Woodward 505HT, Инструкция по установке и эксплуатации

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Manual 35116 505HT for Pelton Turbines
Woodward 58
Load Rejection
The control provides a load rejection algorithm to detect a load surge upon a generator breaker opening
in order to avoid turbine trip due to overspeed. This algorithm is triggered all the following conditions are
present:
•
Load rejection logic is being used
•
Generator breaker is opened
•
Actual speed value is greater than “Max Speed” or speed derivative is greater than “Max Speed
Derivative”
Once triggered this algorithm does the following:
•
Send the Nozzle average demand to “Nozzle Position Value”
•
Send deflector to close position
These two actions are maintained until any of the following conditions occur:
•
Speed is below 102% and Nozzles are positioned at “Nozzle Position Value”
•
“Maximum Algorithm Time” expires
Proper configuration of “Maximum Algorithm Time” is important,
otherwise the turbine speed can experience an undershoot (if both
the “Maximum Algorithm Time” and “Nozzles Close Time” are too
high) or a second overshoot can happen (if “Maximum Algorithm
Time” is too small and “Nozzles Close Time” are too high).
Speed Switches
There are six speed switches that can be used in one of the configurable outputs. All speed switches are
also passed along to Modbus.
The speed switches can be configured as increasing switches or decreasing switches. This means that
the relay energizes as the unit speed is increasing above the set point or decreasing below the set point.
Each speed switch has a High set point and a Low set point. When the speed switch is configured as an
increasing switch, the High set point is the trip point and the Low set point is the switch’s reset point.
When the speed switch is configured as a decreasing switch, the Low set point is the trip point, and the
High set point is the reset point. There are also configurable delays for activation and deactivation of the
switches.
Here is an example of a speed switch setup: A speed switch is desired to turn on the unit’s exciter when
the unit reaches 90% rated speed after a startup. Configurable relay #1 is configured as speed switch #1.
The speed switch is configured as an increasing switch. The High set point is adjusted to 90%. It is
decided that the switch should reset at 80% rated speed, so the Low set point is adjusted to 80%.
A failsafe logic is available in case both speed inputs fails. If this failsafe logic is used the referred output
can be forced to a “Fail Safe State” for the “Time to Disable Fail Safe”, expressed in minutes. After the
“Time to Disable Fail Safe” time expires the switch output gets back to its natural state. If a turbine start
command is issued the failsafe logic is disabled automatically.
Nozzle Average Demand Switches
There are four nozzle switches that can be used in one of the configurable outputs. All speed switches
are also passed along to Modbus.
Released