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G ado Ingenie ía en Tecnologías Indus iales
Technical-economic analysis o
Gas Insula ed Lines
MEMORIA TFG
Au o : Juan Ramón Llo ca O olá
Di ec o : O iol Gomis
Codi ec o : Ma c Cheah
Con oca o ia: Julio 2018
2
Abs ac
The inc easing elec ic demand shows he need o a g id ein o cemen which is going o be
accomplished in he ollowing yea s. These new lines will ha e o be designed ocusing on
e iciency and sus ainabili y in o de o imp o e he pe o mance o he powe g id. These new
pa ame e s gi e us he oppo uni y o alk abou Gas Insula ed Lines (GIL) due o i s low
ansmission losses, and high ansmission capaci y [1].
This p ojec p esen s a echnical-economic analysis o GIL, o app oxima e he o al cos o a
GIL in as uc u e wi h i s singula echnical a angemen s, bo h ini ial in es men cos s and long
e m cos s due o he ope a ion. To accomplish i all cos componen s ha e been app oached as
unc ion o nominal alues o a GIL p ojec ; o his eason a s udy has been done o each single
cos componen o ela e he echnical solu ion wi h cos s.
A numbe o pa ame e s (such as geome ic measu es, mass o insula o gas, conduc o
esis ance, capaci ance o induc ance) o he ins alla ion ha e been ob ained by s a is ic
eg essions based on da a om a ailable sou ces. These pa ame e s ha e been needed o come
up wi h he ins alla ion p ice.
In addi ion a case s udy is p esen ed, whe e di e en echnologies a e compa ed in e ms o
cos . The objec i e is o show di e ences in he p ice o each componen be ween he di e en
echnology a angemen s o he gi en case. I can be seen ha he e a e signi ican di e ences
be ween echnologies in he ini ial in e sion cos and he li e-long ope a ion cos .
Wi h he case s udy which is e e ed o a egula ins alla ion, can be seen which is he cheapes
elec ic solu ion and which is he highe cos e icien echnology, which leads o a low p ice
in es men and ope a ing expenses.
3
Gas Insula ed Lines. Technical-economic analysis
Con en
Abs ac ......................................................................................................................................... 2
Lis o ac onyms ............................................................................................................................ 5
1. In oduc ion .......................................................................................................................... 6
1.1 Fu u e powe supply sys em ......................................................................................... 6
1.2 O e head lines, Unde g ound Cables and Gas Insula ed Lines (GIL) ............................ 7
1.2.1 O e head lines.............................................................................................................. 7
1.2.2 Unde g ound cables .............................................................................................. 8
1.2.3 GIL .......................................................................................................................... 8
1.3 In e es o Gas Insula ed Lines .................................................................................... 10
1.4 Objec i es .................................................................................................................... 11
2. GIL echnical backg ound and pa desc ip ion .................................................................. 13
2.1 Desc ip ion o GIL echnology componen s ................................................................ 13
2.1.1 Insula ion Gas ...................................................................................................... 13
2.1.2 Conduc o and enclosu e se -up ......................................................................... 14
2.2 GIL laying op ions ........................................................................................................ 17
2.2.1 Abo e-g ound ins alla ion ................................................................................... 18
2.2.2 T ench-laid........................................................................................................... 19
2.2.3 Tunnel-laid ........................................................................................................... 19
2.2.4 Di ec ly bu ied ..................................................................................................... 21
3. Cos modelling ..................................................................................................................... 23
3.1 Tool desc ip ion ........................................................................................................... 24
3.2 GIL a iables and modelling ........................................................................................ 24
3.3 Cos dependency on ansmission capaci y and ou ing ............................................ 26
3.3.1 Ou e enclosu e cos dependency ...................................................................... 26
3.3.2 Conduc o cos dependency ............................................................................... 29
3.3.3 Disconnec ing, compensa o uni s and male and emale sliding cos
dependency ......................................................................................................................... 31
3.4 Cos dependency on laying me hods .......................................................................... 32
3.4.1 Di ec ly bu ied laying cos s ................................................................................. 33
3.4.2 T ench laying cos s .............................................................................................. 35
3.4.3 Tunnel laying cos s .............................................................................................. 37
3.4.4 Abo e g ound ins alla ions ................................................................................. 42
3.5 Cos dependency on Gas quan i y .............................................................................. 43
3.5.1 𝐒𝐒𝐒𝐒𝐒𝐒 + 𝐍𝐍𝐍𝐍 ............................................................................................................. 43
3.5.2 𝐂𝐂𝐒𝐒𝐂𝐂𝐂𝐂 ................................................................................................................... 45
4
3.6 Assembly, es ing and anspo cos .......................................................................... 46
3.7 Li e-long cos s .............................................................................................................. 47
3.7.1 Powe losses and powe ansmission capaci y educ ion due o eac i e powe
cos calcula ion .................................................................................................................... 47
3.7.2 Ope a ion and main enance cos ........................................................................ 58
3.8 Dis ance non-dependen cos s. .................................................................................. 59
3.8.1 GIS (GIL e mina ions) ......................................................................................... 59
3.9 P ojec launch and build con ingency ......................................................................... 60
4 Case s udy ........................................................................................................................... 61
4.1 GIL cos s udy and sensi i i y ............................................................................................ 62
4.1.1 Cos s udy o GIL .................................................................................................. 64
4.1.2 Sensi i i y s udy o GIL ........................................................................................ 67
4.2 O e head lines ............................................................................................................ 70
4.2.1 Ini ial in es men cos s. Fixed cos s .................................................................... 70
4.2.2 Va iable cos s ...................................................................................................... 71
4.3 Unde g ound lines ....................................................................................................... 76
4.3.1 Ini ial in es men cos ......................................................................................... 77
4.3.2 Va iable cos s ...................................................................................................... 78
4.4 Case s udy esul s discussion ............................................................................................ 80
5. Conclusion ........................................................................................................................... 83
Re e ences ................................................................................................................................... 84
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Gas Insula ed Lines. Technical-economic analysis
Lis o ac onyms
OHL O e head Lines
GIL Gas Insula ed Lines
GIS Gas Insula ed Swi che
HVAC High Vol age Al e na ing Cu en
HVDC High Vol age Di ec Cu en
UHV Ul a High Vol age
PTC Powe T ansmission Cos
AC Al e na ing Cu en
DC Di ec Cu en
XLPE C oss-linked polye hylene

6
1. In oduc ion
1.1 Fu u e powe supply sys em
Nowadays he en i e wo ld is claiming o a solu ion o he pollu ion p oblems ye isible in many
di e en plane ca as ophes. These wo ies ha e been come h ough in he 2015 Uni ed
Na ions Clima e Change Con e ence, held in Pa is 2015. Howe e he powe consump ion is
inc easing, wha will ha e as a consequence he sea ch o new ene gy sou ces.
To accomplish EU’s a ge o 20% sha e o ene gy om enewable ene gies [2], some changes
mus be in oduced in he powe gene a ion sys em. I means, enewable ene gy sou ces a e
undoub edly going o be he u u e in he elec ic powe ma ke . No mally hese sou ces end
o be a away om he p incipal load cen es and need o be connec ed wi h long and wide
elec ic ne s. This ac o and he inc easing elec ic demand lead o hink abou an op imized
in e na ional long-dis ance high-powe ansmission ne wo k.
Nowadays in he Eu opean Union he e a e weak in e na ional connec ions, which a e wo king
in case o powe misma ch be ween p oduc ion and demand. In o de o ein o ce he
pe cen age o enewable elec ic consump ion, a la ge scale ul a-high ol age (UHV) o
Al e na ing Cu en (AC) o Di ec Cu en (DC) sys em mus be inse ed. This long ansmission
sys em is mo i a ed by he need o aking p o i o enewable ene gy independen ly whe e i is
p oduced. As an example, g ea enewable ene gy sou ces a e loca ed in he no he n seas in
Eu ope o wind powe p oduc ion.
Reliable c oss bo de connec ions a e needed o boos no only he in eg a ion o enewable
ene gies, bu also o ensu e secu i y in ene gy supply. Fo hese easons coun ies in Eu opean
Union mus ha e by 2020 a leas a 10% o o al powe capaci y in e connec ion wi h o he
coun ies [3].
In conclusion, High Vol age Al e na ing Cu en (HVAC) long-dis ance ansmission sys ems a e
needed o ensu e secu i y and eliabili y in he u u e in e na ional g id. Besides i is aking g ea
impo ance he concep o ne e iciency which b ings us o he s udy o Gas Insula e Lines (GIL)
because o i s low ansmission losses and low capaci i e and induc i e compensa ion needs [4].
7
Gas Insula ed Lines. Technical-economic analysis
1.2 O e head lines, Unde g ound Cables and Gas Insula ed Lines (GIL)
An in oduc ion o O e head Lines (OHL) and Unde g ound Cables and GIL is done in o de o
compa e OHL and Unde g ound Cables wi h GIL in e ms o o al cos s in a case s udy done in
chap e 4.
1.2.1 O e head lines
Nowadays OHL is he mos commonly used sys em o UHV AC connec ions be ween powe
s a ions and big consume s; o da e, hey a e he mos cos -e ec i e me hod o HVAC
ansmission [5]. An OHL ou e consis s o conduc o s in o m o cables hanging om owe s.
The ou e design is a balance be ween he size and dis ance o he s uc u e owe s [5]. Also his
decision is aken in o accoun wi h he conside a ions o o he aspec s as isual and
en i onmen al impac . In Spain he OHL ansmission g id (UHV ne wo k) wo ks be ween 220
and 400 kV and has a o al dis ance o mo e han 40.000 km.
In Figu e 1 an OHL owe is shown. The main cha ac e is ics o he ins alla ion shown in his
pic u e a e: i has go wo ci cui s wi h h ee- ou conduc o s pe phase; conduc o s o he same
ci cui and he same phase o m a beam; conduc o s o di e en phases a e sepa a ed a
s ipula ed dis ances o a oid elec ic haza d; conduc o s o ming a beam a e sepa a ed be ween
hem wi h insula o s, as well as conduc o s wi h he owe .
In Figu e 1 is shown a ypical OHL owe , i is he same one as used in he case s udy.
Figu e 1. OHL owe . (Da a sou ce: [6])
8
1.2.2 Unde g ound cables
Unde g ound cables a e used ac oss he wo ld along wi h OHLs. The main eason o using his
sys em is o OHL space and en i onmen al es ic ions, o example en i onmen al p o ec ed
a eas o high densi y popula ed a eas.
