CAT Titan 250 - Manual (Page 43)

Turbomachinery Package Specification Titan 250 Generator Set
During initial turbine generator acceleration, the excitation power is switched off. At
approximately 80% speed, the PMG output is connected to the excitation power contacts
and voltage begins to build. The CGCM then provides controlled exciter field current at a
level to maintain the generator terminal voltage at a predetermined value established by
the operator. A potential transformer (usually supplied with the switchgear) provides a
voltage level signal to the CGCM. By sensing the generator output voltage and controlling
the power to the brushless exciter, the CGCM automatically maintains the generator
output voltage at a constant level at all load conditions.
Since the PMG output power is independent of the main generator line voltage and
current levels, there is no need for additional auxiliary equipment to provide power to the
CGCM during transient conditions. The PMG provides sufficient generator terminal
voltage during conditions of high generator line current to allow for selective tripping
during a short-circuit condition. Current, potential, and cross current transformers
required for input to the CGCM are not included. A cross-current compensating circuit is
included to accommodate reactive load sharing between multiple turbine generators
operating in parallel. Instrumentation transformers are usually supplied with the
switchgear.
10.2.2 Control Modes
In addition to voltage regulation, the following generator control modes are also available:
• Speed/Load Control
− Isochronous (Isoch) Speed Control
− Droop Speed Control
− Kilowatt Import Control
• Reactive Compensation
− Droop Voltage Control
• Power Factor Control
• Reactive Load Volt Amp Reactive Control
− Differential Cross Current Control
10.2.3 Breaker Synchronization
The control system provides automatic generator breaker synchronization control when
paralleling to the bus. Automatic synchronization can be initiated by the operator or by a
remote signal received from a supervisory control system. If manual synchronization is
required, an optional generator metering panel must be included. Synchronization control
is provided by the CGCM.
10.2.4 Auto Start and Synchronizing System
When the generator set is in standby mode, the control system will automatically start the
generator set, accelerate the engine to loading speed, and synchronize the generator
breaker to the bus upon receipt of a supervisory command. If the control system detects
a hot bus, it will synchronize the generator to the bus and close the breaker. If the control
system detects a dead bus, it will close the generator breaker without synchronization.
10.2.5 Kilowatt Import Control
The kW import control system controls the real load (kW) when the generator set is in
parallel with a large power source. When kW import control is enabled, the control
system monitors the load imported from the utility and adjusts the turbine generator set
fuel flow to maintain a preset amount of imported power. When it is not desirable to
export power to the utility, kW import control is normally selected. While in parallel with a
© 2008 Solar Turbines Incorporated. All rights reserved. TPS250GS/908 - Preliminary
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