Perform protective device coordination for the distribution system shown in Figure. 1 based on the information given below.
1. Determine the CT ratio and select the time overcurrent curve (TOC) for the protective devices. Calculate the phase element relay settings for the relay (B3) and the reclosers (R1 and R2). The relay B3 consists of an instantaneous element to improve the response time. Coordinate the settings between B3, R1 and R2 for phase faults (phase-to-phase and three-phase) and with the transformer damage curve.
2. Calculate the ground element relay settings for B3, R1 and R2. Coordinate the settings for single line to ground (SLG) faults and with the transformer damage curve.
3. Calculate the phase element relay settings for the relay B2 on the HV side of the transformer and the line relay B1. Coordinate the settings between the protective devices. Also, the relay B2 has to coordinate with relay B3. The rated load on the transformer is 40 MVA at unity power factor (note that it supplies multiple feeders).
4. Verify the relay settings and coordination using ASPEN. You have to use the ASPEN file from assignment#3.
Additional Information:
1. Assume a coordination time interval of 6 cycles for each device (relay/recloser control).
2. Zero sequence imbalance (3I0) for each load current on the distribution feeder is 20%.
3. The transformer has the phase shift as per the ANSI/IEEE standards.
4. Fault currents are given in the tables below. Note that you will need to refer the currents across the transformer for some coordination cases.