Power Delivery Laws

The complex interaction of a power delivery system is governed by a number of physical laws relating to the natural phenomena that have been harnessed to produce and move electric power. These interactions have created a number of “truths” that dominate the design of delivery systems:

• It is more economical to move power at high voltage. The higher the voltage, the lower the cost per kilowatt, to move power any distance.

• The higher the voltage, the greater the capacity and the greater the cost of otherwise similar equipment. Thus, high voltage lines, while potentially economical, costs a great deal more than low voltage lines, but have a much greater capacity. They are only economical in practice if they can be used to move a lot of power in one block.

• Utilization voltage is useless for transmission of power. Transmitting power at utilization voltage level results in unacceptably high electrical losses, severe voltage drops, and astronomical equipment cost.

• It is costly to change voltage level. Voltage transformation is a major expense, which does nothing to move the power any distance in and itself.

• Power is more economical to produce at very large amounts. Large generators produce power more economically than small ones., thus it is most efficient to produce power at a few locations utilizing large generators.

• Power must be delivered in relatively small quantities at low voltage level.

Source: Power Distribution Planning Reference Book, H. Lee Willis