This article analyzes the Scott connection, Y/V connected balance transformer wattless power, active power and wattless power measurement error. When the secondary load of the traction transformer is out of balance, there exist errors in the measurement of one side or two side wattless opinion; when the Scott transformer is unbalanced for the second time, errors in a side active power measurement also exist. Thus I come to a conclusion by means of the theoretical calculation and numerical simulation that in the low-voltage side of the measurement without power was larger than actual value and a side active power measurement is small.
