claulation for check suitability of ips
TRANSCRIPT
-
7/26/2019 Claulation for check suitability of IPS
1/45
CLIENT:-
Client: Mundra Port & SEZ.
Project:- 220/66/11kV Electrical Distribution. Sales Ref.: IS/WR/
Description:
Amapacity Calculation of 2" IPS AL Tube.
(Schedule 40)
Drawing No.:
Rev G71000-X0009-ED07
Chkd. SO
Date 15.04.2009
Siemens Ltd
KG OfficeRemarks Date
Prep. SGP
Name
Busbar Current Rating and BPI Cantilever Calculation 1/45
-
7/26/2019 Claulation for check suitability of IPS
2/45
1 Introduction
A. A rigid bus is supported on bus post insulators in an out-door substation. These bus post insulators are
subjected to all types of stresses due to electrical and mechanical forces acting on bus bar.
The principal forces on the bus post insulators supporting a rigid conductor are as follows:
a. Short circuit force on bus conductor
b. Wind force on the bus conductor
c. Wind force on the bus post insulatord. Weight of the bus conductor span supported by the bus post insulators
The resultant of these forces, correlated to the type of 'end Connection' of the rigid conductor at the bus
post insulator terminal, gives the values of the net Electromagnetic Force on the bus post insulator. The
values of forces obtained herewith forms valuable input for the design of bus post insulator support structure
and its foundation design.
In this report along with the force on bus post insulators, the maximum permissible unsupported span length
of the rigid bus conductor connecting the bus post insulators is also determined. The maximum permissible
span is calculated within the limits of 'Vertical Deflection' and permissible 'Fiber Stress' corresponding to the
type of 'End Connection' to the supporting bus post insulator terminals at each end of the span. The
calculation is performed on the method stipulated by IEEE 605 and the minimum of the span length obtained
from the calculation is conservatively considered as the maximum allowable unsupported span for all
influencing conditions.
Busbar Current Rating and BPI Cantilever Calculation 2/45
-
7/26/2019 Claulation for check suitability of IPS
3/45
1 Continuous Current Carrying Capacity
Bus bar continuous rating required Amps.
As per INDAL handbook current rating (nominal for outdoor) are as below:-
IPS Aluminum Tube
- Inches Amps.
As per INDAL handbook for the maximum operating temperature of the bus to 75 Deg. C, the deratingfactor to be adopted is 0.88; hence the derated current rating (nominal for outdoor) are as below:-
2 Inches IPS Al Tube - Schedule 40 = 1440 = Amps.
From the above it is summrised that, for the required current carrying capacity of 875 Amps.,
2 Inches IPS Al Tube - Schedule 40 is sufficient.
2 Thermal Effects on IPS Aluminium Tube as per IEEE 605
Bus Bar Selected Inch
Ambient temperature in deg. C (T2)
Final temperature in deg. C (T1)
2.1 Radiation Loss (Qr)From Stefan-Boltzman law,
Qr = 36.9 x 10-12
x e x ( T14-T2
4) x A (Clause No. 3.2.4, IEEE 605)
A = Surface area = 12 x d x = 12 x x = In2/Ft
T1 = Temperature of the bar,oK = + 273 =
0K
T2 = Ambient temperature,oK = + 273 =
0K
E = Emissivity factor =
Qr = 36.9 x 10-12
x 0.6 x (4-
4) x = Watts/Ft
2.2 Convective Loss (Qc)
Heat is dissipated from a tubular bus bar by forced convection
Heat transfer is considered at wind speed 2 fps and 1 atmospheric pressure.
Qc = 0.010 x x A (Clause No. 3.2.2, IEEE 605)d
0.4
A = Surface area = 12 x d x = 12 x x = In2/Ft
d = outside diameter of bus bar in inch = Inch
= Temperature difference between conductor surface & ambient air in deg C = T1 - T2 =
= - = deg. C
Qc = 0.010 x x = Watts/Ft
( )0.4
2.3 Heat Gain Due To Solar Radiation (Qs)
Qs = h x s x d x 12
h = co-efficient of absorption of conductor surface = 0.5
s = intensity of solar radiation in Watts/Inch2= Watts/In
2
Assumed - 849.27 Watts/Mtr.2
d = outside diameter of bus bar in inch = Inch
Qs = 0.5 x 0.5479 x 2.375196 = Watts/Ft
90.0
875
323.0
2.00
50.0
2.38 89.54
Schedule 40 2.00
50.0
1440
12670.88 x
40.0
0.6
363.0 323.0 89.54
25.340
90.0 363.0
2.375
0.5479
2.38 89.54
89.54
90.0 50.0 40.0
2.38
7.81
12.8435
2.38
Busbar Current Rating and BPI Cantilever Calculation 3/45
-
7/26/2019 Claulation for check suitability of IPS
4/45
2.4 Conductor Resistance
Rt2 = 8.145 x 10-
x 1 + 0.00403 x C' x (T1 - 20) (Clause No. 3.2.9, IEEE 605)
C' x A2 61
Rt2 = Direct current resistance at maximum operating temperature
C' = Conductivity as % IACS =
A2 = Cross sectional area in In
d1 = outside diameter of bus bar in inch = Incht = Thickness of tube = Inch
d2 = inside diameter of bus bar in inch = d1- 2t = - 2 x = Inch
A2 = (/4) x (d1 -d2 ) = (/4) x ( - ) = In
T1 = Final temperature in deg. C = deg. C
Rt2 = 8.145 x 10-
x 1 + 0.00403 x x ( - 20 )
x
Rt2 = /Ft
2.5 Skin Effect Ratio
0.5
f = 0.0636 x F (Clause No. 6, IEEE 605)
r 5280 x Rt2
f = Skin Effect Ratio
r = outer diameter / 2 = / 2 = Inch
F = Frequency In Hz = 50 Hz
Rt2 = Direct current resistance at maximum operating temperature = / Ft
f = x 50 0.5
5280 x
=
2.6 Current Rating / Current Carrying Capability
0.5
I = Qc + Qr - Qs (Clause No. 3.2, IEEE 605)
Rt2x f
0.5
= + - = Amps.
x
61
90.0
90.0
55.0
0.0636
1.72924E-05 1.25
55.0 1.07422
25.340 12.8435
1.72924E-05
2.38
7.81 1183.91
2.067
2.38 2.067 1.07422
2.38 0.154
1.187598
1.72924E-05
1.25
1.1876 1.72924E-05
55.0
2.380.154
Busbar Current Rating and BPI Cantilever Calculation 4/45
-
7/26/2019 Claulation for check suitability of IPS
5/45
3 Bus Span Calculations For - 2 Inch IPS Aluminium Tube
Short circuit forces maximum span calculation are as per IEEE 605
Bus Bar Selected Inches Al Tube
Bus Bar outer Diameter in Inches
Bus Bar Cross Section Moment of inertia in cm4
(J)
Bus Bar Section modulus in cm3
(S)
Bus Bar ultimate tensile strength in Kg/mm2
(UT)
Modulus of Elasticity of Busbar in Kg/mm2
(E)
Bus bar Unit Self weight in Kgf/mtr (Fc)
Maximum allowable stress in Kg/mm2
(Fa)
Clamping material unit weight in Kgf/mtr (Fd) 7 Kg x 1 Nos. = 0.88
8.0 mtrs
Bus Phase to Phase Spacing in Mtrs (D)
Short Circuit Fault Level in kA (Isc)
Duration of the short-circuit current in seconds Tk
Rated short time in seconds Tkr
Wind Speed In Mtr/sec (V)
Allowable deflection in inches: 1 time dia of tube
3.1 Force Due to Wind (Fw)
Unit force due to wind on conductor is given by
Fw = C Cd Kz Gf V I (Dia + 2xrI) in Lbf/Ft (Equation No. 9, IEEE 605)
C = 2.132 x 10-4
for English units
Cd = Drag coefficient for smooth tubular conductor = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
Dia = Outer Dia of Conductor in inches = Inch
I = Importance factor = (Clause No. 9.4, IEEE 605)
rI = radial ice thickness in Inches = 0 Inch
Fw = 2.132 x 10-4 x 1 x 1.16 x 0.85 x x x 1.15 x (2.3751968503937 + 2x0)
= Lbf/Ft = x 1.488 = Kgf/mtr
3.2 Short Circuit Force (Fsc)
Short Circuit Force is given by
Fsc = Kf x C x x (Df x 2 x Isc)2
(Equation No. 12, IEEE 605)
D
C = 5.4 x 10-7
for English units
Isc = RMS short circuit current in A kA
D = Phase to Phase Spacing of Busbars in Inch = x 39.37 = Inch
= Constant based on type of short circuit & conductor location =
(Table 2, for 3 phase short circuit on Y phase, IEEE 605)
Kf = Mounting structure flexibility factor = 1
(Figure 4, IEEE 605)
2.00
2.375
27.709
9.186
0.85
2
31.5
1
1
7030.67
1.871
20.5
123.03
2.375
1.15
123.03
55
20.5
1.16
31.5
2 78.74
0.866
123.03
8.69 8.69 12.93294
Busbar Current Rating and BPI Cantilever Calculation 5/45
-
7/26/2019 Claulation for check suitability of IPS
6/45
Df = Decrement factor = (Equation No. 11a, IEEE 605)
Ta = X 1
R 2 x x fX = System Reactance
R = System Resistance
f = System Frequency = 50 Hz
X =
RTa = x 1 =
2 x x 50
tf = Fault current duration = 1 sec.
Df =
Fsc = 1 x 5.4 x 10-7 x 0.866 x ( x 2 x ) = Lbf/Ft
= x 1.488 = Kgf/mtr
3.3 Gravitational Forces (Fg)
Fg = Fc + Fi + Fd (Equation No. 13, IEEE 605)
Fg = Total bus unit weight in kgf/mtr
Fc = Conductor unit weight in kgf/mtr =
Fi = Ice unit weight in kgf/mtr = 0
Fd = Clamping material unit weight I kgf/mtr =
Fg = 1.871 + 0 + 0. = kgf/mtr = / 1.488 = Lbf/Ft
3.4 Total Force (Ft)
Total force on conductor in Horizontal configuration is given by
Ft = (Equation No. 22, IEEE 605)
= ( + )2
+( )2 = Kgf/mtr
4 Calculation Of Allowable Spans
4.1 For continuous bus, the maximum allowable span length based on vertical deflection is (Ld)
Ld = C x (185 x E x J x Ya)1/4
(Equation No. 20, IEEE 605)
Fg
C = for English units
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/in2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
Ya = Allowable Deflection as vertical dimension of tube = 1D = 1 x = Inch
Fg = Total bus unit weight in kgf/mtr = Kgf/mtr = x (1/1.488)
= Lbf/Ft
Ld = 1.86 x ( 185 x 10000000.03 x 2 )1/4
= In
Ld = / 39.37 = Mtrs.
