This person is one of the TNB's Contracter. They were doing testing for Current Transformer. They will inject current to secondary of the CT then the result to find the bending in curve.
Example: First result they get current value is 40 A then voltage they get 37 volt. for the next reading plus 50% from previous read that means 60A the voltage result must get 10% from previous reading that means for 60A they must get 39.7V
