Ref. (4)-G77700-S0019-L061-A
Project: MESNET IZALATORU MEKANIK HESAPLAR
Gilgel Gibe – II PROJECT ETHIOPIA Description:
400 kV SWITCHYARD DESIGN REPORT’s & CALCULATION’s
Subject:
Report on Calculations for Determination of Cantilever Strength of Bus Post Insulators
Note:
This report establishes the sizing of bus post insulators for 400kV switchyard on the basis of cantilever strength.
BPI Selection Design Report : Cantilever Strength Calculation Handling:
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Contents page 1.
Introduction ....................................................................................................................... 4
2.
System Data...................................................................................................................... 4
3.
Conductor Data ................................................................................................................. 4
4.
Bus Post Insulator data ..................................................................................................... 5
5.
Attachments ...................................................................................................................... 6
6.
Conclusion ........................................................................................................................ 6
7.
References........................................................................................................................ 7
Siemens Power Engineering Pvt. Ltd.
The reproduction, transmission or use of this document or its contents is not permitted without express written authority. Offenders will be liable for damages. All rights, including rights created by patent grant or registration of a utility model or design, are reserved.
(4)-G77700-S0019-L061-A
BPI Selection Design Report : Cantilever Strength Calculation Handling:
1
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Introduction The rigid bus in out-door substation is primarily supported on Bus Post Insulators. These bus post insulators are hence subjected to sustain all types of stresses on bus conductor owing to electrically and mechanically originated forces. The principal forces on the bus post insulator are as follows – a. Short circuit current force on the bus conductor. b. Wind force on the bus conductor. c. Wind force on the insulator stack. d. Weight of the bus conductor span supported by the bus post insulator. Since the forces on the bus-conductors are transmitted to the bus post insulators, the strength of the insulator must be considered. With various bus configurations, insulators may be required to withstand cantilever, compressive, tensile and torsional forces. However, only the cantilever force, which is a function of the effective conductor span length supported by the bus post insulator, have been regarded significant and considered for design.
2
System data 400kV AC Switchyard Nominal System Voltage
400 kV
System Frequency
50 Hz
Short Circuit Fault Current
31.5 kA
Duration of Fault Current
1 sec
Maximum Wind Pressure
700 N/m2
Altitude above sea level
>1500 m
3 Conductor Data Rigid Conductor i) 250/6mm Aluminum Tube (AlMgSi0.5F25) Outer Diameter
250 mm
Wall thickness
6 mm
Siemens Power Engineering Pvt. Ltd.
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(4)-G77700-S0019-L061-A
BPI Selection Design Report : Cantilever Strength Calculation Handling:
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Weight
12.4 Kg/m
Weight of Damping Material (Twin 954 MCM Cardinal ACSR)
1829.8 Kg/kM
ii) 120/8mm Aluminum Tube (AlMgSi0.5F25) Outer Diameter
120 mm
Wall thickness
8 mm
Weight
7.6 Kg/m
Weight of Damping Material (Single 954 MCM Cardinal ACSR)
1829.8 Kg/kM
iii) 120/6mm Aluminum Tube (AlMgSi0.5F25) Outer Diameter
120 mm
Wall thickness
6 mm
Weight
5.8 Kg/m
Weight of Damping Material (Single 954 MCM Cardinal ACSR)
1829.8 Kg/kM
Common for all tubes specified above Young’s Modulus
70000 N/mm2
4 Bus Post Insulator data i) C8-1550 Height of Insulator Stack
3350 mm
Maximum Width
310 mm
Minimum Width
140 mm
Weight of Insulator
349 Kg
Cantilever Strength (designated by manufacturer)
800 daN
i) C6-1550 Height of Insulator Stack
3350 mm
Maximum Width
290 mm
Minimum Width
130 mm
Siemens Power Engineering Pvt. Ltd.
The reproduction, transmission or use of this document or its contents is not permitted without express written authority. Offenders will be liable for damages. All rights, including rights created by patent grant or registration of a utility model or design, are reserved.
