Download - Busbar Sizing for Substation
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Busbar sizing for substations
Hasala DharmawardenaEngineer – DesignsLTL Projects PVT. LTD.
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Assumptions
Sizing is relevant only forAl – E91E (6063 T6)Tubular
No structures are attached to the busbar
Busbar
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Contents
1. Minimize bending moment at joints
2. Span width specific requirements
3. Post Insulator Sizing
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1. Bending Moments
For equal Span width, the position of minimum bending
depends only on
• Length of a Span
• The Number of Spans
• The Type of support – e.g. Fixed , Pin
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Assumptions
S= Slip fit Support
F= Fixed Support
E=Expansion Support
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Points of Zero Bending Moment
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Workings of the excel sheet
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Example outputInput are showed in RED boxes
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2. Deflection and Stress
Deflection caused by the weight of the tubeshould be less than 150th of
the length
Total stresses on the tube
should be less than the yield
stress
Both should be
simultaneously satisfied
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Prerequisites
1. Wind Forces
2. Short circuit Forces
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Wind forces
IdCKGVFW2
Where K is a constant depending on height and
exposure , G a constant depending on wind speed,
V wind velocity and d external diameter of the tube.
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Short Circuit Forces
D
IF SCSC
4
2
10
6.1
Where Isc is the maximum Short circuit current and
D is the conductor centerline to centerline spacing
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2.1 Deflection
33
5
384
G
BD F
YJECL
Where L is the maximum span length, Y maximum
deflection, J cross section moment of inertia and F bus unit
weight.
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2.2 Fiber Stress
T
AS F
SFKCL
'
•Where L is the maximum span length, FA maximum fiber
stress of 6063 - T6, S section modulus, K is a constant
which depends on support type and number of supports
and FT is the total force
•Combines both wind forces and gravitational forces
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2.2 Fiber Stress ctd…
Total force FT is given by
])[( 22GSCWT FFFF
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Workings of the excel sheet
Select maximum possible span width to be the minimum of Ls and LD , If not change Di and Do or If possible the span width to be within the bounds defined
by the above conditions.
Secondary CalculationLD
Primary CalculationLS
Get Input dataSpan Width Number of Spans
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Example output
Input are showed in RED boxes
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Example output ctd …
Input are showed in RED boxes
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3. Post Insulator
Total insulator cantilever load is calculated by assuming
vertically mounted insulator with horizontal bus.
Furthermore the effective weight of the mass transmitted
to one bus support depends on the bus configuration and
support conditions.
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3. Post Insulator ctd…)]
)()(
2[
i
SBfi
i
WBfiWIIS H
FHH
H
FHHFKF
Where FIS is the load on the insulator, FWI is the wind force on the PI, FSB is the short circuit force transmitted to the PI, FWB is the wind force transmitted to the PI.
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Example output
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Thank You