“main source of electrical power”

1. The Merchant Shipping (Cargo Ship Construction) Regulations 1997 SI
2. The Merchant Shipping (Passenger Ship Construction: Ships of Classes I, II and II(A)) Regulations 1998 SI
3. The Merchant Shipping (Passenger Ship Construction: Ships of Classes III to VI (A)) Regulations 1998 SI

Definitions are taken from the instruments as published on zoomLaw, for guidance only. Check the instrument itself for its scope and any amendments.