(4)-G77700-S0019-L061-A
BPI Selection Design Report : Cantilever Strength Calculation Handling:
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Weight of Insulator
291 Kg
Cantilever Strength (designated by manufacturer)
600 daN
i) C12.5-1550 Height of Insulator Stack
3350 mm
Maximum Width
360 mm
Minimum Width
160 mm
Weight of Insulator
400 Kg
Cantilever Strength (designated by manufacturer)
1250 daN
Busbar Selection The following types of tubular busbar has been considered in the design : x
250/6 mm AlMgSi0.5F25 Tubular Bus bar to serve as Main Bus Conductor.
x
120/8 mm AlMgSi0.5F25 Tubular Bus bar to serve as Equipment Bus Conductor at the Bus Coupling feeder.
x
120/6 mm AlMgSi0.5F25 Tubular Bus bar to serve as Equipment Bus Conductor at the Transformer & Line feeders.
5 Attachments Attachment-1: Calculation of Cantilever Strength of Bus Post Insulator supporting the Main Bus Attachment-2: Calculation of Cantilever Strength of Bus Post Insulator supporting the Equipment Bus at Coupling Bay Attachment-3: Calculation of Cantilever Strength of Bus Post Insulator supporting the Equipment Bus at Transformer & OHL Feeders.
6 Conclusion 1. The required Cantilever Strength of the C12.5-1550 for supporting the maximum bus span(24 m) of the Main Bus is 995.67 daN, whereas the cantilever strength published by the manufacturer is 1250 daN. Thus the design is safe and Bus Post Insulators of C12.5-1550 type may be used for supporting the Main Bus conductor. 2. The required Cantilever Strength of the C6-1550 for supporting the maximum bus span(12 m) of the Equipment Bus at Coupling Bay is 281.23 daN, whereas the cantilever strength published by Siemens Power Engineering Pvt. Ltd.
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(4)-G77700-S0019-L061-A
BPI Selection Design Report : Cantilever Strength Calculation Handling:
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the manufacturer is 600 daN. Thus the design is safe and Bus Post Insulators of C6-1550 type may be used for supporting the Equipment Bus conductor at the Coupling Bay. 3. The required Cantilever Strength of the C6-1550 for supporting the maximum bus span (12 m) of the Equipment Bus at Transformer & OHL Feeders is 249.28 daN, whereas the cantilever strength published by the manufacturer is 600 daN. Thus the design is safe and Bus Post Insulators of C6-1550 type may be used for supporting the Equipment Bus conductor at Transformer & OHL Feeders.
7 References 1. IEEE Std 605 : 1987 IEEE Guide for Design of Substation Rigid-Bus Structures. 2. Technical Data sheet for Aluminum Alloy Tubular Conductor: Manufacturer – Corus. 3.
Technical Data sheet for Bus Post Insulator: Manufacturer – Porzellanfabrik Frauenthal Insulators.
Siemens Power Engineering Pvt. Ltd.
The reproduction, transmission or use of this document or its contents is not permitted without express written authority. Offenders will be liable for damages. All rights, including rights created by patent grant or registration of a utility model or design, are reserved.
(4)-G77700-S0019-L061-A
S MESNET IZALATORU MEKANIK HESAPLAR (4)-G77700-S0019-L062-A
ATTACHMENT-1 CALCULATION OF CANTILEVER STRENGTH OF BUS POST INSULATOR SUPPORTING THE MAIN BUS SYSTEM VOLTAGE ( IN KV. ): FAULT LEVEL( IK3 ) ( IN KA.):
400 31.5
TUBULAR BUS CONDUCTOR : a) Size : AlMgSi0.5F25 b) Outer dia. 250 mm c) Thickness : 6 mm d) Weight 12.4 Kg/m e) conductor Young's Modulus 7.00E+10 N/m2 f) Conductor spacing 6 m N/mm2 g) Max Allowable stress 115 2 Kg/mm 11.72 h) Max. Span 24 m i) Weight of Damper Material 3.66 Kg/m INSULATOR DATA (Type:C12,5-1550): a. Height 3.35 b. Max. Width 0.36 c. Min. Width 0.16 d Bus Cen. Line height above Insulator 0.215 e. Weight 400
(Twin 954 CARDINAL ACSR Conductor)
m m m m Kg
Max. Wind Pressure(Pmax)
=
700
N/m2
Ambient air density(d) Wind Velocity(V)
= = =
0.613 1/2 (Pmax/d) 33.79
Kg/m m/s m/s
Now, Coss sectional moment of inertia of the tube (J) = = where, DO = Outer Diameter of Conductor = Di = Inner Diameter of Tube = Therefore,
J
= =
Sectional Modulus of the tube
S
=
(as per technical specification) 3
( S/64 ).(Do4 - Di4) 250
mm
238
mm
34231262.64 82.24027953
mm4 in4
J/(DO/2)
= =
273850.1011 16.71125822
mm
3
mm in3
3
Calculation for conductor Wind Force: -4
2
Conductor Wind Force (FW) = 2.132 x 10 CDKZGFV (DO+2r1) Where DO = Outer Diameter of Conductor r1 = Radial Ice thickness.