Hence, maximum allowable span due to vertical deflection is mtrs.
12.35
78.74
15
15 0.0477
1.02
12.35 18.37
1.871
0.875
1.02 31500
2.746 2.746 1.85
12.9329 18.37 2.746 31.43
27.709
27.709 0.67
2.000
1.86
7031
7031 1E+07
0.67 355.52
1.845
355.52 9.03
2.00
2.746 2.746
1.85
9.03
f
a
2t-
Ta
f
T1 + 1 exp
t
2 2
W SC GF F F
Busbar Current Rating and BPI Cantilever Calculation 6/45
-
7/26/2019 Claulation for check suitability of IPS
7/45
4.2 Allowable Span For Fibre Stress (Ls)
Ls = C x ( (28/3) x Fa x S ) (Equation No. 29c, IEEE 605)
Ft
C = for English units
Fa = Maximum allowable stress in Lbf/In2
= Kg/mm2
= x 1422.33 = Lbf/In2
S = Section modulus in In3
For Inch Al Tube, S = cm3
= / 16.3871 = In3
Ft = Total Force in Lbf/Ft
= Kgf/mtr = / 1.488 = Lbf/ft
Ls = 3.46 x ( (28/3) x x ) = Inch
= / 39.37 = Mtrs.
5 Conclusion
As per IEEE 605, page number 25, Clause No. 11.3, the maximum allowable span is the lower of the spans
as calculated for Ld and Ls.
The maximum allowable bus span is Mtrs. for Inches Aluminium tube.
6.1 Natural Frequency of Conductor Span (fb)
fb = x k2 ( E x J ) (Equation No. 5, IEEE 605)
C x L2
m
C = 24 for English units
L = Span length in Feet = Mtrs. = / 0.305 = Feet
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/In2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
m = Mass per unit length = Fc = Kgf/mtr = / 1.488 = Lbf/Ft
k = for two fixed ends
fb = x ( )2
( x ) = Hz
24 x ( )2
Twice the calculated natural frequency of the bus span = 2 x = Hz
6.2 Wind Induced Vibration or Aeolian Force Frequency (fa )
fa = C x V (Equation No. 6, IEEE 605)
d
C = for English units
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
d = Conductor diameter in inches = Inches = x 2.54 = cm
fa = x = Hz
As per IEEE 605, page number 10, clause number 7.2.2, if twice the calculated natural frequency of the
bus span is greater than the Aeolian force frequency, then the bus span should be changed or bus should
be damped.
Since, twice the calculated natural frequency of the bus span is Hz, which is less than the
Aeolian force frequency of Hz, the selected bus span of meters is safe from
Aeolian vibrations.
2.0 9.186 9.186 0.56
3.46
20.5 20.5 29157.8
294.1 7.47
31.43 31.43 21.12
29157.8 0.56
7.47 2.00
7.47 7.47
294.1
21.12
27.709
27.709 0.67
1.871 1.871
24.49
7031
7031 1E+07
2.29
1.26
1.51
1.51 1.150.671E+07
3.26
123.03
2 2
24.49 1.26
1.15
5.08
2.29
79.0 7.47
5.08
3.26 123.03 79.0
Busbar Current Rating and BPI Cantilever Calculation 7/45
-
7/26/2019 Claulation for check suitability of IPS
8/45
7 Insulator Cantilever Strength Calculation As per IEEE 605
Effective Bus Span Length in Mtrs (Le) +
2
= Mtrs.
Height of Insulator Stack in mm (Hi)
Height of Centre Line of Bus over Insulator Height in mm (Hf)
= / 25.4
= Inch
Effective Insulator Diameter in mm (Di) =
7.1 Force Due To Wind On Bus (Fwb)
Fwb = Fw x Le (Equation No. 31, IEEE 605)
Fw = Unit Wind Force On Bus in Lbf/Ft = Lbf/Ft
Le = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fwb = x = Lbf
7.2 Bus Short Circuit Force (Fsb)
Fsb = Fsc x Le (Equation No. 30, IEEE 605)
Fsc = Unit short circuit force on Bus in Lbf/Ft = Lbf/FtLe = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fsb = x = Lbf
7.3 Force Due To Wind On Insulator (Fwi)
Fwi = C x Cd x Kz x Gf x Vx (Di + 2rI) x Hi (Equation No. 32, IEEE 605)
C = for English units Formula as per IEEE 605, 1987
Cd = Drag coefficient = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust Factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr Di = Effective Dia of Insulator in Inch = = / 25.4 = Inch
Hi = Height of insulator in Feet = / (0.305 x 1000) = Feet
rI = Radial ice thickness in Inch = 0 Inch
Fwi = 1.776 x 10-5 x 1 x 1.16 x 0.85x ( )2x( + 2x0 ) x
Fwi = x = Lbf
7.4 Gravitation Force ( Fgb)
Fgb = Fg x Le (Equation No. 34, IEEE 605)
Fg = Total bus unit weight in Lbf/ Ft = Lbf/Ft
Le = Effective Bus Span Length in feet = x (39.37/12) = Feet
Fgb = x = Lbf
80
80
3.15
160
6 6
6
770
8.69
6 19.7
8.69 19.7 171.09
12.356 19.7
12.35 19.7 243.09
160 160 6.30
770 2.52
1.776 x 10-5
1.16
0.85
123.03
19.7
1.85 19.7 36.33
123.03 6.30 2.52
0.00001776 237349 4.21531
1.85
6
Busbar Current Rating and BPI Cantilever Calculation 8/45
-
7/26/2019 Claulation for check suitability of IPS
9/45
7.5 Insulator Cantilever Load (Fis)
(Equation No. 35, IEEE 605)
Fis = K1 x Fwi + ( Hi + Hf ) x Fwb + K2 x ( Hi + Hf ) x Fsb
2 Hi Hi
K1 = Overload factor applied to wind forces =
K2 = Overload factor applied to short-circuit current forces = 1
1x + ( + ) x ) + 1 x
( + ) x = Lbf = x 4.44822
= Newton
Hence, Insulators with 4kN cantilever strength is selected.
1
4.22 30.31 3.15 171.09
459.316 459.316
30.31 2043.14
2 30.31
30.31 3.15 243.09
Busbar Current Rating and BPI Cantilever Calculation 9/45
-
7/26/2019 Claulation for check suitability of IPS
10/45
CLIENT:-
Client: Mundra Port & SEZ.
Project:- 220/66/11kV Electrical Distribution. Sales Ref.: IS/WR/
Description:
Amapacity Calculation of 3" IPS AL Tube.
(Schedule 40)
Drawing No.:
Rev G71000-X0009-ED07Name
Date 15.04.2009
Prep. SGP
Chkd. SO
Siemens Ltd
KG OfficeRemarks Date
Busbar Current Rating and BPI Cantilever Calculation 10/45
-
7/26/2019 Claulation for check suitability of IPS
11/45
1 Introduction
A. A rigid bus is supported on bus post insulators in an out-door substation. These bus post insulators are
subjected to all types of stresses due to electrical and mechanical forces acting on bus bar.
The principal forces on the bus post insulators supporting a rigid conductor are as follows:
a. Short circuit force on bus conductor
b. Wind force on the bus conductor
c. Wind force on the bus post insulatord. Weight of the bus conductor span supported by the bus post insulators
The resultant of these forces, correlated to the type of 'end Connection' of the rigid conductor at the bus
post insulator terminal, gives the values of the net Electromagnetic Force on the bus post insulator. The
values of forces obtained herewith forms valuable input for the design of bus post insulator support structure
and its foundation design.
In this report along with the force on bus post insulators, the maximum permissible unsupported span length
of the rigid bus conductor connecting the bus post insulators is also determined. The maximum permissible
span is calculated within the limits of 'Vertical Deflection' and permissible 'Fiber Stress' corresponding to the
type of 'End Connection' to the supporting bus post insulator terminals at each end of the span. The
calculation is performed on the method stipulated by IEEE 605 and the minimum of the span length obtained
from the calculation is conservatively considered as the maximum allowable unsupported span for all
influencing conditions.
Busbar Current Rating and BPI Cantilever Calculation 11/45
-
7/26/2019 Claulation for check suitability of IPS
12/45
1 Continuous Current Carrying Capacity
Bus bar continuous rating required Amps.
As per INDAL handbook current rating (nominal for outdoor) are as below:-
IPS Aluminum Tube
- Inches Amps.
As per INDAL handbook for the maximum operating temperature of the bus to 75 Deg. C, the deratingfactor to be adopted is 0.88; hence the derated current rating (nominal for outdoor) are as below:-
2 Inches IPS Al Tube - Schedule 40 = 1440 = Amps.
From the above it is summrised that, for the required current carrying capacity of 875 Amps.,
2 Inches IPS Al Tube - Schedule 40 is sufficient.
2 Thermal Effects on IPS Aluminium Tube as per IEEE 605
Bus Bar Selected Inch
Ambient temperature in deg. C (T2)
Final temperature in deg. C (T1)
2.1 Radiation Loss (Qr)From Stefan-Boltzman law,
Qr = 36.9 x 10-12
x e x ( T14-T2
4) x A (Clause No. 3.2.4, IEEE 605)
A = Surface area = 12 x d x = 12 x x = In2/Ft
T1 = Temperature of the bar,oK = + 273 =
0K
T2 = Ambient temperature,oK = + 273 =
0K
E = Emissivity factor =
Qr = 36.9 x 10-12
x 0.6 x (4-
4) x = Watts/Ft
2.2 Convective Loss (Qc)
Heat is dissipated from a tubular bus bar by forced convection
Heat transfer is considered at wind speed 2 fps and 1 atmospheric pressure.
