An apparatus and a method are described for modifying test measurement signals for protective devices for electric power networks. The apparatus has an input interface to receive a first test measurement signal from a test generator, wherein the first test measurement signal is matched to a first electrical input characteristic of a first protective device for a power network. The apparatus further has an electrical modification system coupled to the input interface to convert the first test measurement signal into a second test measurement signal, wherein the second test measurement signal is matched to a second electrical input characteristic of a second protective device for the power network. The apparatus additionally has an output interface to output the second test measurement signal to the second protective device.