Question 4 (20 marks) a) An isolated power system consist of a 600 MVA generating unit having an M of 7.6 pu MW/pu frequency/sec on a machine base. The unit is supplying a load of 450 MVA. The load changes by 2% for a 1% change in frequency. If the load suddenly increases by 20 MVA. Determine using a 1000 MVA base: i. Change in frequency Aco (s) (6 marks) ii. Change in frequency Aco (t) (3 marks) iii. Final value of change in frequency Ao (1 mark) b) Given the block diagram of two interconnected areas as shown in figure 2. ΔΡ 1/R₁ 44 Governor Turbine ቆይ AR Power system A Area 1 A₂ T₁₂ ΔΕ 1/s Governor Turbine Area 2 A Taas-1 49 A 1/R, Δεν Figure 2 Under steady state conditions for a load change in area 1 show that: Aw= 1 1 + -AL₁ + D₁₂+ D₁₂