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Monday, August 5, 2013

PPT On Distribution Substations


Distribution Substations Presentation Transcript: 
1.Power Distribution & Utilization

2.Distribution Substations
To lower the voltage from the high voltage transmission and sub-transmission levels to a voltage that can be safely installed on the streets.

3.Substation Layout Selection Criteria
It depends on many factors.
Load Requirements
Expected Growth
Available Site Space
Location Of Site
Protection System Sophistication & Cost
Other Stations In The General Area
The design of a substation depends on both the sub-transmission and/or transmission voltages available.

4.Voltage And Spacing
Voltage determines the spacing between the conductors and conductor clearance to ground.
Minimum clearances are 22.3 inches for 34.5kV and 13.2 inches for 12.5kV for rigid buses with fixed supports.

The size of the load to be served determines the capacity of substation.
Industrial and commercial loads are served by large substations.(More reliable and contains more than one transformer)
Critical loads such as industrial districts are served by more complex substations designed for maximum reliability and speed of power restoration.

6.Space And Location:
More space allows more construction options.
Densely populated areas may contain few locations suitable for substation construction.
Cost of the land must also be high.
GIS may have to be used in such cases.

7.Distribution Substation Protection Needs:
The level of protection of a substation is determined by how critical the loss of power is to the load.
Loss of power to a hospital or to industrial and commercial areas can result in severe damages, both to human life and economy.
Fault removal must be fast
Automatic switching should be used to decrease the repair time.

8.Construction Methods
Four basic methods exist for substation construction.
Steel Lattice
Steel Low Profile

Wood pole substations are inexpensive.
Can easily use wire bus structures.
Wood is suitable only for small and simple substations.
Very few wood substations are built anymore.

10.Lattice Steel:
It provides structures of low weight and high strength.
Multilevel bus structures can be fabricated.
It is reasonably economical and preferable.

11.Lattice Steel Structure for Grid Station

12.Solid Steel Low Profile:
Superior to lattice or wood.
More expensive than either wood or steel.
Requires more land because multilevel bus structures can not be used.

It is a recent development.
It is factory built and tested.
Shipped in modules and bolted together at sites.
Completely enclosed in metal cladding to deny access to unqualified individuals.

14.Trends In Distribution Substations:
It is difficult to add small increments of capacity to large substations economically.
Maximum economy is realized when low voltage feeder mileage is kept as low as possible.
Smaller substations allow a lower mix of high and low voltage lines, more economical, simpler design, construction and relaying is easier. 

15.Insulation Coordination:
A typical method is to establish a definite common level for all insulation in the station.
Bring all equipment and devices to that insulation level.
Lightening protection is set at least 20% below this level, but above normal peak operating voltages.

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