A 300km three phase double circuit 330kV transmission line is constructed on steel lattice towers. The conductor is a quad bundle of Silicon. The bundle spacing is 450mm. The conductor is initially tensioned to 18% of NBL (Nominal Braking Load) at 15C. The span is 250m. The insulation level is U=362kVrms; specified switching impulse withstand voltage, SSIWV=850k Vrms (Longitudinal and phase to earth); specified lightning impulse withstand voltage, SLIWV=1050k Vp. The conductor bundle centre co-ordinates (x, y) = (distance from centre line of the towers, height above ground) are: Circuit 1: Phase R - (5m, 20m); Phase S - (6m, 27m); Phase T (5m, 34m); Circuit 2: Phase S-(-5m, 20m); Phase T-(-6m, 27m); Phase R-(-5m, 34m); Earth Wire 1 (-3.5m, 43 m); Earth Wire 2 (3.5m, 43m) (d) Is the selected conductor size above or below the optimum economic conductor size? Assume $80/MWhr for losses, suspended conductor cost of $25/kg and net present value multiplier of 11.5 (20years with 6% real rate of interest). (e) Estimate the Surge Impedance Loading of this line (neglect the mutual coupling between the two circuits at the two sides of the tower). (4 marks) Hint: Neglect the mutual inductance/capacitance between the 2 circuits. Number of 280x170mm Disks 10 11 12 13 14 15 16 17 - 18 19 Power Dry 580 625 675 720 760 800 840 880 920 Frequency 20 955 Withstand Wet 375 410 450 485 525 560 600 635 675 Voltage 5 710 Impulse Positive Withstand and 940 1025 | 1155 | 1200 1285 1370 1460 1545 1630 1720 Voltage Negative * Silicon - AAAC 61/3.50; nominal diameter 31.5mm; Cross section 587mm; Approximate mass 1620kg/km; breaking load 127kN; Modulus of Elasticity 64GPa; Coefficient of Thermal Expansion 23x10-6/C; AC Resistance 75C 0.063492; Summer noon still air industrial weathered rating 488A. A 300km three phase double circuit 330kV transmission line is constructed on steel lattice towers. The conductor is a quad bundle of Silicon. The bundle spacing is 450mm. The conductor is initially tensioned to 18% of NBL (Nominal Braking Load) at 15C. The span is 250m. The insulation level is U=362kVrms; specified switching impulse withstand voltage, SSIWV=850k Vrms (Longitudinal and phase to earth); specified lightning impulse withstand voltage, SLIWV=1050k Vp. The conductor bundle centre co-ordinates (x, y) = (distance from centre line of the towers, height above ground) are: Circuit 1: Phase R - (5m, 20m); Phase S - (6m, 27m); Phase T (5m, 34m); Circuit 2: Phase S-(-5m, 20m); Phase T-(-6m, 27m); Phase R-(-5m, 34m); Earth Wire 1 (-3.5m, 43 m); Earth Wire 2 (3.5m, 43m) (d) Is the selected conductor size above or below the optimum economic conductor size? Assume $80/MWhr for losses, suspended conductor cost of $25/kg and net present value multiplier of 11.5 (20years with 6% real rate of interest). (e) Estimate the Surge Impedance Loading of this line (neglect the mutual coupling between the two circuits at the two sides of the tower). (4 marks) Hint: Neglect the mutual inductance/capacitance between the 2 circuits. Number of 280x170mm Disks 10 11 12 13 14 15 16 17 - 18 19 Power Dry 580 625 675 720 760 800 840 880 920 Frequency 20 955 Withstand Wet 375 410 450 485 525 560 600 635 675 Voltage 5 710 Impulse Positive Withstand and 940 1025 | 1155 | 1200 1285 1370 1460 1545 1630 1720 Voltage Negative * Silicon - AAAC 61/3.50; nominal diameter 31.5mm; Cross section 587mm; Approximate mass 1620kg/km; breaking load 127kN; Modulus of Elasticity 64GPa; Coefficient of Thermal Expansion 23x10-6/C; AC Resistance 75C 0.063492; Summer noon still air industrial weathered rating 488A
