Hvdc Transmission Ppt

7/26/2019 Hvdc Transmission Ppt

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HVDC TRANSMISSION



Text Books:

Direct current Transmission by EDARD I!SON

"IMBAR"#i$ey interscience% Ne& york%'()'*+

Hi,- Vo$ta,e D+C+.o&er Transmission system by

"+R+.ADI/AR IISc Ban,a$ore% Ne& A,e Internationa$.ub$is-ers !t0+



O1er1ie&:

2enera$ As3ects o4 DC transmission an0 com3arison o4

it &it- AC transmission+

Con1erter Circuits

Ana$ysis o4 t-e Bri0,e con1erter Contro$ o4 HVDC Con1erters an0 Systems+

.rotection+



.ART A #5nit ' 6 7*

2enera$ As3ects o4 DC Transmission an0 com3arison o4 it&it- AC Transmission

Historica$ Sketc-

Constitution o4 EHV AC an0 DC $inks+

!imitations an0 A01anta,es o4 AC an0 DC transmission+



Historica$ Sketc-:

E1o$ution o4 .o&er Systems:

!ate '8)9s Commercia$ use o4 e$ectricity+

In '887 ;irst E$ectric 3o&er system &-ic- inc$u0es 2enerator%

Cab$e%4use%!oa0 0esi,ne0 by T-omas E0ison at .ear$ Street station in

Ne& york+

It &as DC System #!o& Vo$ta,e ''9V*%un0er,roun0 cab$e is use0 to

0istribute t-e 3o&er to consumers+ On$y <( consumers are bene4ite0

by t-is $o& 1o$ta,e DC system+ Incan0escent $am3s are use0 as a $oa0+

In '88=Motors &ere 0e1e$o3e0 by ;rank S3ra,ue+ A4ter t-e in1ention

o4 motors e$ectricity is use0 more e44ecti1e$y or it &as a33reciate0+In '88> !imitation o4 DC

Hi,- $osses an0 Vo$ta,e Dro3

Trans4ormation o4 Vo$ta,e re?uire0+



Continues@

Trans4ormer an0 AC 0istribution #'<9 $am3s* 0e1e$o3e0 by i$$iamStan$ey o4 estin, -ouse+

In '88( ;irst AC transmission system in 5SA bet&een i$$amette

4a$$s an0 .ort$an0% Ore,on+ It &as '.-ase%="V%O1er 7' "m+

Be4ore t-at in t-e year o4 '888N+Tes$a 0e1e$o3e0 .o$y .-ase

system an0 -a0 3atents o4 2enerator%Motor%Trans4ormer%

transmission $ines+ !ater estin, House bou,-t it+

In '8(9Contro1ersy on &-et-er in0ustry s-ou$0 stan0ar0ie AC or

DC+

E0isonDC System estin, HouseAC System!ater because o4 4eatures o4 AC System% its 0ominate0

'+ Vo$ta,e increase is 3ossib$e

7+ Sim3$er an0 c-ea3er ,enerators an0 motors+



Continues…

In '8(;irst .-ase $ine %7+"V%'7 "m in Ca$i4ornia +

Im3ro1ement in 1o$ta,es year by year%

'(77'><"V

'(779"V

'(<78)"V

'(<9"V

'(><<99"V

'(>>)<"V

'(>()><"V

'((9''99"V



Continues@

Stan0ar0 1o$ta,es are ''<%'8%'>'%79"V 3re4erre0 4or Hi,-

Vo$ta,e #HV*$ines+

Remainin, =<%<99%)><"V are Extra Hi,- Vo$ta,e#EHV*

$ines+ ;or interconnection o4 AC systems% e nee0 4ixe0 4re?uency+

>9H5S an0 Cana0ian countries

<9HEuro3e an0 Asian countries



Entry o4 HVDC system:

HVDC transmission &as 0esi,ne0 by a ;renc- En,ineer%RENE TH5R/+ Simu$taneous$y AC system &as a$so

0e1e$o3e0 s$o&$y+

In bet&een '889'(''%at$east '' T-ury system &ere insta$$e0

in Euro3e+ T-e 3rominent &as Mouteirs to !yons#;rance* in'(9>+ It com3rises '89"m#=+< km un0er,roun0

cab$e*%=+M%<)+>"V%)<A+

Features :

