How to find out which side of transformer the OC and SC tests were performed?
No load test: 400W 10A 110V

If you take the no load case of 400 watts and 10 amps when 110 volts are applied and consider what this would mean if it were conducted on the 2200 volt primary side you would see that it has to be conducted on the load voltage (110 volt) side.

For instance, if 10 amps was flowing (magnetization current) due to only 110 volts applied to the 2200 volt side and you magnified that up to the full 2200 volts applied to the high voltage side, you would have 200 amps flowing at 2200 volts. That in itself is a VA of 440 kVA and far outstrips the 50 kVA rating of the transformer.

Hence the no-load test was performed on the LV side.

Short circuit test: 90V 20.5A 808W

This was performed on the high voltage side because, if it were performed on the low voltage side (110 volts nominal) the applied voltage would be significantly smaller than 110 volts due to the short on the HV winding. Given that 90 volts is 82% of 110 volts, this does not ring true that it could have been applied on the LV side.

Hence the short circuit test was performed on the HV side.