How to obtain realistic inputs to protective devices from fault simulations

The relaying signals by the use of EMT-type programs have demonstrated excellent results, but a quantity of requirements must be taken into account to be considered as realistic inputs for protection relays. This paper is a basic discussion of the factors to be considered when modeling power systems and protection relays for the purpose of developing or testing protection algorithms. Models of transmission lines, transducers, analogical and digital filters are interconnected to obtain digital signals to be applied within algorithms of digital relays.