Wolfram, many thanks!
To originator, reyntjensm:
Please note Mains impedance is a function of distance to distribution transformer, wire gauge and length, other connected loads, etc.
Most interférence is in form of impulses (distribution switching, lightning or breaking inductive load) or wideband EMI created by SMPS, and electronic lighting ballasts.
The allowable EMI spectrum and testing transients are defined by the regulatory and standards industries eg CISPR and IEC 61000-6-4: Emission standard for industrial environments
IEEE defines very well the LISNs and transient waveshape and frequency of occurence.
The design of EMI filters for compliance and transient protection is very well studied and documents for many decades.
Notice the the EMI spectrum starts at 150 kHz or 450 kHz and extends to beyond VHF frequencies.
Testing below 500 kHz is not very effective.
Suggest that reyntjensm first research the many standards and texts on EMI and power transients before expending money time and energy on "reinventing the wheel"
With Kind Regards,
Jon
MSEE, (power electronics, 1968, 1971)