DC series ,enerators &ere use0+

Constant contro$ current mo0e+



Continues@+

In'(79Trans1erter#Mec-anica$con1erter3o$y3-asetrans4ormer*&ere 0e1e$o3e0+ A,ain AC system 0ominate0+

In '(8A$$ t-e T-ury system &ere 0ismant$e0+ Because in

DC system% &e nee0 4re?uent maintenance % cost a$so is not

e44ecti1e+A,ain AC re1o$ution back ti$$ '(<9+ In t-e year o4 '(<9%

Mercury arc 1a$1es #Bu$ky con1erter* it &as 3ossib$e to

con1ert AC to DC+

In '(<=% 4irst HVDC System bet&een S&e0en an0 2ot$an0

is$an0 &as commissione0 by cab$e+ Con1ersion carrie0 out by

Mercury arc recti4ier+ A,ain 3eo3$e t-ink about DC

transmission because o4 t-e $imitation in AC system+



!imitations o4 HVAC

Reacti1e 3o&er $oss

Stabi$ity

Current carryin, ca3acity

Skin an0 ;erranti e44ect

.o&er 4$o& contro$ is not 3ossib$e+



A01anta,es o4 HVDC

No reacti1e 3o&er $oss

No Stabi$ity .rob$em

No C-ar,in, Current

No Skin 6 ;erranti E44ect

.o&er contro$ is 3ossib$e

Re?uires $ess s3ace com3are0 to ac 4or same 1o$ta,e

ratin, an0 sie+

2roun0 can be use0 as return con0uctor !ess corona $oss an0 Ra0io inter4erence



Continues@

C-ea3er 4or $on, 0istance transmission

Async-ronous o3eration 3ossib$e

No s&itc-in, transient

No transmission o4 s-ort circuit 3o&er

No com3ensation 3rob$em

!o& s-ort circuit current

;ast 4au$t c$earin, time



Disa01anta,es o4 HVDC

Cost o4 termina$ e?ui3ment is -i,-

Intro0uction o4 -armonics

B$ockin, o4 reacti1e 3o&er

.oint to 3oint transmission

!imite0 o1er$oa0 ca3acity

Hu,e reacti1e 3o&er re?uirement at t-e con1erter

termina$s+



Com3arison o4 AC an0 DC Transmission

T-e re$ati1e merits o4 t-e t&o mo0es o4 transmission#ACan0 DC* &-ic- nee0 to consi0ere0 by a system 3$anner are

base0 on t-e 4o$$o&in, 4actors:

Economics o4 Transmission

Tec-nica$ 3er4ormance

Re$iabi$ity

A maor 4eature o4 3o&er systems is t-e continuous

ex3ansion necessitate0 by increasin, 3o&er 0eman0 +

T-is im3$ies t-at t-e estab$is-ment o4 a 3articu$ar $ine

must be consi0er as a 3art o4 an o1era$$ $on, term system

3$annin,+



Economics o4 3o&er transmission:

T-e cost o4 transmission $ine inc$u0es t-e in1estment an0o3erationa$ costs+

In1estment cost inc$u0es%

Ri,-t o4 &ay

Transmission to&ers Con0uctors

Insu$ators

Termina$ e?ui3ment

O3erationa$ costs inc$u0es

It main$y 0ue to cost o4 $osses



Ri,-t o4 ay#Ro*:

An e$ectric transmission $ine ri,-to4&ay #RO* is astri3 o4 $an0 use0 by E$ectrica$ uti$ities to construct%

o3erate% maintain an0 re3air t-e transmission $ine

4aci$ities+

Ri,-ts o4 &ay may a$so inc$u0e t-e 3urc-ase o4 ri,-ts toremo1e 0an,er trees+ A 0an,er tree is a tree outsi0e t-e

ri,-t o4 &ay but &it- t-e 3otentia$ to 0o 0ama,e to

e?ui3ment &it-in t-e ri,-t o4 &ay+ I4 t-e 0an,er tree

4a$$s or is cut 0o&n% it cou$0 strike 3o$es% to&ers% &ires%$ines% a33$iances or ot-er e?ui3ment an0 0isru3t t-e 4$o&

o4 e$ectricity to our customers+



Ima,es 4or #Ro*



Continues@





Continues@

T-is Im3$ies t-at 4or a ,i1en 3o&er $e1e$% DC $inesre?uires $ess Ro% Sim3$er % an0 c-ea3er to&ers an0

re0uce0 con0uctors an0 insu$ator costs+

T-e 3o&er $osses are a$so re0uce0 &it- DC as t-ere are

on$y t&o con0uctors are use0+ No skin e44ect &it- DC is a$so bene4icia$ in re0ucin,

