Page 99: of Offshore Engineer Magazine (May/Jun 2014)

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Higher frequencies—up to 200Hz—are supply and to

Subsea found downstream of a variable-speed prevent hydrocar- drive. For some long, step-out applica- bon release into the tions, low-frequency AC transmission or environment.

DC can come into play.

Water Depth/Pressure: Connectors

Specifying wet- • mate connectors must withstand not only the pressures

A high-voltage of deepwater applications, but also different pressure than the surrounding

Fig. 3: Penetrator.

wet-mate con- other harsh conditions. Today, subsea seabed. When possible, subsea mod-

Images from TE Connectivity.

nector is usually processing must withstand depths of up ules are pressure balanced—i.e., ? uid pressures are related to the fact that speci? ed by the following criteria: to 3000m, and, in the next decade, will ? lled—with the ? uid being adjusted • the boosting unit is in contact with the Voltage/Current Rating: Voltage and need to withstand even deeper depths.

at the same sea pressure as outside the • hydrocarbons. In case of a shutdown, the current handling capabilities are the basic Temperature Rating: Seabed tempera- module. This allows for thinner walls, whole reservoir pressure may apply to metrics in choosing any power connector. tures are usually rather low and very reduced weight, and higher reliability the penetrator. Since power in subsea systems is usu- stable, but the connectors and penetrators as seals are not required to withstand

The penetrator serves an environmen- ally three-phase, a connector is speci? ed need to withstand storage temperatures differential pressures. Some modules, tally-important function: an electrical through three values, such as 18/30 (36) that may be in direct sunlight in places such as those containing electronics or failure would mean a loss of production, kV. The ? rst number, 18kV, is the phase- like the hot climate of the Gulf of Mexico, other devices such as circuit breakers, but a mechanical failure would release to-ground rating. The second, 30kV, is the or the cold climate of the Norwegian cannot withstand pressure higher than hydrocarbons into the environment. phase-to-phase rating. The ? nal, 36kV, is Continental Shelf. Penetrators must also atmospheric. Therefore, a penetrator

On other modules not linked to the the maximum system voltage. be able to withstand the high tempera- is used to prevent the seawater from • oil ? ow, the penetrators are the barrier Some operational philosophies require tures generated by the modules (up to leaking into them. On other devices, ensuring the electrical integrity of the the connectors to still operate when 90°C) or the hydrocarbons, which may be such as pumps and compressors, which module, preventing the modules from there is a ground fault on one of the three up to 200°C.

are potentially exposed to the reservoir • being ? ooded with water. phases. In that case, the connector needs A Typical Interconnection System: Fig. shut-in pressures, pressure ratings can

Wet-mate connectors, then, are key to withstand the second value (30kV in 4 shows a typical power-cabling system. get up to 15kpsi/1034bars.

Penetrators are rated for withstanding this example) and is selected accordingly. An umbilical cable is terminated to a elements allowing cost-effective and • pressures—such as 5kpsi, 10kpsi and Frequency: Depending on the connec- subsea umbilical termination assembly technically feasible deployment, while

Deep Ingenuity - Ad 184x130_02.20.14.pdf 1 2/20/2014 9:08:11 AM 15kpsi—which are linked to the reser- tors and the application, the frequency (SUTA), which is roughly equivalent penetrators are essential to preserve the voir pressure. Required withstanding can be low (50 or 60Hz) for transmission. to a wall socket in a home. From the integrity of the complete electrical power

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