2400 VOLTS (2.4 kV) SYSTEM AND TRANSFORMERS BASIC AND TUTORIALS

DISTRIBUTION TRANSFORMER IN THE 2.4 kV SYSTEM TUTORIALS
A Tutorial On The 2.4 kV System and Its Distribution Transformers


In any particular voltage class, the actual rated voltage of a transformer has increased in years past. For example, the 2400-volt class of transformers formerly were rated 2200-110/220, then later they were rated 2300 115/230 and today they are rated 2400-120/240 volts.

This gradual increase in the rated voltage of transformers also occurred in the other voltage classes. Throughout the following material, we will speak of a particular voltage class by using present day rated voltage terminology.

In the early days of urban-electrical distribution, practically all systems were 2400-volt class, delta systems, and the 2400-volt transformer was designed and manufactured for this system. The selection of 2400 volt for distribution was logical from the standpoint of service and economy.

This voltage is high enough to give good system performance on systems where the distribution circuits are not very long. In addition, the voltage is sufficiently low to result in economical distribution equipment.

In recent years most 2400-volt delta systems have been changed over to 2400/4160Y-volt systems. This change was due to the fact that as the 2400-volt delta systems became more heavily loaded it became necessary to put in larger distribution-line conductors or raise the operating voltage in order to maintain proper voltage regulation.

The most economical procedure in this case was to raise the operating voltage to 4160Y, and this was economical because the change did not necessitate a change in transformers or other equipment on the line.

2400/4160-volt distribution systems are used in most urban areas throughout the country. Another factor that has contributed to the change from delta to Y systems is surge protection.

The three-phase four-wire solidly grounded Y system affords good grounds for surge arresters, and therefore, this system is superior from the standpoint of surge protection.