Qc = 0.010 x x A (Clause No. 3.2.2, IEEE 605)d
0.4
A = Surface area = 12 x d x = 12 x x = In2/Ft
d = outside diameter of bus bar in inch = Inch
= Temperature difference between conductor surface & ambient air in deg C = T1 - T2 =
= - = deg. C
Qc = 0.010 x x = Watts/Ft
( )0.4
2.3 Heat Gain Due To Solar Radiation (Qs)
Qs = h x s x d x 12
h = co-efficient of absorption of conductor surface = 0.5
s = intensity of solar radiation in Watts/Inch2= Watts/In
2
Assumed - 849.27 Watts/Mtr.2
d = outside diameter of bus bar in inch = Inch
Qs = 0.5 x 0.5479 x 2.375196 = Watts/Ft
12.8435
2.38
2.38
40.0 25.340
90.0 363.0
363.0
7.81
323.0 89.54
2.375
0.5479
2.38 89.54
89.54
90.0 50.0 40.0
Schedule 40 2.00 1440
12670.88 x
0.6
89.54
875
90.0
50.0 323.0
2.00
50.0
2.38
Busbar Current Rating and BPI Cantilever Calculation 12/45
-
7/26/2019 Claulation for check suitability of IPS
13/45
2.4 Conductor Resistance
Rt2 = 8.145 x 10-
x 1 + 0.00403 x C' x (T1 - 20) (Clause No. 3.2.9, IEEE 605)
C' x A2 61
Rt2 = Direct current resistance at maximum operating temperature
C' = Conductivity as % IACS =
A2 = Cross sectional area in In
d1 = outside diameter of bus bar in inch = Incht = Thickness of tube = Inch
d2 = inside diameter of bus bar in inch = d1- 2t = - 2 x = Inch
A2 = (/4) x (d1 -d2 ) = (/4) x ( - ) = In
T1 = Final temperature in deg. C = deg. C
Rt2 = 8.145 x 10-
x 1 + 0.00403 x x ( - 20 )
x
Rt2 = /Ft
2.5 Skin Effect Ratio
0.5
f = 0.0636 x F (Clause No. 6, IEEE 605)
r 5280 x Rt2
f = Skin Effect Ratio
r = outer diameter / 2 = / 2 = Inch
F = Frequency In Hz = 50 Hz
Rt2 = Direct current resistance at maximum operating temperature = / Ft
f = x 50 0.5
5280 x
=
2.6 Current Rating / Current Carrying Capability
0.5
I = Qc + Qr - Qs (Clause No. 3.2, IEEE 605)
Rt2x f
0.5
= + - = Amps.
x
1.1876 1.72924E-05
55.0
2.380.154
2.067
2.38 2.067 1.07422
2.38 0.154
1.72924E-05
1.187598
1183.91
0.0636
1.72924E-05 1.25
1.25
61
90.0
55.0 1.07422
25.340 12.8435
1.72924E-05
2.38
7.81
90.0
55.0
Busbar Current Rating and BPI Cantilever Calculation 13/45
-
7/26/2019 Claulation for check suitability of IPS
14/45
3 Bus Span Calculations For - 2 Inch IPS Aluminium Tube
Short circuit forces maximum span calculation are as per IEEE 605
Bus Bar Selected Inches Al Tube
Bus Bar outer Diameter in Inches
Bus Bar Cross Section Moment of inertia in cm4
(J)
Bus Bar Section modulus in cm3
(S)
Bus Bar ultimate tensile strength in Kg/mm2
(UT)
Modulus of Elasticity of Busbar in Kg/mm2
(E)
Bus bar Unit Self weight in Kgf/mtr (Fc)
Maximum allowable stress in Kg/mm2
(Fa)
Clamping material unit weight in Kgf/mtr (Fd) 7 Kg x 1 Nos. = 0.88
8.0 mtrs
Bus Phase to Phase Spacing in Mtrs (D)
Short Circuit Fault Level in kA (Isc)
Duration of the short-circuit current in seconds Tk
Rated short time in seconds Tkr
Wind Speed In Mtr/sec (V)
Allowable deflection in inches: 1 time dia of tube
3.1 Force Due to Wind (Fw)
Unit force due to wind on conductor is given by
Fw = C Cd Kz Gf V I (Dia + 2xrI) in Lbf/Ft (Equation No. 9, IEEE 605)
C = 2.132 x 10-4
for English units
Cd = Drag coefficient for smooth tubular conductor = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
Dia = Outer Dia of Conductor in inches = Inch
I = Importance factor = (Clause No. 9.4, IEEE 605)
rI = radial ice thickness in Inches = 0 Inch
Fw = 2.132 x 10-4 x 1 x 1.16 x 0.85 x x x 1.15 x (2.3751968503937 + 2x0)
= Lbf/Ft = x 1.488 = Kgf/mtr
3.2 Short Circuit Force (Fsc)
Short Circuit Force is given by
Fsc = Kf x C x x (Df x 2 x Isc)2
(Equation No. 12, IEEE 605)
D
C = 5.4 x 10-7
for English units
Isc = RMS short circuit current in A kA
D = Phase to Phase Spacing of Busbars in Inch = x 39.37 = Inch
= Constant based on type of short circuit & conductor location =
(Table 2, for 3 phase short circuit on Y phase, IEEE 605)
Kf = Mounting structure flexibility factor = 1
(Figure 4, IEEE 605)
31.5
2 78.74
0.866
123.03
2.375
1.15
123.03 123.03
8.69 8.69 12.93294
55
20.5
1.16
0.85
2
31.5
1
1
7030.67
1.871
20.5
2.00
2.375
27.709
9.186
Busbar Current Rating and BPI Cantilever Calculation 14/45
-
7/26/2019 Claulation for check suitability of IPS
15/45
Df = Decrement factor = (Equation No. 11a, IEEE 605)
Ta = X 1
R 2 x x fX = System Reactance
R = System Resistance
f = System Frequency = 50 Hz
X =
RTa = x 1 =
2 x x 50
tf = Fault current duration = 1 sec.
Df =
Fsc = 1 x 5.4 x 10-7 x 0.866 x ( x 2 x ) = Lbf/Ft
= x 1.488 = Kgf/mtr
3.3 Gravitational Forces (Fg)
Fg = Fc + Fi + Fd (Equation No. 13, IEEE 605)
Fg = Total bus unit weight in kgf/mtr
Fc = Conductor unit weight in kgf/mtr =
Fi = Ice unit weight in kgf/mtr = 0
Fd = Clamping material unit weight I kgf/mtr =
Fg = 1.871 + 0 + 0. = kgf/mtr = / 1.488 = Lbf/Ft
3.4 Total Force (Ft)
Total force on conductor in Horizontal configuration is given by
Ft = (Equation No. 22, IEEE 605)
= ( + )2
+( )2 = Kgf/mtr
4 Calculation Of Allowable Spans
4.1 For continuous bus, the maximum allowable span length based on vertical deflection is (Ld)
Ld = C x (185 x E x J x Ya)1/4
(Equation No. 20, IEEE 605)
Fg
C = for English units
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/in2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
Ya = Allowable Deflection as vertical dimension of tube = 1D = 1 x = Inch
Fg = Total bus unit weight in kgf/mtr = Kgf/mtr = x (1/1.488)
= Lbf/Ft
Ld = 1.86 x ( 185 x 10000000.03 x 2 )1/4
= In
Ld = / 39.37 = Mtrs.
Hence, maximum allowable span due to vertical deflection is mtrs.
1.845
355.52 9.03
9.03
2.000 2.00
2.746 2.746
1.85
0.67 355.52
1.86
7031
7031 1E+07
27.709
27.709 0.67
1.871
0.875
2.746 2.746 1.85
12.9329 18.37 2.746 31.43
1.02
1.02 31500 12.35
78.74
12.35 18.37
15
15 0.0477
f
a
2t-
Ta
f
T1 + 1 exp
t
2 2
W SC GF F F
Busbar Current Rating and BPI Cantilever Calculation 15/45
-
7/26/2019 Claulation for check suitability of IPS
16/45
4.2 Allowable Span For Fibre Stress (Ls)
Ls = C x ( (28/3) x Fa x S ) (Equation No. 29c, IEEE 605)
Ft
C = for English units
Fa = Maximum allowable stress in Lbf/In2
= Kg/mm2
= x 1422.33 = Lbf/In2
S = Section modulus in In3
For Inch Al Tube, S = cm3
= / 16.3871 = In3
Ft = Total Force in Lbf/Ft
= Kgf/mtr = / 1.488 = Lbf/ft
Ls = 3.46 x ( (28/3) x x ) = Inch
= / 39.37 = Mtrs.
5 Conclusion
As per IEEE 605, page number 25, Clause No. 11.3, the maximum allowable span is the lower of the spans
as calculated for Ld and Ls.
The maximum allowable bus span is Mtrs. for Inches Aluminium tube.
6.1 Natural Frequency of Conductor Span (fb)
fb = x k2 ( E x J ) (Equation No. 5, IEEE 605)
C x L2
m
C = 24 for English units
L = Span length in Feet = Mtrs. = / 0.305 = Feet
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/In2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
m = Mass per unit length = Fc = Kgf/mtr = / 1.488 = Lbf/Ft
k = for two fixed ends
fb = x ( )2
( x ) = Hz
24 x ( )2
Twice the calculated natural frequency of the bus span = 2 x = Hz
6.2 Wind Induced Vibration or Aeolian Force Frequency (fa )
fa = C x V (Equation No. 6, IEEE 605)
d
C = for English units
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
d = Conductor diameter in inches = Inches = x 2.54 = cm
fa = x = Hz
As per IEEE 605, page number 10, clause number 7.2.2, if twice the calculated natural frequency of the
bus span is greater than the Aeolian force frequency, then the bus span should be changed or bus should
be damped.
Since, twice the calculated natural frequency of the bus span is Hz, which is less than the
Aeolian force frequency of Hz, the selected bus span of meters is safe from
Aeolian vibrations.
5.08
2.29
79.0 7.47
2 2 5.08
3.26 123.03 79.0
24.49 1.26
1.15 2.29
3.26
123.03
1.26
1.51
1.51 1.150.671E+07
7031 1E+07
27.709
27.709 0.67
1.871 1.871
7.47 2.00
7.47 7.47 24.49
7031
29157.8 0.56 294.1
21.12
294.1 7.47
2.0 9.186 9.186 0.56
31.43 31.43 21.12
3.46
20.5 20.5 29157.8
Busbar Current Rating and BPI Cantilever Calculation 16/45
-
7/26/2019 Claulation for check suitability of IPS
17/45
7 Insulator Cantilever Strength Calculation As per IEEE 605
Effective Bus Span Length in Mtrs (Le) +
2
= Mtrs.
