oercurrent (o%.

Earlier reference to the histor' of fuse deelopment came to li#ht!

Ed%ard )airne in an era of electrostatic electricit' durin# 1**4 %as tr'in# to

safel' dischar#e +e'den "ottles %hose operation is similar to capacitors

usin# %ires %hose len#th is related to the stored ener#'! actin# li,e a resistor

"ut %hen the dischar#e currents %ere too hi#h! the %ire acted li,e a fuse

%hich resulted to the %ire disinte#ratin# into small "alls that are unduloid in

shape.-1

nother earl' reference to fuses can "e found on the paper presented"' . C. Coc,"urn to the Societ' of Tele#raph En#ineers in 1* %hen . 2.

reece stated that platinum %ires had "een used as fuses to protect

su"marine ca"les since 14 and Sir 5aid Salomons referred to the use of

fuses in 1*4. Seeral num"er of deelopment in fuses can "e seen in the

succeedin# 'ears! durin# these times fuses %ere usuall' mounted in %ooden

"o6es! the indiidual elements %ere not other%ise enclosed. $t is in 7a' 10

that T. . Edison patented a fuse in %hich the %ire element %as enclosed in a

#lass enelope in order to protect the surroundin#s from the e8ects of the

disruption durin# operation 9i.e. meltin#! etc...:. S. . Thompson in 1*;

produced %hat he descri"ed as an improed form of fuse or cut


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interruption. 2ence fuses from arious di8erent manufacturers hae di8erent

meltin# cures! in addition to this fuses also has di8erent load


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ta"le proides ma6imum fault currents that the protectin# and protected

fuse are coordinated.-G

Advantages

• Kldest and simplest protectie deice.

• 7an' di8erent t'pes %ith special characteristics are aaila"le that %illaccommodate ar'in# needs %hether speed! relia"ilit'! or ma#nitude.

• Lelatiel' the cheapest option.

• $nherentl' operates automaticall' %ithout an' e6ternal or e6tra

arran#ements for automatic operation.

Disadvantages

• Solel' an oercurrent protectie deice

• Sin#le


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circuit current to "uild up to its full alue! can let an immense amount

of destructie short


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-;

• "a#$aging – uses are aaila"le in seeral pac,a#es cartrid#e!

"lade/spade/plu#


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Circuit Breakers

The circuit "rea,er is "oth a s%itchin# deice and a oercurrent

protectie deice desi#ned to open a circuit automaticall' on a

predetermined oercurrent and close a circuit of non


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"rea,er. $f the recoer' olta#e %ins the race! the arc re


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operated! lar#er units hae solenoids to trip the mechanism! and electric

motors to restore ener#' to the sprin#s. The circuit "rea,er contacts must

carr' the load current %ithout e6cessie heatin#! and must also %ithstand

the heat of the arc produced %hen interruptin# 9openin#: the circuit.

Contacts are made of copper or copper allo's! siler allo's and other hi#hl'

conductie materials. Serice life of the contacts is limited "' the erosion of contact material due to arcin# %hile interruptin# the current. 7iniature and

molded


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-1; The 5$) rail


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feature! %hich trips the circuit "rea,er sooner for lar#er oercurrents

"ut allo%s smaller oerloads to persist for a lon#er time. Kn er' lar#e

oers si=e due to di8erent

technical deelopments in this ?eld of en#ineerin#. The contact

#eometr' is also improin# %ith time! from "utt contact of earl' da's it

#raduall' chan#es to spiral shape! cup shape and a6ial ma#netic ?eld

contact. The acuum circuit "rea,er is toda' reco#ni=ed as most

relia"le current interruption technolo#' for medium olta#e s%itch#ear.

$t re&uires minimum maintenance compared to other circuit "rea,er

technolo#ies.-D0


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-D1

• Air C' < Lated current up to !300 and hi#her for #enerator circuit

"rea,ers. Trip characteristics are often full' adOusta"le includin#

con?#ura"le trip thresholds and dela's. suall' electronicall'

controlled! thou#h some models are microprocessor controlled ia aninte#ral electronic trip unit. Kften used for main po%er distri"ution in

lar#e industrial plant! %here the "rea,ers are arran#ed in dra%


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up%ard due to "oth thermal and electroma#netic e8ects as

