EN 60309 "CeeForm" plugs are generally used for those kinds of scenarios.
These were adopted by the IEC as IEC 60309 (transposing the European standard).
They were adopted originally in the 1960s in the UK as BS4343 and as various other standard numbers in other EU countries. These are all superseded by EN 60309, which is acceptable across the EU.
Just ensure that your connectors are to that standard and not any other.
I would suggest that you contact the customer for advice as they may require a higher than normal IP rating depending on the circumstances.
Single phase 230V - Blue
Three Phase 400V - Red
There's an ABB catalogue for those connectors : http://library.abb.com/GLOBAL/SCOT/SCOT296.nsf/VerityDisplay/12B61B88C2F36C37C1256FFF0077B723/$File/2CMC700001C0201_A_en_Short_Form_Catalogue_29004.pdf
Like NEMA, they come in a LOT of configurations with various pin layouts and keying options.
It's not usually permitted to use any other type of connector in an industrial environment.
Irish regs go as far as requiring them for ALL outdoor setups as BS1363 is considered a shock hazard in a rainy environment due to the proximity of the pins to your fingers and the low IP rating of rewirable plugs.
So, you'll see blue 16A ceeform connectors on patio heaters, xmas light installations etc etc..