Protective relaying for the cogeneration intertie revisited

The author describes how the actual protection scheme required for a specific utility/independent power producer (IPP) interconnection will be determined or recommended by the electric utility concerned. The overall protection philosophy will vary from utility to utility based on individual engineer´s and/or company´s experiences and based on the configuration of the power system to which it is being connected. But the basis for interconnection protection and the basic relay functions are essentially the same. The variation in each utility´s standards can be a source of frustration and confusion for an IPP or consultant who works with more than one utility. Communication among the utility, consultant, and the IPP is the key to a successful, secure installation. The parties involved must balance risk minimization with economic concerns at the IPP/utility interface