3. How to design a power system?
• Efficient from a technological point of view
• Must carry the load imposed on it without causing excessive heating
• Voltage drop throughout the network must be kept to a minimum so as to hold the voltage at the
consumer's terminals within specified limit whatever the loading conditions
• Design to provide for continuity of supply and, should a fault occur on the system, interruptions in
the supply to individual consumers should last for the briefest possible time if they are to occur at
all.
• System should be simple to operate and maintain as possible & losses must be kept at minimum
• Routine maintenance should be done without interruption of supply
• A perfect system according to the above conditions could no doubt be constructed, but the cost
must be prohibitive that leads us to economics basis
• It means ; this is not to equate economy with cheapness but to make the maximum possible use
of the resources which are available
4. Comparison of Copper Efficiencies for various
systems
The amount of copper requires for the transmission of a given amount of power over a given
distance using various system of supply
i. d.c. three wire
ii. a.c. single phase
iii. a.c. three phase
1. OVERHEAD SYSTEM
In this case the conductors are insulated from an earthed support and therefore the cost of
the insulation is determined by the maximum voltage to earth
1. CABLE SYSTEM
In this case an underground cable system the conductors are separated from each other by
solid insulation and the cost of this is determined by the maximum voltage between conductors