Cable Pulling

Calculation for cable pulling tensions & sidewall pressure The calculations are preformed in accordance with the IEEE Std. 525-1992 (Revision of IEEE Std. 525-1987) IEEE guide for the design and installations of cable system in substations. Purpose To calculation for cable pulling tensions & sidewall pressure of the longest cable. 1. Data 1.1 Duct bank Type HDPE Inside diameter (D) 144.6 mm 5.6929 in. Cross section area (AD) 25.4542 in.2 1.2 Cable Configgulation Three cables cradled Type 22 kV XLPE Copper cable Size 249 mm2 Outsize diameter (d) 42 mm 1.6535 in. Cross section area (Ad) 2.1474 in.2 Weight (w) 3.35 kg/m 2.2514 lb/ft 2. General calculations 2.1 Conduit fill Fill (%) (3*ad/AD)*100 % 25.3095 % Allowable fill limits of 40 % for one cable 2.2 Jam ratio (J) This inside diameter of a field bent conduit is usually increased by 5% J 1.05*D/d % 3.62 % Jamming cannot occur (>3.0) 2.3 Maximum allowable pulling tension K 8 lb/kcmil (Tension strength of Copper) A 473.653 kcmil (Cross section area of conductor) Tmax 2*K*A lb (The maximum permitted tension) Tmax 7578.4488 lb

When using a basket-weave type pulling grip applied over a lead-sheathed cable, the force should not exceed 1500 lb (6.67 kN) Note According to IEEE std. 525-1992, the maximum allowable sidewall pressure is show as follow -500 lb/ft for single-conductor power cable #8 AWG (8.37 mm2) and smaller -300 lb/ft for single-conductor power cable #6 AWG (13.3 mm2) and larger 2.4 Calculation of cable-pulling tension and maximum allowable sidewall pressure Pulling method Cable head grip Cable feed-in Duct bank Pulling lubricant NASCO The coefficent of friction f= 0.3 Reel back tension on cables T1 = 100 lb Configgulation Three single cables in triangular configuration Weight correction factor ( c ) c= 1+ 4/3 * (d/(D-d)2) 1.2234 Length of Cable, m Length of Cable, ft Tension, lb T1+(Length of cable * w * f * c) 20 65.6 154.22 lb 69.94 50 164.1 235.56 lb 106.83 100 328.1 371.12 lb 168.31 200 656.2 642.23 lb 291.26 300 984.3 913.35 lb 414.22 500 1640.5 1,455.58 lb 660.13 This is within the maximum allowable tension of 1500 lb

ion of IEEE Std. 525-1987)

re is show as follow