Unlike OHL, unde g ound cables canno use ai as he insula ing medium; as ai can ans e hea
om he conduc o away much be e han cables wi h cable insula ion. The e o e, la ge cables
a e needed o ansmi he same powe as OHL. The p obabili y o using eac i e compensa ion
uni s is ela ed o ope a ion ol age, conduc o size and ci cui leng h; i is impo an o ema k
ha cables do ha e highe induc ance and capaci ance a es.
In Figu e 2 i can be seen a no mal ound unnel wi h h ee cables co esponding pe haps o
di e en phases.
Figu e 2 Unde g ound cable unnel. (Da a sou ce: [13])
1.2.3 GIL
Gas Insula ed lines a e he sa e al e na i e o o e head lines. The low impac on he landscape
and he high ansmission capaci y make GIL a sui able ansmission sys em o ace u u e g id
ein o cemen s. Pe haps i is he p ice he i s disad an age in on o o he ansmission
sys ems; howe e de elopmen s on he ield can ca y cos educ ions.
GIL sys em can handle la ge amoun s o powe , e en mo e han O e head Lines (OHL), due o
i s bigge conduc o a ea. The ol age ange o GIL co e s high ol ages om 100kV o 800kV,
a es whe e mos o UHV lines wo k on. As he a ea is in e sely p opo ional o he esis ance[7],
he ansmission losses o GIL a e much lowe han o e head ansmission lines. GIL is he bes
op ion o high ol ages due o high powe a ing.
The GIL concep was i s ly de eloped in he 1960s, i is known as he GIL 1s gene a ion, which
wo ked only wi h SF6. Fu he in es iga ion and es s did p o e ha mixing SF6 and N2 (GIL 2nd
gene a ion) would educe ins alla ion cos s and gas handling di icul y.
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Gas Insula ed Lines. Technical-economic analysis
Since 1970 mo e han 150 GIL p ojec s ha e been ins alled wo ldwide, all o hem p o ing i s
ou s anding pe o mance capabili y [8]. GIL ins alla ion can be done in dedica ed enches,
abo e-g ound o in unnels. Also, he e is he possibili y o ins alling GIL lines in sha ing
s uc u es such as ailway unnels, highway ne wo ks o e en gas lines.
Nowadays GIL a e based on N2 + SF6 ubula conduc o echnology. As i can be seen in Figu e
3, i consis s o a cen al aluminium conduc o wi h a ypical elec ical c oss sec ion o up o
5300 mm2 [9], inside an ou e enclosu e pipe. The conduc o lies on he cen e o he ou e
enclosu e, es ing on cas esin insula o s. The enclosu e p o ides a solid mechanical and
elec ical con ainmen o he sys em. The ully encapsula ed enclosu e p o ec s GIL agains
ou side in luences and p o ides a ee main enance sys em. The space be ween he ou e
enclosu e and he conduc o is illed wi h he gas mix u e (N2 + SF6) which nowadays his
mix u e is a ound 20% SF6 and 80% N2. This mix u e has been since many yea s es ed o p o e
i s insula ion eliabili y.
Figu e 3 GIL layou . (Da a sou ce: [4])
The high secu i y ha GIL is able o o e di e en ia es GIL om o he ansmission sys ems
which expose he g id e ec i i y o some clima e haza d. The cu en gas mix u e used gi es
e y good elec ical insula ion p ope ies, which enable lexible ou e planning. In addi ion, his
mix u e is non- oxic, ine , non- lammable, non-co osi e and long- ime s able. Howe e , SF6 is
a g eenhouse gas which may be highly ha m ul o he en i onmen , his is he main eason o
doing u he in es iga ion on al e na i e gases.
A he end o i s li e cycle, all ma e ials and he gas mix u e being used can be 100% ecycled.
Some ypical echnical da a o GIL is shown in Table 1 [10]:
16
Figu e 5. Compensa o uni . (Da a sou ce: [9])
2.1.2.4 Conical and suppo insula o s
Conical and suppo insula o s made o epoxy cas esin ha e been de eloped o ix he inne
conduc o o he enclosu e and o sepa a e he gas compa men s. They mus gi e he p ope
mechanical and empe a u e esis ance as well as he discha ge acking wi hs andabili y.
2.1.2.5 S aigh uni
In e e ence o he di e en pa s indica ed in Figu e 4, he enclosu e (1), whe e he inne
conduc o (2) is ixed by conical insula o s (4) and on suppo insula o s (5). The longi udinal
he mal expansion o he conduc o is adjus ed by he sliding con ac sys em (3a male sliding
con ac , 3b emale sliding con ac ). A s aigh uni has a leng h up o 120 m made by di e en
joined sec ions (each sec ion o 12-18 m leng h) welded oge he by an o bi al welding machine
[11]. The s aigh uni only has an insula o posi ioned inside he enclosu e pipe (one each 120
m); see Figu e 6.
Figu e 6. S aigh uni . (Da a sou ce: [9])
2.1.2.6 Angle uni
The bending adius is a basic p ojec planning pa ame e o design he ou ing and o al leng h
o he GIL ins alla ion. Angle uni s a e designed be ween 0-90˚. Due o hei cos s angle uni s

17
Gas Insula ed Lines. Technical-economic analysis
a e only used when smalle han 400 m adius a e needed. Unde mos condi ions o landscape,
no angle uni s a e needed, because he elas ic bending is enough o ollow he con ou .
An angle uni consis s o a single-phase enclosu e made o cas aluminium alloy. In he enclosu e
(1) he inne conduc o (2) is ixed by a conical insula o (4) and on suppo insula o s (5). Angle
uni is connec ed o s aigh uni by o bi al welding. In Figu e 7 is shown a ypical angle uni
Figu e 7. Angle uni . (Da a sou ce [9])
2.1.2.7 Disconnec ing uni
Disconnec ing uni s used in unde g ound sha s o sepa a e gas compa men s and o connec
high- ol age es ing equipmen o he commissioning o GIL. In case i is equi ed o connec
gas compa men s be o e and a e he disconnec ing uni , a bypass can be se . Disconnec ing
uni s a e loca ed a dis ances o 1000 o 1500 m. In Figu e 8 is
shown a disconnec ing uni .
Figu e 8. Disconnec ing uni . (Da a sou ce: [9])
2.2 GIL laying op ions
Di e en laying op ions de ine di e en cos s, he e o e i is impo an o ge o know he main
di e ences be ween each laying op ion and e en o look o al e na i es, such as sha ing
s uc u es.
18
Due o GIL signi ican p ope ies, GIL ha e been se in many di e en layou s, o sol e complex
ou ing. GIL ha e been ins alled in s aigh e ical, a ound buildings abo e and belowg ound,
and e en se pen ine ou ings wi hou angle uni s.
2.2.1 Abo e-g ound ins alla ion
Today, mo e han 50% [11] o GIL ins alla ion a e sol ed by using abo e-g ound in as uc u e.
Cos s o his laying sys em a e lowe han o he op ions because he e a e less ins alla ion
equi emen s. Fu he mo e, in his case isual inspec ions a e easily done.
This laying op ion needs a s eel s uc u e o ix i on g ound; his s uc u e is in no mal condi ions
si ua ed be ween 100-120 [11] m dis ance. Some he mal condi ions mus be conside ed when
designing he s uc u e; o example in cold coun ies whe e snow o ice can come o be an
addi ional load o e en wind which causes bending o ces.
The ype o holding s uc u es can depend on some es ic ions which a y he dis ance o loo .
Laying close o g ound needs smalles and simple s eel s uc u es; bu laying high abo e-g ound
(such as 5-8 m heigh [11]) allows a ic below he GIL bu needs o mo e complex s eel
s uc u es. These s eel s uc u es a e hen ixed o g ound wi h conc e e socke s. In Figu e 9 a e
shown ypical s eel s uc u es.
Figu e 9.Typical s eel s uc u es. (Da a sou ce: [9])
As he enclosu e aluminium is exposed o ai , he oxygen c ea es an oxide laye , which a oids
co osion. Only wa e a e much ime o cons an exposu e, can co ode aluminium, as i begins
a eac ion ha is able o des oy aluminium sel -p o ec ion. To a oid his unwan ed impac ,
p o ec ion is needed by coa ing hose a eas o wa e pene a ion. Fo his coa ing an ex e nal
HDPE pipe is used.
19
Gas Insula ed Lines. Technical-economic analysis
I is demons a ed ha p ice o he High Densi y Polye hylene HDPE coa ing is negligible as a
400 KV GIL has mo e han 40 kg/m o me al [13]. F om he same e e ence, he plas ic coa ing
pipes weigh 9 kg/m [13]. P ice o plas ic is much lowe han p ice o me al; also plas ic
p o ec ion is only needed o hose a eas whe e he e is cons an exposi ion o wa e . Fo his
eason he use o plas ic coa ing won’ be accoun ed in he o al cos o he ins alla ion.
2.2.2 T ench-laid
The easons o he use o ench-laid ins alla ions a e no mally when c ossing o he ins alla ions
in a powe plan . I is a easible solu ion when abo e-g ound solu ions a e no possible. The
laying s uc u es o ench-laid GIL a e e y simila o he abo e-g ound ins alla ions as bo h
su e he same mechanical s ess. The e o e, s eel s uc u e dis ances a e he same.
T enches a e usually made o p e ab ica ed conc e e panels, whe e he s eel s uc u e ixes he
GIL. Al hough being mo e expensi e han abo e-g ound ins alla ions, a e s ill e y accessible
and isual con ol can be p ope ly done. In Figu e 10 is shown a ench laid sys em.
Figu e 10. T ench laid sys em. (Da a sou ce: [9])
In enches layou , he same aspec s abou co osion mus be aken in o accoun . The ench
needs a us ul d ainage and dewa e ing sys em o a oid cons an con ac o wa e o he
enclosu e pipe. In case i canno be assu ed, pain ing is needed and con ol and main enance
a e equi ed.
2.2.3 Tunnel-laid
Tunnel laid ins alla ion, al hough being he mos expensi e laying sys em, hey gi e he
oppo uni y o se a non- isible om abo e and accessible powe ansmission sys em. Besides,
20
no co osion p o ec ion is needed i i can be ensu ed ha no wa e can pene a e in o he
unnel. This laying sys em is mainly used when he di ec ly bu ied laying is no possible.