Hence,
lbf/ft
(Cl. 10. of IEEE:605) 9.84 =
0
CD
= Drag coefficient (Ref. Table 1 of IEEE:605)
=
1
KZ
= Height and exposure factor (Cl. 10.2 of IEEE:605)
=
1
GF V
= Gust factor (Cl. 10.3 of IEEE:605) =Wind speed at 30ft. above ground
= = =
1.3 33.79 75.59
FW
=
inch inch (For Round conductor)
m/s mi/h
15.59 lbf/ft
Calculation for Short Circuit Current Unit Force: Short Circuit Current Unit Force (FSC) =
2
7
27.6* ISC /10 (D)
lbf/ft
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ATTACHMENT-1
Hence,
ISC D *
= Symmettrical short circuit current = Conductor spacing centre to centre = Constant based on type of short circuit and conductor location (Ref. Table 2 of IEEE:605)
FSC
=
= = =
31500 236.22 0.866
A inch
10.04 lbf/ft
Calculation for Gravitational Force: Total bus unit weight (FG) =
FC + FI + FD
lbf/ft
FC
= Conductor unit weight
=
8.33
lbf/ft
FD
= Damping material unit weight
=
2.46
lbf/ft
FI
= Ice Unit weight
=
0
lbf/ft
Hence,
FG
=
10.79 lbf/ft
Calculation for Insulator Strength a.
Calculation for Bus Short circuit Current Force:
FSB
=
LE.FSC
lbf
FSB
= Bus Short Circuit Force transmitted to bus support fitting
LE
= Effective Bus span length
=
78.74 ft
FSC
= Short Circuit Current Unit Force
=
10.04 lbf/ft
Now, for a Rigid Bus Section of Equipment connection in a typical Line bay across the Main Bus (as shown in the figure alongside) 1/2(L1+L2) LE = (Refer Table 5 of IEEE-605) = 78.74016 ft Adjescent Bus Span (L1) = 24 m = 78.74 ft Adjescent Bus Span (L2) = 24 m = 78.74 ft = 790.55 lbf Therefore FSB
P
P
P
24m BPI
24m BPI
BPI
L1 b.
Calculation for Bus Wind Force :
FWB
=
L2 Fig 1
LE.FW
lbf
Where, FWB
= Bus Wind force transmitted to bus support fitting
LE
= Effective Bus span length
=
78.74 ft
FW
= Wind unit force on the bus
=
15.59 lbf/ft
Therefore FWB
=
1227.38 lbf
c.
