The correct answer is: A. Increase of short-circuit current of the system
A constant voltage transmission system is a type of power transmission system in which the voltage at the receiving end is kept constant, regardless of the load on the line. This is achieved by using a voltage regulator, which automatically adjusts the output voltage of the generator to compensate for changes in load.
One of the demerits of a constant voltage transmission system is that it can lead to an increase in the short-circuit current of the system. This is because, when the voltage at the receiving end is kept constant, the current in the line will increase as the load increases. This can lead to an increase in the short-circuit current of the system, which can have a number of negative consequences, such as:
- Increased stress on the insulation of the conductors
- Increased risk of equipment damage
- Increased risk of fire
In order to mitigate the risk of these negative consequences, it is important to design constant voltage transmission systems with sufficient margin for short-circuit current.
The other options are not demerits of a constant voltage transmission system.
Option B: Availability of steady voltage at all loads at the line terminals. This is a benefit of a constant voltage transmission system.
Option C: Possibility of better protection for the line due to possible use of higher terminal reactants. This is a benefit of a constant voltage transmission system.
Option D: Improvement of power factor at times of moderate and heavy loads. This is a benefit of a constant voltage transmission system.
Option E: Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission. This is a benefit of a constant voltage transmission system.