Height of Insulator Stack in mm (Hi)
Height of Centre Line of Bus over Insulator Height in mm (Hf)
= / 25.4
= Inch
Effective Insulator Diameter in mm (Di) =
7.1 Force Due To Wind On Bus (Fwb)
Fwb = Fw x Le (Equation No. 31, IEEE 605)
Fw = Unit Wind Force On Bus in Lbf/Ft = Lbf/Ft
Le = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fwb = x = Lbf
7.2 Bus Short Circuit Force (Fsb)
Fsb = Fsc x Le (Equation No. 30, IEEE 605)
Fsc = Unit short circuit force on Bus in Lbf/Ft = Lbf/FtLe = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fsb = x = Lbf
7.3 Force Due To Wind On Insulator (Fwi)
Fwi = C x Cd x Kz x Gf x Vx (Di + 2rI) x Hi (Equation No. 32, IEEE 605)
C = for English units Formula as per IEEE 605, 1987
Cd = Drag coefficient = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust Factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr Di = Effective Dia of Insulator in Inch = = / 25.4 = Inch
Hi = Height of insulator in Feet = / (0.305 x 1000) = Feet
rI = Radial ice thickness in Inch = 0 Inch
Fwi = 1.776 x 10-5 x 1 x 1.16 x 0.85x ( )2x( + 2x0 ) x
Fwi = x = Lbf
7.4 Gravitation Force ( Fgb)
Fgb = Fg x Le (Equation No. 34, IEEE 605)
Fg = Total bus unit weight in Lbf/ Ft = Lbf/Ft
Le = Effective Bus Span Length in feet = x (39.37/12) = Feet
Fgb = x = Lbf
0.00001776 237349 4.21531
1.85
1.85 19.7 36.33
6 19.7
6.30
770 2.52
123.03 6.30 2.52
1.776 x 10-5
1.16
0.85
123.03160 160
12.356 19.7
12.35 19.7 243.09
8.69
6 19.7
8.69 19.7 171.09
6
770
80
80
3.15
160
6 6
Busbar Current Rating and BPI Cantilever Calculation 17/45
-
7/26/2019 Claulation for check suitability of IPS
18/45
7.5 Insulator Cantilever Load (Fis)
(Equation No. 35, IEEE 605)
Fis = K1 x Fwi + ( Hi + Hf ) x Fwb + K2 x ( Hi + Hf ) x Fsb
2 Hi Hi
K1 = Overload factor applied to wind forces =
K2 = Overload factor applied to short-circuit current forces = 1
1x + ( + ) x ) + 1 x
( + ) x = Lbf = x 4.44822
= Newton
Hence, Insulators with 4kN cantilever strength is selected.
459.316
30.31 2043.14
2 30.31
30.31 3.15 243.09 459.316
1
4.22 30.31 3.15 171.09
Busbar Current Rating and BPI Cantilever Calculation 18/45
-
7/26/2019 Claulation for check suitability of IPS
19/45
CLIENT:-
Client: Mundra Port & SEZ.
Project:- 220/66/11kV Electrical Distribution. Sales Ref.: IS/
Description:
Amapacity Calculation of 3" IPS AL Tube.
(Schedule 40)
Drawing No.:
Rev G71000-X0009-ED07Name
Date 15.04.2009
Prep. SGP
Chkd. SO
Siemens Ltd
KG OfficeRemarks Date
Busbar Current Rating and BPI Cantilever Calculation 19/45
-
7/26/2019 Claulation for check suitability of IPS
20/45
1 Introduction
A. A rigid bus is supported on bus post insulators in an out-door substation. These bus post insulators are
subjected to all types of stresses due to electrical and mechanical forces acting on bus bar.
The principal forces on the bus post insulators supporting a rigid conductor are as follows:
a. Short circuit force on bus conductor
b. Wind force on the bus conductor
c. Wind force on the bus post insulatord. Weight of the bus conductor span supported by the bus post insulators
The resultant of these forces, correlated to the type of 'end Connection' of the rigid conductor at the bus
post insulator terminal, gives the values of the net Electromagnetic Force on the bus post insulator. The
values of forces obtained herewith forms valuable input for the design of bus post insulator support structure
and its foundation design.
In this report along with the force on bus post insulators, the maximum permissible unsupported span length
of the rigid bus conductor connecting the bus post insulators is also determined. The maximum permissible
span is calculated within the limits of 'Vertical Deflection' and permissible 'Fiber Stress' corresponding to the
type of 'End Connection' to the supporting bus post insulator terminals at each end of the span. The
calculation is performed on the method stipulated by IEEE 605 and the minimum of the span length obtained
from the calculation is conservatively considered as the maximum allowable unsupported span for all
influencing conditions.
Busbar Current Rating and BPI Cantilever Calculation 20/45
-
7/26/2019 Claulation for check suitability of IPS
21/45
2 Continuous Current Carrying Capacity
Bus bar continuous rating required Amps.
As per INDAL handbook current rating (nominal for outdoor) are as below:-
IPS Aluminum Tube
- Inches Amps.
As per INDAL handbook for the maximum operating temperature of the bus to 75 Deg. C, the deratingfactor to be adopted is 0.88; hence the derated current rating (nominal for outdoor) are as below:-
3 Inches IPS Al Tube - Schedule 40 = 2350 = Amps.
From the above it is summrised that, for the required current carrying capacity of 263 Amps.,
3 Inches IPS Al Tube - Schedule 40 is sufficient.
3 Thermal Effects on IPS Aluminium Tube as per IEEE 605
Bus Bar Selected Inch
Ambient temperature in deg. C (T2)
Final temperature in deg. C (T1)
3.1 Radiation Loss (Qr)From Stefan-Boltzman law,
Qr = 36.9 x 10-12
x e x ( T14-T2
4) x A (Clause No. 3.2.4, IEEE 605)
A = Surface area = 12 x d x = 12 x x = In2/Ft
T1 = Temperature of the bar,oK = + 273 =
0K
T2 = Ambient temperature,oK = + 273 =
0K
E = Emissivity factor =
Qr = 36.9 x 10-12
x 0.6 x (4-
4) x = Watts/Ft
3.2 Convective Loss (Qc)
Heat is dissipated from a tubular bus bar by forced convection
Heat transfer is considered at wind speed 2 fps and 1 atmospheric pressure.
Qc = 0.010 x x A (Clause No. 3.2.2, IEEE 605)d
0.4
A = Surface area = 12 x d x = 12 x x = In2/Ft
d = outside diameter of bus bar in inch = Inch
= Temperature difference between conductor surface & ambient air in deg C = T1 - T2 =
= - = deg. C
Qc = 0.010 x x = Watts/Ft
( )0.4
3.3 Heat Gain Due To Solar Radiation (Qs)
Qs = h x s x d x 12
h = co-efficient of absorption of conductor surface = 0.5
s = intensity of solar radiation in Watts/Inch2= Watts/In
2
Assumed - 849.27 Watts/Mtr.2
d = outside diameter of bus bar in inch = Inch
Qs = 0.5 x 0.5479 x 3.5 x 12 = Watts/Ft
18.9258
3.50
3.50
40.0 31.977
90.0 363.0
363.0
11.51
323.0 131.95
3.500
0.5479
3.50 131.95
131.95
90.0 50.0 40.0
Schedule 40 3.00 2350
20680.88 x
0.6
131.95
263
90.0
50.0 323.0
3.00
50.0
3.50
Busbar Current Rating and BPI Cantilever Calculation 21/45
-
7/26/2019 Claulation for check suitability of IPS
22/45
3.4 Conductor Resistance
Rt2 = 8.145 x 10-
x 1 + 0.00403 x C' x (T1 - 20) (Clause No. 3.2.9, IEEE 605)
C' x A2 61
Rt2 = Direct current resistance at maximum operating temperature
C' = Conductivity as % IACS =
A2 = Cross sectional area in In
d1 = outside diameter of bus bar in inch = Incht = Thickness of tube = Inch
d2 = inside diameter of bus bar in inch = d1- 2t = - 2 x = Inch
A2 = (/4) x (d1 -d2 ) = (/4) x ( - ) = In
T1 = Final temperature in deg. C = deg. C
Rt2 = 8.145 x 10-
x 1 + 0.00403 x x ( - 20 )
x
Rt2 = /Ft
3.5 Skin Effect Ratio
0.5
f = 0.0636 x F (Clause No. 6, IEEE 605)
r 5280 x Rt2
f = Skin Effect Ratio
r = outer diameter / 2 = / 2 = Inch
F = Frequency In Hz = 50 Hz
Rt2 = Direct current resistance at maximum operating temperature = / Ft
f = x 50 0.5
5280 x
=
3.6 Current Rating / Current Carrying Capability
0.5
I = Qc + Qr - Qs (Clause No. 3.2, IEEE 605)
Rt2x f
0.5
= + - = Amps.
