Get ordinary plug and socket of another country -
Choose one that won't fit into any common socket or adapter in your country. (But there is risk of somebody using adapters, especially the Chinese ones with multiple holes that accept all plugs)
Swiss SN441011 won't fit into any other socket worldwide. The 16A variant is less common, and might have thick enough pins to prevent plugging into adapters
Italy CEI23-50 won't fit into any other socket worldwide. The 16A variant is less common, and have pins spaced far apart so it might prevent plugging into adapters
- The socket is not recessed, and the sleeving on the pins does not make it "fool proof" at HID ignitor voltages. (Don't stick your fingers to the pins)
- The plug is not polarised, but this generally is not an issue for any HID lamp
British BS546 won't fit into any other socket, but in itself is fairly common around the world. The 15A variant have thick pins sufficient to prevent plugging into adapters
- The plug itself is huge, but this is not a bad thing at HID ignitor voltages
Israel SI32 won't fit into any other socket worldwide, but does fit into most adapters
Use IEC 60309 industrial connectors
- Some types (typically Blue 2P+E 16/32A 6h and Red 4P+E 16/32A 6h) are fairly common in industrial use, so in factories etc there will be sockets where it can be plugged in and availability of adapters
- There are more special (and harder to find) plugs in the 60309 series that are not compatible with anything else, like Green 2h for 400Hz
Modify an IEC C connector to make your own special version
-
https://www.lighting-gallery.net/gallery/displayimage.php?album=2096&pos=10&pid=58040 - Keep clearance betwen any conductors you add and the L pin, especially considering HID ignitor voltages
If you use flex cable or moulded plugs with cable - Some flexes - especially the thin ones in the 0.5mm2 range (20AWG) or so - Have too thin insulation to withstand HID ignitor voltages at all
In all cases, any cable after the ignitor does pose some fire risk. If the cable gets damaged or its insulation fails, it will be subjected to ignitor voltage that will keep arcing going, and the ballast will prevent the tripping of any breakers, possibly including AFCIs
If this have to work unattended, either design it so the ignitor is in the luminaire and not in the ballast box, or use shielded cable and GFCI