Page 87 - Oil and Gas Production Handbook An Introduction to Oil and Gas Production

exchanged with mains or other facilities on the HV distribution board. Relays
are used for protection functions.

HV is transformed to MV switchboards to which large consumers are
connected. LV switchboards feed a mix of normal consumers, Motor Control
Centers and variable speed drives for motors up to a few hundred KW (Not
necessarily separate as shown in the figure).

A separate emergency power switchboard provides power for critical
equipment. It can be powered from a local emergency generator if main
power is lost. Computer systems are fed from an Uninterruptible Power
System (UPS) with batteries, connected to the main or emergency
switchboard.

A power management system is used for control of electrical switchgear and
equipment. Its function is to optimize electricity generation and usage and to
prevent major disturbances & plant outages (blackouts). The power
management system includes HV, MV and LV low voltage switchgear plus
Motor Control Centers (MCC) and emergency generator sets. Functions
include prioritization of loads, emergency load shedding (closing down of
non-essential equipment) and prestart of generator sets (e.g. when
additional power to start a big crude pump is required).

Large rotating equipment and generators are driven by gas turbines or large
drives. Gas turbines for oil and gas production are generally modified
aviation turbines in the 10-25 MW range. These require quite extensive
maintenance and have a relatively low overall efficiency (20-27% depending
on application). Also, while a turbine is relatively small and light, it will usually
require large and heavy support equipment such as large gears, air
coolers/filters, exhaust
units, and sound damping
and lubrication units.

Therefore use of large
variable speed drives is
becoming more common.
For pumps on subsea
facilities this is the only
option. For use on remote
facilities, High Voltage DC
transmission and HV
motors can be used, from a
main facility or power from

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