x
1.75 8.33058E-06
55.0
3.500.216
3.068
3.50 3.068 2.22984
3.50 0.216
8.33058E-06
1.75
1964.56
0.0636
8.33058E-06 1.23
1.23
61
90.0
55.0 2.22984
31.977 18.9258
8.33058E-06
3.50
11.51
90.0
55.0
Busbar Current Rating and BPI Cantilever Calculation 22/45
-
7/26/2019 Claulation for check suitability of IPS
23/45
4 Bus Span Calculations For - 3 Inch IPS Aluminium Tube
Short circuit forces maximum span calculation are as per IEEE 605
Bus Bar Selected Inches Al Tube
Bus Bar outer Diameter in Inches
Bus Bar Cross Section Moment of inertia in cm4
(J)
Bus Bar Section modulus in cm3
(S)
Bus Bar ultimate tensile strength in Kg/mm2
(UT)
Modulus of Elasticity of Busbar in Kg/mm2
(E)
Bus bar Unit Self weight in Kgf/mtr (Fc)
Maximum allowable stress in Kg/mm2
(Fa)
Clamping material unit weight in Kgf/mtr (Fd) 7 Kg x 1 Nos. = 0.58
12.0 mtrs
Bus Phase to Phase Spacing in Mtrs (D)
Short Circuit Fault Level in kA (Isc)
Duration of the short-circuit current in seconds Tk
Rated short time in seconds Tkr
Wind Speed In Mtr/sec (V)
Allowable deflection in inches: 1 time dia of tube
4.1 Force Due to Wind (Fw)
Unit force due to wind on conductor is given by
Fw = C Cd Kz Gf V I (Dia + 2xrI) in Lbf/Ft (Equation No. 9, IEEE 605)
C = 2.132 x 10-4
for English units
Cd = Drag coefficient for smooth tubular conductor = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
Dia = Outer Dia of Conductor in inches = Inch
I = Importance factor = (Clause No. 9.4, IEEE 605)
rI = radial ice thickness in Inches = 0 Inch
Fw = 2.132 x 10-4 x 1 x 1.16 x 0.85 x x x 1.15 x (3.5 + 2x0)
= Lbf/Ft = x 1.488 = Kgf/mtr
4.2 Short Circuit Force (Fsc)
Short Circuit Force is given by
Fsc = Kf x C x x (Df x 2 x Isc)2
(Equation No. 12, IEEE 605)
D
C = 5.4 x 10-7
for English units
Isc = RMS short circuit current in A kA
D = Phase to Phase Spacing of Busbars in Inch = x 39.37 = Inch
= Constant based on type of short circuit & conductor location =
(Table 2, for 3 phase short circuit on Y phase, IEEE 605)
Kf = Mounting structure flexibility factor = 1
(Figure 4, IEEE 605)
40
4.25 167.32
0.866
123.03
3.500
1.15
123.03 123.03
12.81 12.81 19.05748
55
20.5
1.16
0.85
4.25
40
1
1
7030.67
3.884
20.5
3.00
3.500
125.606
28.258
Busbar Current Rating and BPI Cantilever Calculation 23/45
-
7/26/2019 Claulation for check suitability of IPS
24/45
Df = Decrement factor = (Equation No. 11a, IEEE 605)
Ta = X 1
R 2 x x fX = System Reactance
R = System Resistance
f = System Frequency = 50 Hz
X =
RTa = x 1 =
2 x x 50
tf = Fault current duration = 1 sec.
Df =
Fsc = 1 x 5.4 x 10-7 x 0.866 x ( x 2 x ) = Lbf/Ft
= x 1.488 = Kgf/mtr
4.3 Gravitational Forces (Fg)
Fg = Fc + Fi + Fd (Equation No. 13, IEEE 605)
Fg = Total bus unit weight in kgf/mtr
Fc = Conductor unit weight in kgf/mtr =
Fi = Ice unit weight in kgf/mtr = 0
Fd = Clamping material unit weight I kgf/mtr =
Fg = 3.884 + 0 + 0. = kgf/mtr = / 1.488 = Lbf/Ft
4.4 Total Force (Ft)
Total force on conductor in Horizontal configuration is given by
Ft = (Equation No. 22, IEEE 605)
= ( + )2
+( )2 = Kgf/mtr
5 Calculation Of Allowable Spans
5.1 For continuous bus, the maximum allowable span length based on vertical deflection is (Ld)
Ld = C x (185 x E x J x Ya)1/4
(Equation No. 20, IEEE 605)
Fg
C = for English units
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/in2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
Ya = Allowable Deflection as vertical dimension of tube = 1D = 1 x = Inch
Fg = Total bus unit weight in kgf/mtr = Kgf/mtr = x (1/1.488)
= Lbf/Ft
Ld = 1.86 x ( 185 x 10000000.03 x 3 )1/4
= In
Ld = / 39.37 = Mtrs.
Hence, maximum allowable span due to vertical deflection is mtrs.
3.002
508.33 12.91
12.91
3.000 3.00
4.467 4.467
3.00
3.02 508.33
1.86
7031
7031 1E+07
125.606
125.606 3.02
3.884
0.583333
4.467 4.467 3.00
19.0575 13.94 4.467 33.30
1.02
1.02 40000 9.37
167.32
9.37 13.94
15
15 0.0477
f
a
2t-
Ta
f
T1 + 1 exp
t
2 2
W SC GF F F
Busbar Current Rating and BPI Cantilever Calculation 24/45
-
7/26/2019 Claulation for check suitability of IPS
25/45
5.2 Allowable Span For Fibre Stress (Ls)
Ls = C x ( (28/3) x Fa x S ) (Equation No. 29c, IEEE 605)
Ft
C = for English units
Fa = Maximum allowable stress in Lbf/In2
= Kg/mm2
= x 1422.33 = Lbf/In2
S = Section modulus in In3
For Inch Al Tube, S = cm3
= / 16.3871 = In3
Ft = Total Force in Lbf/Ft
= Kgf/mtr = / 1.488 = Lbf/ft
Ls = 3.46 x ( (28/3) x x ) = Inch
= / 39.37 = Mtrs.
6 Conclusion
As per IEEE 605, page number 25, Clause No. 11.3, the maximum allowable span is the lower of the spans
as calculated for Ld and Ls.
The maximum allowable bus span is Mtrs. for Inches Aluminium tube.
7.1 Natural Frequency of Conductor Span (fb)
fb = x k2 ( E x J ) (Equation No. 5, IEEE 605)
C x L2
m
C = 24 for English units
L = Span length in Feet = Mtrs. = / 0.305 = Feet
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/In2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
m = Mass per unit length = Fc = Kgf/mtr = / 1.488 = Lbf/Ft
k = for two fixed ends
fb = x ( )2
( x ) = Hz
24 x ( )2
Twice the calculated natural frequency of the bus span = 2 x = Hz
7.2 Wind Induced Vibration or Aeolian Force Frequency (fa )
fa = C x V (Equation No. 6, IEEE 605)
d
C = for English units
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
d = Conductor diameter in inches = Inches = x 2.54 = cm
fa = x = Hz
As per IEEE 605, page number 10, clause number 7.2.2, if twice the calculated natural frequency of the
bus span is greater than the Aeolian force frequency, then the bus span should be changed or bus should
be damped.
Since, twice the calculated natural frequency of the bus span is Hz, which is less than the
Aeolian force frequency of Hz, the selected bus span of meters is safe from
Aeolian vibrations.
7.62
1.17
52.6 12.73
3 3 7.62
3.26 123.03 52.6
41.72 2.61
0.58 1.17
3.26
123.03
2.61
1.51
1.51 0.583.021E+07
7031 1E+07
125.606
125.606 3.02
3.884 3.884
12.73 3.00
12.73 12.73 41.72
7031
29157.8 1.72 501.0
22.38
501.0 12.73
3.0 28.258 28.258 1.72
33.30 33.30 22.38
3.46
20.5 20.5 29157.8
Busbar Current Rating and BPI Cantilever Calculation 25/45
-
7/26/2019 Claulation for check suitability of IPS
26/45
8 Insulator Cantilever Strength Calculation As per IEEE 605
Effective Bus Span Length in Mtrs (Le) +
2
= Mtrs.
Height of Insulator Stack in mm (Hi)
Height of Centre Line of Bus over Insulator Height in mm (Hf)
= / 25.4
= Inch
Effective Insulator Diameter in mm (Di) =
8.1 Force Due To Wind On Bus (Fwb)
Fwb = Fw x Le (Equation No. 31, IEEE 605)
Fw = Unit Wind Force On Bus in Lbf/Ft = Lbf/Ft
Le = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fwb = x = Lbf
8.2 Bus Short Circuit Force (Fsb)
Fsb = Fsc x Le (Equation No. 30, IEEE 605)
Fsc = Unit short circuit force on Bus in Lbf/Ft = Lbf/FtLe = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fsb = x = Lbf
8.3 Force Due To Wind On Insulator (Fwi)
Fwi = C x Cd x Kz x Gf x Vx (Di + 2rI) x Hi (Equation No. 32, IEEE 605)
C = for English units Formula as per IEEE 605, 1987
Cd = Drag coefficient = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust Factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr Di = Effective Dia of Insulator in Inch = = / 25.4 = Inch
Hi = Height of insulator in Feet = / (0.305 x 1000) = Feet
rI = Radial ice thickness in Inch = 0 Inch
Fwi = 1.776 x 10-5 x 1 x 1.16 x 0.85x ( )2x( + 2x0 ) x
Fwi = x = Lbf
8.4 Gravitation Force ( Fgb)
Fgb = Fg x Le (Equation No. 34, IEEE 605)
Fg = Total bus unit weight in Lbf/ Ft = Lbf/Ft
Le = Effective Bus Span Length in feet = x (39.37/12) = Feet
Fgb = x = Lbf
0.00001776 1307151 23.215
3.00
3.00 37.7 113.27
11.5 37.7
11.61
2300 7.54
123.03 11.61 7.54
1.776 x 10-5
1.16
0.85
123.03295 295
9.3711.5 37.7
9.37 37.7 353.55
12.81
11.5 37.7
12.81 37.7 483.22
11.5
2300
130
130
5.12
295
11.5 11.5
Busbar Current Rating and BPI Cantilever Calculation 26/45
-
7/26/2019 Claulation for check suitability of IPS
27/45
8.5 Insulator Cantilever Load (Fis)
(Equation No. 35, IEEE 605)
Fis = K1 x Fwi + ( Hi + Hf ) x Fwb + K2 x ( Hi + Hf ) x Fsb
2 Hi Hi
K1 = Overload factor applied to wind forces =
K2 = Overload factor applied to short-circuit current forces = 1
1x + ( + ) x ) + 1 x
( + ) x = Lbf = x 4.44822
= Newton
Hence, Insulators with 4kN cantilever strength is selected.
895.668
90.55 3984.13
2 90.55
90.55 5.12 353.55 895.668
1
23.22 90.55 5.12 483.22
Busbar Current Rating and BPI Cantilever Calculation 27/45
-
7/26/2019 Claulation for check suitability of IPS
28/45
CLIENT:-
Client: Mundra Port & SEZ.
Project:- 220/66/11kV Electrical Distribution. Sales Ref.: IS/
Description:
Amapacity Calculation of 4" IPS AL Tube.
(Schedule 40)
Drawing No.:
Rev G71000-X0009-ED07
Chkd. SO
Date 15.04.2009
Siemens Ltd
KG OfficeRemarks Date
Prep. SGP
Name
Busbar Current Rating and BPI Cantilever Calculation 28/45
-
7/26/2019 Claulation for check suitability of IPS
29/45
1 Introduction
A. A rigid bus is supported on bus post insulators in an out-door substation. These bus post insulators are
subjected to all types of stresses due to electrical and mechanical forces acting on bus bar.
