Abstract
With the development of high voltage and long distance transmission system, the line charging current is greatly increased. It is a well known fact that when charging such long transmission lines the generator will sometimes be self excited by armature reaction to an abnormally high voltage which threatens the insulation of the system.
This abnormal condition is usually explained by means of two curves; the line charging characteristic and saturation curve excited by armature leading current. This paper describes the precise nature of the two characteristics. Saturation curve excited by armature current can roughly be obtained by graphical method rom no load saturation curve and short circuit characteristic, and more accurately with further knowledge of armature leakage reactance.
The results of actual tests on machines coincide fairly with such curves obtained from the above graphical method. The same method can also be applicable to obtain the saturation curve excited by armature current with some field excitation.
The author compared the results obtained by the above graphical method with the actual test data at Yomikaki Power Station of Daido Electric Power Company, and at Ryushima Power Station of Keihin Electric Power Company and fairly coincidence is pointed out.
The above method holds for both balanced and unbalanced three phase problems.
The author further refers to miscellaneous problems concering the self-excitation.
