9. Calculation of Crippling (Ultimate Transverse) Load on Electrical Pole

CALCULATION OF CRIPPLING (ULTIMATE TRANSVERSE) LOAD ON ELECTRICAL POLE

Wind Speed = 89 Mile/Hr. * Height of Pole=10 Meter * Type of Pole =RCC * Height of Pole in Ground=1.5 Meter. * Pole Section on Bottom of Pole (Length x Width)=400mm x 150mm * Pole Section on Top of Pole (Length x Width)=127mm x 150mm * Conductor Mounting from top of Pole(g)=0.5 Meter. * Distance between Two Pole(s) =20 Meter. * No of Conductor on Pole(n)=3No’s * Size of Conductor(r)= 30mm

CALCULATIONS:

Wind Pressure = 00256 x 2x Wind Speed * Wind Pressure = 00256 x 2x 90 = 20.506 Pound /Sq.Foot * Wind Pressure(Wp) =4.882×20.506 = 100 Kgf/M2 * Wind Load on Conductor/Span(ws)=2/3 x Wp x s x r x n * Wind Load on Conductor/Span(ws)=2/3 x 100 x 20 x 30 x 3 =120 Kg———–(I) * Height of Pole Above Ground (h)= 10-1.5 =8.5 Meter * Total Bending Movement at Ground Level due to Wind Load on All Conductor=ws x h * Total Bending Movement at Ground Level due to Wind Load on All Conductor(b)=120 x 8.5= 960 Kg.Mt * Equivalent Safe Working Load at said Meter from TOP of The Pole corresponding to Wind Load on All Conductors =b / (h- g) = 960 / 8.5-0.5 =120 Kg * Wind Load on Pole Surface above Ground Level (p1)=Wp x h /((l1+w1)/(2×1000)) * Wind Load on Pole Surface above Ground Level (p1)=100×8.5/(400+150/2×1000) =233.75 Kg * Centre of Gravity of Tapering rectangular section of Pole(p2)= (h/3)x((l2+(l1*2))/(l1+l2)) * Centre of Gravity of Tapering rectangular section of Pole(p2)= (5/3)x((127+(400×2)) /(127+400))=4.98Mt * Bending Movement at Ground Level due to Wind Load on Pole(p) =p1 x p2 * Bending Movement at Ground Level due to Wind Load on Pole(p) =233.75×4.98=1164.98 Kg.Mt * Equivalent Safe Working Load at said meter from Top of The Pole corresponding to Wind Load on Pole(wt) = p /(h-g) =1164.98 / (8.5-0.5) = 62 Kg——————————(II) * Total Transverse Load at said meter from Top of The Pole (Due to wind Load on Conductors + Wind Load on Pole Surface) (T)=Ws + Wt = 120+145.62 =256.62 Kg

Type of Pole Safety Factor Wooden Pole 3.5 RCC Pole 2.5 PCC Pole 2.5 Steel Tubular Pole 2 Rail/RSJ Pole 2 Struts (Steel Pole) 2.5 Struts (RCC/PCC) 3 PCC Pole for 33 KV 2

From Above Table Safety Factor=2.5 * Total Transverse Load (Crippling Load) of Pole = T x Safety Factor * Total Transverse Load (Crippling Load) of Pole = 256 x 2.5 =664 Kg. * Total Transverse Load (Crippling Load) of Pole=664 Kg

Max. Length of Pole (Meter) Min. Ultimate Transverse Load from 0.6meter from Top (Kg) 17 3000 17 2300 17 2000 17 1400 16 1100 15 1050 14 1050 13 1000 12 800 11 600 10 500 9 300 8 200 7 200 6 200 5 150 4 150 3 150

From Above Table Min. Ultimate Transverse Load for 10 Meter Pole = 500 Kg and as per our calculation it is 664 Kg hence Selection of Pole if O.K

Results:

Calculated Transverse Load (Crippling Load) of Pole = 664 Kg