Woodward 505E Quick start guide

Installation and Operation Manual
505E Digital Governor
for Extraction Steam Turbines
Volume 1
Manual 85018V1B

WARNING
Read this entire manual and all other publications pertaining to the work to be
performed before installing, operating, or servicing this equipment. Practice all
plant and safety instructions and precautions. Failure to follow instructions can
cause personal injury and/or property damage.
The engine, turbine, or other type of prime mover should be equipped with an
overspeed shutdown device to protect against runaway or damage to the prime
mover with possible personal injury, loss of life, or property damage.
The overspeed shutdown device must be totally independent of the prime mover
control system. An overtemperature or overpressure shutdown device may also be
needed for safety, as appropriate.
CAUTION
To prevent damage to a control system that uses an alternator or battery-charging
device, make sure the charging device is turned off before disconnecting the
battery from the system.
Electronic controls contain static-sensitive parts. Observe the following
precautions to prevent damage to these parts.
• Discharge body static before handling the control (with power to the control
turned off, contact a grounded surface and maintain contact while handling the
control).
• Avoid all plastic, vinyl, and Styrofoam (except antistatic versions) around
printed circuit boards.
• Do not touch the components or conductors on a printed circuit board with
your hands or with conductive devices.
IMPORTANT DEFINITIONS
WARNING—indicates a potentially hazardous situation which, if not avoided, could
result in death or serious injury.
CAUTION—indicates a potentially hazardous situation which, if not avoided, could
result in damage to equipment.
NOTE—provides other helpful information that does not fall under the warning or
caution categories.
Revisions—Text changes are indicated by a black line alongside the text.
Woodward Governor Company reserves the right to update any portion of this publication at any time. Information
provided by Woodward Governor Company is believed to be correct and reliable. However, no responsibility is
assumed by Woodward Governor Company unless otherwise expressly undertaken.
© Woodward 1997
All Rights Reserved

Manual 85018V1 505E Digital Governor
Woodward i
Contents
ELECTROSTATIC DISCHARGE AWARENESS ................................................. VI
CHAPTER 1. GENERAL INFORMATION...........................................................1
Introduction.............................................................................................................1
General Description................................................................................................3
505E Inputs and Outputs........................................................................................4
Control Overview....................................................................................................8
Speed Control.......................................................................................................10
Auxiliary Control ...................................................................................................11
Load Sharing Input...............................................................................................12
Cascade Control...................................................................................................12
Extraction/Admission Control...............................................................................13
Ratio/Limiter .........................................................................................................13
HP and LP Valve Limiters ....................................................................................14
Starting Features..................................................................................................15
Keypad and Display..............................................................................................21
Watchdog Timer/CPU Fault Control.....................................................................23
CHAPTER 2. INSTALLATION PROCEDURES..................................................24
Introduction...........................................................................................................24
Mechanical Data and Hardware Installation.........................................................24
CHAPTER 3. 505E CONTROL DESCRIPTION ...............................................41
Introduction...........................................................................................................41
Ratio/Limiter Configurations.................................................................................41
Speed vs. Extr/Adm Priority..................................................................................48
Turbine Start.........................................................................................................50
Turbine Start Modes.............................................................................................51
Critical Speed Avoidance .....................................................................................54
Idle/Rated .............................................................................................................55
Automatic Start Sequence....................................................................................57
No Idle Programmed ............................................................................................59
Speed Control Overview ......................................................................................59
Speed PID Operational Modes.............................................................................60
Synchronization....................................................................................................69
Extraction and/or Admission Turbine Control.......................................................72
Extraction Control.................................................................................................74
ADMISSION or EXTR/ADM Control.....................................................................75
Remote Extr/Adm Setpoint...................................................................................78
Cascade Control...................................................................................................80
Remote Cascade Setpoint ...................................................................................84
Auxiliary Control ...................................................................................................86
Valve Limiters.......................................................................................................91
Emergency Shutdown ..........................................................................................93
Controlled Shutdown............................................................................................93
Overspeed Test Function.....................................................................................94
Local / Remote Function ......................................................................................95
Function Keys.......................................................................................................96
Relays...................................................................................................................97
CHAPTER 4. CONFIGURATION PROCEDURES............................................100
Program Architecture .........................................................................................100
Programming the 505E ......................................................................................102
Exiting the Program Mode..................................................................................137
Valve / Actuator Calibration and Test.................................................................140

