Question

if the maximum fault currents at Bus A, Bus B and Bus C are 8000A, 4000A and 2500 A respectively. Also, determine the settings of both relays Rb and Ra considering the relays have extremely inverse trip characteristics t = TD x [(28.2/M² -1) + 0.1217]. Using log-log graph, plot the relay characteristics for all three relays.

Answer 1

To determine the settings of relays Ra and Rb based on the maximum fault currents at different buses, you can use the provided equation and substituting the fault currents. Using a log-log graph, you can plot the relay characteristics for all three relays.

Step-by-step explanation:

The settings of relays Ra and Rb can be determined using the equations provided and the given maximum fault currents at Bus A, Bus B, and Bus C. To find the setting of Ra, you can substitute the maximum fault current at Bus A (8000A) into the relay characteristic equation and solve for Ra. Similarly, to find the setting of Rb, substitute the maximum fault current at Bus B (4000A) and solve for Rb. Using the log-log graph, you can plot the relay characteristics of all three relays by varying the fault currents and finding the corresponding relay settings.