Analysis of experiences related with dependability and security fails at the Costa Rican power system protective relaying schemes

The article discusses two very specific study cases where reliability errors occurred at protective relaying functions. The cases took place under fault conditions at the Costa Rican electric power grid. The study cases occurred between 2004 and 2011 in different elements of the transmission system owned by ICE, and they are representative cases in which it was necessary to perform a thorough analysis and laboratory tests. In each case was perform the following tasks: an explanation of the event, a failure categorization under the context of reliability fault type, a relay behavior analysis through its events and disturbance records, laboratory tests conducted to evaluate the behavior of the functions involved, and finally, a description of the corrective actions implemented to solve the detected problem. As a result, was achieved a sample of some of the most interesting experiences in the field of protective relaying maintenance, related to the costarrican electric power transmission network.