BS EN 61000-2-12:2003 relates to conducted disturbances in the frequency range from 0 kHz to 9 kHz, with an extension up to 148.5 kHz specifically for mains signalling systems.
It gives compatibility levels for public medium voltage a.c. distribution systems having a nominal voltage between 1 kV and 35 kV and a nominal frequency of 50 Hz or 60 Hz. The medium-voltage systems covered by this standard are public distribution systems supplying either private installations in which equipment is connected directly or through transformers, or substations feeding public low-voltage distribution systems.