The principal forces on the bus post insulators supporting a rigid conductor are as follows:
a. Short circuit force on bus conductor
b. Wind force on the bus conductor
c. Wind force on the bus post insulatord. Weight of the bus conductor span supported by the bus post insulators
The resultant of these forces, correlated to the type of 'end Connection' of the rigid conductor at the bus
post insulator terminal, gives the values of the net Electromagnetic Force on the bus post insulator. The
values of forces obtained herewith forms valuable input for the design of bus post insulator support structure
and its foundation design.
In this report along with the force on bus post insulators, the maximum permissible unsupported span length
of the rigid bus conductor connecting the bus post insulators is also determined. The maximum permissible
span is calculated within the limits of 'Vertical Deflection' and permissible 'Fiber Stress' corresponding to the
type of 'End Connection' to the supporting bus post insulator terminals at each end of the span. The
calculation is performed on the method stipulated by IEEE 605 and the minimum of the span length obtained
from the calculation is conservatively considered as the maximum allowable unsupported span for all
influencing conditions.
Busbar Current Rating and BPI Cantilever Calculation 29/45
-
7/26/2019 Claulation for check suitability of IPS
30/45
2 Continuous Current Carrying Capacity
Bus bar continuous rating required Amps.
As per INDAL handbook current rating (nominal for outdoor) are as below:-
IPS Aluminum Tube
- Inches Amps.
As per INDAL handbook for the maximum operating temperature of the bus to 75 Deg. C, the deratingfactor to be adopted is 0.88; hence the derated current rating (nominal for outdoor) are as below:-
4 Inches IPS Al Tube - Schedule 40 = 3050 = Amps.
From the above it is summrised that, for the required current carrying capacity of 1250 Amps.,
4 Inches IPS Al Tube - Schedule 40 is sufficient.
3 Thermal Effects on IPS Aluminium Tube as per IEEE 605
Bus Bar Selected Inch
Ambient temperature in deg. C (T2)
Final temperature in deg. C (T1)
3.1 Radiation Loss (Qr)From Stefan-Boltzman law,
Qr = 36.9 x 10-12
x e x ( T14-T2
4) x A (Clause No. 3.2.4, IEEE 605)
A = Surface area = 12 x d x = 12 x x = In2/Ft
T1 = Temperature of the bar,oK = + 273 =
0K
T2 = Ambient temperature,oK = + 273 =
0K
E = Emissivity factor =
Qr = 36.9 x 10-12
x 0.6 x (4-
4) x = Watts/Ft
3.2 Convective Loss (Qc)
Heat is dissipated from a tubular bus bar by forced convection
Heat transfer is considered at wind speed 2 fps and 1 atmospheric pressure.
Qc = 0.010 x x A (Clause No. 3.2.2, IEEE 605)d
0.4
A = Surface area = 12 x d x = 12 x x = In2/Ft
d = outside diameter of bus bar in inch = Inch
= Temperature difference between conductor surface & ambient air in deg C = T1 - T2 =
= - = deg. C
Qc = 0.010 x x = Watts/Ft
( )0.4
3.3 Heat Gain Due To Solar Radiation (Qs)
Qs = h x s x d x 12
h = co-efficient of absorption of conductor surface = 0.5
s = intensity of solar radiation in Watts/Inch2= Watts/In
2
Assumed - 849.27 Watts/Mtr.2
d = outside diameter of bus bar in inch = Inch
Qs = 0.5 x 0.5479 x 4.5 x 12 = Watts/Ft
95.0
1250
318.0
4.00
45.0
4.50 169.65
Schedule 40 4.00
45.0
3050
26840.88 x
50.0
0.6
368.0 318.0 169.65
46.476
95.0 368.0
4.500
0.5479
4.50 169.65
169.65
95.0 45.0 50.0
4.50
14.79
30.4744
4.50
Busbar Current Rating and BPI Cantilever Calculation 30/45
-
7/26/2019 Claulation for check suitability of IPS
31/45
3.4 Conductor Resistance
Rt2 = 8.145 x 10-
x 1 + 0.00403 x C' x (T1 - 20) (Clause No. 3.2.9, IEEE 605)
C' x A2 61
Rt2 = Direct current resistance at maximum operating temperature
C' = Conductivity as % IACS =
A2 = Cross sectional area in In
d1 = outside diameter of bus bar in inch = Incht = Thickness of tube = Inch
d2 = inside diameter of bus bar in inch = d1- 2t = - 2 x = Inch
A2 = (/4) x (d1 -d2 ) = (/4) x ( - ) = In
T1 = Final temperature in deg. C = deg. C
Rt2 = 8.145 x 10-
x 1 + 0.00403 x x ( - 20 )
x
Rt2 = /Ft
3.5 Skin Effect Ratio
0.5
f = 0.0636 x F (Clause No. 6, IEEE 605)
r 5280 x Rt2
f = Skin Effect Ratio
r = outer diameter / 2 = / 2 = Inch
F = Frequency In Hz = 50 Hz
Rt2 = Direct current resistance at maximum operating temperature = / Ft
f = x 50 0.5
5280 x
=
3.6 Current Rating / Current Carrying Capability
0.5
I = Qc + Qr - Qs (Clause No. 3.2, IEEE 605)
Rt2x f
0.5
= + - = Amps.
x
61
95.0
95.0
55.0
0.0636
5.93699E-06 1.13
55.0 3.17415
46.476 30.4744
5.93699E-06
4.50
14.79 3045.32
4.026
4.50 4.026 3.17415
4.50 0.237
2.25
5.93699E-06
1.13
2.25 5.93699E-06
55.0
4.500.237
Busbar Current Rating and BPI Cantilever Calculation 31/45
-
7/26/2019 Claulation for check suitability of IPS
32/45
4 Bus Span Calculations For - 4 Inch IPS Aluminium Tube
Short circuit forces maximum span calculation are as per IEEE 605
Bus Bar Selected Inches Al Tube
Bus Bar outer Diameter in Inches
Bus Bar Cross Section Moment of inertia in cm4
(J)
Bus Bar Section modulus in cm3
(S)
Bus Bar ultimate tensile strength in Kg/mm2
(UT)
Modulus of Elasticity of Busbar in Kg/mm2
(E)
Bus bar Unit Self weight in Kgf/mtr (Fc)
Maximum allowable stress in Kg/mm2
(Fa)
Clamping material unit weight in Kgf/mtr (Fd) 7 Kg x 1 Nos. = 0.58
12.0 mtrs
Bus Phase to Phase Spacing in Mtrs (D)
Short Circuit Fault Level in kA (Isc)
Duration of the short-circuit current in seconds Tk
Rated short time in seconds Tkr
Wind Speed In Mtr/sec (V)
Allowable deflection in inches: 1 time dia of tube
4.1 Force Due to Wind (Fw)
Unit force due to wind on conductor is given by
Fw = C Cd Kz Gf V I (Dia + 2xrI) in Lbf/Ft (Equation No. 9, IEEE 605)
C = 2.132 x 10-4
for English units
Cd = Drag coefficient for smooth tubular conductor = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
Dia = Outer Dia of Conductor in inches = Inch
I = Importance factor = (Clause No. 9.4, IEEE 605)
rI = radial ice thickness in Inches = 0 Inch
Fw = 2.132 x 10-4 x 1 x 1.16 x 0.85 x x x 1.15 x (4.5 + 2x0)
= Lbf/Ft = x 1.488 = Kgf/mtr
4.2 Short Circuit Force (Fsc)
Short Circuit Force is given by
Fsc = Kf x C x x (Df x 2 x Isc)2
(Equation No. 12, IEEE 605)
D
C = 5.4 x 10-7
for English units
Isc = RMS short circuit current in A kA
D = Phase to Phase Spacing of Busbars in Inch = x 39.37 = Inch
= Constant based on type of short circuit & conductor location =
(Table 2, for 3 phase short circuit on Y phase, IEEE 605)
Kf = Mounting structure flexibility factor = 1
(Figure 4, IEEE 605)
4.00
4.500
301.039
52.675
0.85
3
40
3
3
7030.67
5.529
20.5
123.03
4.500
1.15
123.03
55
20.5
1.16
40
3 118.11
0.866
123.03
16.47 16.47 24.50248
Busbar Current Rating and BPI Cantilever Calculation 32/45
-
7/26/2019 Claulation for check suitability of IPS
33/45
Df = Decrement factor = (Equation No. 11a, IEEE 605)
Ta = X 1
R 2 x x fX = System Reactance
R = System Resistance
f = System Frequency = 50 Hz
X =
RTa = x 1 =
2 x x 50
tf = Fault current duration = 3 sec.
Df =
Fsc = 1 x 5.4 x 10-7 x 0.866 x ( x 2 x ) = Lbf/Ft
= x 1.488 = Kgf/mtr
4.3 Gravitational Forces (Fg)
Fg = Fc + Fi + Fd (Equation No. 13, IEEE 605)
Fg = Total bus unit weight in kgf/mtr
Fc = Conductor unit weight in kgf/mtr =
Fi = Ice unit weight in kgf/mtr = 0
Fd = Clamping material unit weight I kgf/mtr =
Fg = 5.529 + 0 + 0. = kgf/mtr = / 1.488 = Lbf/Ft
4.4 Total Force (Ft)
Total force on conductor in Horizontal configuration is given by
Ft = (Equation No. 22, IEEE 605)
= ( + )2
+( )2 = Kgf/mtr
5 Calculation Of Allowable Spans
5.1 For continuous bus, the maximum allowable span length based on vertical deflection is (Ld)
Ld = C x (185 x E x J x Ya)1/4
(Equation No. 20, IEEE 605)
Fg
C = for English units
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/in2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
Ya = Allowable Deflection as vertical dimension of tube = 1D = 1 x = Inch
Fg = Total bus unit weight in kgf/mtr = Kgf/mtr = x (1/1.488)
= Lbf/Ft
Ld = 1.86 x ( 185 x 10000000.03 x 4 )1/4
= In
Ld = / 39.37 = Mtrs.
Hence, maximum allowable span due to vertical deflection is mtrs.
