Transmission and Distribution Interview Questions

What for series and shunt compensation provided in EHV transmission lines?

Series capacitance is provided in EHV lines to artificially reduce the series reactance of the line so as to improve stability, voltage regulation and transmission efficiency

Shunt compensation is provided to artificially reduce the line susceptance so as to improve the voltage regulation under light load condition.

What is the material used for overhead transmission lines?

ACSR conductors are employed.

What are the problems associated with EHV transmission?

The problems associated with EHV transmission are corona loss and radio interference, requirement of heavy supporting structures and insulation requirments.

Why does surge impedance loading (SIL) increase with increase in voltage level?

SIL varies as the square of the operating voltage, so SIL inceases with increase in voltage level.

What are the factors that limit the maximum power transfer capability in a transmission line?

Some of the factors which limits the maximum power transfer are:

1. Electrical phase shift
2. Voltage drop
3. Thermal effects in the line

Explain some of the methods to improve the strength of transmission system?

• Introducing or adding of new transmission lines in to the system to avoid the overloading of the existing lines
• Application of devices such as series capacitors in the right location of power system which helps in increase in the power transfer capability
• Up gradation of the existing transmission system
• Adoption of multi-voltage levels an multi-circuits in the existing ac transmission system

Why phase shift is kept low for transmission of power for large distances?       

Generally  δ is kept low (around 30^o) because any disturbance can affect the stability of the system if δ value is high.