An emulating device for emulating a bimetallic strip, the emulating device comprising a current sensor capable of measuring a line current (IP) flowing through the emulating device, the emulating device being capable of providing a value representative of a cumulative thermal state over time t, which value is referred to as cumulative thermal state, by recursively adding a value representative of an initial thermal state, which value is referred to as initial thermal state, and a value representative of a present thermal state, which value is referred to as present thermal state, which is determined on the basis of the line current (IP).