Page 22 - Offshore Electrical Engineering Manual

Description of a Typical System 9

SECURE ALTERNATING CURRENT AND DIRECT CURRENT POWER
SUPPLIES

On any platform, there are a large number of systems which require supplies derived
from batteries to minimise the risk of system outage due to supply failure.
The following is a typical platform inventory:

1. fire and gas monitoring and protection,
2. process instrumentation and control,
3. emergency shutdown system,
4. emergency auxiliaries for main generator prime movers,
5. emergency auxiliaries for large compressors and pumps,
6. navigational lanterns and fog warning system,
7. emergency and escape lighting,
8. tropospheric scatter link,
9. line of sight links,
10. carrier multiplexing and voice frequency telegraphy equipment,
11. telecoms control and supervisory system,
12. public address,
13. general alarm system,
14. platform private automated branch exchange (PABX),
15. marine radio telephones,
16. aeronautical very-high-frequency (VHF) (AM) radio,
17. VHF (FM) marine radio,
18. aeronautical nondirectional beacon,
19. company high-frequency independent sideband and ultra-high-frequency (FM)
private channel radios,
20. telemetry system,
21. satellite subsea well control systems.

The majority of these systems operate at a nominal voltage of 24 V direct current
(DC), and although it is not necessary for each of the above-mentioned systems to
have separate battery and battery charger systems, the grouping criteria require more
detailed discussion. These are covered in PART 2 Chapter 15, as is the need to pro-
vide dual chargers and batteries for certain vital systems.
In addition to the above-mentioned systems, there are, of course, switchgear trip-
ping/closing supplies and engine start batteries which are dedicated to the equipment
they supply. In the case of engines which drive fire pumps, duplicate chargers and
batteries are also required. This subject is discussed in PART 2 Chapter 12.

DRILLING SUPPLIES
A typical self-contained drilling rig supply system’s single-line diagram is shown in
Fig. 1.1.2.
The usual arrangement is for two or more diesel generators rated at around
1 MVA to feed a main switchboard which also has provision for a supply from the