Guide for Abnormal Frequency Protection for Power Generating Plants
|Publication Date:||16 June 2003|
This guide has been prepared to assist the protection engineer in applying relays for the protection of generating plant equipment from damage caused by operation at abnormal frequencies including overexcitation. Emphasis is placed on the protection of the major generating station components at fossil steam generating stations, nuclear stations, and on combustion turbine installations. Consideration is also given to the effect of abnormal frequency operation on those associated station auxiliaries whose response can affect plant output. The guide also presents background information regarding the hazards caused by operating generation equipment at abnormal frequencies. It documents typical equipment capabilities and describes acceptable protective schemes. Underfrequency protection can be provided by either load shedding or a discrete underfrequency protective function. If both load shedding and a discrete protective function are used, then they must be coordinated.
It should be borne in mind that much of the information concerning the operation of turbines and generators at off-nominal frequency, very often, do not belong to the public domain and may vary from one manufacturer to another. In view of that situation, it is recommended that any piece of data presented in the guide as fictitious, example or typical should be discussed with the equipment supplier in order to obtain the relevant and detailed information for a particular equipment or installation.
Furthermore, when specifications or clauses originating from international standards are presented and discussed, it is by no means meant that these specifications are automatically applicable. Verification should be made with the manufacturer about which standards the equipment has been designed to comply with.
When reference is made in the text to rated frequency, it is meant as 60 Hz or 50 Hz. When examples are provided at the specific frequency of 60 Hz, they are also applicable to 50 Hz.