505E Digital Governor Manual 85018V1
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Contents
CHAPTER 5. 505E OPERATION ................................................................145
Run Mode Architecture...................................................................................... 145
Keypad and Display........................................................................................... 148
Run Mode Front Panel Keys ............................................................................. 149
Starting Procedures........................................................................................... 150
Overspeed Test Function.................................................................................. 154
F3 and F4 Keys ................................................................................................. 156
Limiter (LMTR) Key Screens............................................................................. 156
Actuator (ACTR) Key Screens .......................................................................... 158
Control (CONT) Key Screens............................................................................ 159
Dynamics (DYN) Key Screens .......................................................................... 161
Stop Key Screens.............................................................................................. 162
Auxiliary (AUX) Key Screens............................................................................. 163
Remote / Speed Bias (RMT) Key Screens........................................................ 166
Cascade (CAS) Key Screens............................................................................ 169
Extraction/ Admission (EXT/ADM) Key Screens............................................... 172
Alarms................................................................................................................ 175
Trips................................................................................................................... 177
Speed, Casc, Aux, and Ext/Adm Dynamics Adjustments................................. 178
CHAPTER 6. COMMUNICATIONS................................................................182
Modbus Communication.................................................................................... 182
Port Adjustments ............................................................................................... 185
505E Control Modbus Addresses...................................................................... 185
Specific Address Information............................................................................. 198
CHAPTER 7. SERVICE OPTIONS................................................................201
Product Service Options.................................................................................... 201
Returning Equipment for Repair........................................................................ 202
Replacement Parts............................................................................................ 203
How to Contact Woodward................................................................................ 203
Engineering Services......................................................................................... 204
Technical Assistance......................................................................................... 205
APPENDIX. 505E PROGRAM MODE WORKSHEET......................................206

Manual 85018V1 505E Digital Governor
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Illustrations and Tables
Figure 1-1a. Overview of 505E Functionality (Notes) ............................................5
Figure 1-1b. Overview of 505E Functionality.........................................................6
Figure 1-1c. Overview of 505E Functionality .........................................................7
Figure 1-2. Typical Extraction and/or Admission Steam Turbine...........................9
Figure 1-3. Typical Admission Steam Turbine.....................................................10
Figure 1-4. Overview with Auxiliary Configured as a Limiter ...............................17
Figure 1-5. Overview with Auxiliary Configured as a Controller...........................18
Figure 1-6. Overview with Decoupled HP & LP Ratio/Limiter, Auxiliary Configured
as a Limiter......................................................................................19
Figure 1-7. Overview with Decoupled HP & LP Ratio/Limiter, Auxiliary Configured
as a Controller .................................................................................20
Figure 1-8. 505E Key Pad and Display................................................................21
Figure 2-1. 505E Control Layout (Standard Enclosure).......................................26
Figure 2-2. 505E Bulkhead-Mounted Enclosure..................................................27
Figure 2-3. Jumper Options..................................................................................28
Figure 2-4. Jumper Locations...............................................................................28
Figure 2-5. CageClamp Terminal Blocks.............................................................29
Figure 2-6. Control Wiring Diagram .....................................................................30
Figure 2-7. Representative 505E I/O Schematic..................................................31
Figure 2-8. Fuse Location ....................................................................................33
Figure 2-9. Shielded Wire Connections ...............................................................34
Figure 2-10. Typical RS-232 Communications ....................................................38
Figure 2-11. Typical RS-422 Communications ....................................................39
Figure 2-12. Typical RS-485 Communications ....................................................39
Figure 2-13a. Preferred Multipoint Wiring............................................................40
Figure 2-13b. Alternate Multipoint Wiring.............................................................40
Figure 3-1. Basic Control Overview......................................................................41
Figure 3-2. Coupled HP & LP Mode.....................................................................45
Figure 3-3. Decoupled Inlet (HP) Mode ...............................................................46
Figure 3-4. Decoupled Exhaust (LP) Mode..........................................................47
Figure 3-5. Decoupled HP & LP Mode.................................................................48
Figure 3-6. Priority Flow Diagram.........................................................................49
Figure 3-7. Manual Start Mode Example .............................................................52
Figure 3-8. Semiautomatic Start Mode Example .................................................53
Figure 3-9. Automatic Start Mode ........................................................................54
Figure 3-10. Idle / Rated Start..............................................................................56
Figure 3-11. Automatic Start Sequence...............................................................57
Figure 3-12. Speed Control Functional Diagram..................................................60
Figure 3-13. Speed PID Control Modes...............................................................61
Figure 3-14. Frequency and Unit Load Relationship ...........................................63
Figure 3-15. Speed Relationships........................................................................64
Figure 3-16. Loadsharing Logic............................................................................71
Figure 3-17. Extr/Adm Control Diagram...............................................................73
Figure 3-18. Cascade Functional Diagram ..........................................................81
Figure 3-19. Aux Control Overview......................................................................86
Figure 4-1. Basic Program Architecture.............................................................100
Figure 4-2. Initial 505E Program Mode Entry.....................................................101
Figure 4-3a. Program Mode Blocks ...................................................................103
Figure 4-3b. Program Mode Blocks ...................................................................104
Figure 4-3c. Program Mode Blocks....................................................................105
Figure 4-3d. Program Mode Blocks ...................................................................106
Figure 4-3e. Program Mode Blocks ...................................................................107
Figure 4-3f. Program Mode Blocks.....................................................................108
Figure 4-4. Typical Extraction Steam Map.........................................................120
Figure 4-5. Typical Admission Steam Map ........................................................122