Tunnel cos s depend much on he way hey a e buil : om close- o- he -su ace unnels, wa e
igh , o deep-unde g ound unnels. In each case a singula s udy mus be done o op imize
p ojec cos s. Nowadays p e ab ica ed s uc u al elemen s a e educing cons uc ion du a ion
and cons uc ion cos s.
• Open T ench-Laid Tunnel (squa ed unnel sec ion) is he sui able op ion when close- o-
he-su ace unnels can be buil . In his case a ench is opened om he g ound and
unnel conc e e segmen s, which can be p e ab ica ed o p oduced on-si e, a e
assembled. Finally, hey a e co e ed wi h soil (minimum co e ing heigh 1 m). The GIL
sys ems lies in a small space o 2,5 m2 o wo GIL sys ems, which lea es enough space
o a walkway in he cen e o 0,8 m wide. In Figu e 11 can be seen a no mal sec ion and
dis ibu ion o a squa ed unnel.
Figu e 11. Open ench-laid unnel. (Da a sou ce: [9])
• The Bo ed Tunnels a e ound and usually ha e a diame e o 3-4 m o wo GIL sys ems.
Highly au oma ized machines can dig unde g ound o cons uc bo ed unnels; high
de elopmen in his Bo ed Tunnels does p o ide highe speed, accu acy and lowe cos s
(s ill being e y high).
In unnel-laid ins alla ion GIL lays ixed o he unnel walls. The laying o ces a e simila o abo e-
g ound ins alla ions. In bo h cases s eel s uc u es hold he s aigh uni laid on sliding ixing
poin s o allow he mal expansion o he enclosu e. The laying s uc u es o unnel-laid GIL a e
si ua ed no mally a dis ances o 28 m.
21
Gas Insula ed Lines. Technical-economic analysis
2.2.4 Di ec ly bu ied
The di ec ly bu ied laying sys em o GIL is ge ing highe impo ance in GIL o unde g ound
powe ansmission. This is he powe ansmission op ion o long-dis ance applica ions,
p e e ably o open landscape ac oss he coun y; i o e s an economical and as laying
solu ion. In Figu e 12 is shown a ypical h ee phase Di ec ly Bu ied layou .
The laying me hods a e adap ed o oil and gas pipeline laying echniques, as hey ha e been o
long p o ed in long-dis ance supply o ene gy:
• When he GIL ins alla ion is di ec ly bu ied in o he soil, he ou e enclosu e needs an
ou e passi e co osion p o ec ion made o polye hylene o polyp opylene coa ings. The
join a ea, p oduced by an o bi al welding join ing machine, has a special coa ing o
p o ec he weld. Fo he same eason explained in chap e 2.2.1, hei p ice is no
accoun ed in he cos s udy.
• The su ounding soil needs o be ee o s ones, o p e en GIL pipe om being
damaged; he minimum co e age soil is 1 m. The back ill ma e ial is ypically a sand and
clay mix u e so as o keep wa e in he soil o imp o e hea conduc i i y. No mally
back ill ma e ials a e used a e il e ing hem o ocks and s ones. In he a eas whe e
GIL has been laid no digging execu ions can’ be done. Fu he mo e, no all ees can be
plan ed.
• In o de o ge his minimum heigh (1 m) o a single-phase and h ee-phase GIL a 2-2,5
m dep h ench is dug. In case o h ee-phase elec ical ansmission, he dis ance
be ween he enclosu e pipes is 0,5-0,8 m. This dis ance depends on he mal and
accessibili y a ai s. The expec ed wid h o a h ee-phase GIL is 4,5-5 m. All his igu es
ha e been gi en o a 500 mm enclosu e pipe diame e . In Figu e 12 a ypical layou can
be seen; he a es indica ed in Figu e 10 may a y due o di e ences in echnical
a angemen s.
• In his laying me hod he s aigh uni s do no ha e o be ixed in he g ound o a oid
longi udinal mo emen ; in he soil he GIL is ancho ed due o i s weigh , so no addi ional
compensa ion elemen s a e needed.
• Disconnec ing uni s a e placed in conc e e sha s. The disconnec ing uni s allow access
o GIL; in hese sha s measu emen senso s such as p essu e moni o ing a e loca ed,
o con ol GIL wo king condi ions. As i is indica ed in he Disconnec ing Uni sec ion
(2.1.2.7), each sha mus be si ua ed each 1000-1500 m.

22
Figu e 12. Th ee-phase di ec ly bu ied sec ion. (Da a sou ce: [12])
In e ms o o ces, di ec ly bu ied GIL pipes, ha e o ace he weigh o he soil laying on he
pipe. Tha means ha a leas 1 m heigh and 0.5 m wid h sec ion o soil. In addi ion, in case o
ha ing a ic abo e hem o snow, u he loads ha e o be suppo ed by he enclosu e pipe.
23
Gas Insula ed Lines. Technical-economic analysis
3. Cos modelling
The main aim o his hesis is o de elop a ool o calcula ing o al GIL in as uc u e cos s, om
ini ial in es men o powe losses and li e-long cos s. No e ha o he associa ed cos s, such as
g id ein o cemen s o insu ance cos s a e ou o he scope. In o de o simpli y calcula ion i
has been dispa aged he ansien beha iou , and only ocused on he s a iona y s a e.
This chap e explains i s ly how does he ool wo ks, secondly which a e he equa ions ha
ela e he main pa ame e s o he ins alla ion wi h he cos , he echnical conside a ions
employed, and unc ions and a iables used o de elop he ool.
The me hodology used in his economic cos s udy conside s a g ea a ie y o asse ypes, o
be able o p edic cos s o any di e en layou . Tha means ha he cos is calcula ed in
e e ence o he ype o laying, he ou ing (numbe o angle uni s, e c) and he dimensions o
he in as uc u e depending on echnical pa ame e s. The p ice o ma e ials used is also a
pa ame e o be in oduced in he sys em o imp o e he quali y o he cos app oxima ion.
GIL sys ems ha e go many di e en echnical speci ica ions a iables and i ems ha in luence
g ea ly in he inal cos and make he cos es ima ion ex emely complex. In o de o simpli y
cos calcula ion, he cos componen s ha e been sepa a ed in o:
1. Fixed cos s ela ed o ini ial in es men
• Pipe and conduc o
• Ci il wo ks
• Gas
• T anspo and ins alla ion
• Rou ing (angle uni s, disconnec ing uni s)
• GIS + T ans o me s + Tes ing + Reac i e powe compensa ion
• P ojec con ingency
• P ojec managemen
2. Va iable cos s
• Powe losses
• Cos o educed powe ansmission capaci y due o eac i e powe
• Losses in he compensa ion uni
• Ope a ion and main enance
24
Finally, in he cos app oxima ion o a h ee-phase enclosed GIL i has been always s udied he
case which each phase conduc o is inside a di e en pipe, and no he case which all conduc o s
a e inside he same enclosu e pipe.
3.1 Tool desc ip ion
The ool wo ks wi h he ollowing p inciples: i s , use s in oduce he main da a ega ding GIL
echnology (see chap e 3.2). The ool de e mines he cos s o he en i e p ojec e u ning he
o al cos and also he cos associa ed o each componen .
An app oach o minimize he numbe o inpu s has been done whene e i has been possible.
Howe e in he sea ch o be ealis ic and do an accu a e p edic ion, use s, do ha e o in oduce
some eal in o ma ion such as cu en p ices o ma e ials used in he in as uc u e (me al, gas
p ices), o some da a e e ed o he in as uc u e.
3.2 GIL a iables and modelling
Rega ding GIL in as uc u e cos calcula ion, many a iables a e signi ican ly dependen o he
inal cos . To achie e a model o calcula ing he inal cos , i s o all, inpu s and a iables a e
needed o p o ide di e en scena ios.
The main inpu s used in his ool a e he nominal ol age in kV and he nominal appa en powe ;
bu some o he in o ma ion has o be in oduced which is indica ed in Table 2.
25
Gas Insula ed Lines. Technical-economic analysis
Table 2. Main a iables.
Va iable Uni
Nominal appa en powe MVa
Nominal ol age kV
Li e ime Yea s
Discoun a e (pe uni )
To al leng h ( e e ing leng h o ype o laying and
soil) m
Cos o MW/h €/MWh
Single/Th ee phase -
Numbe o pa allel uni s -
P ice Aluminium ou e enclosu e €/kg
P ice Aluminium conduc o €/kg
P ice
SF6
€/kg
P ice
N2
€/kg
Numbe o ans o me s -
Numbe o GIS (Gas insula ed swi che s) -
Wi h he nominal ol age (V) and he appa en powe (S), in ensi y (I) pe conduc o can be
calcula ed. No e ha in he (1), (2) V is e e ed o he phase- o-phase ol age.
• Single phase sys ems: Ss−p = V * I (1)
• Th ee phase sys ems S −p= 3 * V
√3 * I (2)
A numbe o o he pa ame e s no speci ied in Table 2 di ec ly depend on he speci ied a iables
used in his ool. When he o al leng h is indica ed hen he numbe o disconnec ing uni s,
male and emale sliding, and compensa o uni s is known. Disconnec ing uni s a e si ua ed a
dis ances o 1000-1500 m (in he ool is used 1250 m) o sepa a e gas compa men s and
connec es ing ha dwa e. Male and emale sliding con ac uni s a e si ua ed each 100 m o cope
wi h he mal expansion. Compensa o uni s a e si ua ed a dis ances o 300-400 m (in he ool
32
Figu e 16. Disconnec ing uni , Solid Wo ks design. Sou ce Solid Wo ks.
No e ha in case o ha ing mo e han one pipe, he cos is calcula ed by mul iplying he o al
numbe o pipes.
Rega ding male and emale sliding con ac as hey a e wo pipes one inside he o he , i has no
been conside ed a special p ice as no special machining is necessa y unlike angle uni s and
disconnec ing uni s.
3.4 Cos dependency on laying me hods
Ci il wo k cos s o GIL depend much on he si e, he laying me hod and local condi ions.
Op imising he GIL laying and ou ing migh be signi ican in he o al cos o he in as uc u e;
o his eason when designing a new ansmission line, i is necessa y o do a p e ious esea ch
wo k s udying di e en ou e planning wi h hei di e en laying me hods and ypes o soil,
he e o e, aking in o accoun all he condi ionings, o come up wi h he mos sui able solu ion.