Calculation for Insulator wind force:
FWI
=
Where, FWI
= Wind Force on Insulator
Hi
= Insulator Height
Di
= Effective insulator diameter = (D1+D2)/2
=
10.2362 inch
D1
= Max. Insulator Width
=
14.1732 inch
D2
= Min. Insulator Width
=
6.2992 inch
-5
2
1.776 x 10 CDKZGFV (Di+2r1)Hi
=
lbf
131.89 Inch
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(4)-G77700-S0019-L062-A
ATTACHMENT-1 r1
= Radial Ice thickness
=
CD
= Drag coefficient
=
1 (For 'round conductor' as per Table 1 of IEEE:605)
KZ
= Height and exposure factor
=
1 (as per Cl. 10.2 of IEEE:605)
GF V
= Gust factor =Wind speed at 30ft. above ground
Therefore FWI
=
0 inch
= = =
1.3 (as per Cl. 10.3 of IEEE:605) 33.79 m/s 75.59 mi/h
178.11 lbf
Calculation for Total Insulator Cantilever load FIS
=
K1 [ FWI/2 + {(Hi+Hf)/Hi} FWB] + K2 [{(Hi+Hf)/Hi} FSB]
lbf
FIS
= Total Cantilever load acting at the end of Insulator
FWI
= Wind force on the insulator in lbf
=
FSB
= Bus Short Circuit Force transmitted to bus support fitting
=
790.55 lbf
FWB
= Bus Wind force transmitted to bus support fitting
=
1227.38 lbf
Hi
= Insulator Height
=
131.89 inch
Hf
= Bus Cen. Height above Insulator
=
8.46 inch
K1
= Overload Factor applied to wind force
=
1
K2
= Overload Factor applied to short circuit force
=
1
= 2236.49 lbf Therefore FIS Now Effective weight of bus transmitted to bus support fitting LE.FG FGB lbf = where, LE = Effective Bus span length FG = Total Bus Unit Weight Therefore FGB
fi where, Ki
=
178.11 lbf
=
78.74 ft
=
10.79 lbf/ft
849.83 lbf
Natural Frequency of the Insulator with effective weight of the conductor span : (1/2S) [Ki g / (0.226FGI + FGB)]1/2 = = Insulator cantilever Spring Constant
=
g FGI
= gravitional constant = Weight of the insulator
= =
386 inch/s 881.85 lbf
FGB
= Effective weight of bus transmitted to bus support fitting
=
849.83 lbf
Therefore fi As
fi
= < 50Hz
2
0.10 Hz =>
K2
=
FIS (Eqp) Cantilever Load on the Support Insulator (in the direction of the Equipment Connection) =>
1 lbf/inch
1 =
Reqiured cantilever Strength of the Supporting Insulator =
(Refer Cl. No. 13.2 of IEEE: 605) 1015.37
Kgf
995.67
daN
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ATTACHMENT-2 CALCULATION OF CANTILEVER STRENGTH OF BUS POST INSULATOR SUPPORTING THE EQUIPMENT BUS AT COUPLING BAY SYSTEM VOLTAGE ( IN KV. ): FAULT LEVEL( IK3 ) ( IN KA.):
400 31.5
TUBULAR BUS CONDUCTOR : a) Size : AlMgSi0.5F25 120 mm b) Outer dia. c) Thickness : 8 mm d) Weight 7.6 Kg/m e) conductor Young's Modulus 7.00E+10 N/m2 f) Conductor spacing 6.5 m N/mm2 g) Max Allowable stress 115 2 Kg/mm 11.72 h) Max. Span 12 m i) Weight of Damper Material 1.83 Kg/m INSULATOR DATA (Type:C6-1550): a. Height b. Max. Width c. Min. Width d Bus Cen. Line height above Insulator e. Weight
3.35 0.29 0.13
m m m
0.15 291
m Kg
(Single 954 CARDINAL ACSR Conductor)
2
Max. Wind Pressure(Pmax)
=
700
N/m
Ambient air density(d) Wind Velocity(V)
= = =
0.613 1/2 (Pmax/d) 33.79
Kg/m m/s m/s
Now, Coss sectional moment of inertia of the tube (J) = = where, DO = Outer Diameter of Conductor = Di = Inner Diameter of Tube = Therefore,
J
= =
Sectional Modulus of the tube
S
=
(as per technical specification) 3
4 4 ( S/64 ).(Do - Di )
120
mm
104
mm
4433981.44 10.6525978
mm4 in4
J/(DO/2)
= =
73899.69067 4.509608754
mm
3
mm3 in3
Calculation for conductor Wind Force: Conductor Wind Force (FW) = 2.132 x 10-4 CDKZGFV2 (DO+2r1) Where DO = Outer Diameter of Conductor r1 = Radial Ice thickness.