505E Digital Governor Manual 85018V1
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Illustrations and Tables
Figure 4-6. Typical Extraction & Admission Steam Map................................... 123
Figure 4-7. Exiting the Program Mode .............................................................. 137
Figure 4-8. Stroke Actuator/Valve ..................................................................... 144
Figure 5-1. Basic Program Architecture............................................................ 145
Figure 5-2a. Overview of Run Mode ................................................................. 147
Figure 5-2b. Overview of Run Mode ................................................................. 148
Figure 5-3. 505E Keypad and Display............................................................... 149
Figure 5-4. SPEED Key Screens ...................................................................... 151
Figure 5-5. Direct Setpoint Entry....................................................................... 154
Figure 5-6. Overspeed Test Enable Key Screens............................................. 155
Figure 5-7. LMTR Key Screens......................................................................... 157
Figure 5-8. ACTR Key Screens......................................................................... 158
Figure 5-9. CONT Key Screens ........................................................................ 159
Figure 5-10. DYN Key Screens......................................................................... 162
Figure 5-11. STOP Key Screens....................................................................... 163
Figure 5-12. AUX Key Screens ......................................................................... 163
Figure 5-13. RMT Key Screens......................................................................... 166
Figure 5-14. KW Key Screens........................................................................... 169
Figure 5-15. CAS Key Screens ......................................................................... 170
Figure 5-16. EXT/ADM Key Screens................................................................. 172
Figure 5-17. ALARM Screen ............................................................................. 176
Figure 5-18. TRIP Screen.................................................................................. 177
Figure 5-19. Typical Response to Load Change............................................... 181
Figure 6-1. ASCII/RTU Representation of 3...................................................... 183
Figure 6-2. Modbus Frame Definition................................................................ 184
Table 2-1. Jumper Options Chart.........................................................................29
Table 3-1. On-Line / Off-Line Dynamics Selection...............................................67
Table 3-2. Load Sharing Logic .............................................................................72
Table 4-1. Actuator Driver Limits....................................................................... 141
Table 5-1. Overview of Run Mode..................................................................... 146
Table 5-2. Idle/Rated Messages ....................................................................... 152
Table 5-3. Auto Start Messages........................................................................ 153
Table 5-4. Controlling Parameter Messages..................................................... 160
Table 5-5. Priority Messages............................................................................. 161
Table 5-6. Auxiliary Messages (if using Aux enable)........................................ 164
Table 5-7. Auxiliary Messages (if using Aux as a limiter).................................. 165
Table 5-8. Remote AUX Messages................................................................... 165
Table 5-9. Remote Speed Messages................................................................ 167
Table 5-10. Control Messages.......................................................................... 168
Table 5-11. Cascade Control Messages........................................................... 171
Table 5-12. Remote Cascade Messages.......................................................... 171
Table 5-13. Extr/Adm Control Messages .......................................................... 174
Table 5-14. Remote Extr/Adm Messages ......................................................... 175
Table 5-15. Alarm Messages ............................................................................ 176
Table 5-16. Trip Messages................................................................................ 177
Table 6-1. ASCII vs RTU Modbus..................................................................... 183
Table 6-2. Modbus Function Codes.................................................................. 184
Table 6-3. Modbus Error Codes........................................................................ 185
Table 6-4. Maximum Modbus Discrete and Analog Values.............................. 186
Table 6-5. Boolean Write Addresses................................................................. 187
Table 6-6a. Boolean Read Addresses .............................................................. 188
Table 6-6b. Boolean Read Addresses .............................................................. 189