This hesis assumes ha he ou e and laying me hods a e de ined p e iously in each p ojec
and ha his ool only p o ides he necessa y cos s. No e also ha he ou e does in luence he
o al cos o main enance and o he a iable cos s as powe losses.

33
Gas Insula ed Lines. Technical-economic analysis
Rega ding he pa h, s anda d GIL ins alla ions end o be done close o oads o o he
communica i e sys ems, as accessibili y, main enance, join ing and welding he pipes is c ucial
o GIL ins alla ion, and o p ice educ ion.
3.4.1 Di ec ly bu ied laying cos s
Di ec ly bu ied GIL is gaining impo ance nowadays o unde g ounding a GIL in as uc u e. This
laying me hod is a con inuous p ocess and i can co e long dis ances much as e han o he
laying me hods like unnels. Ano he ad an age is ha he mal compensa ion elemen s a e no
needed because GIL is held in place by he weigh o he soil and ic ion be ween he soil and
he pipe. Also no s eel ixing s uc u e is needed.
The g ea es di e ence wi h o he laying me hods is ha GIL pipes a e exposed o ex e nal
condi ioning wi h pe manen con ac wi h wa e o humidi y, he e o e, he aluminium pipe
mus be bounded o a oid co osion. Pipes a e equipped wi h a XLPE ex e nal p o ec i e coa ing.
Table 8 gi es a cos app oxima ion on he cos (€/m3) o each ype o soil exca a ion. [21]
Table 8. P ices o each ype o e ain
Type o e ain
Type o machine
P ice(€/m3)
Disagg ega e (a)
Exca a o
4,73
Loose (b)
Exca a o
5,67
Compac (c)
Exca a o
7,09
Ha d (d)
Comp esso
12,29
So ock (e)
Comp esso
24,59
Ha d ock ( )
Comp esso
39,34
Now, in o de o calcula e cos s, i is necessa y o es ima e he amoun o soil ha needs o be
ex ac ed. In he Figu e 17 can be seen he pa ame e s o exca a ing he ench.
Figu e 17. Di ec ly bu ied sec ion. (Da a sou ce: [16])
34
A eg ession wi h each pa ame e is done o gi e a ela ionship be ween hem and he a ed
ol ages ins alled. No e ha pa ame e s J, G, H, F a e om a h ee phase GIL sys em. Impo an ,
in he ollowing equa ions, V e e s o ol age be ween phase and neu al. Equa ions a e
collec ed a he end.
-F [19]
Table 9. Values o F.
Vol age (kV)
145
242
362
420
800
1200
F (m)
0,368
0,457
0,559
0,711
0,813
1,016
-J [19]
Table 10. Values o J.
Vol age (kV)
145 kV 242kV 362 kV 420 kV 800 kV 1200 kV
J (m)
1,27 1,5 1,8 2,28 2,64 3,1
-H [19]
Table 11. Values o H.
Vol age (kV)
145 kV
242kV
362 kV
420 kV
800 kV
1200 kV
J (m)
1,21
1,2
1,2
1,3
1,5
1,6
-G [19]
Table 12. Values o G.
Vol age (kV)
145 kV
242kV
362 kV
420 kV
800 kV
1200 kV
J (m)
0,91
0,91
0,91
0,91
1,07
1,21
Table 13. S a is ic eg ession o he dimensions
Equa ion
R²
F (12)
0,0006V + 0,3464
0,9304
J (13)
0,0017V + 1,207
0,9173
H (14)
0,0004V + 1,1115
0,9420
G (15)
0,0003V + 0,8235
0,9423
35
Gas Insula ed Lines. Technical-economic analysis
Whe e;
V: ol age phase-phase (kV).
Digging cos s a e calcula ed by mul iplying o al cubic m ex ac ed wi h digging p ices,
di e encing hem be ween each soil ype:
• Single phase sys ems:
Cd= n*J/3*H*∑di∗pi
i=
i=a (16a)
• Th ee phase sys ems:
Cd= n*J*H*∑di∗pi
i=
i=a (16b)
whe e;
J and H: pa ame e s indica ed in Figu e 17 [m];
dx: dis ance o each ype o soil [m];
pi: p ice o exca a ing o each ype o soil [kg/m3];
n: numbe o pa allel uni s.
In o de o calcula e digging cos s o single-phase GIL in as uc u e, a simpli ica ion is done,
he p ice will be he p ice o a h ee-phase sys em di ided by h ee. In he case o mul iple
pa allel h ee-phase sys ems, digging p ice will be calcula ed mul iplying he numbe o pa allel
h ee-phase sys ems, wi h he p ice o a single one.
3.4.2 T ench laying cos s
The ench laying layou is e y simila o di ec ly bu ied bu soil ex ac ed is no back illed.
T enches a e made o conc e e panels. This laying ype is mo e expensi e han abo e-g ound
ins alla ions, bu less expensi e han unnels [11].
In his case unlike di ec ly bu ied laying, s eel s uc u es like ubbing hange s, conc e e inse s
a achmen s, e c, a e needed o ix he ou e enclosu e pipe o conc e e. They a e si ua ed a
dis ances o 100-120 m [22].
P ice o all his s uc u al a achmen s pieces ha e no been in oduced in he calcula ion ool
as hey a e insigni ican among he cos o o he componen s like pipes, bu hey can be ound
in [23]. In e e ence o [24] he s eel /i on s uc u es cos is a ound 1,91 €/kg.
36
In o de o calcula e cos s, measu es o di e en ol age a es a e showed in Figu e 18, in o de
o es ablish a ela ionship be ween hem and ol age. As well as i has been explained in uni
3.4.1 (di ec ly bu ied), he same conside a ions will be aken o single-phase and o pa allel
h ee-phase sys ems. In addi ion, a simila o mula used o calcula e he di ec ly bu ied laying
sys em cos s is used o calcula e he digging cos s, di e en ia ing he ha dness o he soil.
Figu e 18. T ench laying sec ion.
Digging cos s is exp essed as:
Cd= B*H*∑di∗pi
i=
i=a (17)
whe e;
• Th ee phase sys ems: H= 4A+3D and he no mal alue o A is 0,3 m.
• Single phase sys ems: H= 2A+D and he no mal alue o A is 0,3 m.
B and C: a e pa ame e s ha depend on each p ojec and a e indica ed in Figu e 18. In he cos
calcula ion ool hese alues mus be in oduced as a iables.
To calcula e he cos o he conc e e pla o ms:
• Single phase sys em
Cconc e e = p ∗n∗2d ∗(B + C)+ d ∗(4A +3D) (18a)
• Th ee phase sys em
Cconc e e = p ∗n∗2d ∗(B + C)+ d ∗(2A + D) (18b)
whe e;
37
Gas Insula ed Lines. Technical-economic analysis
d: dis ance o he ench [m];
D: enclosu e pipe diame e [m]
n: numbe o pa allel uni s
p: p ice o conc e e panels [€/m2]
Being p ice pe squa e me e o he s anda d conc e e panels 17,97 €/m2 [25]:
3.4.3 Tunnel laying cos s
Tunnel laying is no mally used when he di ec bu ial ins alla ion in enches is no easible.
Tunnels when laid om he op ha e a squa ed o m; no mally his sec ion is used in u al a eas
wi h low popula ion densi y. Fo highe densi y a eas ound sec ion unnels a e done as hey
a e much deepe han he i s ones. Tunnel laying cos s a e sensi i e o ou e leng h and unnel
diame e . I is no ed ha his laying me hod is he mos expensi e one.
Dimensions o squa ed and ound unnels wi h wo pa allel GIL sys ems, a e exp essed as
unc ion o he ou e enclosu e pipe diame e . The mos ypical a angemen o he unnel
laying is h ee phase sys ems [26].
In he unnel laying me hod, ixing s eel s uc u es a e needed, hey a e si ua ed each 28 m [11].
As well as i has been done in he ench laying me hod, he p ice o his s eel s uc u es is no
included in he calcula ion ool as he s eel s uc u es may a y in ela ion o he enginee ing
p ojec ; u he mo e p ice can a y be ween di e en p o ide s. Fo example a p o ide o his
s uc u al objec s is [23]. The mos impo an eason o no conside ing hei cos is ha i is
insigni ican among he cos o o he componen s o he GIL in as uc u e.
As he e a e h ee di e en unnel op ions, h ee di e en ways o app oaching i s cos s a e
explained:
3.4.3.1 Squa ed sec ion unnels
Tunnels a e buil in an open ench in segmen s using p e ab ica ed conc e e panels assembled
on-si e and hen co e ed wi h soil wi h a co e age heigh o 1 o 2 m. To calcula e cos s i will
be conside ed 1,5 m. GIL is hen ixed o he unnel walls. In Figu e 19 is shown wo h ee-phase
uni s in a squa ed sec ion unnel.

38
Figu e 19. Squa ed sec ion unnel. (Da a sou ce: [26])
Sec ion S exp essed in m2 o a squa ed sec ion:
• Tunnel sec ion o wo pa allel h ee phase sys ems:
S= (0,224*2 + 1,128 + 2 *D) * (0,2115*2+2*0,213+3*D) (19a)
• Tunnel sec ion o a h ee phase sys em and o single phase sys em:
S= (0,224*2 + 1,128 + 2 *D) * (0,2115*2+2*0,213+3*D)/1,5 (19b)
whe e;
D: diame e o he ou e enclosu e [m].
Cos o squa ed unnels is calcula ed as sum o digging cos and conc e e:
1. Cos o digging
• Two pa allel h ee phase sys ems:
Cd=(S + (0,224 ∗2 + 1,128 + 2 ∗D)∗1,5)∗l∗p (20a)
• A h ee phase sys em o a single phase sys em:
Cd=(S + (0,224 ∗2 + 1,128 + 2 ∗D)∗1,5)/1,5 ∗l∗p (20b)
whe e;
39
Gas Insula ed Lines. Technical-economic analysis
Cd: cos o digging [€];
D: diame e o he ou e enclosu e pipe [m];
l: leng h [m];
p: p ice [€/m3].
P ices o digging o each ype o soil a e indica ed Table 8.