sho%n in the ?#ure. s the arc is drien up%ard it enters in the

arc chute! consistin# of splitters. The arc in chute %ill "ecome

colder! len#then and split hence arc olta#e "ecomes much

lar#er than s'stem olta#e at the time of operation of air circuit

"rea,er! and therefore the arc is &uenched ?nall' durin# thecurrent =ero.-D0

D. ir Blast CB < %ere used for the s'stem olta#e of D4G RV! 4D0

RV and een more! especiall' %here faster "rea,er operation %as

re&uired. Seeral adanta#es oer Kil CBs are there is no

chance of ?re ha=ard caused "' oil! the "rea,in# speed of circuit

"rea,er is much hi#her durin# operation of air "last circuit

"rea,er! arc &uenchin# is much faster durin# operation of air

"last circuit "rea,er! the duration of arc is same for all alues of

small as %ell as hi#h currents interruptions! as the duration of arc

is smaller! so lesser amount of heat reali=ed from arc to currentcarr'in# contacts hence the serice life of the contacts "ecomes

lon#er! the sta"ilit' of the s'stem can "e %ell maintained as it

depends on the speed of operation of circuit "rea,er! re&uires

much less maintenance compared to oil circuit "rea,er.

5isadanta#es of ir Blast CBs are in order to hae fre&uent

operations! it is necessar' to hae suMcientl' hi#h capacit' air

compressor! fre&uent maintenance of compressor! associated air

pipes and automatic control e&uipment is also re&uired! due to

hi#h speed current interruption there is al%a's a chance of hi#h

rate of rise of re


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cham"er is also ?tted at the same ali#nment of "last pipe!

so that the air comes from "last pipe can strai#htl' enter

into e6haust cham"er throu#h the contact #ap of the

"rea,er. The e6haust cham"er is spit %ith arc splitters.

hen moin# contact is %ithdra%n from ?6ed contact! an

arc is esta"lished in "et%een the contact! and at the sametime hi#h pressure air comin# from "last pipe %ill pass

throu#h the contact #ap and %ill forcefull' ta,e the arc into

e6haust cham"er %here the arc is split %ith the help of arc

splitters and ultimatel' arc is &uenched.-D0

• %F( C' < e6tin#uish the arc in a cham"er ?lled %ith sulfur he6a(uoride

#as. circuit "rea,er in %hich the current carr'in# contacts operate in

sulphur he6a(uoride or S #as. 2ence! for heaier and less mo"ile

char#ed particles in S #as! it ac&uires er' hi#h dielectric stren#th.

)ot onl' the #as has a #ood dielectric stren#th "ut also it has the

uni&ue propert' of fast recom"ination after the source ener#i=in# thespar, is remoed. The #as has also er' #ood heat transfer propert'.

5ue to its lo% #aseous iscosit' 9"ecause of less molecular mo"ilit':

S #as can eMcientl' transfer heat "' conection. So due to its hi#h

dielectric stren#th and hi#h coolin# e8ect S #as is appro6imatel'

100 times more e8ectie arc &uenchin# media than air. 5ue to these

uni&ue properties of this #as S circuit "rea,er is used in complete

ran#e of medium olta#e and hi#h olta#e electrical po%er s'stem.

These circuit "rea,ers are aaila"le for the olta#e ran#es from 33RV

to 00RV and een more.-1;-D0

-D0

• )il C' < mineral oil has "etter insulatin# propert' than air. $n oil circuit

"rea,er the ?6ed contact and moin# contact are immer#ed inside theinsulatin# oil. heneer there is a separation of current carr'in#

contacts in the oil! the arc in circuit "rea,er is initiali=ed at the moment

of separation of contacts! and due to this arc the oil is apori=ed and

decomposed in mostl' h'dro#en #as and ultimatel' creates a

h'dro#en "u""le around the arc. This hi#hl' compressed #as "u""le

around the arc preents res hae a

discussion. hen the current carr'in# contacts in the oil are separatedan arc is esta"lished in "et%een the separated contacts. ctuall'!

%hen separation of contacts has Oust started! distance "et%een the

current contacts is small as a result the olta#e #radient "et%een

contacts "ecomes hi#h. This hi#h olta#e #radient "et%een the

contacts ioni=ed the oil and conse&uentl' initiates arcin# "et%een the

contacts. This arc %ill produce a lar#e amount of heat in surroundin#

oil and apori=es the oil and decomposes the oil in mostl' h'dro#en

and a small amount of methane! eth'lene and acet'lene. The

h'dro#en #as cannot remain in molecular form and it is "ro,en into its

atomic form releasin# lot of heat. The arc temperature ma' reach up toG000 R. 5ue to this hi#h temperature the #as is li"erated surround the


