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Load Shedding |
Industrial power systems usually feature one or more interconnections with larger systems (power utilities), on-site generation systems, and loads (engines, pumps, compressors, heaters, rectifies, etc.) with distinct degrees of importance and relevance, depending on features and steps of the production process. Another feature common to industrial power systems is that they are designed and built with high-reliability requirements, as undesired shutdowns may cause significant losses. A simple interruption of continuous industrial processes may lead to reprocessing, or even discarding, a large amount of raw materials. In addition, reestablishing some processes may take hours or even days, drastically affecting plant's productivity and efficiency.
The main goal when operating any power system is to meet the demand of all loads sufficiently, by keeping the frequency and voltage in their nominal values. When this goal is achieved, a system is said to be in a normal state of operation. Another essential feature for operational security is that the point of operation be stable and that, when contingencies and disturbances occur, the power system reaches a new point of operation equally stable.
On an industrial plant, maintenance of a power system in a normal and stable state of operation is a critical function when severe contingencies occur that may cause deficiencies of generation, such as loss of connection with the power utility, loss of generator units, and opening interconnections. Ideally, a good load shedding system must quickly identify a deficiency of generation, determine precisely the amount of load to shed, select the loads for shedding and preserve priority loads, identify breakers that must be maneuvered, and finally perform all maneuvers needed.