Voltage oscillations in armature windings under lightning impulses-I

Abstract

Synopsis.-Experience has shown that rotating machinery theory developed, and oscillographic evidence supporting their connected directly to overhead lines is more vulnerable to surges reliability is given. A generalized theory of neutral protection is than many other types of apparatus. This fact together with a proposed. The importance of wave-front, surge impedance of desire on the part of some to connect important units to the line incoming line, arrester resistance, and other factors is discussed. in this manner, has necessitated a study of the protection problem. Methods for protection of the turn insulation and the insulation to Such a study is here described, showing oscillograms taken when ground of such machines are suggested, showing that the lightning steep voltage surges were applied to machine windings, measuring arrester only limits the potential of waves entering the machine and internal voltages to ground which are 200 per cent of the voltage cannot control oscillations which may take place within the machine. allowed by the terminal lightning arrester. A simple traveling wave The advantages of thyrite as a neutral resistor are pointed out in analysis of these oscillations is developed, which has successfully connection with the short-circuit protection, telephone interference, explained the peculiarities of over 400 oscillograms taken under and lighting protection problems of such machines. In Appendix A various terminal conditions. Practical methods of eliminating th.e the test circuits and methods used in the laboratory are discussed in oscillations with neutral impedance are outlined in the light of the relation to actualfield conditions.

Method to Predict the Non-Uniform Potential Distribution in Random Electrical Machine Windings under Pulse Voltage Stress

“…As presented in a recently published article [1], research concerning non-uniform potential distributions in electrical machine windings dates back to 1930 [2] and even back to 1902 for transformers [3]. It was observed that non-uniform potential distributions occur during voltage transients at the machine terminals which impose abnormal stress on the insulation.…”