Transient undervoltages in the electricity supply system and their consequences in cement plants

Repeatedly transient (brief) undervoltages give rise to production losses which could be avoided in many cases. Transient over- and undervoltages are part of every electricity supply system. The article describes how the various kinds of undervoltage originate and introduces a classification system which should simplify communication for further discussion. Precautions that can be taken by consumers to permit operation as free as possible from disturbance in spite of undervoltages, are explained. Closer attention is paid to high-voltage motors which are fed direct from the system because here the possible means of exerting an influence are smallest and, on the other hand, serious electrical and mechanical damage could occur in the event of a fault. The undervoltage ride-through capabilities of the various large variable speed drive systems are commented upon. In conclusion a mode of proceeding is described, showing how to identify, localise and eliminate components sensitive to undervoltage.