16-07-2012, 01:27 PM
MODERN TRENDS IN POWER TRANSMISSION SYSTEM
MODERN TRENDS.ppt (Size: 795 KB / Downloads: 69)
INTRODUCTION
The concept of six phase transmission lines was introduced by Barns & Barthold during 1972. Six phase power system is a part of multiphase power system. Due to harmonics effect and various other reasons Six phase systems and six phase machines are not popular but six phase transmission lines are more popular due to its increased power transfer capability by times, maintaining the same conductor configuration, rights of way, better efficiency, better voltage regulation, greater stability and greater reliability.
Reliability
Power system operators often describe two elements of
electric system reliability:-
Adequacy is the ability of the electric system to supply the electrical demand and energy requirements of customers at all times, taking into account scheduled and unscheduled outages of power lines and power plants.
Security is the ability of the electric system to withstand sudden disturbances such as electric short circuits or unanticipated loss of system facilities such as a power plant or a power line.
Flexibility
Transmission allows power systems to use diverse resources such as wind, coal or geothermal energy, even if they are located far from the people that use electricity.
A strong transmission system gives power companies the flexibility to consider several alternatives to meet the demand for power, including natural gas plants built close to electric load or other power plants built far from the load.
Economics
With many different power plants operating across the country, some can produce power more cheaply than others. The transmission system allows the less expensive generators to deliver power in competition with other, more expensive, generators.
THERMAL LOADING
Thermal loading follows a straight line relationship with phase order. Thus if thermal loading is the criterion for circuit rating, the capacity increase is proportional to number of phases. Thus 6 phase systems will have more thermal loading which is an advantage.