ISO 13297:2000(E)

7.2.2 A manually reset trip-free circuit-breaker shall be installed within 0,5 m of the source of power or, if
impractical, the conductor from the source of power to the panel-board circuit-breaker shall be contained within a
protective covering, such as a junction box, control box, enclosed panel-board, or within a conduit or cable trunking
or equivalent protective covering. If the location of the main shore-power inlet circuit-breaker exceeds 3 m from the
shore-power inlet connection or the electrical attachment point of a permanently installed shore-power cord,
additional fuses or circuit-breakers shall be provided within 3 m of the inlet or attachment point to the electrical
system in the craft, measured along the conductor.

Ce n’est donc pas franco-français, mais on peut aller au delà de 50cm, jusqu’à 3m sans trop de complications ....