EE6402 Important Questions Transmission and Distribution
EE6402 Important Questions Transmission and Distribution Regulation 2013 Anna University
Sample EE6402 Important Questions
1. Why all transmission and distribution systems are 3 phase systems?
A 3 phase a.c circuit using the same size conductors as the single phase circuit can carry three times the power which can be carried by a 1 phase circuit and uses 3 conductors for the 2 phases and one conductor for the neutral. Thus a 3 phase circuit is more economical than a 1 phase circuit in terms of initial cost as well as the losses. Therefore all transmission and distribution systems are 3 phase systems.
2. Why the transmission systems are mostly overhead systems?
Because of the cost consideration, the transmission systems are mostly overhead systems.
3. Why all overhead lines use ACSR conductors?
ACSR conductors comprises of hard drawn aluminium wires stranded around a core of single or multiple strand galvanized steel wire. They provides the necessary conductivity while the steel provides the necessary mechanical strength. Has less corona loss. The breaking load is high and has less weight.
4. Why transmission lines are 3 phase 3 wire circuits while distribution lines are 3 phase 4 wire circuits?
A Balanced 3 phase circuit does not require the neutral conductor, as the instantaneous sum of the 3 line currents are zero. Therefore the transmission lines and feeders are 3 phase 3 wire circuits. The distributors are 3 phase 4 wire circuits because a neutral wire is necessary to supply the 1 phase loads of domestic and commercial consumers.
5. Why overhead line conductors are invariably stranded?
They are stranded to make them flexible during erection and while in service.
6. State the advantages of interconnected systems.
Any area fed from one generating station during overload hours can be fed from another power station and thus reserved capacity required is reduced, reliability of supply is increased and efficiency is increased.
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