Damage?
If you apply on the primary/source side of the switchgear, you're probably doing voltage withstand normal frequency/insulation test, no current will be flowing through the bus, so no current/voltage will be built up at secondary side of the CT.
When you apply, current test to the...
When you applied primary voltage, there will be current flow and built up the secondary voltage. If you can't control your primary voltage and primary current...you will get uncontrolled voltage at secondary?
Just currious, you don't need to do this..for further how to test the CT, chek megger...
since you run out the medium voltage feeder, it depends on your transformer rating, you would need transformer protection either fuse or circuit breaker at the source side of the transformer which will protect the system or transformer from any shortcircuit at downstream of the fuse.
You may...