Hence,
lbf/ft
(Cl. 10. of IEEE:605) 4.72 =
0
CD
= Drag coefficient (Ref. Table 1 of IEEE:605)
=
1
KZ
= Height and exposure factor (Cl. 10.2 of IEEE:605)
=
1
GF V
= Gust factor (Cl. 10.3 of IEEE:605) =Wind speed at 30ft. above ground
= = =
1.3 33.79 75.59
FW
=
inch inch (For Round conductor)
m/s mi/h
7.48 lbf/ft
Calculation for Short Circuit Current Unit Force: Short Circuit Current Unit Force (FSC) =
27.6* ISC2 /107(D)
lbf/ft
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ATTACHMENT-2
Hence,
ISC D *
= Symmettrical short circuit current = Conductor spacing centre to centre = Constant based on type of short circuit and conductor location (Ref. Table 2 of IEEE:605)
FSC
=
= = =
31500 255.91 0.866
A inch
9.27 lbf/ft
Calculation for Gravitational Force: Total bus unit weight (FG) =
FC + FI + FD
lbf/ft
FC
= Conductor unit weight
=
5.11
lbf/ft
FD
= Damping material unit weight
=
1.23
lbf/ft
FI
= Ice Unit weight
=
0
lbf/ft
Hence,
FG
=
6.34 lbf/ft
Calculation for Insulator Strength a.
Calculation for Bus Short circuit Current Force:
FSB
=
LE.FSC
lbf
FSB
= Bus Short Circuit Force transmitted to bus support fitting
LE
= Effective Bus span length
=
FSC
= Short Circuit Current Unit Force
=
Now, for a Rigid Bus Section of Equipment connection in a typical Line bay across the Equipment Bus in Coupling bay(as shown in the figure alongside) 1/8(3L1+4L2) LE = (Refer Table 5 of IEEE-605) = 31.98819 ft Adjescent Bus Span (L1) = 12 m = 39.37 ft Adjescent Bus Span (L2) = 10.5 m = 34.45 ft = 296.45 lbf Therefore FSB
31.99 ft 9.27 lbf/ft
F
12m ISO(Panto)
P
P
BPI
10.5m CT
L1 b.
Calculation for Bus Wind Force :
FWB
=
LE.FW
lbf
Where, FWB
= Bus Wind force transmitted to bus support fitting
LE
= Effective Bus span length
=
FW
= Wind unit force on the bus
=
Therefore FWB
L2 Fig 1
=
31.99 ft 7.48 lbf/ft
239.34 lbf
c.
Calculation for Insulator wind force:
FWI
=
Where, FWI
= Wind Force on Insulator
Hi
= Insulator Height
Di
= Effective insulator diameter = (D1+D2)/2
=
8.2677 inch
D1
= Max. Insulator Width
=
11.4173 inch
D2
= Min. Insulator Width
=
5.1181 inch
-5
2
1.776 x 10 CDKZGFV (Di+2r1)Hi
=
lbf
131.89 Inch
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ATTACHMENT-2 r1
= Radial Ice thickness
=
CD
= Drag coefficient
=
1 (For 'round conductor' as per Table 1 of IEEE:605)
KZ
= Height and exposure factor
=
1 (as per Cl. 10.2 of IEEE:605)
GF V
= Gust factor =Wind speed at 30ft. above ground
Therefore FWI
=
0 inch
= = =
1.3 (as per Cl. 10.3 of IEEE:605) 33.79 m/s 75.59 mi/h
143.86 lbf
Calculation for Total Insulator Cantilever load FIS
=
K1 [ FWI/2 + {(Hi+Hf)/Hi} FWB] + K2 [{(Hi+Hf)/Hi} FSB]
lbf
FIS
= Total Cantilever load acting at the end of Insulator
FWI
= Wind force on the insulator in lbf
=
143.86 lbf
FSB
= Bus Short Circuit Force transmitted to bus support fitting
=
296.45 lbf
FWB
= Bus Wind force transmitted to bus support fitting
=
239.34 lbf
Hi
= Insulator Height
=
131.89 inch
Hf
= Bus Cen. Height above Insulator
=
5.91 inch
K1
= Overload Factor applied to wind force
=
1
K2
= Overload Factor applied to short circuit force
=
1