3o&er $oss mar,ina$$y+

T-e 0ie$ectric $osses in case o4 3o&er cab$es is a$so 1ery

$ess 4or DC transmission+T-e corona e44ects ten0s to $ess si,ni4icant on DC

con0uctors t-an 4or AC an0 t-is $ea0s to c-oice o4

economic sie o4 con0uctors &it- DC transmission+



Continues@

T-e ot-er 4actors t-at in4$uence t-e $ine cost are t-e costo4 com3ensation an0 termina$ e?ui3ment+

In 0c $ines 0o not re?uire com3ensation but t-e termina$

e?ui3ment costs are increase0 0ue to t-e 3resence o4

con1erters an0 4i$ters+



Variation o4 cost &it- $ine $en,t-:



Descri3tion:

AC ten0s to be more economica$ t-an DC 4or 0istances$ess t-an Break e1en 0istance an0 cost$ier 4or $on,er

0istances+

T-e breake1en 0istances can 1ary 4rom <99"m to

899"m in o1er-ea0 $ines+



Tec-nica$ 3er4ormance

T-e DC transmission -as some 3ositi1e 4eatures &-ic-are $ackin, in AC transmission+ T-ese are main$y 0ue to

t-e 4ast contro$$abi$ity o4 3o&er in DC $ines t-rou,-

con1erter contro$+

Advantages:Full control over power transmitted.

The ability to enhance transient and dynamic

stability in associated AC networks.

Fast control to limit fault currents in DC lines.

This makes it feasible to avoid DC breakers in two

terminal DC links.



Continues@

STA!"!T# "!$!TS:

T-e 3o&er trans4er in AC $ines is 0e3en0ent on t-e an,$e

0i44erence bet&een 1o$ta,e 3-asors at t-e t&o en0s+ ;or a

,i1en 3o&er $e1e$% t-is an,$e increases &it- 0istance+

T-e maximum 3o&er trans4er is $imite0 by t-e

consi0erations o4 stea0y state an0 transient stabi$ity+ T-e

3o&er carryin, ca3abi$ity o4 an AC $ine as a 4unction o4

0istance+

But in DC $ines &-ic- is una44ecte0 by t-e 0istance o4transmission+



.o&er trans4er ca3abi$ity Vs+ Distance



Continues@

%&"TA'( C&)T*&"

T-e 1o$ta,e contro$ in AC $ines is com3$icate0 by $ine

c-ar,in, an0 in0ucti1e 1o$ta,e 0ro3s+

T-e 1o$ta,e 3ro4i$e in a AC $ine re$ati1e$y 4$at on$y 4or

4ixe0 $e1e$ o4 3o&er trans4er corres3on0in, to sur,eim3e0ance $oa0in, #SI!* or norma$ $oa0in,+

T-e Vo$ta,e 3ro4i$e 1aries &it- t-e $ine $oa0in,+ ;or

constant 1o$ta,e at t-e $ine termina$% t-e mi0 3oint 1o$ta,e

is re0uce0 4or $ine $oa0in, -i,-er t-an SI! an0 increase04or $oa0in,s $ess t-an SI!+



Variation o4 Vo$ta,e a$on, t-e $ine:



Continues@

"ine compensation:AC $ines re?uire s-unt an0 series com3ensation in $on,

0istance transmission% main$y to o1ercome o4 t-e $ine

c-ar,in, an0 stabi$ity $imitations+

Series ca3acitors an0 s-unt in0uctors are use0 4or t-is

3ur3ose+

T-e increase in 3o&er trans4er an0 1o$ta,e contro$ is

3ossib$e t-rou,- t-e Static Var Systems #SVS*+

In AC cab$e transmission% it is necessary to 3ro1i0e s-unt

com3ensation at re,u$ar inter1a$s+



A &-o$e 3icture o4 ;ACTS 0e1ices 4ami$y:



Continues@

+*&"($S &F AC !)T(*C&))(CT!&):-en t&o 3o&er systems are connecte0 t-rou,- AC

ties#Sync-ronous interconnection*%t-e automatic ,eneration

contro$ o4 bot- systems -a1e to be coor0inate0 usin, tie $ine

3o&er an0 4re?uency si,na$s+

E1en &it- coor0inate0 contro$ o4 interconnecte0 systems% t-e

o3eration o4 AC ties can be 3rob$ematic 0ue to

a* T-e 3resence o4 $ar,e 3o&er osci$$ations &-ic- can $ea0 to

4re?uent tri33in,+

b* Increase in 4au$t $e1e$

c* Transmission o4 0isturbances 4rom one system to t-e ot-er



Continues@

T-e contro$$abi$ity o4 3o&er 4$o& in DC $ines e$iminatesa$$ t-e abo1e 3rob$em+ In a00ition% 4or async-ronous DC

ties% t-ere is no nee0 o4 coor0inate0 contro$+

It is ob1ious t-at t&o systems &-ic- -a1e 0i44erent

nomina$ 4re?uencies cannot be interconnecte0 0irect$y&it- AC ties an0 re?uire t-e use o4 DC $inks+



Continues@

'*&,)D !$+(DA)C(:

In AC transmission% t-e existence o4 ,roun0#ero

se?uence*current cannot be 3ermitte0 in stea0ystate 0ue to

-i,- ma,nitu0es o4 ,roun0 im3e0ance &-ic- &i$$ not on$y

a44ect e44icient 3o&er trans4er% but a$so resu$t in te$e3-oneinter4erence+

But ,roun0 im3e0ance ne,$i,ib$e 4or DC currents an0 a DC

$ink can o3erate one con0uctor &it- ,roun0

return# Mono3o$ar o3eration*+ T-e ,roun0 return is

obectionab$e on$y &-en burie0 meta$$ic structures #Suc- as

3i3es* are 3resent an0 are subect to corrosion &it- DC

current 4$o&+



Re$iabi$ity:

T-e re$iabi$ity o4 DC transmission is ?uite ,oo0 an0com3arab$e to t-at AC systems+

An ex-austi1e recor0 o4 existin, HVDC $inks in t-e

&or$0 is a1ai$ab$e 4rom &-ic- t-e re$iabi$ity statistics

cab be com3ute0+ It must be remembere0 t-at t-e 3er4ormance o4

T-yristor 1a$1es is muc- more re$iab$e t-an mercury arc

1a$1es an0 4urt-er 0e1e$o3ments in 0e1ices% contro$%

3rotection is $ike$y to im3ro1e t-e re$iabi$ity $e1e$+



Continues@

T-ere are t&o measures o4 o1era$$ system re$iabi$ity

a* Ener,y a1ai$abi$ity

b* Transient re$iabi$ity



Ener,y a1ai$abi$ity:

E?ui1a$ent outa,e time is t-e 3ro0uct o4 t-e

actua$ outa,e time an0 t-e 4raction o4 system

ca3acity $ost 0ue to outa,e+



Transient re$iabi$ity:

T-is is t-e 4actor s3eci4yin, t-e 3er4ormance o4 HVDC systems

0urin, recor0ab$e 4au$ts on t-e associate0 AC systems+

Recor0ab$e AC system 4au$ts are t-ose 4au$ts &-ic- cause one ormore AC bus 3-ase 1o$ta,es to 0ro3 be$o& (9 o4 t-e 1o$ta,e 3rior

to t-e 4au$t+

It is assume0 t-at t-e s-ort circuit $e1e$ a4ter t-e 4au$t is not be$o&

t-e minimum s3eci4ie0 4or satis4actory con1erter o3eration+

oth energy availability and transient reliability of e-isting

DC systems with thyristors valves is /0 or more.