2. Cos o conc e e panels:
Being p ice pe squa e me e is 17,97 €/m2 [25]:
• Two pa allel h ee phase sys ems:
Cconc e e =[2∗(0,224 ∗2 + 1,128 + 2 ∗D)+ 2 ∗(0,2115 ∗2+2∗0,213 + 3 ∗D)]∗
p∗l (21a)
• A h ee phase sys em o a single phase sys em:
Cconc e e =[2∗(0,224 ∗2 + 1,128 + 2 ∗D)/1,5 + 2 ∗(0,2115 ∗2+2∗0,213 + 3 ∗
D)]∗p∗l (21b)
whe e;
Cconc e e: cos o he conc e e panels [€];
D: diame e o he ou e enclosu e pipe [m];
l: leng h [m];
p: p ice [€/m2].
3.4.3.2 Bo ed unnels:
As bo ed unnels a e deep unde g ound, a sha is buil o in oduce he bo ing machine and he
p e ab ica ed conc e e segmen s. In Figu e 20 is shown a ypical ound unnel sec ion.
40
Figu e 20. Round sec ion unnel. (Da a sou ce: [13])
The sec ion S o a ound unnel exp essed in m2 o a ound sec ion is calcula ed wi h he
ollowing equa ions:
• Two pa allel h ee phase sys ems:
S = (0,450 + 0,150 ∗ 2 + 0,350 + 3 ∗D ) 2 * π
4 (22a)
• A h ee phase sys em o a single phase sys em
S = (0,450 + 0,150 ∗ 2 + 0,350 + 3 ∗D ) 2 /1,8* π
4 (22b)
whe e;
D: diame e o he ou e enclosu e [m].
No ice ha in case o ha ing a single phase o one h ee-phase sys em o al sec ion will be
calcula ed by di iding by 1,8 he p e ious sec ion. This numbe has been se aking in o accoun
ha enough space is le o main enance wo ks.
To come wi h a cos calcula ion model, cos is only es ima ed o he ube ci il wo ks. The
me hod used exp esses he cos pe longi udinal me e o he unnel, in e e ence o he
a iables RMR index and he exca a ion sec ion (S) [27]. The RMR is an index ha gi es a
classi ica ion o he ha dness o he ock being exca a ed.
To al cos o unnelling is calcula ed[27]:
C unnelling =(83.93 ∗S−148,189 ∗RMR +9578.3)∗l (23)
whe e;
41
Gas Insula ed Lines. Technical-economic analysis
C unnelling: cos o unnelling [€/m]
S: sec ion [m2];
RMR: index;
l: leng h [m].
3.4.3.3 Mul ipu pose unnels
An app op ia e way o cos educ ion when unnel laying is necessa y, i is o sha e he s uc u e
wi h o he use s. Two di e en p inciples o mul ipu pose unnels can be seen. Fi s ly Round
Tunnels, made by a bo ing machine which gi es a ound sec ion o he unnel. Usually, as he
loo is needed o be la , he space be ween he oad and he conc e e panels can be used o
ix he GIL pipes. This ype o unnels a e shown Figu e 21.
Figu e 21 Mul ipu pose unnels. Round Tunnels (Da a sou ce: [22])
Secondly, hose unnels which ha e been cons uc ed in he adi ional building p ocess known
as ‘D ill and blas ’. The e is he possibili y o ix he GIL pipes on he oo . This ype o unnels
a e shown in Figu e 22.
48
C: equi alen capaci y;
L: equi alen induc ance;
R: equi alen esis ance;
I: in ensi y;
Vab: ol age in he load (phase-neu al);
P: ac i e powe consumed by he load.
In o de o calcula e powe losses and eac i e powe consump ion o gene a ion, he ollowing
assump ions ha e been done:
• V e phase is 0º.
• The appa en powe a he load side is assumed as ull ac i e powe (cos φ =1).
To come up wi h powe losses and he eac i e powe in he line, in ensi y lowing by he
induc ance, capaci o and esis ance mus be calcula ed. In Figu e 26 he equi alen o The enin
is shown as i is used o calcula e ol age in he load Vab (phase-neu al). Knowing V e and Vab
we a e able wi h his aluess o calcula e he in ensi y I lowing h ough he equi alen
esis ance and induc ance in he pi ci cui (see Figu e 25).
Figu e 26. The enin equi alen ci cui . (Da a sou ce: EE ETSEIB)
All pa ame e s indica ed in Figu e 26 a e associa ed o he The enin’s heo em.
The pa ame e s o he The enin heo em E h and Z h a e calcula ed o p o ide U h=Vab which
e e s o he ol age in he load:
1. E h = Vab when no load is connec ed o he ansmission ci cui .
(31)

49
Gas Insula ed Lines. Technical-economic analysis
2. Z h which e e s o he equi alen impedance o The enin when he ol age sou ces a e
sho -ci cui ed and he in ensi y sou ces a e opened.
Z h = −2jXC (−2jXC+jXL+R)
−4jXc+jXL+R (32)
whe e;
Z h: The enin’s impedance [Ω];
R: Resis i e impedance [Ω] ( e e ed o Figu e 25);
XC: Capaci i e impedance [Ω] ( e e ed o Figu e 25);
XL: Induc i e impedance [Ω] ( e e ed o Figu e 25).
Finally he ollowing equa ion is sol ed in o de o ge V2= U h = Vab. Values associa ed o his
The enin equa ion a e ela ed o alues shown in Figu e 26.
V2
4+ V2
2 �2R hP + 2X hQ−E h2�+�R h2+ X h2�(P2+ Q2)= 0 (33)
whe e;
R h: Equi alen The enin’s esis ance [Ω] ( e e ed o Figu e 25);
X h: Equi alen The enin’s eac i e impedance [Ω] ( e e ed o Figu e 25);
P: Powe consumed in he load ( e e ed o Figu e 25);
Q: Reac i e powe consumed o gene a ed in he load ( e e ed o Figu e 25).
In his case all he a iables a e associa ed o Figu e 26. In o de o calcula e ol age in he load
(V2= Vab), i is calcula ed wi h he ollowing equa ion:
(34)
We ha e o know alues o ZPQ which e e s o he impedance o he load and I h which e e s
o he The enin’s in ensi y. Following equa ions a e used o come up wi h he V2 alue.
(35)
Finally, once ha we know V2 (phase o neu al ol age), i can be calcula ed he in ensi y
h ough he esis ance and induc ance in he PI ci cui (Figu e 25). In ensi y is used o calcula e
he powe losses in he esis ance due o Joule’s e ec , and o calcula e he eac i e powe
50
consumed in he induc ance. On he o he hand, V2 is used as well as V1=V e o calcula e he
capaci i e powe gene a ed in he condensa o .
(36)
All his calculus a e e e ed o single phase sys ems. In case o h ee phase sys ems i has been
used he single phase equi alen by using V e as ol age be ween phase and neu al. Then o
calcula e ene gy losses and eac i e powe , he esul s should be mul iplied by 3.
3.7.1.1 Powe losses
In o de o come up wi h powe losses alues i is necessa y o know he esis ance pa ame e .
The line esis ance depends on he ou e enclosu e diame e and he wall hickness o he ou e
enclosu e and conduc o pipe[11], u n, hey depend on he ol age a ing. Ac i e powe
ansmission losses a e ela ed o he squa e o he ansmi ed cu en as:
Pl= R ∗I2 (37)
This alues shown in he p e ious equa ion a e e e ed o Figu e 25.
To c ea e he cos calcula ion ool, i has been necessa y o app oxima e esis ance pe phase
and m o each ol age a e. Da a om wo di e en bibliog aphic sou ces Table 15 om [19]
and Table 16 om [16] ha e been collec ed:
Table 15. Resis ance. (Da a sou ce: [19])
Vol age (kV)
138
230
345
500
μΩ/m
26,017
17,257
12,598
9,186
Table 16. Resis ance ( Da a sou ce: [16])
Vol age (kV)
145 / 170
245 / 300
362
420 / 550
800
1200
μΩ/m
18
16
13
11
10
8
In Figu e 27 is shown he s a is ic eg ession be ween esis ance (μΩ/m) and a ed ol age kV.
51
Gas Insula ed Lines. Technical-economic analysis
Figu e 27. Resis ance pe m.
= 254,16V-0,501 (38) R² = 0,8944
whe e;
: esis ance [μΩ/m];
V: ol age [kV].
The powe losses cos is calcula ed as he cos o he ene gy no sold du ing he wo king hou s
o he li e- ime pe iod o he GIL in as uc u e. The quan i y o wo king hou s pe yea
conside ed a e 8760 h. The ene gy selling p ices ha e been aken by de aul as 50 €/MWh [30].
Depending on he ype o ansmission sys em (single-phase and h ee-phase), yea ly cos o
losses a e exp essed as:
• Single-phase:
Pl =10−6 ∗ ∗I2 (39a)
Cos APL =10−12 ∗ ∗I2∗nH ∗Ce∗d (40a)
• Th ee phase:
Pl = 3 ∗10−6 ∗ ∗I2 (39b)
Cos APL =10−12 ∗3∗ ∗I2∗nH ∗Ce∗d (40b)
y = 254,16x-0,501
R² = 0,8944
0,00
5,00
10,00
15,00
20,00
25,00
30,00
0,00 200,00 400,00 600,00 800,00 1000,00 1200,00 1400,00
Vol age
52
whe e;
Cos APL: cos € powe losses in a yea o wo king GIL sys em [€];
nH: numbe o wo king hou s pe yea : 8760 h [13];
𝐂𝐂𝐞𝐞: cos o ene gy [€/MWh];
: esis ance pe me e [μΩ/m];
d:dis ance o he line [m];
I: in ensi y [A] see Figu e 25.
In o de o p esen he alue o he sum o he annual o al cos s o he powe losses o e he n
yea s o he p ojec li e ime, EA, can be ob ained[13]:
EA=(1+i)n−1
i(1+i)n∗ Cos APL (41)
whe e;
n: ins alla ion’s numbe o yea s o li e;
i: discoun a e (pe uni ).
3.7.1.2 Powe ansmission capaci y educ ion due o eac i e powe
Reac i e powe a e a consequence o he induc ance and capaci ance o he ansmission line.
Reac i e powe gene a ed o consumed in a ansmission line educes he o al capaci y o
ac i e powe ansmission o a line. Un il now, only AC GIL sys ems ha e been de eloped as a
consequence o p oblems in he de elopmen o DC GIL sys ems [11].