Manual 85018V1 505E Digital Governor
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Illustrations and Tables
Table 6-7a. Analog Read Addresses .................................................................190
Table 6-7b. Analog Read Addresses .................................................................191
Table 6-7c. Analog Read Addresses .................................................................192
Table 7-8. Analog Write Addresses ...................................................................192
Table 6-9a. Control Status .................................................................................193
Table 6-9b. Control Status .................................................................................194
Table 6-10. Analog Input Configuration .............................................................194
Table 6-11. Analog Output Configuration...........................................................195
Table 6-12a. Relay Configuration.......................................................................195
Table 6-12b. Relay Configuration.......................................................................196
Table 6-13. Contact Input Configurations ..........................................................197
Table 6-14. Units Configuration..........................................................................198
Table 6-15. Units Configuration..........................................................................198

505E Digital Governor Manual 85018V1
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Electrostatic Discharge Awareness
All electronic equipment is static-sensitive, some components more than others.
To protect these components from static damage, you must take special
precautions to minimize or eliminate electrostatic discharges.
Follow these precautions when working with or near the control.
1. Before doing maintenance on the electronic control, discharge the static
electricity on your body to ground by touching and holding a grounded metal
object (pipes, cabinets, equipment, etc.).
2. Avoid the build-up of static electricity on your body by not wearing clothing
made of synthetic materials. Wear cotton or cotton-blend materials as much
as possible because these do not store static electric charges as much as
synthetics.
3. Keep plastic, vinyl, and Styrofoam materials (such as plastic or Styrofoam
cups, cup holders, cigarette packages, cellophane wrappers, vinyl books or
folders, plastic bottles, and plastic ash trays) away from the control, the
modules, and the work area as much as possible.
4. Do not remove the printed circuit board (PCB) from the control cabinet
unless absolutely necessary. If you must remove the PCB from the control
cabinet, follow these precautions:
•Do not touch any part of the PCB except the edges.
•Do not touch the electrical conductors, the connectors, or the
components with conductive devices or with your hands.
•When replacing a PCB, keep the new PCB in the plastic antistatic
protective bag it comes in until you are ready to install it. Immediately
after removing the old PCB from the control cabinet, place it in the
antistatic protective bag.
CAUTION
To prevent damage to electronic components caused by improper handling,
read and observe the precautions in Woodward manual 82715, Guide for
Handling and Protection of Electronic Controls, Printed Circuit Boards, and
Modules.

Manual 85018V1 505E Digital Governor
Woodward 1
Chapter 1.
General Information
Introduction
This manual (85018) describes the Woodward 505E Digital Governor for steam
turbines with controlled extraction and/or admission pressure control. English
versions are 9907-165, 9907-166, and 9907-167. The option charts below show
the differences between the part numbers. Volume 1 of this manual provides
installation instructions, describes the control, and explains the configuration
(programming) and operating procedures. Volume 2 includes notes on applying
the control to specific applications, Service mode information, and 505E
hardware specifications.
This manual does not contain instructions for the operation of the complete
turbine system. For turbine or plant operating instructions, contact the plant-
equipment manufacturer.
Manual 85017 describes the 505 Digital Governor for steam turbines without
extraction pressure control.
Part Number Options
Part Number Power
9907-165 HVAC (180–264 Vac)
9907-166 AC/DC (88–132 Vac) or (90–150 Vdc)
9907-167 LVDC (18–32 Vdc)
Optional Bulkhead Mounting Box (NEMA 4X) P/N 8923-439
General Installation and Operating Notes and Warnings
This Equipment is suitable for use in Class I, Division 2, Groups A, B, C, and D
(Class I, Zone 2, Group IIC) or non-hazardous locations.
This equipment is suitable for use in European Zone 2, Group II environments
per compliance with EN60079-15, Electrical apparatus for explosive
atmospheres – Type of protection ‘n’
These listings are limited only to those units bearing the certification
identification.
Field wiring must be rated at least 75 °C for operating ambient temperatures
expected to exceed 50 °C.
Peripheral equipment must be suitable for the location in which it is used.
Wiring must be in accordance with North American Class I, Division 2 or
European Zone 2 wiring methods as applicable, and in accordance with the
authority having jurisdiction.

