31-07-2013, 04:39 PM
Supply Systems
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Conductor System
Electrical energy is transported from a power
station to a consumer by the conductor system.
Parts of conductor system are transmission and
distribution.
Transmission
Primary Transmission.
Secondary transmission.
Primary Distribution
Secondary Distribution
Feeders and Distributors
Distribution system can be subdivided into
Feeders, Distributors and service mains.
Feeders and Distributors
Feeders are the conductors which connect the substations to
the areas served by these substations. Current loading is same
along the whole of its length.
Distributors are characterized by the numerous tapings which
are taken from them from the supply to the consumers. It has
a distributed current loading.
Service mains
Service mains are the connecting links between distributors
and consumer terminals.
Voltage Fluctuations
voltage drop along all conductors.
However, large fluctuations is undesirable
from the customer point of view.
The fluctuations can only be reduced by
decreasing the conductor resistance. Therefore,
increase in cross-
cross-section and cost of conductor.
Effect of System Voltage
The effect of system voltage on the size of distributor
can be calculated as follows.
As most of the voltage drop variation occur in the
distributor, therefore the percentage drop can be
regarded as constant.
Consider a section of distributor and let the current be
I and let the drop along it be V.
Thus the resistance is V/I equal to R.
If the system voltage is increase n fold, for same power
delivered, the current is reduced to 1/n
1/n.