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arc er' rapidl' and forms an e6cessiel' fast #ro%in# #as "u""le

around the arc. $t is found that the mi6ture of #ases occupies a

olume a"out one thousand times that of the oil decomposed. rom

this ?#ure %e can assume ho% fast the #as "u""le around the arc %ill

#ro% in si=e. $f this #ro%in# #as "u""le around the arc is compressed

"' an' means then rate of de – ioni=ation process of ioni=ed #aseousmedia in "et%een the contacts %ill accelerate %hich rapidl' increase

the dielectric stren#th "et%een the contacts and conse&uentl' the arc

%ill "e &uenched at =ero crossin# of the current c'cle. This is the "asic

operation of oil circuit "rea,er. $n addition to that coolin# e8ect of

h'dro#en #as surround the arc path also helps! the &uic, arc

&uenchin# in oil circuit "rea,er.-D0 T'pes

1. Bul, Kil CB < %here oil is used as arc &uenchin# media as %ell as

insulatin# media "et%een current carr'in# contacts and earthed

parts of the "rea,er. The oil used here is same as transformerinsulatin# oil.

-D0hen the current carr'in# contacts in the oil are separated

an arc is esta"lished in "et%een the separated contacts. This arc

%ill produce rapidl' #ro%in# #as "u""le around the arc. s the

moin# contact moe a%a' from ?6ed contact the len#th of arc

is increased as a result the resistance of the arc increases. Theincreased resistance causes lo%erin# the temperature and hence

reducin# the formation of #asses surround the arc. The arc

&uenchin# in "ul, oil circuit "rea,er ta,es place %hen current

passes throu#h =ero crossin#. $f %e #o throu#h the arc &uenchin#

phenomenon more thorou#hl' %e %ill ?nd man' other factors

e8ects the arc &uenchin# in "ul, oil circuit "rea,er. s the #as

"u""le is enclosed "' the oil inside the totall' air ti#ht essel!

the oil surround it %ill appl' hi#h pressure on the "u""le! %hich

results hi#hl' compressed #as around the arc. s the pressure is

increased the de – ioni=ation of #as increases %hich helps the arc&uenchin#. The coolin# e8ect of h'dro#en #as also helps in arc

&uenchin# in oil circuit "rea,er. T'pes

Single Break < $n sin#le "rea, "ul, oil circuit "rea,er thereis one pair of current carr'in# contacts for each phase of

po%er circuit. The each pair of current carr'in# contacts in

this "ul, oil circuit "rea,er consists of one ?6ed contact and

one moin# contact. i6ed contact is stationar' contact and

moin# contact moes a%a' from ?6ed contact durin#

openin# of the circuit "rea,er. s the moin# contact is

"ein# moed a%a' from ?6ed contact the arc is produced


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in "et%een the contacts and it is e6tin#uished durin# =ero

crossin# of the fault current! due to the reasons as e6plain

in preious chapter. s the da's #o on further research

%or,s hae "een done to improe "etter arc control in

sin#le "rea, "ul, oil circuit "rea,er.

Double Break < Various improements in the desi#n of "ul,oil circuit "rea,er hae "een su##ested to satisfactor' and

safe arc interruption especiall' at currents "elo% the rated

ma6imum. Kne solution to this pro"lem is to use an

intermediate contact "et%een to% current carr'in#

contacts. The arc is here split into t%o parts in series. The

aim here is to e6tin#uish the second arc &uic,l' "' usin#

the #as pressure and oil momentum due to the ?rst arc. $n

dou"le "rea, "ul, oil circuit "rea,er! there are t%o ?6ed

contact and are "rid#ed "' one moin# contact. The

moin# contact is ?tted %ith driin# mechanism of the oilcircuit "rea,er "' means of an insulated rod. s the moin#

contact "rid#e moes do%n%ards the contact #aps are

created %ith ?6ed contacts at "oth end of the intermediate

moin# contact "rid#e. 2ence arcs are produced at "oth

contacts #ap.D. 7inimum Kil CB < places the interruptin# unit in insulatin#

cham"er at lie potential. The insulatin# oil is aaila"le onl' in

interruptin# cham"er. The feature of desi#nin# 7KCB is to

reduce re&uirement of oil. $n this t'pe of circuit "rea,er the arc

interruptin# deice is enclosed in a tan, of insulatin# material

%hich as a %hole is at lie potential of s'stem. This cham"er is

called arcin# cham"er or interruptin# pot. The #as pressure

deeloped in the arcin# cham"er depends upon the current to "e

interrupted. 2i#her the current to "e interrupted causes lar#er

the #as pressure deeloped inside the cham"er! hence "etter the

arc &uenchin#. But this put a limit on the desi#n of the arc

cham"er for mechanical stresses. ith use of "etter insulatin#

materials for the arcin# cham"ers such as #lass ?"er! reinforced

s'nthetic resin etc..! the minimum oil circuit "rea,er are a"le to

meet easil' the increased fault leels of the s'stem.

