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Terna Rete Italia – Head of Research Center -Florence
Chairman Comitato Nazionale CIGRE-Italia
M. Rebolini
CIGRE ATLASOFHVDCSYSTEMSWITHITALIANTSO EXPERIENCE
2
1987 40 HVDC System 11 mercury-arc valves29 thyristor valves
ATLAS OF HVDC SYSTEM
3
2009 103 HVDC System in operation 8 HVDC System retired3 HVDC System BtB( Austria-
Hungary & Germany-Cech Republic & Austria) and after retired17 HVDC System in construction5 VSC in operation
2015 166 HVDC System in operation ( 3 UHVDC +/- 800 kV)61 HVDC System in construction/planned10 VSC in operation1 Hybrid System ( LCC-VSC)
2015-2020 28 UHVDC(±800 kV, ±1100 kV) planned for
implementation
ATLAS OF HVDC SYSTEM
4
Number of HVDC installations by Year
7 10
23
4650
29
165
0
20
40
60
80
100
120
140
160
180
50-70 70-80 80-90 90-2000 2000-2010 2010-Today Total
40
136
165
ATLAS OF HVDC SYSTEM
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HVDC From Global Interconnection to ……. ATLAS OF HVDC SYSTEM
HVDC & FACTS for SubTransmission & Industrial
Distribution Systems
ATLAS OF HVDC SYSTEM
7
HVDC From Interconnection to …..Connection
ATLAS OF HVDC SYSTEM
More HVDC investments in the nextyears
Global Investment in HVDC Transmission Systems 2012-2020 120 Billion $ (1)
(1) Source Pyke Research
ATLAS OF HVDC SYSTEM
(1) Source Technavio Analyst Report
Converter Stations account for about 12 Billion $ per year ( 5% of total network investments) other are related to HVDC OHL and sea cables CAGR from 2014 to 2019 20% New Market analysis (1) gives grow of HVDC Converter at a CAGR of 24,1% 2016-2020Market share 2015 : EMEA (Europe, MiddleEast,Africa ) 36,12%, APAC (Asia Pacific) 32,65%, Americas 31,32%.
ATLAS OF HVDC SYSTEM
One third ( 33% of totalinvestment ) 50 billion € (56 billion $) are submarine HVDC interconnections
Also Europe strong increasinginvestments on HVDC Systems
ATLAS OF HVDC SYSTEM
HVDC is integral part of «smart grid solutions»Power flow & frequency control
WHY HVDC?
HVDC used in the connection of offshore Wind Farms
HVDC used in the integration of Networks ( mainly with long sea link )
HVDC used as BtB Systems for interconnection of asynchronous Networks
HVDC used for Very Long Distance Huge Power Transfer
HVDC become more acceptable ( both with OHLs and cables ) in Authorization/Environment Assessment vs. AC OHL technology
Now
Classical
ATLAS OF HVDC SYSTEM
System description LCC-HVCD VSC-HVDC
System ratings in operation ±800 kV, 7000 MW ±320 kV, 600 MW
System ratings available ±1100 kV, 13000 MW ±500 kV, 2000 MW
Operational experience 50 years 15 years
Lifetime 30 years 30 years
Converter Losses(at full load ,per converter ) 0.75 % 1,1 %
Availability (per system) >98% >98%
System Capabilities
Transmission Capacity ••• ••
Power Flow Control ••• •••
Transient Stability •• •••
Voltage stability • •••Power Oscillation damping •• •••
Reactive Power demand ••• •
System perturbation ••• •
Reactive Injection possible no yes
Easy meshing no yes
Black starting no Yes
SCR AC grid > 2,5 No problem
Investment costs per MW •• •••
Legenda: •small; • •medium; • • • strong
WHICH KIND HVDC-Technology ?