505E Digital Governor Manual 85018V1
2 Woodward
WARNING
Explosion Hazard–Do not connect or disconnect while circuit is live unless
area is known to be non-hazardous.
Explosion Hazard–Substitution of components may impair suitability for
Class I, Division 2 or Zone 2 applications.
AVERTISSEMENT
Risque d’explosion–Ne pas raccorder ni débrancher tant que l’installation
est sous tension, sauf en cas l’ambiance est décidément non dangereuse.
Risque d’explosion–La substitution de composants peut rendre ce matériel
inacceptable pour les emplacements de Classe I, applications Division 2 ou
Zone 2.
505E Software Changes Covered in this Manual Revision
1. PROGRAM MODE: Made all start modes default to false to ensure a
customer programmed the unit. Also added an error check to ensure Rated
Speed (when programmed as a gen set) was less than max gov.
2. SERVICE MODE: Changed the hold changes for Min Load to come from the
Breaker Logic header's Hold Changes input. Previously the hold changes
command was selected under the Speed Control Settings header.
3. SPEED SETPOINT RATES: Changed the minimum adjustment range for all
speed setpoint rates to 0.01 (was 0.1).
4. AUX LIMITER or CONTROLLER: Added logic to ensure the inhibited status
of Aux control when the input is failed. In addition, changed Aux re-enable
logic such that when a failed aux input is restored there is no glitch to the
speed LSS. Also changed breaker open logic to correct a Gen Opening Aux
actuator output glitch.
5. AUX CONTROLLER: Changed the speed setpoint aux biasing logic to only
allow the speed control limiting action (while in aux control) to be active when
the speed setpoint reaches max gov. Prior to this fix the speed limiter could
come into control during an extreme transient.
6. AUX DIRECT ENTERED SETPT: Changed Aux Entered setpoint to be reset/
stopped on a shutdown pulse rather than held disabled on a shutdown
condition. This change allows the Aux Limiter function direct setpoint entry
even when the unit is tripped.
7. AUX, CASC, and EXTR DROOP: Changed the droop feedback lag-tau
tunable range from a max of 10 to a max of 1000.
8. DECOUPLED CASCADE CONTROL: Added a lag to the speed the speed
setpoint is using during a utility tie breaker open setback. Also updated the
logic used to reset the speed setpoint to minimize to bump experienced
when Decoupled Casc is disabled. Changed logic to fix a problem where
breaker opening while in the Cascade decoupled mode would cause the HP
valve to close then open unexpectedly.
9. MODBUS: Changed the Gen and Tie Open alarms for Aux, Casc, and
Remote to match the Modbus®* listing—the software eventlatch inputs were
reversed/backwards with the Modbus listing.
*—Modbus is a trademark of Modicon, Inc.
10. CONTROLLED STOP: Made the Controlled Stop abort if speed raise/lower
is selected or another control mode is selected. This can be tuned-out by
setting CNTRL_STOP.RL_STOP.IN_2=*false in the debug mode.

Manual 85018V1 505E Digital Governor
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11. ANALOG INPUTS: Changed max setting on the delay time’s tunable range
from 3 ms to 3000 ms. The analog input failure delay setting is defaulted to
zero but can be adjusted up to 3000msec using the debug mode
MAIN.AIx.LATCH_DLY where x is the analog input number. Added a tunable
single pole filter (LAG) to each analog input. Output/input = 1/(1+st) where t
= 1/(2(pi)f) = LAG_TAU. The Lag-tau is defaulted to zero but can be adjusted
in the debug mode using MAIN.AIx_LAG.LAG_TAU where x is the analog
input number (1-6).
General Description
General
The 505E is a 32-bit microprocessor-based control designed to control single
extraction, extraction/admission, or admission steam turbines. The 505E is field
programmable which allows a single design to be used in many different control
applications and reduces both cost and delivery time. It uses menu driven
software to instruct site engineers on programming the control to a specific
generator or mechanical drive application. The 505E can be configured to
operate as a stand-alone unit or in conjunction with a plant’s Distributed Control
System.
Operator Control Panel
The 505E is a field configurable steam turbine control and operator control panel
(OCP) integrated into one package. A comprehensive operator control panel,
including a two- line (24 characters each) display, and a set of 30 keys is located
on the 505E’s front panel. This OCP is used to configure the 505E, make On-
Line program adjustments, and operate the turbine/system. Easy to follow
instructions are presented in English through the OCP’s two-line display and
operators can view actual and setpoint values from the same screen.
Turbine Control Parameters
The 505E interfaces with two control valves (HP & LP) to control two parameters
and limit an additional parameter, if desired. These two controlled parameters
are typically speed (or load) and extraction/admission pressure (or flow),
however, the 505E could be utilized to control or limit: turbine inlet pressure or
flow, exhaust (back) pressure or flow, first stage pressure, generator power
output, plant import and/or export levels, compressor inlet or discharge pressure
or flow, unit/plant frequency, process temperature, or any other turbine related
process parameter. Refer to Volume 2 for details on applications.
Communications
The 505E can communicate directly with plant Distributed Control Systems
and/or CRT based operator control panels, through two Modbus®
communication ports. These ports support RS-232, RS-422, or RS-485
communications using ASCII or RTU MODBUS transmission protocols.
Communications between the 505E and a plant DCS can also be performed
through hardwired connections. Since all 505E PID setpoints can be controlled
through analog input signals, interface resolution and control is not sacrificed.