-D0

• )utdoor*+ndoor C'

• %pring*"neumati#*Hydrauli# C'

Protective Relays


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rela' is an electric deice that is desi#ned to interpret input

conditions in a prescri"ed manner and after speci?ed conditions are met! it is

to respond to cause a contact operation or similar a"rupt chan#e in its

associated electric control circuit.- protectie rela' in particular is one

%hose function is to detect defectie lines or apparatus or other po%er

s'stem conditions of an a"normal or dan#erous nature and to initiateappropriate control circuit action.

The plun#er t'pe oercurrent rela' %as ?rst introduced in 1;0*! in

1;G3 transformer protection rela' "ased on percenta#e current di8erential

method is introduced! phase comparison rela's %ere introduced later in 1;G

as %ell as static "us "ar protection rela's. B' 1;* *G0,V transmission lines

%ere deeloped "' E and in 1;; the %orld>s ?rst static phase comparison

rela' %as introduced. The deelopment of the transistor "ou#ht a"out t%o

,e' results in the ?eld of protectie rela'in# and protectie rela's < the

a"ilit' to inte#rate multiple and more comple6 protection functions for "oth

economic and s'stem protection reasons! and the unfortunate realit' of ho%

a ne% technolo#' must "e suria"le in the po%er s'stem. Earl' adopters of

static


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adOusta"le time/current 9or other operatin# parameter: operatin#

characteristics. rotection rela's ma' use arra's of induction dis,s! shaded<

pole! ma#nets! operatin# and restraint coils! solenoid


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• Lelatiel' more relia"le.

• Easil' con?#ure settin#s %ithout an' special pro#rammin# deice.

• Eas' to learn.

• Can isolate faulted section from the oerall s'stem.

Disadvantages• ear and tear causes (u6 lin,a#es to %ea,en in time.

• #in# causes chan#es to settin#s %hich causes misoperation and false

trippin#.

• Le&uires hi#h capacit' of its T and CT transformers.

• Le&uires periodical cali"ration and testin#.

• )o directional features.

• Speed of operation is limited "' mechanical aspects and

characteristics.

• Can perform onl' for a sin#le function.

Classifcations

rom Construction• Attra#ted Armature*Armature Type


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deried from a separate suppl'! not from the si#nal circuits. Static

rela's eliminated or reduced contact "ounce! and could proide fast

operation! lon# life and lo% maintenance.-DD

• Digital < 5i#ital protectie rela's %ere in their infanc' durin# the late

1;0s. n e6perimental di#ital protection s'stem %as tested in the la"

and in the ?eld in the earl' 1;*0s. nli,e the rela's mentioned a"oe!di#ital protectie rela's hae t%o main parts hard%are and soft%are.

The %orld>s ?rst commerciall' aaila"le di#ital protectie rela' %as

introduced to the po%er industr' in 1;4. $n spite of the deelopments

of comple6 al#orithms for implementin# protection functions the

microprocessor "ased


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$nstrument transformers are hi#h accurac' class electrical deices

used to isolate or transform olta#e or current leels. The most common

usa#e of instrument transformers is to operate instruments or meterin# from

hi#h olta#e or hi#h current circuits! safel' isolatin# secondar' control

circuitr' from the hi#h olta#es or currents. The primar' %indin# of the

transformer is connected to the hi#h olta#e or hi#h current circuit! and themeter or rela' is connected to the secondar' circuit. $nstrument transformers

ma' also "e used as an isolation transformer so that secondar' &uantities

ma' "e used in phase shiftin# %ithout a8ectin# other primar' connected

deices.-DCharacteristics, Operation, and Coordination Basic function of $nstrument transformers is to step do%n the .C.S'stem olta#e P current. The olta#e P current leel of po%er s'stem is

er' hi#h. $t is er' diMcult P costl' to desi#n the measurin# instruments for

measurement of such hi#h leel olta#e P current. Ienerall' measurin#

instruments are desi#ned for G P 110V. The measurement of such er'lar#e electrical &uantities can "e made possi"le "' usin# the $nstrument

transformers %ith these small ratin# measurin# instruments. Therefore these

instrument transformers are er' popular in modern po%er s'stem.-D

Advantages

• Sin#le ran#e ammeters and oltmeters can measure %ide ran#e of

currents and olta#es %hen used %ith CTs and Ts

• The measurin# instruments li,e ammeter! oltmeter and %attmeter are

incorporated in the secondar' circuit and hence the' are totall'

se#re#ated from the hi#h olta#e! there"' ensurin# safet' for theoperator and o"serer

• The meter need not "e insulated for hi#h olta#es %hich %ould "e the

case if the' are directl' included in a hi#h olta#e circuit.

