high voltage direct current

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EECE492 -Presentation on High Voltage Direct Current

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Presentation Transcript

High Voltage Direct Current :

High Voltage Direct Current TingFu Lin Jason Hsu Yichi Zhang UBC-EECE 492

Slide 2:

1. History 2. Configurations 3. HVDC Converters 4. Thyristor Valves 5. Advantages of HVDC 6. Cost of HVDC 7. Environmental Impact 8. Trans Bay Cable 9. Future Implications

What is HVDC?:

High Voltage Direct Current A High voltage electrical power transmission system that uses DC rather than the traditional AC Typically used for long-distance transmissions What is HVDC?

1. History:

1882- first demo of a 2.5 kW HVDC 1889- Rene Thury developed a new 630 kW system that transmitted power at 14 kV DC over 120 km 1913- fifteen Thury systems were in place, some up to 100 kV 1930- Thury systems were obsolete due to high maintenance costs and energy losses 1. History

1. History:

1906~1936 – Moutiers -Lyon system transmitted 8,600 kW of power over 124 miles, 6 of which was underground 1932- General Electric used mercury-vapor valves and a 12 kV DC transmission line in Mechanicville, New York. 1941- Berlin used a similar line underground, however, project terminated due to the fall of the government in 1945 1. History

1. History:

1950- first modern HVDC system was in service between Sweden and the island Gotland by ASEA (Swedish industry company) 1960- Three additional orders were received by ASEA in New Zealand, Sweden/Denmark, and Japan 1969- First HVDC system to use solid state valves 1970s- First HVDC system implemented within an AC network. (Los Angeles, California) 1. History

2. Configuration:

Monopole Bipolar Back to Back 2. Configuration

2.1 Monopole:

One rectifier terminal is connected to Earth ground, the other of higher or lower potential is connected to the transmission line 2.1 Monopole

2.1 Monopole-Advantages:

Most common type for moderate power HVDC Modern versions of monopole carry 1,500 MW for overhead transmission lines 600 MW for underground or underwater systems A good base for future expansions and upgrades into bipolar lines Simple and cheap Only require two converters and one high-voltage insulated cable 2.1 Monopole-Advantages

2.2 Bipolar:

Two opposite polarity, high potential conductors are used More expensive than monopole due to the required full insulation of the lines 2.2 Bipolar

2.2 Bipolar-Advantages:

Negligible earth-current flows under normal load, which reduces environmental effects and return loss With return electrodes, a fault on one line will still allow the rest of system to function as a monopole Conductors may be on separate transmission towers to prevent both being damaged at once by harsh conditions Carry up to 3,200 MW at +/- 600 kV May be upgraded from monopole system 2.2 Bipolar-Advantages

2.3 Back to Back:

2.3 Back to Back A short DC line where static inverters and rectifiers operate together DC voltage along the intermediate circuit may be selected

2.3 Back to Back-Advantages:

Couple different frequency electricity mains Couple two networks with varying phase relationship but the same frequency Change frequency and phase number like traction converter plants 2.3 Back to Back-Advantages

3.HVDC Converters:

Two types of converters Current Source Converter (CSC) Voltage Source Converter (VSC) CSC was dominating the market before 1990s, however, the newly developed VSC has some significant advantage comparing to CSC. 3.HVDC Converters

3.CSC and VSC:

3.CSC and VSC

4. Thyristor Valve:

HVDC converters are an assembly of valves that are conducting in the forward direction and blocking in the reverse direction. Thyrisor valves are a collection of many thyrstor cells. Thyristor valves eliminated the arc backs which were caused by mercury arc valves due to the failure to block in the reverse direction. 4. Thyristor Valve

4.Layout of Thyristor:

4.Layout of Thyristor

5.Advantages of HVDC:

The main application of HVDC is long distance bulk power transmission. AC transmission is mainly limited by the following factors: 1. Due to skin effect 2. AC resistance of a conductor is higher than that of a DC resistance which leads to a higher power loss 3. AC transmission has more corona effect and radio interference 4. AC transmission produces and consumes reactive power. 5.Advantages of HVDC

Comparison of DC and AC:

Comparison of DC and AC

6.Cost of HVDC:

6.Cost of HVDC

Cost comparison of HVDC and HVAC:

Cost comparison of HVDC and HVAC

7.Environmental Impact:

A DC line has less visual impact The size of right-of-way width of a DC line is reduced compared to an AC line Less corona effect Less radio noise DC lines have unchanging electric field There is no evidence supporting that DC lines generate free electrons, N2 or O3. 7.Environmental Impact

8. Case Study – Trans Bay Cable:

A 53 mile (85 km) long transmission infrastructure from Pittsburgh to San Francisco Undersea DC transmission Construction began in 2007 In commercial operation from late 2010 Cost over USD $500M 8. Case Study – Trans Bay Cable Info and photos taken from www.transbaycable.com

8. Case Study – Trans Bay Cable:

8. Case Study – Trans Bay Cable Info and photos taken from www.transbaycable.com

8. Case Study – Trans Bay Cable:

Rating 400MW (40 % of San Francisco’s peak demand) ± 200 kV DC, 230 kV /115 kV, 60 Hz Use modular multilevel converter (MMC) 8. Case Study – Trans Bay Cable

8. Case Study – Trans Bay Cable:

Extruded Insulation A bundle of transmission cable, return cable, fiber optic communication cable 8. Case Study – Trans Bay Cable Info and photos taken from www.transbaycable.com

8. Case Study – Trans Bay Cable:

Project Benefits Eliminated the need for a new generation plant Decreased grid transmission congestion Minimal environmental impact DC transmission does not expose electromagnetic radio to sea life 8. Case Study – Trans Bay Cable

9. Future Implications:

HVDC may be the Supergrid solution European Supergrid Trans America Grid Possible conversion of existing 3-phase AC lines into bipolar DC with neutral return Potential improvements in Converter HVDC Circuit Breaker New cable types XLPE – cross-linked polyethylyne Lapped thin film insulation 9. Future Implications

Summary:

Timeline from 1882 to 1970s Configurations Converter theory Comparison with AC Environmental impact Trans Bay Cable case study Future implications Summary