In the below distribution system in Figure 2, calculate:
a) the Load Currents at Bus A, Bus B and Bus C. (20 marks)
b) the settings for relays R1, R2 and R3. (30 marks)
Assumptions:
Master of Engineering (Electrical Systems) 6
MEE512_Assessment3_PaperA_v1.2
• Bus A: CT ratios, 250/5A, Isc = 16750A
• Bus B: CT ratios, 150/5A, Isc = 4000A
• Bus C: CT ratios, 150/5A, Isc = 3360A
• Relays R1 to R3 have standard inverse curves
• P.S is changing from 50% to 200% in steps of 10%
• Consider OLF = 1.1
• Consider TMS between 0.1 and 1 with steps of 0.05
• Consider coordination time as 0.4 seconds
• Consider Sbase = 100 MVA
• Consider P.S (R1) = 100%
• TMS (R3) = 0.1