Woodward 505HT, Installation And Operation Manual

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Manual 35116 505HT for Pelton Turbines
Woodward 47
The Control must be configured according to the type of speed signal being provided, the rated speed
(rpm) of the turbine, the number of gear teeth (if applicable), and the system frequency (50 Hz or 60 Hz).
The Control then converts the speed signal frequency into percent of rated speed. All speed values
during the configuration and operation of the control are in terms of percent of rated speed unless stated
otherwise.
The Control monitors speed signal failures and overspeed. When the turbine is stopped or moving very
slowly, the control will not have a valid speed signal, but the control should not see this as a speed signal
failure. When the turbine is started, the speed signal is ignored by the control until the “Time to Start
Speed” expires. When the turbine is stopped, the speed signal is ignored once the speed drops below
50% and the nozzles are closed. In addition to the previous speed override conditions if a speed input is
configured for “PT Sensor” its speed value is overridden/neglected if the generator breaker opened. If
more than one speed inputs are used, both would have to fail to cause a shutdown.
The Control has an electronic overspeed detection, which issues a shutdown to the control. The
“Overspeed” value configured in the control is in percent of rated speed. The overspeed detection is also
ignored at the same time the speed signal failure is ignored, as mentioned above.
An overspeed test feature is available so that the mechanical overspeed (or independent secondary
overspeed) trip can be easily tested. To enable the overspeed test, the turbine should be at the rated
speed, not in manual control and the breaker should be opened. The test enable switch is hooked up to a
configurable timer so that the test is not accidentally left enabled. When the overspeed test is enabled,
the electronic overspeed trip is disabled, the isochronous speed reference ceiling is raised to the
overspeed test limit, and the raise/lower rate on the isochronous speed reference is increased to the
overspeed test rate. The speed reference must be raised until the turbine trips from the mechanical
overspeed. When the overspeed test is disabled and the speed setpoint is automatically ramped back to
the “Max Reference Offline”.
The Control has a speed deadband function that can be enabled. The speed deadband function is a
configurable window around rated speed within which the Control will not respond to speed changes. The
deadband window has configurable set points above and below rated speed. In the example below, the
high set point is 100.05% rated speed (60.03 Hz on a 60 Hz system), and the low set point is 99.97%
rated speed (59.98 Hz on a 60 Hz system). When the unit’s speed fluctuates around rated speed the
control will not respond unless the speed gets outside the configurable window.
Figure 3-2. Speed Deadband Function
Sometimes it is not desirable to have the unit responding to these slight frequency fluctuations. The
speed deadband can be enabled and the deadband window adjusted accordingly. When the speed
deadband function is set up, there are three options. The speed deadband function can be enabled at all
times, disabled at all times, or only when the unit is online.
Offline/Isochronous Speed Control
The Control has two PID control algorithms, an on-line/droop algorithm and an off-line/isochronous
algorithm. When the unit is off-line or in isochronous on-line control, the Off-line/Isochronous algorithm is
Released