Secondary network equipment

THE PROBLEM of servicing large concentrated loads has been met successfully in the past by using spot networks and raising the distribution voltage from 208 volts to 480 or 575 volts line-to-line. The use of 480 or higher voltage systems offers definite advantages in reduction of size and cost per kva of the secondary network equipment. This equipment includes the network transformer, network protector, relays, fuses, and limiters. Along with the advantages gained, the use of the higher voltage secondary-network equipment has presented certain problems in the design of this equipment. For instance, the network protector is basically a current-carrying device, but the use of the higher voltages requires a careful consideration of such design features as relaying and fusing. To the transformer designer, the use of the larger kva ratings made possible by the higher secondary voltages has presented such problems as maintaining minimum dimensions, providing low sound levels, and the consideration of more efficient cooling methods.