Water wheel generators and synchronous condensers for long transmission lines

E.B. Shand : It is desired to draw attention to the conditions of line charging by an a-c. generator. One method which has been frequently used to determine this effect consists in taking the voltage characteristics of the generator when excited by the armature current directly from the no-load saturation, and the short-circuit saturation curves. By plotting the volt-ampere characteristics for the capacity effect of the external circuit, the intersection of the two curves will give the value to which the terminal voltage will rise, with the field un-excited. This method involves quite an appreciable error, due to the fact that when the generator is excited from the field, the voltage is generated only by the flux in the magnetic circuit of the armature, but when excited from the armature an additional voltage is generated due to the leakage fluxes which are not present in the other case. It is evident, therefore, that the relation between voltage and ampere turns will differ under the two conditions of excitation.