HVDC outa,e statistics:

T-e a1era,e 4ai$ure rate o4 t-yristors in a 1a$1e is $ess t-an 9+>

3er o3eratin, year+ T-e maintenance o4 t-yristor 1a$1es is a$so

muc- sim3$er t-an t-e ear$ier mercury arc 1a$1es+



Ty3es o4 HVDC $inks:

Mono3o$ar $ink Bi3o$ar $ink

Homo3o$ar $ink



Mono3o$ar $ink:

Ha1in, one con0uctor #Ve .o$arity* an0 ,roun0 is use0 as return

3at-+

e can o3erate0 eit-er in FVe or GVe 3o$arity%but usua$$y

3re4erre0 Ve 3o$arity in or0er to re0uce t-e Corona e44ect+

T-e maor 0ra&back in t-is system is 3o&er 4$o& is interru3te0

0ue to eit-er con1erter 4ai$ure or DC $ink+

T-e ,roun0 return is obectionab$e on$y &-en burie0 meta$$ic

structures #Suc- as 3i3es* are 3resent an0 are subect to

corrosion &it- DC current 4$o&+



Bi3o$ar $ink:

T-ere are t&o con0uctors % one is o3erates at 3ositi1e an0 ot-er is

ne,ati1e+ Durin, 4au$t in one 3o$e it &i$$ o3erate as mono3o$ar

$ink+ T-is is 1ery 3o3u$ar $ink in HVDC



Homo3o$ar $ink:

In t-is $ink% t&o or more con0uctors -a1e same 3o$arity+

Norma$$y ne,ati1e 3o$arity are use0#to $ess corona $oss an0 ra0iointer4erence*+

2roun0 is a$&ays use0 as return 3at-+

Durin, 4au$t in one 3o$e it &orks as mono3o$ar+



A33$ication o4 HVDC:

T-e main areas o4 a33$ication base0 on t-e economics an0tec-nica$ 3er4ormances% are

!on, 0istance bu$k 3o&er transmission+

T-e un0er,roun0 o4 submarine cab$es+

Async-ronous connection o4 AC system &it- 0i44erent4re?uencies+

Contro$ an0 stabi$ie t-e 3o&er system &it- 3o&er 4$o&

contro$+

Base0 on t-e interconnection% t-ree ty3es o4 HVDC is 3ossib$e+ Bu$k .o&er transmission

Back to back connection

Mo0u$ation o4 AC system



.ur3ose o4 HVDC base0 on interconnection:

ulk power transmission#Trans4er t-e 3o&er 4rom one en0 to anot-er en0 &it-out

ta33in, 3o&er in bet&een*+;or t-is DC system is t-e best

o3tion+ #Or* HVDC transmission &-ere bu$k 3o&er is

transmitte0 4rom one 3oint to anot-er 3oint o1er $on, 0istance+

+ower flow control 1ack to ack 2%DC3

I4 t&o re,ions are 1ery nearby% &e can monitor t-e 3o&er

4$o& 4rom one re,ion to anot-er to contro$% emer,ency su33ort

as 3er our re?uirement+#Or*Back to Back $ink &-ere

recti4ication an0 in1ersion is carrie0 out in t-e same con1erterstation &it- 1ery sma$$ or no DC $ines



Continues@

To provide stability to AC systemT-is is basica$$y use0 to contro$ t-e 3o&er an0 stabi$ie t-e

system+ It is a$so use0 to connect t&o 0i44erent 4re?uencies

system+

#Mo0u$ation o4 AC* AC system is connecte0 3ara$$e$ &it- DCsystem+#or*.ara$$e$ connection o4 AC an0 DC $inks+ -ere bot-

AC an0 DC run 3ara$$e$+ It is main$y use0 to mo0u$ate t-e

3o&er o4 AC $ines+

2%DC is the better option for above cited purposes while

compare with its AC system.



Principle parts of HVDCTransmission:



Various .arts o4 HVDC transmission:

Con1ertersCon1erter trans4ormers

Smoot-in, reactors

Harmonic 4i$tersO1er-ea0 $ines

Reacti1e 3o&er source

Eart- e$ectro0es



CONVERTERS

Con1erters are t-e main 3art o4 HVDC system+ Eac- HVDC $ines -as at$east t&o con1erters% one at eac- en0+

Sen0in, en0 con1erter &orks as Recti4ier #It con1erts AC

3o&er to DC 3o&er*+ Ho&e1er con1erter as recei1in, en0

&orks as In1erter # it con1erts DC 3o&er to AC 3o&er*+ In case 4or re1ersa$ o4 o3eration% Recti4ier can be use0 as

in1erter or 1ice 1ersa+ So ,enera$$y it is ca$$ it as

CONVERTERS+

Se1era$ t-yristors are connector in series an0or in 3ara$$e$ to

4orm a 1a$1e to ac-ie1e -i,-er 1o$ta,e current ratin,s+

Note Va$1es #Combinations o4 se1era$ t-yristors* +



Various T-yristor Ratin,s:



Continues@How to achieve required voltage and

current ratings?T-e current ratin, o4 con1erter stations can be increase0 by

3uttin,

Va$1es in 3ara$$e$

T-yristors in 3ara$$e$ Bri0,es in 3ara$$e$

Some combinations o4 abo1e+

T-e 1o$ta,e ratin,s o4 con1erter stations can be increase0 by

3uttin, Va$1es in series

Bri0,es in series

Combination o4 abo1e+

Bri0,e con1erters are norma$$y use0 in HVDC systems+



Main re?uirement o4 t-e Va$1es are:

To a$$o& current 4$o& &it- $o& 1o$ta,e 0ro3 across it0urin, t-e con0uction 3-ase an0 to o44er -i,- resistance

4or non con0uctin, 3-ase+

To &it-stan0 -i,- 3eak in1erse 1o$ta,e 0urin, non

con0uctin, 3-ase+To a$$o& reasonab$y s-ort commutation an,$e 0urin,

in1erter o3eration+

Smoot- contro$ o4 con0uctin, an0 non con0uctin,

3-ases+



Continues@

T&o 1ersions o4 s&itc-in, con1erters are 4easib$e0e3en0in, on &-et-er DC stora,e 0e1ice uti$ie0 is+

An in0uctorCurrent source con1erter

A Ca3acitorVo$ta,e source con1erter+

CSC is 3re4erab$e 4or HVDC system

VSC is 3re4erab$e 4or ;ACTS $ike STATCOM%SVC%etc

Comparison of CSC and



Comparison of CSC andVSC:

CSC VSCInductor is used in DC side Capacitor is used in DC side

Constant current Constant voltage

Higher losses More ecient

Fast accurate control Slow control

arger and more e!pensive Smaller and less e!pensive

More fault tolerant and morerelia"le

ess fault tolerant and lessrelia"le

Simpler control Comple! control

#asil$ e!panda"le for in series #asil$ e!panded in parallel forincreased rating

C%&V#'(#'



C%&V#'(#' (')&SF%'M#'S:;or six 3u$se con1erter% a con1entiona$ t-ree 3-ase or

t-ree sin,$e 3-ase trans4ormer is use0+

Ho&e1er 4or '7 3u$se con4i,uration% 4o$$o&in,

trans4ormer are use0+

Six sin,$e 3-ase t&o &in0in,s T-ree sin,$e 3-ase t-ree &in0in,s

T&o t-ree 3-ase t&o &in0in,s

In con1erter trans4ormer it is not 3ossib$e to use &in0in,

c$ose to yoke since 3otentia$ o4 its &in0in, connection is

0etermine0 by con0uctin, 1a$1es+

Here entire &in0in, are com3$ete$y insu$ate0+



Continues@

As $eaka,e 4$ux o4 a con1erter trans4ormer contains 1ery -i,--armonic contents% it 3ro0uces ,reater e00y current $oss an0

-ot s3ot in t-e trans4ormer tank+

In case o4 '7.u$se con4i,uration% i4 t&o t-ree 3-ase

trans4ormers are use0% one &i$$ -a1e starstar connection% an0

anot-er &i$$ -a1e star 0e$ta connection to ,i1e 3-ase s-i4t o4

9J+

Since 4au$t current 0ue to 4au$t across 1a$1e is 3re0ominant$y

contro$$e0 by trans4ormer im3e0ance% t-e $eaka,e im3e0ance

o4 con1erter trans4ormer is -i,-er t-an t-e con1entiona$trans4ormer+

On$ine ta3 c-an,in, is use0 to contro$ t-e 1o$ta,e an0

reacti1e 3o&er 0eman0+



SMOOTHIN2 REACTORS:

As its name% t-ese reactors are use0 4or smoot-in, t-e0irect current out3ut in t-e DC $ine+

