HVDC TRANSMISSION F. M. Gatta, A. Geri, S. Lauria, M. Maccioni, G. M. Veca Università degli Studi di Roma “La Sapienza” Dipartimento di Ingegneria Elettrica Via Eudossiana n° 18, 00184 Roma, Italia Presented by Prof. Stefano Lauria 28/03/08 @ 14.30.00
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
HVDC TRANSMISSION
F. M. Gatta, A. Geri, S. Lauria, M. Maccioni, G. M. VecaUniversità degli Studi di Roma “La Sapienza”
Dipartimento di Ingegneria ElettricaVia Eudossiana n° 18, 00184 Roma, Italia
Presented by Prof. Stefano Lauria
28/03/08 @ 14.30.00
INTRODUCTION
In the past ...
Today ...
In Europe ...
2
Introduction
Applications
Integration
NAIG links
HVDC BERLIN '08Prof.Giuseppe Veca
At the beginning of 20th century, DC (Direct Current) was superseded by AC (Alternating Current) for large-scale electrification. DC power did nevertheless survive, in applications like electric traction and drives.
Today, bulk power systems are 3-phase AC, while utilization is either 1-phase or 3-phase AC.
Continental Europe is actually a single AC power system, running synchronously at 50 Hz, spanning from Portugal to Poland and Greece!
28/03/08 @ 14.30.00
UCTE
3
Introduction UCTE History
Applications
Integration
NAIG links
HVDC BERLIN '08Prof.Giuseppe Veca
28/03/08 @ 14.30.00
History of events
1930s
1940s
1954
1970s
Today ...4
Introduction UCTE History
Applications
Integration
NAIG links
HVDC BERLIN '08Prof.Giuseppe Veca
Efficient static AC/DC conversion (mercury arc valves) was made possible.
High Voltage DC (HVDC) bulk power transmission was studied in Germany.
First commercial application in Sweden: submarine link bet-ween mainland and Gotland island (100 kV-20 MW-90 km).
Thyristors (SCRs) took over; today, HVDC operation voltages attain 600 kV, transmitted power over 3000 MW.
DC made its way back into bulk power systems!
28/03/08 @ 14.30.00
TYPICAL HVDC APPLICATIONS
There are three typical HVDC applications:
5
Introduction
Applications
Integration
NAIG links
HVDC BERLIN '08Prof.Giuseppe Veca
1. Interconnection of non-synchronous AC power systems, even at different frequencies.
2. Power transmission over long undersea cable links, if the AC solution requires intermediate compensation.
3. Point-to-point, long-distance transmission of large blocks of power.
For entries 1. and 2., HVDC is the only practical solution.
For entry 3. the choice of DC or AC transmission is a matter of technical-economic convenience.
28/03/08 @ 14.30.00
Submarine transmission 1
For a 380 kV-50 Hz AC submarine cable
A bipolar HVDC submarine link can transmit 1000 MW over several hundreds of km, with 2 cables
Several HVDC links in operation or planned in Italy
1. The AC nodes at the HVDC line terminals must be able to supply/evacuate the rated power of the DC link.
2. The rated power of the DC link must be compatible with the TSO’s operation rules: f.i. UCTE takes at 3000 MW the largest single loss of generation in the European system.
3. AC short-circuit power at the conversion stations must be sufficiently larger than DC rated power (say, ESCR>3; depends on adopted technology).
28/03/08 @ 14.30.00
North Africa to Italy 1
13
Introduction
Applications
Integration
NAIG links NA to Italy 1 NA to Italy 2 Italy to G 1 Italy to G 2
HVDC BERLIN '08Prof.Giuseppe Veca
There are no particular shortcomings aside from the cost of submarine cables: in the first stage (say, 3000 MW power transfer) up to 3 cables per pole are needed
Other key points are:— Individuation and survey of cable routes in deep sea
(see f.i. studies conducted for Sa.Pe.I. link)— Identification of suitable EHV terminals in the Italian
network (several powerful nodes on the Tyrrhenian coast, from Naples to Suvereto)
28/03/08 @ 14.30.00
North Africa to Italy 2
14
Introduction
Applications
Integration
NAIG links NA to Italy 1 NA to Italy 2 Italy to G 1 Italy to G 2
HVDC BERLIN '08Prof.Giuseppe Veca
SAPEI cable route attains 1600 m depth and required extensive surveys by means of Remotely Operated Vehicles (ROVs)
28/03/08 @ 14.30.00
Italy to Germany 1
15
Introduction
Applications
Integration
NAIG links NA to Italy 1 NA to Italy 2 Italy to G 1 Italy to G 2
HVDC BERLIN '08Prof.Giuseppe Veca
At an initial stage (e.g. 2-3000 MW) the existing 380 kV AC network could be used.
Italy permanently imports 6000 to 7000 MW through the alpine interconnections, mainly from France and Germany; the new, northbound flow would be mainly virtual.
This solution, however, potentially interferes with the Italian energy market, capping the transfer capability between network zones “Center”, “Center-North” and “North”. Network expansion could be required.
Dedicated HVDC lines would solve Italian network problems. The key issue here, however, is the strong NIMBY attitude in Italy.
28/03/08 @ 14.30.00
Italy to Germany 2
16
Introduction
Applications
Integration
NAIG links NA to Italy 1 NA to Italy 2 Italy to G 1 Italy to G 2
HVDC BERLIN '08Prof.Giuseppe Veca
The best long-term choice is probably represented by 800 kV overhead lines, despite their visual obtrusiveness. Routing is undoubtedly a problem.
At a significant cost, HVDC underground cables could solve the public acceptance problem.
If the auxiliary galleries of new railway tunnels are made available, cables would greatly simplify crossing the Alps.