Multi-phase (6-phase & 12-phase) Power Transmission Systems with Thyristor Controlled Series Capacitor

Multi-phase (employing phases more than three) power transmission systems have been investigated as a potential alternative to conventional three-phase systems for bulk power transmission at EHV and UHV levels in the past. The technology has been found to be effective to remove some of the limitations of threephase system arising out of the use of extremely high voltages to increase power capability of lines, excessive rights-of-way (ROW) requirement and several environmental problems. A recently conducted survey reveals that the integration of flexible A.C. transmission system (FACTS) devices into conventional three-phase transmission system for enhancement and control of power flow is well established, however, this aspect has not been investigated for multi-phase power transmission systems. This paper therefore attempts to study: a FACTS device i.e. thyristor controlled series capacitor (TCSC), its model and effect on power flow and load ability of multi-phase EHV transmission lines. Sample systems are employed to study quantitative benefits of six-phase and twelve-phase lines over their three-phase counter parts. Key-Words: Multi-phase, Power-transmission, Rights-of-way, Flexible A.C. transmission system, Thyristor controlled series capacitor, Loadability.