CHARACTERISTICS

Power electronics can be used to control the flow of electrical energy, making better utilization of the transmission system possible, effectively increasing transmission capacity.

The Thyristor Controlled Series Capacitor (TCSC) uses advanced solid-state switches that direct the flow of electric power more precisely along specific transmission lines and swiftly stabilize power swings caused by short circuits and other disturbances; this gives significantly greater control and efficiency on utility transmission lines compared with conventional equipment. TCSC also makes it possible to achieve a much higher level of compensation and optimization of power delivery strategies

System optimization will allow more effective integration and use of renewables, energy storage, and demand-side management leading to possible GHG reductions. Spinning reserve requirements–the generating capacity used as backup power–could be reduced, also resulting in lower air pollutant and GHG emissions. The balancing of phase currents reduces the losses associated with residual currents. However, increasing current flow on a transmission line increases line losses, which can reduce or offset the net GHG emission reductions.

SIZE:
Feasible for all transmission voltages

FEATURES:
Increases transmission capacity on existing lines while improving control of power flow. by increasing stability and decreasing the effective "length" of the lines.

COST:
Prices are quoted in $ per kVAr of capacitor rating

CURRENT USAGE:
Currently in use on power systems in U.S., Canada and Europe

POTENTIAL USAGE:
Can be used on any bulk power alternating and direct current transmission systems. Development is underway of a Flexible Alternating Current Transmission Systems (FACTS)–a collection of power transmission control technologies that are faster and less susceptible to wear than conventional mechanical devices, that will improve controls of system volt-amperes-reactive (VARS) and system impedances (TCSC) (also system voltages).

ISSUES ASSOCIATED WITH IMPLEMENTING ACTION

• In many cases, transmission line flows may already be sufficiently controlled such that further line flow controls may not be cost-effective.
• Research and development is needed in protection and real time control areas, and in flexible AC transmission system (FACTS) device technology.
• Higher line currents will produce greater magnetic fields, resulting in electro-magnetic health concerns.
• Series capacitor installations that compensate more than 25% of line impedance should be studied for potential sub-synchronous resonance problems.

CLIMATE CHANGE IMPACT

EMISSION EFFECT:
    

CONDITIONS FOR EMISSIONS MITIGATION:

• Reduces losses thereby avoiding demand. However, if demand shifts, total emissions may not be reduced.

EMISSION ESTIMATE:
Varies according to the fuel source used to generate electricity.

COST-EFFECTIVENESS:
N/A

SECONDARY EFFECTS:
Varies according to the fuel source used to generate electricity.

RESOURCES

• Numerous applications of improved power electronics exist in the U.S. including: 1) series compensation of a 500 kV line and other projects to improve power flow and system stability, 2) projects testing EPRI/Slatt Thyristor switched capacitor; 3) investigation of dynamic rating of transmission line conductors. More specific information is available in the U.S. DOE Climate Challenge Options Workbook. http://www.eren.doe.gov/climatechallenge/
• The Institute of Electrical and Electronics Engineers (IEEE) has a Capacitor Subcommittee of its Transmission & Distribution Committee. The Subcommittee has various working groups including: Thyristor Controlled Series Capacitor Working Group. Shunt Capacitor Standard Working Group and a Series Capacitor Standard Working Group. http://www.electrotek.com/ieee/capsub/capsub.htm.
• West Virginia University Electricity Restructuring Research Group, 1998, "Transmission Enhancement and Expansion," Interim Report No. 5 (January). http://www.nrcce.wvu.edu/special/electricity/elecpaper5.htm.
• Electric Power Research Institute, Guide for Economic Evaluation of Flexible Access Transmission Systems (FACTS) in Open Access Environments (TR-108500).
• Institute of Electrical and Electronics Engineers, Subsynchronous Resonance Counter-Measures, PES publication 81 TH0086-9-PWR.

CONTACTS

ABB Power T&D
Henry Chao
Raleigh, NC
Tel: (919) 856-2394
http://www.abb.se/pow/home.htm

Electric Power Research Institute
Mark Wilhelm
Director, Power Delivery Group
Palo Alto, CA
Tel: (650) 855-2772
mwilhelm@epri.com
http://www.epri.com

Harza Engineering
Peter Donalek
Electric Power Systems Department
Chicago, IL
Tel: (312) 831-3170
Fax: (312) 831-3999
pdonalek@harza.com
http://www.harza.com

Oak Ridge National Laboratory
Jim Van Coevening
Power Systems Technology Program
Energy Division
Oak Ridge, TN
Tel: (615) 574-4829
http://www.ornl.gov

Tennessee Valley Authority
Jeffrey Nelson
Chairman
IEEE Capacitor Subcommittee
Knoxville, TN
Tel: (423) 751-8275
Fax: (423) 751-4788
jhnelson@tva.gov
http://www.tva.gov