The term voltage control refers to the method of controlling variations of voltage at the consumer’s terminals. Whenever the electric load on the supply system changes, the voltage at the consumer’s terminals also changes. This voltage variation at consumer terminals is undesirable and it should be kept within prescribed limits. Voltage control is primarily required for three major reasons.
Impact on Motor Operations
In case of electrical power loads comprising of induction motors, the voltage variations result in erratic operation. A voltage supply higher than normal will cause the motors to operate with a saturated magnetic circuit, resulting in large magnetizing current. It will cause heating and low power factor. On the other hand, if voltage is too low, it will significantly reduce the starting torque of the motor.
Impact on Lighting Loads
As a result of voltage variations, the lamp characteristics are highly impacted. If supply voltage to an incandescent lamp decreases by 6% of rated value, then illuminating power may decrease by a percentage of 20%. On the other side, if supply voltage is 6% above the rated value, the life of the lamp will be reduced by 50% because of rapid deterioration of the filament.
Impact on Distribution Transformers
Apart from loads, voltage variation also impacts operation of distribution transformers. As a result of this ratings of transformers are reduced to a considerable extent.