12.87
118.11
15
15 0.0477
1.01
12.87 19.15
5.529
0.583333
1.01 40000
6.112 6.112 4.11
24.5025 19.15 6.112 44.08
301.039
301.039 7.23
4.000
1.86
7031
7031 1E+07
7.23 628.41
4.108
628.41 15.96
4.00
6.112 6.112
4.11
15.96
f
a
2t-
Ta
f
T1 + 1 exp
t
2 2
W SC GF F F
Busbar Current Rating and BPI Cantilever Calculation 33/45
-
7/26/2019 Claulation for check suitability of IPS
34/45
5.2 Allowable Span For Fibre Stress (Ls)
Ls = C x ( (28/3) x Fa x S ) (Equation No. 29c, IEEE 605)
Ft
C = for English units
Fa = Maximum allowable stress in Lbf/In2
= Kg/mm2
= x 1422.33 = Lbf/In2
S = Section modulus in In3
For Inch Al Tube, S = cm3
= / 16.3871 = In3
Ft = Total Force in Lbf/Ft
= Kgf/mtr = / 1.488 = Lbf/ft
Ls = 3.46 x ( (28/3) x x ) = Inch
= / 39.37 = Mtrs.
6 Conclusion
As per IEEE 605, page number 25, Clause No. 11.3, the maximum allowable span is the lower of the spans
as calculated for Ld and Ls.
The maximum allowable bus span is Mtrs. for Inches Aluminium tube.
7.1 Natural Frequency of Conductor Span (fb)
fb = x k2 ( E x J ) (Equation No. 5, IEEE 605)
C x L2
m
C = 24 for English units
L = Span length in Feet = Mtrs. = / 0.305 = Feet
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/In2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
m = Mass per unit length = Fc = Kgf/mtr = / 1.488 = Lbf/Ft
k = for two fixed ends
fb = x ( )2
( x ) = Hz
24 x ( )2
Twice the calculated natural frequency of the bus span = 2 x = Hz
7.2 Wind Induced Vibration or Aeolian Force Frequency (fa )
fa = C x V (Equation No. 6, IEEE 605)
d
C = for English units
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
d = Conductor diameter in inches = Inches = x 2.54 = cm
fa = x = Hz
As per IEEE 605, page number 10, clause number 7.2.2, if twice the calculated natural frequency of the
bus span is greater than the Aeolian force frequency, then the bus span should be changed or bus should
be damped.
Since, twice the calculated natural frequency of the bus span is Hz, which is less than the
Aeolian force frequency of Hz, the selected bus span of meters is safe from
Aeolian vibrations.
4.0 52.675 52.675 3.21
3.46
20.5 20.5 29157.8
594.6 15.10
44.08 44.08 29.62
29157.8 3.21
15.10 4.00
15.10 15.10
594.6
29.62
301.039
301.039 7.23
5.529 5.529
49.51
7031
7031 1E+07
1.07
3.72
1.51
1.51 0.547.231E+07
3.26
123.03
4 4
49.51 3.72
0.54
10.16
1.07
39.5 15.10
10.16
3.26 123.03 39.5
Busbar Current Rating and BPI Cantilever Calculation 34/45
-
7/26/2019 Claulation for check suitability of IPS
35/45
8 Insulator Cantilever Strength Calculation As per IEEE 605
Effective Bus Span Length in Mtrs (Le) +
2
= Mtrs.
Height of Insulator Stack in mm (Hi)
Height of Centre Line of Bus over Insulator Height in mm (Hf)
= / 25.4
= Inch
Effective Insulator Diameter in mm (Di) =
8.1 Force Due To Wind On Bus (Fwb)
Fwb = Fw x Le (Equation No. 31, IEEE 605)
Fw = Unit Wind Force On Bus in Lbf/Ft = Lbf/Ft
Le = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fwb = x = Lbf
8.2 Bus Short Circuit Force (Fsb)
Fsb = Fsc x Le (Equation No. 30, IEEE 605)
Fsc = Unit short circuit force on Bus in Lbf/Ft = Lbf/FtLe = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fsb = x = Lbf
8.3 Force Due To Wind On Insulator (Fwi)
Fwi = C x Cd x Kz x Gf x Vx (Di + 2rI) x Hi (Equation No. 32, IEEE 605)
C = for English units Formula as per IEEE 605, 1987
Cd = Drag coefficient = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust Factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr Di = Effective Dia of Insulator in Inch = = / 25.4 = Inch
Hi = Height of insulator in Feet = / (0.305 x 1000) = Feet
rI = Radial ice thickness in Inch = 0 Inch
Fwi = 1.776 x 10-5 x 1 x 1.16 x 0.85x ( )2x( + 2x0 ) x
Fwi = x = Lbf
8.4 Gravitation Force ( Fgb)
Fgb = Fg x Le (Equation No. 34, IEEE 605)
Fg = Total bus unit weight in Lbf/ Ft = Lbf/Ft
Le = Effective Bus Span Length in feet = x (39.37/12) = Feet
Fgb = x = Lbf
172
172
6.77
182
12 12
12
1472
16.47
12 39.4
16.47 39.4 648.29
12.8712 39.4
12.87 39.4 506.75
182 182 7.17
1472 4.83
1.776 x 10-5
1.16
0.85
123.03
39.4
4.11 39.4 161.72
123.03 7.17 4.83
0.00001776 516125 9.16639
4.11
12
Busbar Current Rating and BPI Cantilever Calculation 35/45
-
7/26/2019 Claulation for check suitability of IPS
36/45
8.5 Insulator Cantilever Load (Fis)
(Equation No. 35, IEEE 605)
Fis = K1 x Fwi + ( Hi + Hf ) x Fwb + K2 x ( Hi + Hf ) x Fsb
2 Hi Hi
K1 = Overload factor applied to wind forces =
K2 = Overload factor applied to short-circuit current forces = 1
1x + ( + ) x ) + 1 x
( + ) x = Lbf = x 4.44822
= Newton
Hence, Insulators with 4kN cantilever strength is selected.
1
9.17 57.95 6.77 648.29
1294.6 1294.6
57.95 5758.66
2 57.95
57.95 6.77 506.75
Busbar Current Rating and BPI Cantilever Calculation 36/45
-
7/26/2019 Claulation for check suitability of IPS
37/45
CLIENT:-
Client: Mundra Port & SEZ.
Project:- 220/66/11kV Electrical Distribution. Sales Ref.: IS/WR
Description:
Amapacity Calculation of 4.5" IPS AL Tube.
(Schedule 40)
Drawing No.:
Rev G71000-X0009-ED07Name
Date 15.04.2009
Prep. SGP
Chkd. SO
Siemens Ltd
KG OfficeRemarks Date
Busbar Current Rating and BPI Cantilever Calculation 37/45
-
7/26/2019 Claulation for check suitability of IPS
38/45
1 Introduction
A. A rigid bus is supported on bus post insulators in an out-door substation. These bus post insulators are
subjected to all types of stresses due to electrical and mechanical forces acting on bus bar.
The principal forces on the bus post insulators supporting a rigid conductor are as follows:
a. Short circuit force on bus conductor
b. Wind force on the bus conductor
c. Wind force on the bus post insulatord. Weight of the bus conductor span supported by the bus post insulators
The resultant of these forces, correlated to the type of 'end Connection' of the rigid conductor at the bus
post insulator terminal, gives the values of the net Electromagnetic Force on the bus post insulator. The
values of forces obtained herewith forms valuable input for the design of bus post insulator support structure
and its foundation design.
In this report along with the force on bus post insulators, the maximum permissible unsupported span length
of the rigid bus conductor connecting the bus post insulators is also determined. The maximum permissible
span is calculated within the limits of 'Vertical Deflection' and permissible 'Fiber Stress' corresponding to the
type of 'End Connection' to the supporting bus post insulator terminals at each end of the span. The
calculation is performed on the method stipulated by IEEE 605 and the minimum of the span length obtained
from the calculation is conservatively considered as the maximum allowable unsupported span for all
influencing conditions.
Busbar Current Rating and BPI Cantilever Calculation 38/45
-
7/26/2019 Claulation for check suitability of IPS
39/45
2 Continuous Current Carrying Capacity
Bus bar continuous rating required Amps.
As per INDAL handbook current rating (nominal for outdoor) are as below:-
IPS Aluminum Tube
- Inches Amps.
As per INDAL handbook for the maximum operating temperature of the bus to 75 Deg. C, the deratingfactor to be adopted is 0.88; hence the derated current rating (nominal for outdoor) are as below:-
4.5 Inches IPS Al Tube - Schedule 40 = 3420 = Amps.
From the above it is summrised that, for the required current carrying capacity of 1250 Amps.,
4.5 Inches IPS Al Tube - Schedule 40 is sufficient.
3 Thermal Effects on IPS Aluminium Tube as per IEEE 605
Bus Bar Selected Inch
Ambient temperature in deg. C (T2)
Final temperature in deg. C (T1)
3.1 Radiation Loss (Qr)From Stefan-Boltzman law,
Qr = 36.9 x 10-12
x e x ( T14-T2
4) x A (Clause No. 3.2.4, IEEE 605)
A = Surface area = 12 x d x = 12 x x = In2/Ft
T1 = Temperature of the bar,oK = + 273 =
0K
T2 = Ambient temperature,oK = + 273 =
0K
E = Emissivity factor =
Qr = 36.9 x 10-12
x 0.6 x (4-
4) x = Watts/Ft
3.2 Convective Loss (Qc)
Heat is dissipated from a tubular bus bar by forced convection
Heat transfer is considered at wind speed 2 fps and 1 atmospheric pressure.
