Electrical Considerations for HVDC Transmission Lines Joe Mooney, PE
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Learning Objectives At the end of this presentation you will be able to: Identify the electrical requirements for HVDC lines. Identify the components used in AC to DC conversion. Understand the history of HVDC conversion and transmission Understand the operation of HVDC conversion technology. Understand the requirements of an HVDC convertor station. Understand the differences between classic HVDC and new HVDC technology. Understand the fundamental requirements of HVDC transmission line design. Understand the insulation requirements for an HVDC line.
HVDC A Brief History First HVDC System Commissioned in 1954 Gotland, Sweden ±100kV, 20MW, 60miles of submarine cable First Installation in North America in 1969 Vancouver Island, BC ±260kV, 312MW, 46miles of submarine cable
HVDC A Brief History Last Mercury Arc Valve Installation Pacific DC Intertie 1970 1440MW, ±400kV Currently at 3100MW, ±500kV Graphic Courtesy ABB Photo Courtesy ABB
HVDC A Brief History Longest Distance in Operation 1062 miles Democratic Republic of Congo, Africa 1983, ±500kV, 560MW, overhead line Highest Voltage in Operation ±600kV Itaipu, Brazil 1987, two circuits@3150mw each, 490+ miles Graphic Courtesy ABB Graphic Courtesy ABB
HVDC A Brief History First Multi Terminal HVDC System Quebec New England 1992, ±450kV, 2000MW Longest Submarine Cable Norway to Netherlands 362 Miles 2008, ±450kV, 700MW Graphic Courtesy ABB
HVDC A Snapshot of the Future Highest Voltage ±800kV Two circuits i in China 5000MW, 890 miles (2010) Graphic Courtesy ABB 6400MW, 1295 miles (2011) Longest Circuit Over 1550 miles Rio Maderia in Brazil ±600kV, 3150MW Scheduled to be in operation in 2012 Graphic Courtesy Siemens Graphic Courtesy ABB
When to Use HVDC Long Distance Long Underground/Submarine Cables Asynchronous Systems Controlled Power Transfer Reduce Right of Way
HVDC Projects Planned in China Source: MarketAvenue
6000MW HVDC vs. AC Right of Way Comparison ±500kV DC 500kV AC ±500kV vs. 500kV AC ±800kV vs. 800kV AC
Typical HVDC Converter Station Graphic Courtesy ABB
HVDC Technology HVDC Classic Line Current Commutated; Thyristors Large blocks of power; 1000 s of MW High voltage applications; ±800kV HVDC Light/PLUS Voltage Source Commutated; IGBT Small blocks of power; 100 s of MW Lower voltages; ±200kV
HVDC Classic Design Twelve Pulse Converter Requires Specially Designed Transformers Power System Must Supply Reactive Power Thyristors are Switched on and turned off by reverse voltage Harmonic Filters are required
HVDC Classic Valve Groups Photos Courtesy Siemens
HVDC Classic Converter Transformer Photos Courtesy ABB
Photos Courtesy ABB HVDC Classic AC Filters
3000MW HVDC Classic Station Photo Courtesy ABB
HVDC Light Design Insulated Gate Bipolar Transistors Off the shelf transformer Switched on and off Pulse Width Modulation Power factor can be controlled Simple high pass filter for high order harmonics Graphic Courtesy ABB
HVDC Light Components Photos Courtesy ABB
Photos Courtesy ABB HVDC Light Station
HVDC Operation Monopole Single positive dc voltage (e.g., +500kV) One high voltage conductor Neutral return Metallicreturn via lowvoltage conductor Earth return through ground electrode Limited Operation Fault or maintenance results in outage
AC Power System AC Power System Monopole HVDC AC Power Syst tem AC Power System
HVDC Operation Bipole Positive and negative voltage (e.g., ±500kV) Two high voltage conductors Neutral return Metallic return via low voltage conductor Earth return through ground electrode Best Operational Flexibility Operate in monopoleconfiguration asneeded Allows for maintenance or outage of one pole Up to half of rated power output
Bipole Operation Earth Return HVDC Cable/OH Line AC Powe er System Earth Return Ground Electrode AC Powe er System HVDC Cable/OH Line
Bipole Operation Metallic Return HVDC Cable/OH Line AC Power System LVDC Cable/OH Line AC Powe er System HVDC Cable/OH Line
Cost Comparison HVDC vs. AC HVDC has a higher installation cost due to the converter stations and filtering requirements. The cost of an HVDC line is less than the cost of an AC line. Long AC lines are more expensive due to shunt and series compensation requirements.
