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a) Explain the acronyms ACSR and AAAC in the context of overhead line conductors. Explain why pure aluminium or copper conductors are not normally used. [2 marks] Review the advantages and disadvantages of ACSR and AAAC conductors. [4 Marks) An ACSR conductor of nominal cross sectional area of 400 mm’ is described as 54/7/3.18. Explain the information contained within this nomenclature. [1 Mark] b) A proposed dual-circuit, three-phase transmission line configuration is shown in Fig QI (overleaf). This system is required to operate at 400kV and to deliver 200MVA over a 100km distance at a power factor of 0.8 lag. Given the data below, analyse the design in the following respects: - (1) To ensure thermal balance, check that the conductor operating temperature will not exceed the specified limit. [5 Marks) At the maximum operating temperature, check that the voltage regulation remains within statutory limits. [3 Marks) (i) Determine the critical discharge voltage and the corona discharge loss along the length of the transmission line [8 Marks] (ii) ) (iv) Hence comment on the suitability or otherwise of this design configuration [2 Marks) Data Max operating temp = 75°C Max ambient temp = 30°C (self-hcating limit 45°C) Minimum ambient air pressure = 72 cm Hg Conductor resistance (ac) @ 20°C -0.067492/km Resistance temperature coefficient a = 0.0039°C Conductor reactance =0.0850/km Conductor diameter = 28.62mm Irregularity coefficient m=0.85 Heat loss due to convection = 6.4kW/km Heat loss due to radiation - 10.2kW/km Heat gain due to solar radiation activity = 3.25kW/km Voltage regulation limit= 10% drop from nominal voltage at point of utilisation
3.5m r1 4.5m b2 O 4.0m У1. 5.5m y2 4.0m b1 4.5m r2 O O Fig Q1 - Proposed Dual Circuit, Three-phase configuration for 400kV 200MVA capacity [Total: 25 marks]