It a$so $imits t-e rate o4 rise o4 t-e 4au$t current in t-e

case o4 DC $ine s-ort circuit+

Norma$$y .artia$ or tota$ air core0 ma,netica$$y s-ie$0e0reactor are use0+

Disc coi$ ty3e &in0in,s are use0 an0 brace0 to

&it-stan0 t-e s-ort circuit current+

T-e saturation in0uctance s-ou$0 not be too $o&+



Harmonic 4i$ters

Harmonics ,enerate0 by con1erters are o4 t-e or0er o4 n3K'in ACsi0e an0 n3 is t-e DC si0e+ -ere 3 is number o4 3u$ses an0 n is

inte,er+

;i$ter are use0 to 3ro1i0e $o& im3e0ance 3at- to t-e ,roun0 4or t-e

-armonics current+

T-ey are connecte0 to t-e con1erter termina$s so t-at -armonicss-ou$0 not enter to AC system+

Ho&e1er% it is not 3ossib$e to 3rotect a$$ -armonics 4rom enterin,

into AC system+

Ma,nitu0es o4 some -armonics are -i,- an0 4i$ters are use0 4or

t-em on$y+

T-ese 4i$ters are use0 to 3ro1i0e some reacti1e 3o&er com3ensation

at t-e termina$s+



O1er-ea0 $ines:

As mono3o$ar transmission sc-eme is most economica$ an0 t-e 4irstconsi0eration is to use ,roun0 as return 3at- 4or DC current+

But use o4 ,roun0 as con0uctor is not 3ermitte0 4or $on,er use an0 a

bi3o$ar arran,ement is use0 &it- e?ua$ an0 o33osite current in bot-

3o$es+

In case o4 4ai$ure in any 3o$es% ,roun0 is use0 as a return 3at-tem3orari$y+

T-e basic 3rinci3$e o4 0esi,n o4 DC o1er-ea0 $ines is a$most same

as AC $ines 0esi,n suc- as con4i,urations%to&ers%insu$ators etc+

T-e number o4 insu$ators an0 c$earances are 0etermine0 base0 on

DC 1o$ta,e+

T-e c-oice o4 con0uctors 0e3en0s main$y on corona an0 4ie$0 e44ect

consi0erations+



Reacti1e 3o&er source

As suc- con1erter 0oes not consume reacti1e 3o&er but 0ueto 3-ase 0is3$acement o4 current 0ra&n by con1erter an0 t-e

1o$ta,e in AC system% reacti1e 3o&er re?uirement at t-e

con1erter station is about <9>9 o4 rea$ 3o&er trans4er%

&-ic- is su33$ie0 by 4i$ters%ca3acitors%an0 sync-ronous

con0ensers+ Sync-ronous con0ensers are not on$y su33$yin, reacti1e

3o&er but a$so 3ro1i0e AC 1o$ta,es 4or natura$ commutation

o4 t-e in1erter+

Due to -armonics an0 transient% s3ecia$ 0esi,ne0 mac-ines isuse0+



Eart- e$ectro0es:

T-e eart- resisti1ity o4 at u33er $ayer is -i,-er #L=999 o-mm* an0e$ectro0es cannot be ke3t 0irect$y on t-e eart- sur4ace+

T-e e$ectro0e are burie0 into t-e eart- &-ere t-e resisti1ity is

aroun0 #'9 o-mm* to re0uce transient o1er 1o$ta,es 0urin, $ine

4au$ts an0 ,i1es $o& DC e$ectric 3otentia$ an0 3otentia$ ,ra0ient at

t-e sur4ace o4 t-e eart-+ T-e $ocation o4 eart- e$ectro0e is a$so im3ortant 0ue to

.ossib$e inter4erence o4 DC current ri33$e to 3o&er $ines%

communication systems o4 te$e3-one an0 rai$&ay si,na$s%etc+

Meta$$ic corrosion o4 3i3es% cab$e s-eat-s %etc+

.ub$ic sa4ety+

T-e e$ectro0e must -a1e $o& resistance #!ess t-an 9+' o-m* an0

burie0 u3to <99 meters into t-e eart-+



Constitution o4 EHV AC an0 DC $inks:

