Three-phase power system is the polyphase system used world wide for the generation, transmission, and distribution of the electrical power. As the number of phases increases, more the power which can be transmitted. If so, 6 or 12 phase systems could be a good option for EHV (Extra High Voltage) systems. Even then, why we stick on with the 3-phase systems? This article would help in a better understanding of this question.
Can the supply voltage be 6 phase?
A 3-phase system can transmit three times the power than a single phase power supply system. So it is clear that as the number of phases increases, the more the power a system can transmit. But to transmit this power, a substation requires as many number of conductors, circuit breakers, busbars and transformers.
Cost and Complexity
In a 3-phase transmission system, each line requires its circuit breaker and busbar for coupling into the substation. So a total of 3 CBs, 3 busbars along with other equipments for the reliable transmission.
Likewise, for a higher phase system, the need of as many number of circuit breakers, busbars, conductors, transformers etc. would naturally peaks up the cost and complexity. Also, the increased number of lines enhances the potential of the complexity in the transmission and detection in the event of faults. Thus phases above three just complicates the working of motor, generator, switchgear, transformer and the overall transmission system. Hence the three-phase system is considered optimum.
