Woodward 505XT, Инструкция по установке и эксплуатации

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Manual 35018V1 505XT Digital Control System for Steam Turbines
Woodward 70
When configured for generator applications a Minimum Load set point can be used by the 505 to reduce the
chance of reverse powering a unit upon closing the generator breaker. With the utility tie breaker closed,
when a generator breaker closed indication is received, the Speed set point is stepped to the Minimum Load
setting. The Minimum Load setting is defaulted to 3% (changeable in the Service Mode). To disable the use
of the Minimum Load Set Point, set the ‘Use Min Load’ setting (under the Service mode’s ‘BREAKER
LOGIC’ header) to ‘Unchecked’ (Not Used).
As a related feature, if ‘Use Min Load’ is selected and the parameter ‘Reverse Power on Controlled Stop’ in
OPERATING PARAMETERS is NOT selected, then the 505 will use this Minimum Load setting as the lower
speed setpoint limit whenever the breaker is closed
When the 505 is configured for a mechanical drive application, a contact input can be configured to instantly
step the speed setpoint to the minimum governor speed. This feature can only be used after the startup
sequence has been completed. In addition to stepping the speed setpoint to the minimum governor speed,
closing the contact input will also disable the Cascade and Auxiliary controls.
See Chapter 6 for a list of all speed set point related Modbus parameters.
Frequency Arm/Disarm
The Frequency Arm/Disarm feature can be used only when load sharing is not being performed, to allow
multiple units to operate on the same isolated bus. With this feature, one unit on a multiple unit isolated
bus controls frequency and the other units operate in a unit-load mode. The unit controlling frequency is
referred to as the “Swing Machine” because its load will swing (vary) depending on the load of the plant.
Caution should be taken with this configuration to not overload or reverse power the “Swing Machine”.
This feature, when programmed, allows an operator to Arm or Disarm a unit’s Frequency control mode
while it is in operation. When Armed, a unit will switch to Frequency control if the plant-to-utility tie breaker
opens. When Disarmed, a unit will stay in a unit-load control mode when the plant-to-utility tie breaker
opens.
To use this feature, the program’s ‘Use Freq Arm/Disarm’ setting box must be checked, the Sync/Load
Sharing mode cannot be programmed, and a discrete command must programmed. The Frequency
Arm/Disarm mode can be selected from a programmed contact input, Function key, or Modbus command.
When the programmed contact input is closed the unit’s Frequency control mode is Armed. When the
programmed contact input is open the unit’s Frequency control mode is Disarmed.
Depending on a unit’s size, health, and running status, an operator may select which unit is designated as
the plant Frequency control unit if or when the plant- to-utility tie breaker opens. Frequency control can be
Armed at any time, but it will only go into control when the generator breaker is closed and the utility tie
breaker is open.
Only one unit at a time should have its Frequency control mode
armed. If multiple units try to control plant frequency at the same
time, they may fight and cause system instability, with the potential of
damage to the equipment due to overloading or reverse-powering a
machine.
If the ‘Use Freq Arm/Disarm’ setting box is unchecked, Frequency control is always Armed and the unit
will go into Frequency control when the utility tie contact is open. If the program’s ‘Use Freq Arm/Disarm’
setting box is checked, then Frequency control must first be armed before the unit will switch into
Frequency control when the utility tie contact is open.