Cost vs. Distance for HVDC and AC
Electrical Considerations Insulation Metallic or earth return (ground electrode) Audible Noise Magnetic and Electric Fields
Insulation Requirements Air Clearance Requirements Switching Performance Lightning Altitude Pollution/Contaminants
8 6 4 2 0 8 6 4 2 Air Clearance Requirements EHVAC Air Clearance Requirements (meter) 2.6 p.u. 1.8 p.u. EHV AC Switching primary Lightning secondary HVDC Switching secondary System voltage (kv) 500 800 1100 HVDC Air Clearance Requirements (meter) 0 400 600 System voltage (±kv) 800 Graphic Courtesy ABB Lightning primary Air Clearance Requirements are Significantly Lower for HVDC.
Effect of Altitude 1.30 1.25 1.20 1.15 1.10 105 1.05 1.00 0.95 0.90 Relative increase in insulation requirements with altitude Lightning Switching Pollution 0 500 1000 1500 2000 Graphic Courtesy ABB Altitude (meter) EHV AC Air Clearance (switching) Insulation (pollution) HVDC Air Clearance (lightning) Insulation (creepage) Insulation Requirements for HVDC are More Sensitive to Altitude
Earth Return Metallic Return Same current rating as main conductor Insulated for voltage drop caused by current flow Earth Return Expansive ground electrode Requires significant study Gravity survey, hydrological survey, electrical resistivity survey, geological modeling
IPP Southern Electrode
IPP HVDC Ground Electrode Connection to Tower
Corona and Audible Noise Weather has Smaller Effect on Corona Losses for HVDC Lines Requirement for Conductor Bundling is Reduced for HVDC Lines to Meet Audible Noise Requirements
Corona and Audible Noise Typical corona losses (kw/km) 1000 100 10 Frost Rain Fair EHVAC HVDC Corona Losses on HVDC are less Sensitive to Weather Conditions 1 Graphic Courtesy ABB EHVAC, HVDC 0 500 1000 1500 2000 Altitude (m)
UHVAC Conductor Bundles for 55dB Maximum 2000 6 6 9 1500 Altitude (meter) 1000 5 6 8 500 5 4 8 0 700 800 900 1000 1100 System voltage (kv) Graphic Courtesy ABB
HVDC Conductor Bundles for 45dB Maximum 2000 3 4 6 7 1500 Altitude (meter) 1000 2 4 5 6 500 2 3 4 5 0 400 500 600 700 800 System voltage (±kv) Graphic Courtesy ABB
Magnetic and Electric Fields No Magnetic Induction from DC Current flow in Opposite Directions Cancel Magnetic Field Effect on HVDC Comparable to Earths Magnetic Field (50µT) Field Requirements for DC are less Stringent than AC Greater Public Acceptance
Itaipu HVDC and EHV System HVDC Line Cost about 70% of AC Line ITAIPU 2 x 6300 MW 3 x 765 kv AC, 2 intermediate S/S 6300 MW with SC 4500 MW without SC 3 i it 2 x ± 600 kv DC 6300 MW, 2 converters per pole 4700 MW with pole outage 4 l 3 circuits 4 poles Photo Courtesy ABB
Itaipu 765kV Ac Lines Line 1. 891 km 1982, 86, Line 2. 891 km 1989 Line 3. 915 km 1999, 00, 01 About 70% Guyed Vee Average weight 8500 kg, guyed Self supporting, weight 14000 kg 15.80 m Phase spacing, guyed 14.30 m Phase spacing, self support Conductor 4xBluejay 564 mm² ACSR 450 mm subconductor spacing 35 Insulators 95 m RoW one line Photo Courtesy ABB 178 m RoW two lines
Itaipu ±600kV HVDC Lines Bipole 1792 km 1984 Bipole 2820 km 1987 About 80% Guyed Mast Average weight 5000 kg, guyed Self supporting, weight 9000 kg Conductor 4xBittern 644 mm² 45/7ACSR 450 mm subconductor spacing 32 Insulators 510 mm creep, 27 mm/kv 16.40 m pole spacing 72 m RoW per circuit Photo Courtesy ABB
Thank you for your time. QUESTIONS? This concludes the educational content of this activity. Joe Mooney, P.E. Sr. Project Manager www.powereng.com March 2010