= 631.71 lbf Therefore FIS Now Effective weight of bus transmitted to bus support fitting LE.FG FGB lbf = where, LE = Effective Bus span length FG = Total Bus Unit Weight Therefore FGB
fi where, Ki
=
=
31.99 ft
=
6.34 lbf/ft
202.72 lbf
Natural Frequency of the Insulator with effective weight of the conductor span : (1/2S) [Ki g / (0.226FGI + FGB)]1/2 = = Insulator cantilever Spring Constant
=
g FGI
= gravitional constant = Weight of the insulator
= =
386 inch/s 641.54 lbf
FGB
= Effective weight of bus transmitted to bus support fitting
=
202.72 lbf
Therefore fi As
fi
= < 50Hz
2
0.17 Hz =>
K2
=
FIS (Eqp) Cantilever Load on the Support Insulator (in the direction of the Equipment Connection) =>
1 lbf/inch
1 =
Reqiured cantilever Strength of the Supporting Insulator =
(Refer Cl. No. 13.2 of IEEE: 605) 286.80
Kgf
281.23
daN
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ATTACHMENT-3 CALCULATION OF CANTILEVER STRENGTH OF BUS POST INSULATOR SUPPORTING THE EQUIPMENT BUS AT TRANSFORMER & OHL BAY SYSTEM VOLTAGE ( IN KV. ): FAULT LEVEL( IK3 ) ( IN KA.):
400 31.5
TUBULAR BUS CONDUCTOR : a) Size : AlMgSi0.5F25 120 mm b) Outer dia. c) Thickness : 6 mm d) Weight 5.8 Kg/m e) conductor Young's Modulus 7.00E+10 N/m2 f) Conductor spacing 6.5 m N/mm2 g) Max Allowable stress 115 2 Kg/mm 11.72 h) Max. Span 12 m i) Weight of Damper Material 1.83 Kg/m INSULATOR DATA (Type:C6-1550): a. Height b. Max. Width c. Min. Width d Bus Cen. Line height above Insulator e. Weight
3.35 0.29 0.13
m m m
0.15 291
m Kg
(Single 954 CARDINAL ACSR Conductor)
2
Max. Wind Pressure(Pmax)
=
700
N/m
Ambient air density(d) Wind Velocity(V)
= = =
0.613 1/2 (Pmax/d) 33.79
Kg/m m/s m/s
Now, Coss sectional moment of inertia of the tube (J) = = where, DO = Outer Diameter of Conductor = Di = Inner Diameter of Tube = Therefore,
J
= =
Sectional Modulus of the tube
S
=
(as per technical specification) 3
4 4 ( S/64 ).(Do - Di )
120
mm
108
mm
3498701.04 8.405595626
mm4 in4
J/(DO/2)
= =
58311.684 3.558375932
mm
3
mm3 in3
Calculation for conductor Wind Force: Conductor Wind Force (FW) = 2.132 x 10-4 CDKZGFV2 (DO+2r1) Where DO = Outer Diameter of Conductor r1 = Radial Ice thickness.
Hence,
lbf/ft
(Cl. 10. of IEEE:605) 4.72 =
0
CD
= Drag coefficient (Ref. Table 1 of IEEE:605)
=
1
KZ
= Height and exposure factor (Cl. 10.2 of IEEE:605)
=
1
GF V
= Gust factor (Cl. 10.3 of IEEE:605) =Wind speed at 30ft. above ground
= = =
1.3 33.79 75.59
FW
=
inch inch (For Round conductor)
m/s mi/h
7.48 lbf/ft
Calculation for Short Circuit Current Unit Force: Short Circuit Current Unit Force (FSC) =
27.6* ISC2 /107(D)
lbf/ft
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ATTACHMENT-3
Hence,
ISC D *
= Symmettrical short circuit current = Conductor spacing centre to centre = Constant based on type of short circuit and conductor location (Ref. Table 2 of IEEE:605)
FSC
=
= = =
31500 255.91 0.866
A inch
9.27 lbf/ft
Calculation for Gravitational Force: Total bus unit weight (FG) =
FC + FI + FD
lbf/ft
FC
= Conductor unit weight
=
3.90
lbf/ft
FD
= Damping material unit weight
=
1.23
lbf/ft
FI
= Ice Unit weight
=
0
lbf/ft
Hence,
FG
=
5.13 lbf/ft
Calculation for Insulator Strength a.
