Tuesday, December 2, 2014

ELECTRICAL POWER DISTRIBUTION & UTILIZATION



The electrical power distribution system is that part of the electric utility system between the
bulk power source and the customers’ service switches. This definition of the distribution
system includes the following components:
1.  Subtransmission system2.  Distribution substations   [T/Fs, buses & switchgears]3.  Distribution or primary feeders [4.16 to 34.5kV(11kV Pak)]4.  Distribution transformers5.  Secondary circuits6.  Service drops/mains
Some distribution system engineers prefer to define the electrical distribution system as that part of the electric utility system between the distribution substations and the consumers’ service entrance.
A one line diagram of a typical distribution system.
The subtransmission circuits delivers energy from bulk power sources to the distribution substations. The distribution voltage ranges between 12.47 and 245kV.
The distribution substation reduces the subtransmission voltage for local distribution. The 3-phase primary feeders usually operate in between 4.16 to 34.5kV (11kV Pak)
Theses primary feeders distribute energy from the low – voltage bus of the substation to its load centers where it branches into 3-phase sub feeders and single phase laterals.Distribution transformers ranging from 10 to 500kVA, are usually connected to each primary feeder, sub feeders, and laterals. They reduce the distribution voltage to the utilization voltage.The secondary of the distribution transformers are connected to the consumer’s service mains/service
drops 


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