The Dalton-Cameron method is well-known as a method for determining direct and quadrature axis subtransient reactance (x_d" and x_q") by standstill response testing. This method entails calculating x_d" and x_q" from the voltage and current measured when a rated-frequency single-phase voltage is applied to each armature winding (U-V, V-W and W-U) in turn. The authors have developed a new method to calculate x_d", x_q" and the impedance loci by means of applying a D. C. voltage instead of a single-phase voltage, and named it the expanded Dalton-Cameron method. This method is a small-capacity standstill test, and is carried out by the following three steps. The first is to short-circuit the U and V terminals while a D. C. current flows between these terminals, to measure the voltage and current (V_DC and I_DC) when the D. C. current flows between these terminals, and to record the D. C. decay current (i(t)) after these terminals are short-circuited. This same procedure is also performed for the V-W and W-U terminals in turn. The second is to draw the impedance loci from the measured V_DC, I_DC and i(t) by means of Fourier transformation, and to divide it into the directand quadrature-axis impedance loci (Z_d(js), Z_q(js)). The third is to calculate from Z_d(js) and Z_q(js) values of x_d" and x_q" and the starting performance on the basis of two-reaction theory. Experimental and calculation results on starting performance as well as a comparison with calculation results of x_d" and x_q" by Dalton-Cameron method clearly show that this method is very useful.