Calculation for Bus Short circuit Current Force:
FSB
=
LE.FSC
lbf
FSB
= Bus Short Circuit Force transmitted to bus support fitting
LE
= Effective Bus span length
=
FSC
= Short Circuit Current Unit Force
=
Now, for a Rigid Bus Section of Equipment connection in a typical Line bay across the Equipment Bus in Transformer & OHL bay(as shown in the figure alongside) 1/8(3L1+4L2) LE = (Refer Table 5 of IEEE-605) = 27.88714 ft Adjescent Bus Span (L1) = 12 m = 39.37 ft Adjescent Bus Span (L2) = 8m = 26.25 ft = 258.45 lbf Therefore FSB
27.89 ft 9.27 lbf/ft
F
P
P 8m
12m ISO(Panto)
BPI
10.5m CB
L1 b.
Calculation for Bus Wind Force :
FWB
=
L2 Fig 1
LE.FW
lbf
Where, FWB
= Bus Wind force transmitted to bus support fitting
LE
= Effective Bus span length
=
FW
= Wind unit force on the bus
=
Therefore FWB
P
=
27.89 ft 7.48 lbf/ft
208.65 lbf
c.
Calculation for Insulator wind force:
FWI
=
Where, FWI
= Wind Force on Insulator
Hi
= Insulator Height
Di
= Effective insulator diameter = (D1+D2)/2
=
8.2677 inch
D1
= Max. Insulator Width
=
11.4173 inch
D2
= Min. Insulator Width
=
5.1181 inch
-5
2
1.776 x 10 CDKZGFV (Di+2r1)Hi
=
lbf
131.89 Inch
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ATTACHMENT-3 r1
= Radial Ice thickness
=
CD
= Drag coefficient
=
1 (For 'round conductor' as per Table 1 of IEEE:605)
KZ
= Height and exposure factor
=
1 (As per Cl. 10.2 of IEEE:605)
GF V
= Gust factor =Wind speed at 30ft. above ground
Therefore FWI
=
0 inch
= = =
1.3 (As per Cl. 10.3 of IEEE:605) 33.79 m/s 75.59 mi/h
143.86 lbf
Calculation for Total Insulator Cantilever load FIS
=
K1 [ FWI/2 + {(Hi+Hf)/Hi} FWB] + K2 [{(Hi+Hf)/Hi} FSB]
lbf
FIS
= Total Cantilever load acting at the end of Insulator
FWI
= Wind force on the insulator in lbf
=
143.86 lbf
FSB
= Bus Short Circuit Force transmitted to bus support fitting
=
258.45 lbf
FWB
= Bus Wind force transmitted to bus support fitting
=
208.65 lbf
Hi
= Insulator Height
=
131.89 inch
Hf
= Bus Cen. Height above Insulator
=
5.91 inch
K1
= Overload Factor applied to wind force
=
1
K2
= Overload Factor applied to short circuit force
=
1
= 559.95 lbf Therefore FIS Now Effective weight of bus transmitted to bus support fitting LE.FG FGB lbf = where, LE = Effective Bus span length FG = Total Bus Unit Weight Therefore FGB
fi where, Ki
=
=
27.89 ft
=
5.13 lbf/ft
142.99 lbf
Natural Frequency of the Insulator with effective weight of the conductor span : (1/2S) [Ki g / (0.226FGI + FGB)]1/2 = = Insulator cantilever Spring Constant
=
g FGI
= gravitional constant = Weight of the insulator
= =
386 inch/s 641.54 lbf
FGB
= Effective weight of bus transmitted to bus support fitting
=
142.99 lbf
Therefore fi As
fi
= < 50Hz
2
0.18 Hz =>
K2
=
FIS (Eqp) Cantilever Load on the Support Insulator (in the direction of the Equipment Connection) =>
1 lbf/inch
1 =
Reqiured cantilever Strength of the Supporting Insulator =
(Refer Cl. No. 13.2 of IEEE: 605) 254.22
Kgf
249.28
daN
Gilgel Gibe II Hydroelectric Project Page 3 OF 3