In GIL ins alla ions, o e long dis ances o 60-80 km, no eac i e powe compensa ion is equi ed
[11]. In his hesis he u iliza ion o compensa o uni s is conside ed; when he a io Q/P>0,2
[13], which P and Q e e o:
• P: powe consumed by he load (see Figu e 25).
• Q: eac i e powe a he beginning o he GIL in as uc u e, e e ing o he eac i e
powe ha is consumed o gene a ed by he GIL ins alla ion, so ha he assump ion done
ha in he load he powe is ully ac i e is accomplished. (See Figu e 25)
53
Gas Insula ed Lines. Technical-economic analysis
Ne e heless in case he a io Q/P is lowe han 0,2 (no compensa o uni is used) all he eac i e
powe consumed o gene a ed in he line is conside ed in he cos calcula ion, as a educ ion o
he capaci y o ac i e powe ansmission.
Fi s ly, o calcula e he alue o capaci i e powe , da a o capaci ance o di e en GIL p ojec s
ha e been ob ained o gi e a ela ionship be ween capaci ance and ol age a es. Capaci ance
is exp essed in picoF/m and is e e ed o a single phase. Values a e shown in Table 17 and Table
18.
Table 17. Capaci ance. (Da a sou ce: [16])
Vol age (kV)
145
242
362
550
800
1200
pF/m
59,5
52,6
53,1
54,2
45,1
42,7
Table 18. Capaci ance. (Da a sou ce: [19])
Vol age (kV)
138 kV
230 kV
345 kV
500 kV
750 kV
pF/m
56,743
46,364
44,500
46,364
42,138
In Figu e 28 is shown he s a is ic eg ession o he capaci ance alue (picoF/m) o each a ed
ol age (kV).
Figu e 28. Capaci ance.
C = -0,0168V + 59,951 (42) R² = 0,7224
whe e;
C: capaci ance pe phase and me e [pF/m]
y = -0,0168x + 59,951
R² = 0,7224
0
10
20
30
40
50
60
70
0 100 200 300 400 500 600 700 800 900
CAPACITANCE
VOLTAGE

54
V: ol age [kV]
To calcula e o al capaci ance eac i e powe :
• Single phase:
Qc=|V|2
Z∗=−4π∗ eq∗c
1012 ∗(|V1∗103|2+|V2∗103|2)∗d (43a)
• Th ee phase:
Qc= j 3 ∗ 4π∗ eq∗c
1012 ∗(|V1∗103|2+|V2∗103|2)∗d (43b)
whe e;
Qc: capaci i e powe [VA ];
C: capaci ance pe phase and me e [pF/m];
eq: equency [Hz] (in he ool used he Eu opean equency 50Hz);
V: ol age (kV) (see Figu e 25);
d: dis ance [m].
Secondly o calcula e he induc i e powe o he conduc o , da a o induc ance om di e en
GIL p ojec s a e collec ed o come up wi h a ela ionship be ween induc ance and ol age.
Induc ance is exp essed in μH/m and e e ed o a single phase. Values a e shown in Table 19
and Table 20.
Table 19. Induc ance
Vol age (kV)
138
230
345
500
μH/m
0,196
0,211
0,209
0,209
Table 20. Induc ance
Vol age (kV)
145
242
362
550
800
μH/m
0,187
0,211
0,210
0,205
0,247
55
Gas Insula ed Lines. Technical-economic analysis
In Figu e 29 is shown he s a is ic eg ession o he induc ance pa ame e (μH/m) ela ed o
each a ed ol age.
Figu e 29.Induc ance.
L = 0,1886e0,0003V (45) R² = 0,6594
whe e;
L: induc ance pe me e [μH/m]
V: ol age [kV]
To calcula e induc ance eac i e powe pe yea :
• Single phase:
QI= 10−6 ∗ (2 ∗π∗ eq ∗ L ∗I2∗d) (46a)
• Th ee phase:
QI= 3 ∗10−6 ∗(2 ∗π∗ eq ∗L∗I2∗d) (46b)
whe e;
Ql: induc i e powe [VA ];
I: cu en lowing in he PI ci cui (see Figu e 25) [A].
The cos ela ed o he educ ion o powe ans e due o eac i e powe is calcula ed in a
simila way o he powe losses. This cos is associa ed o he educ ion o he ansmission
y = 0,1886e0,0003x
R² = 0,6594
0,000
0,050
0,100
0,150
0,200
0,250
0,300
0 100 200 300 400 500 600 700 800 900
INDUCTANCE
VOLTAGE
INDUCTANCE PER METER (VOLTAGE)
[MICROH/M]
56
capaci y, ha means ene gy ha canno be ansmi ed. The cos associa ed o he eac i e
powe in he GIL sys em (QI−QC), is app oxima ed by calcula ing he sub ac ion be ween o al
cos o ene gy a he beginning o GIL and powe consumed in he load and in he ci cui due o
losses (Sgene a o − P − Pl).
The powe a he beginning o GIL is calcula ed wi h he ollowing equa ion:
Sgene a o = �(P + Pl)2+ (QI−QC)2 (47)
Re e ing o cos o educ ion o ansmission capaci y due o he eac i e powe pe yea :
Cos RP = �Sgene a o − P − Pl�∗nH ∗Ce (48)
whe e;
P: o al powe consumed in he load [kW];
Pl: o al powe losses in he GIL in as uc u e [kW]
Cos RP: cos o eac i e powe [€/yea ];
nH: numbe o wo king hou s pe yea [h];
𝐂𝐂𝐞𝐞: cos o ene gy [€/kWh];
In o de o p esen he alue o he sum o he annual o al cos s o e he n yea s o he ci cui
li e ime, ER is ob ained[13]:
ER=(1+i)n−1
i(1+i)n ∗ Cos RP (49)
whe e;
i: discoun a e.
n: ins alla ion’s numbe o yea s o li e.
Finally, o al cos o powe losses and he cos ela ed o educ ion o powe ans e due o
eac i e powe is calcula ed as:
ET=EA+ ER (50)
3.7.1.3 T ansmission leng h and phase compensa ion
57
Gas Insula ed Lines. Technical-economic analysis
The limi ing leng h wi hou he use o phase compensa ion is o high impo ance in o de o
calcula e o al cos o he ansmission line. The c i e ia used o de e mine he use o
compensa o s is he a io Q/P=0,2 (cosφ=0,98), whe e P e e s o ac i e powe consumed by
he load.[26]
In case GIL does no need eac i e powe compensa ion (Q/P < 0,2), his eac i e powe can be
quan i ied in cos s as he ex a uel needed o be consumed o p oduce he powe ha inally is
con e ed in o eac i e powe ; no e ha all his eac i e ene gy ansmi ed ha canno be
used, causes an inc ease on he p ice o he ins alla ion. Tha means a powe in as uc u e is
designed by a es o ol age and appa en powe . In his i s case as eac i e powe is no
compensa ed he in as uc u e mus be o e dimensioned.
In case he a io Q/P is g ea e han 0,2 eac i e compensa ion de ices a e used. The e a e wo
main op ions, ixed- alue compensa o s, and a iable compensa o s. On he one hand, ixed
alue compensa o s, such as shun eac o s a e cheape and occupy less space, bu he
compensa ion a es a e ixed. On he o he hand, a iable compensa o s such as STATCOMs
(S a ic Synch onous Compensa o ) a e mo e expensi e, bu hey can compensa e exac ly each
alue desi ed in each momen .
I i is he case o cons an wo king pa ame e s, he a ia ion o he eac i e powe is low. In his
case, he compensa ion me hod used is a mix u e o a base cons an compensa ion (shun
eac o ) and an addi ional compensa ion capaci y gi en by he a iable compensa ion done by
STATCOM.
F om [30] is ob ained he cos o a shun eac o and a STATCOM compensa o .
• STATCOM:
The app oxima e cos is 0,086 M€/MVA .
• Shun eac o s
The cos o eac o s is se a 0,01 M€/MVA .
In o de o calcula e he cos o compensa ion a a io ha accoun s he a ia ion o eac i e
powe is in oduced o calcula e he cos o he STATCOM compensa o .
Ccompensa ion = 0,01 ∗|q o |+ 0,086 ∗R∗|q o | (51)
whe e;
Ccompensa ion : cos o he compensa o s [M€];
64
4.1.1 Cos s udy o GIL
In he cos s udy, he cos has been di ided in wo di e en componen s, ini ial in es men
(shown in Table 26) and li e-long cos s.
1. Ini ial in es men
Table 26. Ini ial in es men
Million €
€/m
€/MVA
Pipe + Conduc o
54,7
576,1
22.421,3
Ci il wo ks
5,6
59,0
2.296,2
Gas (
N2
+
SF6
)
88,5
931,6
36.258,1
Rou ing (angle + disconnec ing uni s)
0,3
3,0
117,7
T anspo , ins alla ion es ing
143,5
1.510,8
58.797,1
GIS + Compensa o
9,5
99,6
3.876,4
P ojec con ingency
45,3
477,0
18.565,0
P ojec managemen and launch
40,8
429,3
16.706,9
To al ixed cos s
388,2
4.086,5
159.038,6
I is no ed he impo ance o he aluminium pipes, gas and anspo , ins alla ion and es ing on
o al cos . Tha con i ms wha is s a ed in [11] ha a no mal dis ibu ion o he ini ial cos o
in es men is 40 % o ma e ials (gas, pipes, angle uni s, and disconnec ing uni s), 40% o
ins alla ion, anspo and es ing and inally 20% is o p ojec launch, managemen and
enginee ing. In Figu e 32 is shown he ini ial in es men dis ibu ion.

65
Gas Insula ed Lines. Technical-economic analysis
Figu e 32. Ini ial in es men .
Rema k ha he componen ou ing e e s o hose componen s o he pipes ha a e angle
uni s, disconnec ing uni s, male and emale sliding con ac , and compensa o s.
2. Li e-long cos s
No e ha his cos s ha e been calcula ed o he whole p ojec li e ime o he line which is
conside ed 40 yea s. The discoun a e index is assumed as 0,05. Fu he mo e, as he a io
Q/P<0,2 (see chap e 3.7.1.2) he e a e no compensa ion uni s and eac i e powe educes he
maximum capaci y o he line. In Figu e 33 is shown he cos dis ibu ion o he a iable cos s,
and in Table 28 a e shown all he a iable cos s.
