Why short circuit is performed on high voltage side?

This is because of two reasons:

1. Primarily because SC test is performed at rated Current(as we calculate series parameters-leakage impedance-in SC test). As the rated current on hv side is much less than lv side(VI = constant), so the rated hv side current is easily achieved(compared to lv side). Vice-versa is true for Open circuit test.

2. Also because we cannot short-circuit hv side, as, if we short-circuit hv side, V of hv side essentially falls to zero and since VI(KVA power)=constant, so the hv current will be very high(compared to low rated current on hv side), and will burn the winding.

When short-circuiting lv side, the current also increases but this increase does not burn winding due to low rated V and high rated I (You can consider the example of 220/11V)on lv side. So,SC test is performed on hv side while shorting the lv side.

Also SC test can be performed on either sides for small transformer rating. The above care must be taken for big transformer(High KVA rating)..