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Turbomachinery Package Specification Titan 250 Generator Set
The fuel control valve gradually opens and admits fuel into the combustor through the
injectors. The inlet guide vanes open and the bleed valve gradually closes. Fuel flow,
engine temperature, and turbine speed all increase. Once starter dropout speed is
exceeded, the starter freewheels and is de-energized. The engine continues to
accelerate under its own power.
The generator is loaded by closing the generator circuit breaker. The circuit breaker can
be closed to a dead (de-energized) or a hot (energized) bus. If a dead bus is detected,
the circuit breaker may be closed without synchronization. If a hot bus is detected, the
system must synchronize the generator output to the bus before the circuit breaker is
closed. Typically, synchronization and closing of the breaker are done automatically.
Manual synchronization is available as an option.
9.4.2 Steady-State Control
During steady-state operation, the control system keeps the equipment within specified
operating conditions. The maximum power limit is determined by engine temperature and
speed.
Temperature control is based on the third-stage nozzle temperature (T5). A set of
thermocouples arranged circumferentially around the turbine are used and the values
averaged. If one thermocouple has a value that deviates from the average by more than
a preset amount, an alarm is generated by the control system. If two thermocouples
deviate, the package is shut down.
Special sensors continuously monitor the gas turbine speed and the control system
makes adjustments to meet operating requirements and to keep the speed within
specified limits. A separate backup overspeed detection system provides additional
protection by automatically shutting the engine down if a preset overspeed limit is
reached.
9.4.3 Stopping
The gas turbine may be shutdown either manually or automatically.
The Normal Stop command initiates a cooldown stop. The generator circuit breaker is
opened and the gas producer runs at idle speed for a preset time to allow the gas turbine
and driven equipment to cool, then the fuel valves close. The Emergency Stop
command results in the immediate opening of the generator circuit breaker and closure of
the fuel valves without a cooldown period.
In the event of a hazardous condition or equipment malfunction, the control system will
shut the package down automatically. These shutdowns are divided into four categories:
• Cooldown stop nonlockout (CN)
• Cooldown stop lockout (CL)
• Fast stop nonlockout (FN)
• Fast stop lockout (FL)
Cooldown and fast stops correspond to the manual normal and emergency stops
respectively. Lockout stops inhibit operation of the control system and prevent restarting
until the malfunction is reset. Lockout stops result from serious malfunctions that require
corrective action before the system can be restarted. Nonlockout stops result from an
operational disruption or abnormal condition and can be reset when conditions return to
normal.
To protect the rotor from deformation and to enable a prompt restart of the package, the
turbine does not come to a complete stop unless the shutdown is the result of fire being
detected. The starter motor, or the DC backup turning gear mechanism in the case of
loss of AC power, engages the turbine at low speed and maintains rotation until the
cooldown cycle is complete. At the same time, the control system initiates and supervises
© 2008 Solar Turbines Incorporated. All rights reserved. TPS250GS/908 - Preliminary
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