Power generation - Power transmission and distribution
To cope with the large amounts of electric power required
by the refrigeration-compressor drivers and short-circuit
currents in the electrical system, E-LNG plants call for stateof-
the-art high-voltage transmission systems with an excellent
30+ years service history. For maximum reliability and
complete freedom of maintenance, Siemens uses fully
encapsulated gas-insulated switchgears (GIS) in voltage
ratings of typically 132 or 230 kV.
The high-voltage power transmission and distribution system
forms an integral part of Siemens’ E-LNG concept and
its electrical distribution system. It is fully protected with
microprocessor-based relays, and centrally controlled and
monitored by the superimposed electrical network monitoring
and control (ENMC) system. The equipment is maintenance
free for 10+ years. As it is not normally possible
to initiate and propagate arcing faults inside the gastight
and grounded compartments, single busbar systems are
preferred. Installed in lightweight site-erected buildings with
a minimal footprint, the GIS is fully weather-protected.
The SF6 puffer-type circuit breakers with spring or
electrohydraulic
operating mechanism are extremely reliable and
maintenance-free. Harmful gas leakages from the GIS are
virtually impossible.
High-voltage power
distribution systems
with gas-insulated
switchgear (GIS) provide
an absolutely
safe and maintenancefree
subsystem.
Designed to last
Climate control is required for the electronic control and
protection equipment only, which is installed in the same
pre-fabricated modules as the motor-compressor and the
power-plant supervisory control equipment. The high-voltage
sides of the unit transformers at the generators and the converter transformers at the compressor-driver side are
connected to the GIS by single-phase shielded cross-linked polyethylene (XLPE) insulated power cables which are directly
buried in the ground, or laid in covered concrete trenches.
These high voltage cables are generally protected by optical
pilot-wire differential relays; their conductor size is determined
using sophisticated finite element analysis (FEA)
thermal analysis tools. In general, the oil-filled unit and
converter transformers are naturally cooled (ONAN) for
added reliability, with sealed oil systems and additional
protection equipment.
