Q. What is a load curve?
Q. What is the difference between base load and peak load?
Peak load: The various peak demands of load over and above the base load of the station is known as peak load.
Q. What is power factor?
Q. What are the disadvantages of low power factor and how to improve it?
The low power factor is mainly due to the fact that most of the power loads are inductive and, therefore, take lagging currents. In order to improve the power factor, some device taking leading power should be connected in parallel with the load. One of such devices can be a capacitor. The capacitor draws a leading current and partly or completely neutralizes the lagging reactive component of load current. This raises the power factor of the load.
Q. Why is a.c transmission preferred over d.c transmission?
2. The maintenance of a.c. sub-stations is easy and cheaper.
3. The a.c. voltage can be stepped up or stepped down by transformers with ease and efficiency.
Although a.c transmission is preferred due to the above reasons d.c transmission is superior (2 conductors instead of 3, no inductance, capacitance, no corona, no skin effect etc).
Q. Why is electric power transmitted at higher voltages?
Efficiency will be high at higher voltages.
Percentage line drop will be less.
Q. What are the different types of insulators in Overhead lines?
Q. What is string efficiency?
Q. What are the different methods used to improve string efficiency?
Q. What is corona?
Q. What are the advantages and disadvantages of corona?
1. Due to corona formation, the air surrounding the conductor becomes conducting and hence virtual diameter of the conductor is increased. The increased diameter reduces the electrostatic stresses between the conductors.
2. Corona reduces the effects of transients produced by surges.
1. Corona is accompanied by a loss of energy. This affects the transmission efficiency of the line.
2. Ozone is produced by corona and may cause corrosion of the conductor due to chemical action.
3. The current drawn by the line due to corona is non-sinusoidal and hence non-sinusoidal voltage drop occurs in the line. This may cause inductive interference with neighboring communication lines.
Q. How to reduce the corona effect?
1. Increasing the conductor size
2. Increasing the conductor spacing
Q. What is sag? Explain its importance?
If the conductors are too much stretched between supports in a bid to save conductor material, the stress in the conductor may reach unsafe value and in certain cases the conductor may break due to excessive tension. In order to permit safe tension in the conductors, they are not fully stretched but are allowed to have a dip or sag.