ATLAS OF HVDC SYSTEM
Malta Sicily
SAPEI
Sorgente - Rizziconi
Italy- France
0
100
200
300
400
500
600
0 100 200 300 400 500 600 700
Rat
ed
Vo
ltag
e (
kV)
cable length (km)
Uneconomical Voltage Levels
AC
3 p
has
eHVDC - LCC
HVDC- VSC1st generation
HVDC-VSC2nd generation
HVDC-VSC3nd generation
ATLAS OF HVDC SYSTEM
MAIN CHALLENGES &ITALIAN VIEW from TSO EXPERIENCE SOME CASES
15
SACOI 1 1967-1992
SACOI 21992-today
• Voltage: ±200 kV LCC
(Line Commutate Converter• Air cooled Thyristors Valves
• Rated power: 300 MW
• Nominal Current 1500 A
• Total Length 385 km :121 km
sea cables, 264 km DC OHL
The world first triterminal HVDC( 1987)
• Voltage: ±200 kV LCC
(Line Commutate ConverterMercury Valves )
• Rated power: 200 MW
• Nominal Current 1500 A
• Max Depth 500 m
• Total lengh 413 km :292 km
DC OHL and 121 km sea
cables
• 1987 Lucciana Tap (250 A;
50 MW)
Was connected
To 380 kV grid
TERNA HVDC Plants
HVDC Italy-Greece Link
The world first deepest submarine HVDC cable
(1.000 m)
In operation 2001
Voltage: ±400 kV LCC
Monopolar with marine electrodes
Rated power: 500 MW
Nominal Current : 1250 A
Length 316 km ( dc UG -OFcable 43 km
Italy side , 160 km sea cable and 113 km
dcOHL Greek side )
TERNA HVDC Plants
HVDC link that increases security
of supply and improves market
competitiveness in Sardinia
• Voltage: ±500 kV LCC
(Line Commutate ConverterThyristor water cooling)
• Rated power: 1.000 MW
HVDC LINK SARDINIA-MAINLAND
«SAPEI» In Operation 2011The longest HVDC cable at time of construction
(435 km)
The world deepest submarine HVDC cable
(1.640 m)
TERNA HVDC Plants
Under construction
New HVDC interconnection
• Voltage: ±500 kV LCC(Bipolar )
• Rated power: 1.200 MW
Length 400 km.
Depth: 1200 m
NEW INTERCONNECTION ITALY-MONTENEGROFirst electricity HVDC link
between Europe and the
Balkans
TERNA HVDC Plants
SACOI GRITA SAPEI MONITAManufacturer Converter / Thyristor
GE-Ansaldo ABB ABB TOSHIBA / Infineon
Valve Number 12 12 12 12Modules for Valve 7 10 8 3+3Thyristors for Module 8 6 9 12+13Number Thyristors for valve…
56 60 72 75
…redundancy 3 2 3 3Number Thyristors for a pole
672 720 864 900
AccensioneETT=elettrically triggered thyristorLTT=light triggered thyristor
ETT ETT ETT LTT
Thyristor Current [A] 1500 1250 1000 1200Tensione tiristore VBO [kV]
4,5 8,5 7,5
Cooling air water water water
TERNA HVDC Plants
Under construction
New HVDC interconnection
• Voltage: ±320 kV VSC
(Voltage Source Converter)• Rated power: 2x600 MW
• Total length 190 km
NEW INTERCONNECTION FRANCE-ITALY
• The first synergy between HVDC link and highway
infrastructure crossing Alps in Service Tunnel of
Frejus
TERNA HVDC Plants
21
What are main challenges for HVDC
Economics
Long Duration of Design ( all phases)
Obsolescence Risks-Life exstension
Authorization/ Environmental Phases Risks
Technological Risks ( some cases)
22
Economics
23
Substation cost
Trasmission Line costs
Reactive Power Compensation costs
Operation & Maintenance costs
Loss evaluation costs
Right of way costs
Economics
24
Other economics evaluationto consider
Economics
25
Long Duration of Design ( all phases)
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2003 -Feasibility Study
2010 New evaluation !!
Due to economical crisis and phase out of some Thermal PP in Sardinia the ESCR falls down in the range 1,4-1,7 p.u. !
Long Duration of Design ( all phases)
27
Long Duration of Design ( all phases)
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AGEING Lifetime
Spare parts criteria
Digital Control System:Life time critical point
Obsolescence Risks
Fast development of new power electronics devices while beneficial in terms of technology improvement may be an issue for recently proposed projects, in terms of technology obsolescence.Obsolescent topologies:• 2 and 3 level large HVDC VSC links started
commercial operation in the 2000s (Cross Sound,Murraylink ). Nowadays this topology is alreadyobsolete.
• DC neutral is ungrounded in most recent modularmultilevel converter up to 320 kV. DC groundingwill most probably be adopted in the future forhigher voltage level.