EHV transmission $inks% su3er3ose0 on a $o&er 1o$ta,e ACnet&orks% or interconnectin, t&o suc- net&orks% or

connectin, 0istant ,eneratin, 3$ants to an ac system% are

com3are0 as to t-eir 3rinci3$e com3onents an0 arran,ements

t-ereo4% accor0in, to &-et-er t-e $ine o3erates on AC or DC+

Be$o& sin,$e $ine 0ia,ram% is sin,$e circuit t-ree 3-ase AC

$ine+ In suc- system re?uires trans4ormer at bot- en0sste3 u3

trans4ormers at t-e sen0in, en0 an0 ste3 0o&n trans4ormer at

t-e recei1in, en0+

Most $on, o1er-ea0 AC $ines re?uire series com3ensation o4 3art o4 t-e in0ucti1e reactance+#one bank o4 series ca3acitor*



Continues…

T-e t-ree 3-ase AC $ines cannot be o3erate0% exce3t 4or a 1erys-ort time#$ess t-an ' sec* &it- one or more con0uctors are o3en%

because suc- o3eration causes unba$ance0 1o$ta,es in t-e AC

system an0 inter4erence in 3-one te$e3-one $ines+

T-ere4ore t-ree3o$e s&itc-in, is a$&ays use0 to c$ear t-e

3ermanent 4au$ts% a$t-ou,- suc- 4au$t may in1o$1e in any onecon0uctor+ T-is bein, so% t&o 3ara$$e$ t-ree 3-ase circuits re?uire0

4or re$iab$e transmission+



Continues…

T-e $ine itse$4 usua$$y -as t&o con0uctors% a$t-ou,- some$ines -a1e on$y one% t-e return 3at- bein, in t-e eart- or sea

&ater or bot-+

At bot- en0 o4 t-e $ines are con1erters% t-e com3onents o4

&-ic- are trans4ormers an0 ,rou3 o4 mercury arc 1a$1es+

T-e con1erter at t-e sen0in, en0 Recti4ier+

T-e con1erter at t-e recei1in, en0In1erter+

Eit-er con1erter can 4unction as recti4ier or in1erter%

3ermittin, 3o&er to be transmitte0 in eit-er 0irection+ O4

course it is 3re4erre0 4or AC $ine% a$so -as t-is re1ersibi$ity+ T-e circuit breaker are insta$$e0 on$y on t-e AC si0e o4 t-e

con1erters+ T-ese breakers are not use0 4or c$earin, 4au$ts on

t-e 0c $ine or miso3erations o4 t-e 1a$1es% 4or t-ese 4au$ts



Continues…

Can be c$eare0 more ra3i0$y by ,ri0 contro$ o4 t-e 1a$1es+Ho&e1er breaker is a$so re?uire0 4or c$earin, t-e 4au$ts in

trans4ormers or takin, t-e &-o$e DC $ink out o4 ser1ice+

Harmonic 4i$ters an0 s-unt ca3acitors 4or su33$yin, reacti1e

3o&er to t-e con1erters are connecte0 to AC si0es o4 t-e

con1erter+

!ar,e in0uctance ca$$e0 0c smoot-in, reactors are connecte0

in series &it- eac- 3o$e o4 t-e DC $ine+



Continues…

I4 -i,-er re$iabi$ity is re?uire0 o4 a DC $ine t-an t-at 3ro1i0e0

by t&o con0uctors% t-ree or 4our con0uctors may be 3ro1i0e0+

Here one 3o$e o4 4our con0uctor $ine is s-o&n &it- t&o

con1erters 3er termina$+

T-e bustie s&itc-es ' are norma$$y o3en+ I4 a 3ermanent

4au$t occurre0 on t-e $o&er con0uctor% t-e con1erters

connecte0 to it &ou$0 be contro$$e0 so as to brin, t-e 1o$ta,e

an0 current on it to ero+ T-en s&itc-es &ou$0 be o3ene0%

iso$atin, t-e 4au$te0 $ine+



Continues…

Next t-e con1erter 1o$ta,es &ou$0 be raise0 to e?ua$ity &it-t-ose o4 t-e res3ecti1e a0acent con1erters% a4ter &-ic-

s&itc- ' &ou$0 be c$ose0+

T-e ca3abi$ity o4 a$$ con1erter &ou$0 be usab$e% an0 t-e

3o&er norma$$y carrie0 by t&o con0uctors &ou$0 t-en be

carrie0 by one+



























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Hvdc Transmission Ppt