Bandwidth for power amplifier to play-out Comtrade Files

[521AB]

We are trying to create an amplifier for injection of comtrade files (or anyway power system waveforms) into the numerical relays.
The question now is: what should be the frequency response of the amplifiers?
I have done a lot of thoughts, and I will post them here, but not now, as I might be wrong and drive you into the wrong path.
I am mainly talking about cut-off frequency, known also as -3dB frequency, so the higher part of the bandwidth. But if you have some concerns also on the lower part.. welcome!
Thanks for your inputs

 

[521AB]

Application is Power System Relays, and NOT any issue in the power quality world like flicker, dips etc.
Just waveforms for relay protection in High Voltage networks (solidly grounded), eventually also for Medium Voltage networks (Petersen Coil grounded or isolated).