2. An overcurrent relay is set to operate at 15 A, and is connected to a CT with a 300:5 ratio. The CT characteristics are given in the figure below. Determine the minimum primary fault current that the relay will detect if the burden, Z is (a) 2 £2, (b) 5£2, (c) 8 N. Current Tum Sea ratio ratio res 100:5 20:1 0.05 200:5 40:1 0.10 300:5 60:1 0.15 400:5 80:1 0.20 500:5 100:1 0.25 600:5 1000 120:1 0.31 800:5 160:1 0.41 900:5 180:1 0.46 1000:5 200:1 0.51 45° 1200:5 240:1 0.61 1200:5 "OHMS AT 75° C 1000:5 100 Below this line the exciting current for a given voltage for any unit will not exceed the curve value by more than 25% 900:5 800.5 500:5 500:5 400:5 300:5 200:5 Secondary RMS exciting volts, Vef 10 10 0.001 0.01 0.1 1.0 Secondary RMS exciting AMPS, le 100:5 10 100