- Q6 The Radial Feeder To Be Protected Is Shown In Fig 26 The Current Characteristics Of The Feeder Is Presented In Tab 1 (128.73 KiB) Viewed 74 times
Q6. The radial feeder to be protected is shown in Fig. 26. The current characteristics of the feeder is presented in Table 26. (15 marks) Design the feeder protection using inverse definite minimum time (IDMT) overcurrent relays (with very inverse characteristics) and based on the following rules: . O The current setting of each relay should be set to a value that is well above the maximum load current in the feeder segment (such as larger than 120%) that it protects and well below the value of the minimum fault level (such as smaller than 60%) at the location of the relay. There should be at least 10% difference in the current settings of consecutive relays. Relay-relay grading margin is 0.35s. The overcurrent relay has the following current settings: 4, 5, 6, 7, 8, 10 and 12 A. . . Very inverse characteristics: 13.5 operation = TMS maximum fault current 1. = currents setting Suppose that Relay RC has already been set considering the coordination with the downstream fuses. Current setting CSc = 10 A (i.e. 200A at primary side) and time multiplier setting TMSc = 0.1. А B с 80 A RA RB RC 22 kV 200 MVA V 150 A 100 A Fig. 26 Radial feeder to be protected Table Q6 Radial Feeder Current Characteristics Location CT Ratio A B с Fault Level (A) Maximum Minimum 5250 2800 3175 2000 2100 1750 Maximum Load Current 250 150 80 300/5 200/5 100/5