• sin# current transformer %ith suita"le split and hin#ed core! it eas' to

measure hea' currents in the "us"ar %ithout hain# to "rea, the

conductor carr'in# current. The core of the Current Transformer 9CT: is

opened at the hin#e! the current carr'in# conductor is introduced in

the center of the core throu#h an openin# made and the core is ti#htl'

closed a#ain. The conductor itself acts as a sin#le turn primar' %indin#

of the CT.Disadvantages• Can onl' "e used for C s'stems.

• The instrument transformers cannot "e used for dc measurements. The

current transformer in operation sli#htl' di8ers from that po%er

transformer. $n case of current transformer as the load impedance or

U"urden> on the secondar' is er' small! so the current transformer

operates on short circuit conditions.ClassifcationsCurrent Transformers

Current transformers 9CT: are a series connected t'pe of instrument

transformer. The' are desi#ned to present ne#li#i"le load to the suppl' "ein#measured and hae an accurate current ratio and phase relationship to

ena"le accurate secondar' connected meterin#. Current transformers are

often constructed "' passin# a sin#le primar' turn 9either an insulated ca"le

or an uninsulated "us "ar: throu#h a %ell


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9i.e. G ammeter:. t'pical connection dia#ram of a current transformer is

sho%n in ?#ure "elo%.

rimar' of C.T. is hain# er' fe% turns. Sometimes "ar primar' is also

used. rimar' is connected in series %ith the po%er circuit. Therefore!

sometimes it also called series transformer. The secondar' is hain# lar#eno. of turns. Secondar' is connected directl' to an ammeter. s the ammeter

is hain# er' small resistance. 2ence! the secondar' of current transformer

operates almost in short circuited condition. Kne terminal of secondar' is

earthed to aoid the lar#e olta#e on secondar' %ith respect to earth. hich

in turns reduce the chances of insulation "rea,do%n and also protect the

operator a#ainst hi#h olta#e. 7ore eer "efore disconnectin# the ammeter!

secondar' is short circuited throu#h a s%itch US> as sho%n in ?#ure a"oe to

aoid the hi#h olta#e "uild up across the secondar'.-DPotential Transformers

Volta#e transformers 9VT:! also called potential transformers 9T:! are a

parallel connected t'pe of instrument transformer. The' are desi#ned topresent ne#li#i"le load to the suppl' "ein# measured and hae an accurate

olta#e ratio and phase relationship to ena"le accurate secondar' connected

meterin#.-D*

otential transformer is used to step do%n the olta#e of po%er s'stem

to a lo%er leel to ma,e is feasi"le to "e measured "' small ratin# oltmeter

i.e. 110 – 1D0 V oltmeter. t'pical connection dia#ram of a potential

transformer is sho%in# ?#ure "elo%.

rimar' of .T. is hain# lar#e no. of turns. rimar' is connected acrossthe line 9#enerall' "et%een on line P earth:. 2ence! sometimes it is also

called the parallel transformer. Secondar' of .T. is hain# fe% turns P

connected directl' to a oltmeter. s the oltmeter is hain# lar#e

resistance. 2ence the secondar' of a .T. operates almost in open circuited

condition. Kne terminal of secondar' of .T. is earthed to maintain the

secondar' olta#e %ith respect to earth. hich assures the safet' of

operators.-D

Reclosers and Sectionalizers

Leclosers are predominantl' located on the distri"ution feeder! thou#has the continuous and interruptin# current ratin#s increase! the' are seen in


22/25


su"stations! %here traditionall' a circuit "rea,er %ould "e located. Leclosers

hae t%o "asic functions on the distri"ution s'stem relia"ilit' and

oercurrent protection. Leclosers are fre&uentl' applied to increase

relia"ilit'! mainl' due to three of their "ene?ts reclosin# capa"ilit'! sin#le

phase reclosin#! and automated loop capa"ilities.-30

-3D

Sectionali=ers are an economical solution to sectionali=in# lar#e

outdoor net%or,s! and often used in locations %here coordination %ith other

deices is diMcult. Sectionali=ers are suita"le for use on outdoor medium

olta#e oerhead distri"ution net%or,s! in conOunction %ith automatic circuit

recloser protection.-D; The sectionali=er is a self


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dela' and one recloseF if the last attempt is not successful! the recloser %ill

loc, out and re&uire human interention to reset. $f the fault is a permanent

fault 9do%ned %ires! tree lim"s l'in# on the %ires! etc.: the autorecloser %ill

e6haust its pre


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-GBersano, 6. +., 7r. %&'


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ee 104 assignment.doc

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