505E Digital Governor Manual 85018V1
4 Woodward
Additional Features
The 505E also provides the following features: First-Out Trip Indication (5 total
trip inputs), Critical Speed Avoidance (2 speed bands), Auto Start Sequence (hot
& cold starts), Dual Speed/Load Dynamics, Zero Speed Detection, Peak Speed
Indication for Overspeed trip, and Isochronous Loadsharing between units.
Using the 505E
The 505E control has two normal operating modes, the Program Mode and the
Run Mode. The Program Mode is used to select the options needed to configure
the control to your specific turbine application. Once the control has been
configured, the Program Mode is typically never again used, unless turbine
options or operation changes. Once configured, the Run Mode is used to operate
the turbine from start-up through shutdown. In Addition to the Program and Run
modes, there is a Service Mode which can be used to enhance system operation
while the unit is running. Refer to Volume 2 for information on the Service Mode.
505E Inputs and Outputs
Control Inputs
Two speed inputs which are jumper configurable for MPU (magnetic pickup
units) inputs or proximity probes.
Six analog inputs are available. One is dedicated as the extraction/admission
input. The remaining five are configurable. The sixth analog input has isolation
circuitry and should be used for a self-powered signal that is not isolated.
Sixteen contact inputs are available. Four are dedicated for shutdown, reset,
raise speed setpoint, and lower speed setpoint. Another two contact inputs must
be dedicated for generator breaker and utility tie breaker if the control is used in
a generator application. Ten additional contact inputs can be configured. If the
unit is not used in a generator application, then twelve additional contact inputs
can be configured.
Four function keys on the front panel of the control. F1 and F2 are dedicated to
alarm and overspeed test, respectively. F3 and F4 can be used to enable or
disable various functions of the control.
Control Outputs
Two actuator outputs with linearization curves for the HP and the LP valve
outputs.
Six 4–20 mA outputs, for meters or other readouts.
Eight Form-C relay contact outputs, six that are configurable. The two dedicated
relay outputs are for shutdown and alarm indication.

Manual 85018V1 505E Digital Governor
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Control Communications
Two Modbus ports, to be used as control interfaces. The protocol can be either
ASCII or RTU and the communications can be RS-232, RS-422, or RS-485.
One computer (PC) port to be used for program configuration storage.
An overview of the 505E functions is shown in Figure 1-1. Use this block diagram
to match the control features to the site-specific application required.
Figure 1-1a. Overview of 505E Functionality (Notes)

505E Digital Governor Manual 85018V1
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Figure 1-1b. Overview of 505E Functionality

Manual 85018V1 505E Digital Governor
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Figure 1-1c. Overview of 505E Functionality

