This part of IEC 61892 specifies requirements for the choice and installation of electrical cables intended for fixed electrical systems in mobile and fixed offshore units, including pumping or pigging stations, compressor stations and exposed location single buoy moorings, used in the offshore petroleum industry for drilling, production, processing and for storage purposes. The reference to fixed electrical systems includes those that are subjected to vibration due to the movement of the unit, e.g. cables installed on a drag chain, and not those that are intended for repeated flexing. Cables suitable for repeated flexing use are detailed in other IEC specifications, e.g. IEC 60227 and IEC 60245, and their uses on board offshore units are restricted to those situations which do not directly involve exposure to a marine environment, e.g. portable tools, domestic appliances, etc. The following types and applications of cables are not included: optical fibre cables, sub-sea and umbilical cables, cables supplying downhole pumps, data, telecommunication and radio frequency cables or in tankers.