A protection relay for protecting an electric system, includes means a manner of a time multiplier value, a manner of calculating, with the received time multiplier value, and an inverse definite time dependency having an exponentiation function. The dependency defines a relationship between an excitation level of an input signal to the relay and an operating time of the relay. The relay further a manner of shifting the dependency to a predefined calculation space, and includes a manner of applying, during execution, the dependency shifted to the predefined calculation space when determining an operating condition of the relay.