The alues o esis ance, capaci ance and induc ance calcula ed by he ool a e shown in Table
27.
Table 27. RLC alues
Line Da a
R
[Ω/km]
L
[mH/km]
C
[μF/km]
0,0126
0,21
0,053
PIPE AND
CONDUCTOR COST
14%
CIVIL COST
2%
GAS PRICE N2+SF6
23%
TRANS. INSTAL.
TESTING
38%
ROUTING
0%
PROJECT
CONTINGENCY
12%
PROJECT LAUNCH
AND MANAGEMENT
11%
66
Table 28. Va iable cos s.
Million €
€/km
€/MVA
€/yea
Powe losses
85,8
902,7
35.130,0
2.143.805,9
Cos educ.T ansm. Capac
5,6
58,7
2.285,0
139.444,4
Powe losses in he
compensa ion uni 0,0 0,0 0,0 0,0
Ope a ion and main enance
29,4
310,0
12.063,2
736.158,8
To al a iable cos s
120,8
1.271,3
49.478,2
3.019.409,0
Figu e 33. Li e long cos dis ibu ion.
In his dis ibu ion i can be con i med ha ansmission wha is epo ed in [11] ha powe
losses a e he majo ac o o he ope a ion cos . They ep esen he 80% o he o al a iable
cos s.
3. To al cos
In Table 29 a e shown o al cos alues, and in Figu e 34 is shown he cos dis ibu ion.
Powe losses
71%
Cos educ.T ans.
Capac
5%
Compensa ion
0%
Ope a ion and
main enance
24%
67
Gas Insula ed Lines. Technical-economic analysis
Table 29. To al cos
Million €
€/km
€/MVA
€/yea
TOTAL COST
509,0
5.357,8
208.516,8
3.019.409,0
In Figu e 34 is shown he o al cos dis ibu ion.
Figu e 34. To al cos dis ibu ion.
4.1.2 Sensi i i y s udy o GIL
The analysis o sensi i i y shows he e ec ha di e en a iables ha e on he inal cos o he
GIL in as uc u e. In he p e ious g aphic i can be seen ha each cos does no ha e he same
impo ance. Pipe and conduc o cos and powe losses a e mo e signi ican han he o he s.
No mally in a sensi i i y s udy o an ins alla ion he p o i abili y s udy is done o come up wi h
impo an economic a iables as VAN and TIR o e en Pay-Back ime. Howe e in his p ojec ,
his pa ame e s a e no calcula ed as he inpu s o money ecei ed due o ope a ion and
main enance o he line a e no a ailable o a pa o a bid g id. In case o GIL di e en
a angemen s ha e been done, o see which a e he mos impo an sensibili ies ha can ha e
signi ican impac on he inal p ice o he in as uc u e.
PIPE AND
CONDUCTOR COST
12%
TRANS. INSTAL.
TESTING
28%
CIVIL COST
1%
GAS PRICE N2+SF6
16%
GIS+Compensa o
2%
PROJECT
CONTINGENCY
4%
PROJECT LAUNCH
AND MANAGEMENT
13%
Powe losses
17%
Cos educ.T ans.
Capac
1%
Ope a ion and
main enance
6%
68
4.1.2.1 Type o laying (soil: so ock)
Fi s o all, he ci il wo k cos does no seem impo an in his p ojec . In Table 30 i can be seen
ha he ype o laying does ha e a li le e ec on he inal cos . This cos anges om 4,5 million
o a di ec ly bu ied o 34,5 million o squa ed unnels.
Table 30. Type o laying sensi i i y.
Ci il wo ks cos
Million €
€/m
€/MVA
Di ec ly bu ied
5,6
59,0
2.296,2
T ench
27,9
293,7
11.429,9
Squa ed unnel
41,2
433,6
16.873,3
4.1.2.2 Type o soil o a di ec ly bu ied sys em
Secondly he ype o soil is s udied (Table 31). The columns e e o he same meaning as he
p e ious s udy. I can be seen ha independen ly o he ype o soil ci il wo ks a e s ill almos
insigni ican o he o al cos e e ing o less o 2%.
Table 31. Type o soil sensi i i y.
Million €
€/m
€/MVA
Disagg ega e
1,1
11,3
441,7
Loose
1,3
13,6
529,5
Compac
1,6
17,0
662,0
Ha d
2,8
29,5
1.147,6
So ock
5,6
59,0
2.296,2
Ha d ock
9,0
94,4
3.673,5
4.1.2.3 To al cos unc ion o me al p ice
In his case s udy he p ice o me al is in e e ence o Table 25 4,2 €/kg o he ou e enclosu e
pipes and 5,2 €/kg o he conduc o pipes. As can be seen in he p e ious cha s, he p ice o
he pipes is one o he mos signi ican componen s o he GIL ins alla ion, he e o e, i is o huge
in e es o know he e ec ha he aluminium p ice has on he o al cos .
69
Gas Insula ed Lines. Technical-economic analysis
In Table 32 can be app ecia ed as o al cos o GIL in as uc u e does highly depend on p ice o
me al. This shows he g ea impo ance ha ha e me al p ices o y o educe as much as
possible ins alla ions p ice.
Table 32. Sensi i i y s udy o he p ice o me al
P ice o me al
Cos o me al pa s (M€)
TOTAL COST (M€)
%
2€/kg
24,4
426,6
5,7
3€/kg
36,5
459,1
8,0
4€/kg
48,57
491,6
9,9
5€/kg
60,6
524,1
11,6
4.1.2.4 Gas mix u e
The gas mix u e used nowadays does ha e high en i onmen al conce ns due o he p esence o
SF6. Since many yea s al e na i e gases ha e been s udied o y o eplace SF6. Pe haps he
insula ing gas CF3I can be he al e na i e in he nea u u e. Techniques o p oducing his gas
a e being highly imp o ed, he e o e i s p ice is being cons an ly educed. Fu he mo e his new
p oduc ion me hods may each necessa y equi emen s o ensu e massi e indus ial
p oduc ion. In e e ence o [12] he p ice o CF3I has been educed o e 630 £/kg o 62,86 £/kg
in 2014. The change a e used be ween £ and € is 1,1 € is 1£.
The mass o gas equi ed o 1 km single phase GIL is 5,72 onnes, which makes 1.630 onnes o
he s udied case, ha is o a h ee phase sys em 95 km long [12]. Wi h his in o ma ion is made
he sensi i i y s udy o he al e na i e gas CF3I. In Table 33 a e shown alues o o al cos in
e e ence o gas p ices.
Table 33. Gas sensi i i y
P ice 𝐂𝐂𝐒𝐒𝐂𝐂𝐂𝐂 [€/kg]
To al cos (M€)
Gas P ice (M€)
%
69,15 (2014)
575,4
112,7
19,6
50
490,1
81,5
16,6
25
380,4
40,8
10,7
10
314,6
16,3
5,2
5
292,7
8,2
2,3
I can be seen ha o al p ice o he GIL in as uc u e a 2014 p ices is much mo e expensi e
han when SF6 is used. This high p ice may make GIL no an app op ia e al e na i e o be used.
In case p ices we e educed, p obably he CF3I gas would be he al e na i e.

70
4.2 O e head lines
I is o high in e es o compa e o al cos o in es men and li e-long expenses be ween GIL
ins alla ions and OHL. This in e es is mo i a ed because, no mally ansmission sys em
ope a o s end o selec OHL ins alla ions ins ead o o he sys ems such as unde g ound lines o
e en GIL, due o hei lowe cos . The OHL will be compa ed o he GIL op ion o he p esen ed
case s udy. Fu he mo e in his case s udy i is especially impo an o see i he e a e any
cheape echnologic solu ion o ace en i onmen al es ic ions[32].
To s udy he cos s o o e head and unde g ound lines, he cos s o ins alla ion ha e been
ob ained om [37][38]. This documen p esen s cos s associa ed o he cons uc ion and
main enance o ansmission lines, i.e. OHL and unde g ound cables, in Spain.
Rega ding da a o he cons uc ion o he OHL sys em de ined by REE in [39] and [32] o he
connec ion be ween Pinilla and Co en es, i is collec ed in Table 34.
Table 34. P ojec cons uc ion pa ame e s.
Sys em
Al e na ing h ee phase cu en
Vol age
400 kV
Conduc o ’s maximum empe a u e
85 ºC
Numbe o ci cui s
2 (1 ins alled)
Numbe o conduc o s pe phase
3
Type o conduc o
Condo AW
O he impo an da a e e ed o his p ojec such as li elong ime, discoun a e, wo king hou s,
e c, is he same as o he GIL ins alla ion.
4.2.1 Ini ial in es men cos s. Fixed cos s
Acco ding o he in o ma ion gi en o he ini ial in es men cos s in [37], p ice o he s udied
400 kV line is 373.047 €/km. This cos e e s o cables, s uc u es, ci il wo ks, ins alla ion cos
and e en launch, managemen and con ingency. No ice ha he selec ed ype o OHL p ojec is
400 kV ( iplex) simple ci cui which e e s o he ins alled ci cui .
Apa om he dis ance dependen cos s, he cos o GIS ins alled a each end o he
in as uc u e also ha e o be included. Acco ding o [34] each GIS o a 400 kV and 63 kA sys em
is 2,5 M€.
71
Gas Insula ed Lines. Technical-economic analysis
To al ini ial in es men cos s a e shown in Table 35:
Table 35. To al ini ial cos .
Million €
€/m
€/MVA
€/yea
Ini ial in es men
Dis ance dependen cos s
35,4
373,0
14518,4
885986,6
Dis ance non-dependen cos s
5,0
52,9
2058,6
125628,3
To al ini ial ins alla ion cos
40,5
425,9
16577,1
1011614,9
4.2.2 Va iable cos s
The a iable cos s o ins alla ion include he ope a ion, main enance, he cos o powe losses
and he cos ela ed o a educ ion o powe capaci y o he line due o eac i e powe .
4.2.2.1 Ope a ion and main enance
Cos s o main enance and ope a ion a e ob ained om he e e ence [37]. I can be seen ha
he main enance cos pe yea o a 400 kV line is 3.106 €/km.
In o de o calcula e he o al cos o he li e-long ime o he ins alla ion (40 yea s) he
ollowing equa ion is used:
M&O=(1+i)n−1
i(1+i)n ∗ Cos M&O (66)
whe e;
i: discoun a e;
n: ins alla ion’s numbe o yea s o li e;
In he s udied case M&O= 5,1 M€ o he li e ime pe iod.
