During normal operation of an electrical power system, there will be some conditions like faults or other disturbances which may cause loss of synchronism between areas. When loss of synchronism takes place, asynchronous areas should be separated to avoid equipment damaged or extensive outages. This paper describes the assessment of the protection system of a part of the Uruguayan power system.

nbsp, The focus is on the incorporation of a big consumer with generation capacity. The involved added apparent power generation is about 10% of the maximum historical Uruguayan load. The article describes a set of studies on the protective system associated to transmission lines feeding the new consumer.

nbsp, Particular attention is paid to blocking power swing functions of the involved relays. Power system simulations and relay tests have been performed, to evaluate the performance of the relays under power swing conditions. The foreknowledge makes possible to avoid undesired operation. Index Terms : Out-of-step, Power swing, Power swing blocking, Power system stability, Power system transient stability.

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