A method for dynamic signal switching with multiple measurement sources, for a merging unit in an electrical power system, said power system comprising at least one current transformer and at least one intelligent electronic device, said method comprising the following steps performed by the merging unit: an input receiving step of receiving at the merging unit at least two input signals (A,B) from at least one current transformer measuring the same physical primary quantity to give redundancy in measurement or for different measuring ranges and accuracy classes, wherein the at least one current transformer is two current transformers, or two output cores from the same current transformer wherein the input signals are each a three phase set of phase current transformer inputs: - a current transformer live level detection step, in which is determined which current input signals have a level of load or fault current flowing such as to indicate that the current transformer may be considered potentially suitable to be taken as a valid measurement source, - a current transformer supervision step, in which is determined which three phase current input signals of the current input signals is/are healthy, - a current transformer saturation detection step in which is determined whether saturation for any current transformer is present or the onset of said saturation is detected, - a current level detection step, in which is determined which inputs risk exceeding accuracy limits, - a step of real-time selection from the input signals (A,B), as a function of the results of the previous steps, wherein the selection is derived from (a) input signal B if B is live, B is healthy, B has no saturation, and B has no current excess (b) input signal A if A is live, A is healthy, and B fails any healthiness, saturation or dynamic range excess test as set out in the previous steps; and - said method further comprising a step of outputting from the merging unit a single combined signal as digitized output to at least one intelligent electronic device. - a current transformer live level detection step, in which is determined which current input signals have a level of load or fault current flowing such as to indicate that the current transformer may be considered potentially suitable to be taken as a valid measurement source, - a current transformer supervision step, in which is determined which three phase current input signals of the current input signals is/are healthy, - a current transformer saturation detection step in which is determined whether saturation for any current transformer is present or the onset of said saturation is detected, - a current level detection step, in which is determined which inputs risk exceeding accuracy limits, - a step of real-time selection from the input signals (A,B), as a function of the results of the previous steps, wherein the selection is derived from (a) input signal B if B is live, B is healthy, B has no saturation, and B has no current excess (b) input signal A if A is live, A is healthy, and B fails any healthiness, saturation or dynamic range excess test as set out in the previous steps; and (a) input signal B if B is live, B is healthy, B has no saturation, and B has no current excess (b) input signal A if A is live, A is healthy, and B fails any healthiness, saturation or dynamic range excess test as set out in the previous steps; and - said method further comprising a step of outputting from the merging unit a single combined signal as digitized output to at least one intelligent electronic device.