Due to a paper numbering error, this number was also assigned to a paperpresented at the 1976 Offshore Technology Conference. To distinguishbetween the two papers, the filename extension -B has been added to the 1976paper and the filename extension -A has been added to this paper.
This paper brings into focus some design and application features of insulatedcables for offshore production platforms and drilling rig electrical systemsand how they relate to the new 1975 National Electrical Code. A discussion isprepared on submarine cable design and installation for supplying power to theplatform from onshore. A resume pertaining to wiring methods and how theyaffect the electrical design engineer is outlined.
There is increasing interest in submarine cables for transmitting electricalpower from the mainland to offshore drilling rigs and production platforms. Oilexpansion programs for installing more oil rigs have created greater importanceto the evaluation of submarine power cable systems feeding the platforms andtheir satellites.
Of equal importance are the wiring systems on the production platforms anddrilling rigs and how they relate to the new 1975 National Electrical Code, IEEE-45 or other governing standards. In Gulf of Mexico waters (OuterContinental Shelf) OCS Order No.8, Federal Register, Vol. 40, No. 14, January21, 1975 states that wiring methods which conform to the NEC or IEEE-45 ineffect at the time of installation are acceptable. These governing standards orother governing standards for other waters regulate the wiring systems to beinstalled.
The first requisite is a means of supplying electric power to the productionplatforms and drilling rigs.
One system is the use of high voltage submarine cables from existing facilitiesonshore. Since a high degree of reliability is required, the cable designbecomes more specialized because of the environment in which it is installed. Each system must be treated individually and may be unique in its electricaldemands, geographic position, water depth, etc., which in turn influence thecable design.
In proposing a submarine electric power system the following electrical circuitparameters must be recognized.
Operating, emergency and short circuit load conditions.
Operating voltage and ground fault clearance time.
Switching, impulse voltages and lightning conditions.
Other information necessary in evaluating a submarine power system is:
Geographic location, site, conditions, transportation and unloadingfacilities.
Distance between onshore and offshore terminals, water depths, bottomcontour and underwater hazards.
Cable laying method, such as jetting, trenching or laying directly on thebottom.
Types of terminal installations.
A submarine power cable must meet the same basic requirements most other highvoltage cable s must meet with the addition of more stringent mechanical, chemical, and environmental conditions. In general, high voltage submarinecables for 3-phase ac operations consist of a three conductor core protected'by spiralled metallic armor wires. There are some selective applications, under unique conditions where a special cable design requires no metallic armorwires.
There are two types of submarine power cables, classified as a dry core and awet core. The wet core submarine cable utilizes no jacket under the armorwires, exposing the insulated conductors to the water (Figure 1).