Qc = 0.010 x x A (Clause No. 3.2.2, IEEE 605)d
0.4
A = Surface area = 12 x d x = 12 x x = In2/Ft
d = outside diameter of bus bar in inch = Inch
= Temperature difference between conductor surface & ambient air in deg C = T1 - T2 =
= - = deg. C
Qc = 0.010 x x = Watts/Ft
( )0.4
3.3 Heat Gain Due To Solar Radiation (Qs)
Qs = h x s x d x 12
h = co-efficient of absorption of conductor surface = 0.5
s = intensity of solar radiation in Watts/Inch2= Watts/In
2
Assumed - 849.27 Watts/Mtr.2
d = outside diameter of bus bar in inch = Inch
Qs = 0.5 x 0.5479 x 5 x 12 = Watts/Ft
27.0368
5.00
5.00
40.0 39.607
90.0 363.0
363.0
16.44
323.0 188.50
5.000
0.5479
5.00 188.50
188.50
90.0 50.0 40.0
Schedule 40 4.50 3420
30100.88 x
0.6
188.50
1250
90.0
50.0 323.0
4.50
50.0
5.00
Busbar Current Rating and BPI Cantilever Calculation 39/45
-
7/26/2019 Claulation for check suitability of IPS
40/45
3.4 Conductor Resistance
Rt2 = 8.145 x 10-
x 1 + 0.00403 x C' x (T1 - 20) (Clause No. 3.2.9, IEEE 605)
C' x A2 61
Rt2 = Direct current resistance at maximum operating temperature
C' = Conductivity as % IACS =
A2 = Cross sectional area in In
d1 = outside diameter of bus bar in inch = Incht = Thickness of tube = Inch
d2 = inside diameter of bus bar in inch = d1- 2t = - 2 x = Inch
A2 = (/4) x (d1 -d2 ) = (/4) x ( - ) = In
T1 = Final temperature in deg. C = deg. C
Rt2 = 8.145 x 10-
x 1 + 0.00403 x x ( - 20 )
x
Rt2 = /Ft
3.5 Skin Effect Ratio
0.5
f = 0.0636 x F (Clause No. 6, IEEE 605)
r 5280 x Rt2
f = Skin Effect Ratio
r = outer diameter / 2 = / 2 = Inch
F = Frequency In Hz = 50 Hz
Rt2 = Direct current resistance at maximum operating temperature = / Ft
f = x 50 0.5
5280 x
=
3.6 Current Rating / Current Carrying Capability
0.5
I = Qc + Qr - Qs (Clause No. 3.2, IEEE 605)
Rt2x f
0.5
= + - = Amps.
x
2.5 5.03945E-06
55.0
5.000.247
4.506
5.00 4.506 3.68608
5.00 0.247
5.03945E-06
2.5
3005.68
0.0636
5.03945E-06 1.10
1.10
61
90.0
55.0 3.68608
39.607 27.0368
5.03945E-06
5.00
16.44
90.0
55.0
Busbar Current Rating and BPI Cantilever Calculation 40/45
-
7/26/2019 Claulation for check suitability of IPS
41/45
-
7/26/2019 Claulation for check suitability of IPS
42/45
Df = Decrement factor = (Equation No. 11a, IEEE 605)
Ta = X 1
R 2 x x fX = System Reactance
R = System Resistance
f = System Frequency = 50 Hz
X =
RTa = x 1 =
2 x x 50
tf = Fault current duration = 1 sec.
Df =
Fsc = 1 x 5.4 x 10-7 x 0.866 x ( x 2 x ) = Lbf/Ft
= x 1.488 = Kgf/mtr
4.3 Gravitational Forces (Fg)
Fg = Fc + Fi + Fd (Equation No. 13, IEEE 605)
Fg = Total bus unit weight in kgf/mtr
Fc = Conductor unit weight in kgf/mtr =
Fi = Ice unit weight in kgf/mtr = 0
Fd = Clamping material unit weight I kgf/mtr =
Fg = 6.423 + 0 + 0. = kgf/mtr = / 1.488 = Lbf/Ft
4.4 Total Force (Ft)
Total force on conductor in Horizontal configuration is given by
Ft = (Equation No. 22, IEEE 605)
= ( + )2
+( )2 = Kgf/mtr
5 Calculation Of Allowable Spans
5.1 For continuous bus, the maximum allowable span length based on vertical deflection is (Ld)
Ld = C x (185 x E x J x Ya)1/4
(Equation No. 20, IEEE 605)
Fg
C = for English units
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/in2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
Ya = Allowable Deflection as vertical dimension of tube = 1D = 1 x = Inch
Fg = Total bus unit weight in kgf/mtr = Kgf/mtr = x (1/1.488)
= Lbf/Ft
Ld = 1.86 x ( 185 x 10000000.03 x 4.5 )1/4
= In
Ld = / 39.37 = Mtrs.
Hence, maximum allowable span due to vertical deflection is mtrs.
4.887
679.30 17.25
17.25
4.500 4.50
7.271 7.271
4.89
10.44 679.30
1.86
7031
7031 1E+07
434.683
434.683 10.44
6.423
0.848485
7.271 7.271 4.89
27.225 13.94 7.271 41.81
1.02
1.02 40000 9.37
167.32
9.37 13.94
15
15 0.0477
f
a
2t-
Ta
f
T1 + 1 exp
t
2 2
W SC GF F F
Busbar Current Rating and BPI Cantilever Calculation 42/45
-
7/26/2019 Claulation for check suitability of IPS
43/45
5.2 Allowable Span For Fibre Stress (Ls)
Ls = C x ( (28/3) x Fa x S ) (Equation No. 29c, IEEE 605)
Ft
C = for English units
Fa = Maximum allowable stress in Lbf/In2
= Kg/mm2
= x 1422.33 = Lbf/In2
S = Section modulus in In3
For Inch Al Tube, S = cm3
= / 16.3871 = In3
Ft = Total Force in Lbf/Ft
= Kgf/mtr = / 1.488 = Lbf/ft
Ls = 3.46 x ( (28/3) x x ) = Inch
= / 39.37 = Mtrs.
6 Conclusion
As per IEEE 605, page number 25, Clause No. 11.3, the maximum allowable span is the lower of the spans
as calculated for Ld and Ls.
The maximum allowable bus span is Mtrs. for Inches Aluminium tube.
7.1 Natural Frequency of Conductor Span (fb)
fb = x k2 ( E x J ) (Equation No. 5, IEEE 605)
C x L2
m
C = 24 for English units
L = Span length in Feet = Mtrs. = / 0.305 = Feet
E = Modulus of Elasticity in Lbf/In2
= Kgf/mm2
= x 1422.34 = Lbf/In2
J = Cross sectional moment of inertia in In4
= cm4
= x (1 / 41.623) = In4
m = Mass per unit length = Fc = Kgf/mtr = / 1.488 = Lbf/Ft
k = for two fixed ends
fb = x ( )2
( x ) = Hz
24 x ( )2
Twice the calculated natural frequency of the bus span = 2 x = Hz
7.2 Wind Induced Vibration or Aeolian Force Frequency (fa )
fa = C x V (Equation No. 6, IEEE 605)
d
C = for English units
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr
d = Conductor diameter in inches = Inches = x 2.54 = cm
fa = x = Hz
As per IEEE 605, page number 10, clause number 7.2.2, if twice the calculated natural frequency of the
bus span is greater than the Aeolian force frequency, then the bus span should be changed or bus should
be damped.
Since, twice the calculated natural frequency of the bus span is Hz, which is less than the
Aeolian force frequency of Hz, the selected bus span of meters is safe from
Aeolian vibrations.
11.43
0.92
35.1 17.25
4.5 4.5 11.43
3.26 123.03 35.1
56.57 4.32
0.46 0.92
3.26
123.03
4.32
1.51
1.51 0.4610.441E+07
7031 1E+07
434.683
434.683 10.44
6.423 6.423
17.25 4.50
17.25 17.25 56.57
7031
29157.8 4.18 696.0
28.10
696.0 17.68
4.5 68.454 68.454 4.18
41.81 41.81 28.10
3.46
20.5 20.5 29157.8
Busbar Current Rating and BPI Cantilever Calculation 43/45
-
7/26/2019 Claulation for check suitability of IPS
44/45
8 Insulator Cantilever Strength Calculation As per IEEE 605
Effective Bus Span Length in Mtrs (Le) +
2
= Mtrs.
Height of Insulator Stack in mm (Hi)
Height of Centre Line of Bus over Insulator Height in mm (Hf)
= / 25.4
= Inch
Effective Insulator Diameter in mm (Di) =
8.1 Force Due To Wind On Bus (Fwb)
Fwb = Fw x Le (Equation No. 31, IEEE 605)
Fw = Unit Wind Force On Bus in Lbf/Ft = Lbf/Ft
Le = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fwb = x = Lbf
8.2 Bus Short Circuit Force (Fsb)
Fsb = Fsc x Le (Equation No. 30, IEEE 605)
Fsc = Unit short circuit force on Bus in Lbf/Ft = Lbf/FtLe = Effective Bus Span Length in Feet = x (39.37/12) = Feet
Fsb = x = Lbf
8.3 Force Due To Wind On Insulator (Fwi)
Fwi = C x Cd x Kz x Gf x Vx (Di + 2rI) x Hi (Equation No. 32, IEEE 605)
C = for English units Formula as per IEEE 605, 1987
Cd = Drag coefficient = 1 (Table 1, IEEE 605)
Kz = Height & Exposure factor = (Clause No. 9.2, for category D, IEEE 605)
Gf = Gust Factor = (Clause No. 9.3, for category C&D, IEEE 605)
V = Wind speed in Miles/hr
= 55 x ( 1/ 0.44704) = Miles/hr Di = Effective Dia of Insulator in Inch = = / 25.4 = Inch
Hi = Height of insulator in Feet = / (0.305 x 1000) = Feet
rI = Radial ice thickness in Inch = 0 Inch
Fwi = 1.776 x 10-5 x 1 x 1.16 x 0.85x ( )2x( + 2x0 ) x
Fwi = x = Lbf
8.4 Gravitation Force ( Fgb)
Fgb = Fg x Le (Equation No. 34, IEEE 605)
Fg = Total bus unit weight in Lbf/ Ft = Lbf/Ft
Le = Effective Bus Span Length in feet = x (39.37/12) = Feet
Fgb = x = Lbf
0.00001776 1307151 23.215
4.89
4.89 54.1 264.54
16.5 54.1
11.61
2300 7.54
123.03 11.61 7.54
1.776 x 10-5
1.16
0.85
123.03295 295
9.3716.5 54.1
9.37 54.1 507.26
18.30
16.5 54.1
18.30 54.1 990.45
16.5
2300
130
130
5.12
295
16.5 16.5
Busbar Current Rating and BPI Cantilever Calculation 44/45
-
7/26/2019 Claulation for check suitability of IPS
45/45
8.5 Insulator Cantilever Load (Fis)
(Equation No. 35, IEEE 605)
Fis = K1 x Fwi + ( Hi + Hf ) x Fwb + K2 x ( Hi + Hf ) x Fsb
2 Hi Hi
K1 = Overload factor applied to wind forces =
K2 = Overload factor applied to short-circuit current forces = 1
1x + ( + ) x ) + 1 x
( + ) x = Lbf = x 4.44822
= Newton
Hence, Insulators with 8kN cantilever strength is selected.
1593.97
90.55 7090.34
2 90.55
90.55 5.12 507.26 1593.97
1
23.22 90.55 5.12 990.45