Obsolescent power electronics:• IGCT ( Integrated-Gate Commutated Thyristor )
IGBT ( Insulated-Gate Bipolar Transistor)• Press Pack (direct / indirect pressure)• Silicon Carbide ( SiC ) power device in the future.
Obsolescence Risks
- 30 -
Technological Risks :operating experience important factor
In order to verify the quality of the operatingdata, TERNA has adopted the requirements ofthe protocol established by the B4 Committee ofC.I.G.R.E.
In the follwing slides are summarized the resultsof operation of SACOI2 link from 1993 to 2013
SA.CO.I.2 Report of performances 1993-2013 (1/3)
The figure 3 shows that the availability ofthe Link is almost a constant value from 1993to 2013 (above 90% ).
The utilization of the link has been growingfrom 2002 (average 58.44%) compared to arather low average (33.72%) in previousyears.
Fig.2 Direction of power flow between Sardinia and Tuscany
Fig.3 Energy utilization (U) and Energy Availability (EA)
Direzione Ingegneria
Fig.1 Total Energy transmitted
SA.CO.I Report of performances 1993-2013 (2/3)
Failures on cable have a big impact on the total forcedoutage period (91%), but slightly affect the values ofreliability because the presence of the second cableallows to operate the link even if with reducedperformance 50%
Figure 6 FEU in equivalent outage hours
CAUSE OF FAILURE OF CABLES FROM 1967 TO 2013
SA.CO.I Report of performances 1993-2013 (3/3)
Fig.6 Main substation forced outageFigures 7 and 8 show in terms of equivalent hours and percentage,forced outages attributable to the main converter stations.
• The control and protection system and the AC yardequipments (especially the filters) are the two leading causes.
• No problem with thyristors;the total number of failures is not increasing
Fig.8 Breakdown of substation forced outage by equipment categories
Fig. 7
Fig. 9
34
Technological Risks: Fire
GRITA DESIGN Improve requirements vs Fire Events
Fire Risk in these years become very important because of several disastrous fire incidents in HVDC Plants ,the last occurred in autumn 1993 in Sylmar East Station full destroying one quadruple valve.
35
Model scenario of fire in valve hall was used for computer simulation.Oil spill fire was based on insulation oil spread out on the floor while the fire in the thyristor module was upper 4 meters below ceiling ( impact on average T gas layer).Smoke ventilation in operation.
36
-Mimize amount of combustible material – Material selection and mechanical features-Sectionize equipment and segregation barriers to prevent spread of fire or leak water-valves designed exclude corona in operation voltage to avoid degradation of plastic materials( checked type and routine test)-Detect a fire in incipient stage using Fast Acting ( <10’) Fire Detection devices ( like VESDA or IFD )-Exstinguish a possible fire-Minimize secondary damages caused by increased T and combustion product
VALVE HALL CRITERIA adopted vs. RISK of FIRE
37
Technological Risks: Fire
To keep oil filled equipment out of valve hallwas decided to avoid oil smoothing reactorand using air cooled type smoothing reactor
38
Technological Risks: Earthquake
GRITA DESIGN Improve requirements bothConverter Station vs Earthquake , do to Arachtossite
Suspended Valves
The seismic design of the CS equiment was based onTwo level severity:OBE and MDE ( Maximum Design Eartquake).Qualification methods followsTest procedure and seismicverification was developed with a linear elastic modal analysisprocedure.
Technological Risks:Transport
Technological Risks: Permitting Phase Risks
SAPEI Architecture Design To Improve public acceptance and speedup Permitting phase
SAPEI Marine Impact Assessment on mammals life ( dolphins, whales etc)
Technological Risks: Converter Transformer failure risk
SAPEI PROJECT : After design review was performed a special test : short circuit on unit of Converter Transformer at KEMA Platform test.
Technological Risks: Pollution and Insulation
GRITA design taking in to consideration 500 kV wall bushingsflash over( mainly in rainy weather )
in Ghenzuoba -ShangaiHVDC System experience .Was installed a silicone bushing rather thanporcelain
SAPEI adopted indoor type Solution for all equipment in Sardinia side for salt and coal pollution
Technological Risks: Pollution and Insulation
Technological Risks: Organization Task
More than 70 people TSO involved in SAPEI Project Management and Test
45
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