Modeling a Current Transformer on the neutral side of the Generator windings


Basics: - In PTW, relay and its associated CT are modeled as a single device and the location of the CT is considered at the insertion point of relay symbol. There is no separate ground or neutral connection in PTW but the current of these points is calculated from the sequence impedances.

1. Click on the Generator symbol to insert a Generator on the one line.

2. Similarly using the Annotation 1-Node symbols insert the Generator Star and Virtual Ground in the one line.

3. Now click on the Relay symbol to insert a relay on the one line and connect this relay in between the Generator Star and the Virtual Ground as shown in below.

4. Run the Balanced System Study.

5. Go to Run menu select Datablock format and then select Brach Fault currents (comprehensive). Click on edit button and add the “Init RMS SLG Neutral” attribute for and apply this datablock to one-line.

6. Enter the read current from step 7 manually in the “Isc Amps” field in Device
Tab of Captor.