505E Digital Governor Manual 85018V1
8 Woodward
Control Overview
The 505E Digital Governor is designed to control extraction, extraction/
admission, or admission steam turbines. The difference between these turbines
is the capability of the turbine to allow low pressure steam, which is at a lower
pressure than the inlet, to enter and/or exit the turbine. An extraction turbine
allows the lower pressure (extraction) steam to exit the turbine only and will have
a non-return valve in the extraction header/line to prevent steam from entering
the turbine. An admission turbine (also called induction) will allow excess header
steam to enter the turbine through the low pressure inlet. An
extraction/admission turbine will allow low pressure header steam to enter or exit
the turbine depending on system pressures. A turbine with admission capability
will have a stop valve or trip-and-throttle valve in the low pressure line to prevent
steam from entering the turbine when the unit is tripped. The type of turbine used
will depend on the system requirements and must be designed by the turbine
manufacturer to perform the functions required.
The 505E has two independent control channels available, the speed/load and
auxiliary controllers. The outputs of these two controllers are low-signal-selected
(LSS) to provide to speed/load demand signal to the ratio/limiter. In addition to
these channels, the speed/ load controller can be manipulated by another
controller, the cascade controller. The cascade controller is ‘cascaded’ into the
speed controller, whereby the speed controller setpoint is changed directly by the
cascade controller output. The auxiliary controller can act as either a control
channel or as a limiting channel. All three of these PID controllers have the
option of utilizing an analog input signal to remotely position their setpoints.
Additional features of the 505E include frequency control, isochronous
loadsharing, critical speed avoidance, idle/rated control, and an automatic start
sequence. There are two serial communications ports which can be used to
monitor and control the turbine using Modbus protocol.
Extraction Turbines
The 505E control can be configured to operate single automatic extraction
turbines by controlling the interaction of the governor (HP or high pressure) valve
and the extraction (LP or low pressure) valve. (The 505E can also operate the
governor valve and the first extraction valve of multiple extraction turbines).
Single automatic extraction turbines have a high pressure stage and a low
pressure stage, each controlled by a valve. Steam enters the turbine through the
HP valve (see Figure 1-2). At the downstream end of the HP turbine stage and
before the LP valve, steam can be extracted. The LP valve controls the entry of
steam into the LP turbine stage, and the diverting of steam through the extraction
line. As the LP valve is opened, more steam enters the LP stage and less is
extracted.
In most cases, the operator of an extraction turbine needs to maintain both
turbine speed/ load and extraction pressure/flow at constant levels. Changing the
position of either the HP valve or the LP valve affects both turbine speed/load
and extraction. If either the load on the turbine or the extraction demand
changes, both the HP valve position and the LP valve position must be changed
to maintain speed/load and extraction. The movement of both valves is
automatically calculated by the 505E’s ratioing logic based on the turbine
performance parameters to minimize valve/process interaction.

Manual 85018V1 505E Digital Governor
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Figure 1-2. Typical Extraction and/or Admission Steam Turbine
Admission Turbines
The 505E control can be configured to operate single automatic admission
turbines by controlling the interaction of the governor (HP or high pressure) valve
and the extraction (LP or low pressure) valve.
Single automatic admission turbines have a high pressure stage and a low
pressure stage, each controlled by a valve. Steam enters the turbine through the
HP valve (see Figure 1-3) and at the downstream end of the HP turbine stage,
before the LP valve. The LP valve controls the entry of steam into the LP turbine
stage and through the admission line. As the LP valve is opened, more steam
enters the LP stage.
In most cases, the operator of an admission turbine needs to maintain both
turbine speed/ load and admission pressure/flow at constant levels. Changing
the position of either the HP valve or the LP valve affects both turbine speed/load
and admission. If either the load on the turbine or the admission demand
changes, both the HP valve position and the LP valve position must be changed
to maintain speed/load and admission.
The movement of both valves is automatically calculated by the 505E’s ratioing
logic based on the turbine performance parameters to minimize valve/process
interaction.

505E Digital Governor Manual 85018V1
10 Woodward
GOVERNOR VALVE
INLET
STEAM
T&T
VALVE
EXHAUST
STEAM
855−665
VALVE
T&T
GOVERNOR VALVE
STEAM
INLET
HP/ACT1
LP/ACT2 98−03−12 JMM
Figure 1-3. Typical Admission Steam Turbine
Extraction and Admission Turbines
The 505E control can be configured to operate single automatic extraction and
admission turbines by controlling the interaction of the governor (HP or high
pressure) valve and the extraction (LP or low pressure) valve.
Single automatic extraction and admission turbines have a high pressure stage
and a low pressure stage, each controlled by a valve. Steam enters the turbine
through the HP valve (see Figure 1-2). At the downstream end of the HP turbine
stage and before the LP valve, steam can either be extracted or admitted
(inducted) into the LP turbine stage. The LP valve controls the entry of steam into
the LP turbine stage. As the LP valve is opened, more steam enters the LP stage
and less is extracted.
In most cases, the operator of an extraction turbine needs to maintain both
turbine speed/ load and extraction or admission pressure/flow at constant levels.
Changing the position of either the HP valve or the LP valve affects both turbine
speed/load and extraction or admission. If either the load on the turbine or the
extraction / admission demand changes, both the HP valve position and the LP
valve position must be changed to maintain speed/ load and extraction/
admission. The movement of both valves is automatically calculated by the
505E’s ratioing logic based on the turbine performance parameters to minimize
valve/process interaction.
Speed Control
The speed control receives a turbine speed signal from one or two magnetic
pickups or proximity probes. The speed PID (proportional, integral, derivative)
control amplifier then compares this signal to the speed setpoint to generate an
output signal to the ratio/ limiter (through a low signal select bus).

