What are the requirements of satisfactory electric supply?

The universally adopted electric power system is three-phase AC operating at a constant frequency such as 50 Hz in India and 60 Hz in USA, etc. The power system delivers power to the consumers through its transmission and distribution systems.

It is important that the electric power supply should be satisfactory. Let us take a look at the primary requirements to have satisfactory electric supply.

Good Voltage Regulation

The power system must have a good voltage regulation because the voltage variations disturb the operation of both power equipment and lights. For example, an electric motor is designed to have its best operating characteristics at the rated voltage. Therefore, a voltage that is too high or too low will result in a decrease in the efficiency of the motor.

Also, if the variation in the voltage is sudden, it may cause the undesirable tripping of circuit breakers and hence interruptions in the services. In practice, the voltage regulation of the electric power system is improved by keeping the resistance and reactance of the transmission lines and feeders low.

Constant Frequency

The frequency of the electric power system must be maintained constant. It is because a change in the supply frequency would change the speed of the electric motors and hence disturbs their operation and the manufacturing processes.

Balanced Voltage

One of the important requirement of satisfactory electric supply is that the system voltage in a poly-phase electric system should be balanced. If an unbalanced voltage is supplied to the consumers, it will result in a decrease in the efficiency of his equipment such as induction or synchronous motors and also a decrease in its maximum power output. Also, the unbalanced terminal voltage is liable to considerable damage to the electric motors due to overheating.

The voltage balance in a poly-phase electric power system can be achieved by connecting balance loads to the system.

Dependability and Uninterrupted Service

It is the important requirement of satisfactory electric supply that it is to furnish uninterrupted service. It is because the losses which an industrial or commercial consumer sustains due to failure of electric power supply are usually very high than the actual value of power that he would use during this period. Hence, the interruptions to service cause irritation and are sometimes dangerous to life and property.

For instance, the failure of electric power supply in hospitals, theatres, factories and stores may lead to grave consequences. Hence, it is the duty of electric utility company to keep the power system going and to furnish uninterrupted service.

Sinusoidal Waveform

The alternating voltage supplied to the consumer should have a sine waveform. It is because any harmonics present in the supply would have detrimental effect upon the efficiency and maximum power output of the equipment. The harmonics present in the supply may be avoided by using alternator of good design which can produce absolute sinusoidal waveform and by avoiding of high flux densities in the transformers.

Free from Inductive Interference

The electric power lines running parallel to the communication line (such as telephone lines or TV cables, etc.) produce electromagnetic and electrostatic interference. These interferences cause objectionable noise and hums in the devices connected to the communication lines.

The inductive interference with the communication lines may be avoided by limiting as much as possible the amount of zero-sequence and harmonic currents and by the proper transposition of both power lines and communication lines.