4.2.2.2 Powe losses in cables and educ ion o ansmission ene gy due o eac i e powe
The s udy o he cos s o hese pa ame e s seem impo an as hey may ha e a g ea e ec on
o al inal cos o a high ol age line. In o de o come up wi h hese pa ame e s, powe losses
and he capaci i e and induc i e powe in he line, i is necessa y o know he alues o
esis ance (Ω) capaci ance (F) and induc ance (H).
The OHL conduc o used in his p ojec has been indica ed a he p ojec done by he company
REE, o his speci ic new elec ic in e connec ion [38]. The main p ope ies o he cable a e
72
indica ed in p oduc speci ica ions ables as [40]. No e ha he conduc o used is Condo /AW
which is o med by aluminium wi es, concen ically s anded a ound a s eel co e wi e. In Table
36 signi ican da a has been collec ed [40]:
Table 36. Conduc o 's da a.
Mass
1116,2 kg/km
Resis ance
0,069 Ω/km
To al diame e
27,73 mm
S eel diame e (co e)
9,24 mm
Aluminium c oss sec ion a ea
402,6 mm2
To al cable sec ion
603,48 mm2
No e ha he esis ance pe km has been indica ed o a empe a u e o 25 ºC.
F om [41], he ela ionship be ween esis ance and empe a u e is:
R2= R1 [1 + α(T2−T1)] (59)
whe e;
Ri: esis ance a empe a u e (Ti [K]) [Ω];
α: empe a u e coe icien [1/K].
Fo aluminium he empe a u e coe icien is 4,46 ∗10−3 [1/K] [42]; i is only conside ed he
coe icien o empe a u e o aluminium as he g ea pa o he conduc o ’s sec ion is made o
aluminium.
The wo king empe a u e depends highly on many pa ame e s, mos o hem uncon ollable; in
o de o gi e an app oxima ion o he esis ance a no mal condi ions, he empe a u e
conside ed is 85ºC [38]. Wi h his assump ion, he esis ance o each conduc o in OHL is:
R2= R1 [1 + α(T2−T1)] = 0,069 [1 + 4,46 ∗10−3(85 −25)]=0,087 Ω/km (60)
In ensi y pe cable o he e e ed line which has one ci cui and h ee conduc o s pe phase is:
I = S
3∗√3∗400 =2441
3∗√3∗400 = 1,17 kA (61)
To calcula e he induc ance and capaci ance pa ame e s o he s udied line, i is impo an o
know hei dependence on he geome y o he owe s and he ma e ial o he conduc o . In
his case he e is a beam o h ee conduc o s pe phase colloca ed a he e ex o a egula
polygon, in his case an equila e al iangle.
73
Gas Insula ed Lines. Technical-economic analysis
The geome y and dis ances be ween conduc o s o a beam and he dis ances be ween phases
o he sys em a e shown in Figu e 35.
Figu e 35. Dis ances o beams o conduc o s. (Da a sou ce: [37])
The ype o owe and dimensions ha e been ob ained om a simila p ojec done by REE. In
Figu e 36 a e indica ed hei dimensions. No ice ha in he p ojec Pinilla – Co en es, al hough
he owe used can sus ain wo ci cui s, o da e only one ci cui has been ins alled [38], ha
means ha only one o he symme ic pa s is used.
Figu e 36. OHL owe . (Da a sou ce: [39])
The induc ance pe km is calcula ed [41]:
L = ln DMG
RMG [mH/km] (62)
80
The esis ance, capaci ance and induc ance pa ame e s o he unde g ound cable ins alla ion
esul o be:
Table 42. RLC alues
Line Da a
R
[Ω/km]
L
[mH/km]
C
[µF/km]
0,00832
0,35
0,23
Wi h alues ob ained ( a io Q/P<0.2), no compensa ion uni s a e needed; he e o e he e a e
no losses e e ed o he compensa ion uni s; howe e he cos o powe capaci y educ ion due
o eac i e powe has o be s udied. In Table 43 a e shown he a iable cos s o he
Unde g ound Cable ins alla ion. I is ema kable o ou line he low p ices o powe losses; his
low a es a e a consequence o he low esis ance alues ound o he cables used in his
ins alla ion.
Table 43. Va iable cos s
Million €
€/m
€/MVA
€/yea
Powe losses
27,9
293,3
11.415,7
696.643,5
Cos educ .T ans. Capac
8,3
87,4
3.400,9
207.541,0
Losses in Compensa ion
0,0
0,0
0,0
0,0
To al a iable cos s
36,2
380,7
14.816,6
904.184,6
Table 44. To al cos
Million €
€/m
€/MVA
€/yea
TOTAL COST
526,7
5.544,1
215.769,2
13.167.312,8
4.4 Case s udy esul s discussion
F om he compa ison s udy o he Pinilla-Ayo a-Co en es elec ic line has been done a cos
app oxima ion o h ee di e en elec ic echnologies. These cos app oxima ions a e o high
in e es o na ional g id companies as bo h he di e ences be ween he cos componen s can
be ou lined and o al cos s o lines can be p edic ed. P ices go o his ins alla ion compa ison
can be ex apola ed o o he simila ins alla ions.

81
Gas Insula ed Lines. Technical-economic analysis
In e e ence o he case s udy done, i can be seen ha as i was p edic ed GIL ins alla ions may
ha e mo e expensi e cos a es han OHL; u he mo e, in his case he cos s associa ed o GIL
and Unde g ound Cable ins alla ions, a e e y simila . This simila i y be ween p ices o bo h
echnologies can be explained by he highe capaci y o GIL o low g ea e quan i ies o cu en
[45].
No ice ha his compe i i eness in p ice be ween Unde g ound Cable ins alla ions and GIL
depends much on he signi ican sensible cos pa ame e as i is he me al p ice; in Table 45 is
gi en a sum up o all he main cos componen s o each s udied echnology o he case o he
new ins alla ion Pinilla – Co en es. Di e en me al p ice scena ios can be seen o ealize when
would be a GIL ins alla ion cheape han o he ypes o echnologies depending on his
sensi i i y; also a e shown di e en p ice scena ios o he gas CF3I which may be he u u e o
GIL ins alla ions.
Table 45. Cos compa ison GIL OHL and Unde g ound cables.
GIL
Million €
Ini ial in es men
388,2
Va iable cos s
120,8
To al cos
509,0
GIL sensi i i y
P ice o me al
To al cos
2 €/kg
426,6
3 €/kg
459,1
4 €/kg
491,6
5 €/kg
524,1
P ice o gas (CF3I)
To al cos
5 €/kg
292,7
10 €/kg
314,6
25 €/kg
380,4
50 €/kg
490,1
69,15 €/kg (2014)
575,4
OHL
Ini ial in es men
40,5
Va iable cos s
277,8
To al cos
318,2
Unde g ound Cables
Ini ial in es men
490,5
Va iable cos s
36,2
To al cos
526,7
This p e ious able and he cos s udy done can p o ide some conclusions:
82
• The p ice sensi i i y shows how much is impo an he me al p ice and he gas
p ice in o de o ensu e GIL o be an al e na i e o be implemen ed in HVAC
ins alla ions, a leas in compa ison wi h unde g ound cable ins alla ions.
• Rega ding a iable cos s, i is signi ican ha he e can be seen big di e ences
in he powe losses cos and he cos due o educ ion o powe capaci y as a
cause o he a ia ion o he esis ance, induc ance and capaci ance pa ame e s
o he di e en echnologies. No e ha his di e ences in cos ange om 36,2
million € o an Unde g ound Cable ins alla ion o 277,8 million € o an
O e head Line. No e he low a iable cos s o unde g ound ins alla ions, which
a e a mainly a consequence o he low esis ance alues o he cable used.
• The a iable cos s o OHL ins alla ions a e huge due o high powe losses, mainly
a consequence o he high esis ance alue o he conduc o . This can be
con as ed wi h low ini ial in es men , which is o lowes in e e ence o GIL and
Unde g ound Cables.
In he end i can be said ha GIL can become a compe i i e solu ion in compa ison o OHL and
Unde g ound Cables in many cases i me al and gas p ices a e low enough ha ensu e GIL
compe i i eness.
83
Gas Insula ed Lines. Technical-economic analysis
5. Conclusion
Finally wi h he de eloped ool i is possible o ins i u ions and elec ic companies o do a cos
s udy o he GIL echnology. O cou se, his ool is going o enease he GIL implemen a ion, as a
cos s udy gi es he oppo uni y o compa e echnologies wi h economic pa ame e s.
Fu he mo e, i can be s a ed ha GIL is no so a away om being a mo e used HVAC elec ic
sys em; his is because on he one hand elec ic in e connec ions will need o ha e highe powe
a es a compe i i e p ices, and his is an ad an age o GIL; on he o he hand he g ea isual
and en i onmen al impac ha c ea e OHL is willing o be de ea ed; i can be done by using he
unde g ound layou o GIL.
Wi h his hesis and ool, he oppo uni y o design and see he cos o di e en ins alla ion
a angemen s is possible, he e o e i may become simple he possibili y o s udying which a e
hose op imum echnical solu ions ha come wi h he bes en i onmen al a angemen .
In he end, his wo k has p o ided some cos unc ions ha we e p e iously no ound in he
li e a u e. The e o e, he aim o his inal deg ee p ojec s is conside ed o be accomplished,
ha ing p o ided a ool which gi es a cos app oxima ion o all echnical a angemen s o GIL
ansmission sys em.
On he o he hand, some u u e wo k is able o be done o expand he u ili y o he echnical-
economic analysis o GIL:
• Pe haps he mos in e es ing one would be o gi e a comple e ool ha would gi e a
he same ime a cos app oxima ion o he main elec ic ansmission echnologies
(OHL and Unde g ound Cables) wi h GIL.
• Ano he poin ha can be imp o ed, echnical alues o GIL do no only depend on
ol age and appa en powe , bu hey depend on many o he aspec s as wo king
empe a u e; i would be o high in e es o come up wi h an imp o ed ool ha akes
in o accoun o he pa ame e s no used o app oxima e cos .
• The nex s ep o he designed ool is he possibili y o i o ge om he in e ne cu en
and upda ed alues o he ma e ial p ices.
84
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