All Day Efficiency
Large capacity transformers used in power systems are classified broadly into Power transformers and Distribution transformers. The former variety is seen in generating stations and large substations. Distribution transformers are seen at the distribution substations.
The basic difference between the two types arises from the fact that the power transformers are switched in or out of the circuit depending upon the load to be handled by them. Thus at 50% load on the station only 50% of the transformers need to be connected in the circuit. On the other
hand a distribution transformer is never switched off. It has to remain in the circuit irrespective of the load connected. In suchh cases the constant loss of the transformer continues to be dissipated. Hence the concept of energy based efficiency is defined for such t ransformers. It is called ’all day’ efficiency.
All day efficiency = Energy out put of the transformer over a day/ Corresponding energy input.