Manual 85018V1 505E Digital Governor
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The speed control amplifier can also receive a programmable (optional) droop
feedback signal to increase the stability of the turbine/governor system. This
droop signal can be proportional to the controller’s output signal or to the
system’s generator load (kW) signal.
The speed control’s setpoint is adjustable with raise or lower commands through
the keypad on the front of the control, remote contact inputs or Modbus. The
setpoint can also be directly set by entering the new setpoint from the keypad, or
through either Modbus communications link. In addition, a remote speed setpoint
analog input can be programmed to remotely position the speed setpoint.
Remote Speed Setpoint
One of the 4–20 mA inputs can be configured to remotely adjust the speed
setpoint. Typically, a process control external to the 505E interfaces with this
input to regulate the turbine’s speed or load to control a related process.
The remote speed setpoint input directly affects the 505E’s speed setpoint. The
maximum rate at which the remote input signal can change the speed setpoint is
programmable. When the remote setpoint is enabled, the speed setpoint will
move at a much slower rate until the two settings are matched, at which time the
speed setpoint will be allowed to move at the maximum rate. The remote speed
function can be enabled and disabled as required from the front-panel keypad,
remote contact inputs or the communication line.
Auxiliary Control
The Auxiliary control channel can be used to either control a parameter or limit a
parameter. The Auxiliary PID controller can be used to control or limit unit
load/power, plant import/export levels, inlet pressure, exhaust pressure,
temperature or any other process directly related to turbine load.
The Auxiliary input is a 4–20 mA current signal. The Auxiliary PID control
amplifier compares this input signal with a setpoint to produce a control output to
the digital LSS (low-signal select) bus. The LSS bus sends the lowest signal to
the ratio/limiter logic which determines HP and LP valve positions. The Auxiliary
control amplifier can also receive a programmable (optional) droop feedback
signal to increase system stability. This is a direct feedback using a portion of the
Auxiliary control amplifier output.
The Auxiliary setpoint is adjustable with raise or lower commands through the
keypad on the front of the control, through remote contact inputs or through the
communication links. Also, the setpoint can be directly set by entering the new
setpoint from the keypad or through Modbus. In addition, an analog input can be
programmed to remotely position the Auxiliary setpoint.

505E Digital Governor Manual 85018V1
12 Woodward
Remote Aux Setpoint
One of the 4–20 mA inputs can be configured to remotely adjust the Auxiliary
setpoint. The remote aux setpoint input directly affects the auxiliary setpoint. The
maximum rate at which the remote input signal can change the auxiliary setpoint
is programmable. When the remote setpoint is enabled, the auxiliary setpoint will
move at a much slower rate until the two settings are matched at which time the
setpoint will be allowed to move at the maximum rate. The remote aux function
can be enabled and disabled as required from the front panel keypad, the remote
contact inputs, or the communication links.
Load Sharing Input
The 505E is capable of using an analog input to accept a load sharing signal
from Woodward’s Digital Synchronizer and Load Control (DSLC™). This input in
conjunction with the DSLC allows the control to isochronously loadshare with any
other system using a DSLC. The 505E’s internal summing junction adds this
signal with the speed/load PID’s reference. In addition to loadsharing, the DSLC
input to the 505E can be used to synchronize the unit to either the plant bus or to
the utility.
Cascade Control
The Cascade control can be configured to control any system process, related to
or affected by turbine speed or load. Typically this controller is used as a turbine
inlet or exhaust pressure controller.
The Cascade control is a PID controller that compares a 4–20 mA process signal
with the Cascade setpoint. The PID controller sets the speed controller setpoint
until the process signal and the setpoint match. The Cascade control can also
receive a programmable (optional) droop feedback signal to increase control
loop stability. This is a direct feedback using a portion of the cascade control
amplifier’s output.
The Cascade setpoint is adjustable with raise or lower commands through the
keypad on the front of the control, the remote contact inputs, or the
communication links. Also, the setpoint can be directly set by entering the new
setpoint from the keypad or through either Modbus communications link. In
addition, a remote cascade setpoint analog input can be programmed to
remotely position the cascade setpoint.
Remote Cascade Setpoint
One of the 4–20 mA inputs can be configured to remotely adjust the Cascade
setpoint. The remote cascade setpoint input directly affects the 505E’s Cascade
setpoint. The maximum rate at which the remote input signal can change the
Cascade setpoint is programmable and can be changed in the Run mode. When
the remote setpoint is enabled, the Cascade setpoint will move at a much slower
rate until the two settings are matched at which the setpoint will be allowed to
move at the maximum rate. The remote cascade function can be enabled and
disabled as required from the front-panel keypad, the remote contact inputs or
either Modbus communication link.