Find attached an excerpt from a test report showing the iEM32xx meter's conformity to impulse voltage test under EN 50470-1:2006 clause 7.3.3.
Key Words and Phrases: Associated / related standards: IEC61010, EN 61439-1 + 2, EN 60664-1, BS EN 61439-1:2011, Overvoltage category III, surge withstand capability
Supplementary Information: Looking up the EN 60664-1 standard, it is titled "Insulation coordination for equipment within low-voltage systems". It is a British Standard (BS). Apparently, there is an IEC equivalent of it of the same number namely IEC 60664-1 which is also titled "Insulation coordination for equipment within low-voltage systems".
The other standard they refer to (the first one) is BS EN 61439-1:2011 "Low-voltage switchgear and controlgear assemblies - General rules".