Basler DECS-250 User manual

INSTRUCTION MANUAL
FOR
DECS-250
Digital Excitation Control System
Publication: 9440300990
Revision: J May-15

9440300990 Rev J i
DECS-250 Preface
Preface
This instruction manual provides information about the installation and operation of the DECS-250 Digital
Excitation Control System. To accomplish this, the following information is provided:
•General Information
•Human-machine interface
•Functional description
•Installation
•BESTCOMSPlus®software
•Setup
•Communication protocols
•Maintenance
•Specifications
•Expansion modules
Conventions Used in this Manual
Important safety and procedural information is emphasized and presented in this manual through
warning, caution, and note boxes. Each type is illustrated and defined as follows.
Warning!
Warning boxes call attention to conditions or actions that may cause
personal injury or death.
Caution
Caution boxes call attention to operating conditions that may lead to
equipment or property damage.
Note
Note boxes emphasize important information pertaining to installation
or operation.
Note
Be sure that the device is hard-wired to earth ground with no smaller
than 12 AWG (3.3 mm2) copper wire attached to the case ground
terminal. When the device is configured in a system with other
devices, a separate lead should be connected from the ground bus to
each device.
Current transformer (CT) grounding should be applied in accordance
with local codes and conventions.

ii 9440300990 Rev J
Preface DECS-250
12570 State Route 143
Highland IL 62249-1074 USA
www.basler.com
[e-mail]
Tel: [phone]
Fax: [phone]
© 2015 by Basler Electric
All rights reserved
First printing: October 2012
Warning!
READ THIS MANUAL. Read this manual before installing, operating, or maintaining the DECS-250.
Note all warnings, cautions, and notes in this manual as well as on the product. Keep this manual with
the product for reference. Only qualified personnel should install, operate, or service this system.
Failure to follow warning and cautionary labels may result in personal injury or property damage.
Exercise caution at all times.
Basler Electric does not assume any responsibility to compliance or noncompliance with national code, local code,
or any other applicable code. This manual serves as reference material that must be well understood prior to
installation, operation, or maintenance.
For terms of service relating to this product and software, see the Commercial Terms of Products and Services
document available at www.basler.com/terms.
This publication contains confidential information of Basler Electric Company, an Illinois corporation. It is loaned for
confidential use, subject to return on request, and with the mutual understanding that it will not be used in any
manner detrimental to the interests of Basler Electric Company and used strictly for the purpose intended.
It is not the intention of this manual to cover all details and variations in equipment, nor does this manual provide
data for every possible contingency regarding installation or operation. The availability and design of all features
and options are subject to modification without notice. Over time, improvements and revisions may be made to this
publication. Before performing any of the following procedures, contact Basler Electric for the latest revision of this
manual.
The English-language version of this manual serves as the only approved manual version.

9440300990 Rev J iii
DECS-250 Preface
This product contains, in part, open source software (software licensed in a way that ensures freedom to run,
copy, distribute, study, change, and improve the software) and you are granted a license to that software under the
terms of either the GNU General Public License or GNU Lesser General Public License. The licenses, at the time
of sale of the product, allow you to freely copy, modify, and redistribute that software and no other statement or
documentation from us, including our End User License Agreement, places any additional restrictions on what you
may do with that software.
For at least three (3) years from the date of distribution of this product, a machine-readable copy of the complete
corresponding source code for the version of the programs distributed to you will be sent upon request (contact
in
formation is provided above). A fee of no more than our cost of physically performing the source code distribution
is charged.
The source code is distributed in the hope that it will be useful, but WITHOUT ANY REPRESENTATION or
WARRANTY or even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Refer to the source code distribution for additional restrictions regarding warranty and copyrights.
For a complete copy of GNU GENERAL PUBLIC LICENSE Version 2, June 1991 or GNU LESSER GENERAL
PUBLIC LICENSE Version 2.1, February 1999 refer to www.gnu.org or contact Basler Electric. You, as a Basler
Electric Company customer, agree to abide by the terms and conditions of GNU GENERAL PUBLIC LICENSE
Version 2, June 1991 or GNU LESSER GENERAL PUBLIC LICENSE Version 2.1, February 1999, and as such
hold Basler Electric Company harmless related to any open source software incorporated in this product. Basler
Electric Company disclaims any and all liability associated with the open source software and the user agrees to
defend and indemnify Basler Electric Company, its directors, officers, and employees from and against any and all
losses, claims, attorneys' fees, and expenses arising from the use, sharing, or redistribution of the software.
Review the software website for the latest version of the software documentation.
Portions of this software are copyright ©2014 The Free Type Project (www.freetype.org). All rights reserved.

iv 9440300990 Rev J
Revision History DECS-250

9440300990 Rev J v
DECS-250 Contents
Contents
Introduction .................................................................................................................................................1
Features and Functions.............................................................................................................................1
Applications ...............................................................................................................................................2
Package.....................................................................................................................................................2
Optional Features and Capabilities ...........................................................................................................2
Style Number .........................................................................................................................................3
Storage......................................................................................................................................................3
Electrolytic Capacitor Considerations....................................................................................................3
Controls and Indicators..............................................................................................................................5
Front Panel Illustration and Description ....................................................................................................5
Menu Navigation........................................................................................................................................6
Adjusting Settings......................................................................................................................................7
Display Setup ............................................................................................................................................7
LCD........................................................................................................................................................7
Sleep Mode............................................................................................................................................7
Language...............................................................................................................................................7
Screen Scrolling.....................................................................................................................................8
Power Inputs................................................................................................................................................9
Control Power............................................................................................................................................9
Operating Power........................................................................................................................................9
Inrush Current Reduction Module (ICRM).............................................................................................9
Power Stage...............................................................................................................................................11
Voltage and Current Sensing...................................................................................................................13
Generator Voltage...................................................................................................................................13
Generator Current ...................................................................................................................................13
Phase Sensing.....................................................................................................................................13
Cross-Current Compensation..............................................................................................................14
Bus Voltage .............................................................................................................................................15
Synchronizer .............................................................................................................................................17
Generator Synchronization......................................................................................................................17
Frequency Correction ..........................................................................................................................17
Voltage Correction...............................................................................................................................17
Angle Compensation ...........................................................................................................................18
Failure of Synchronization ...................................................................................................................18
Voltage Matching.....................................................................................................................................19
Breaker Hardware Configuration.............................................................................................................19
Breaker Failure ....................................................................................................................................19
Generator Breaker...............................................................................................................................19
Generator and Bus Condition Detection..................................................................................................20
Generator Condition.............................................................................................................................20
Generator Stability...............................................................................................................................21
Bus Condition.......................................................................................................................................21
Bus Stability .........................................................................................................................................21
Generator Governor Control....................................................................................................................23
Regulation..................................................................................................................................................25
Regulation Modes....................................................................................................................................25
AVR......................................................................................................................................................25
FCR......................................................................................................................................................25
FVR......................................................................................................................................................25
Var .......................................................................................................................................................26
Power Factor........................................................................................................................................26

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Contents DECS-250
Pre-Position Setpoints.............................................................................................................................27
Transient Boost .......................................................................................................................................28
Operation with Paralleled Generators.....................................................................................................28
Reactive Droop Compensation............................................................................................................29
Cross-Current Compensation..............................................................................................................29
Network Load Sharing .........................................................................................................................29
Line Drop Compensation.....................................................................................................................30
Autotracking.............................................................................................................................................31
Internal Setpoint Tracking....................................................................................................................31
External Setpoint Tracking...................................................................................................................32
Setpoint Configure...................................................................................................................................32
Auxiliary Control .......................................................................................................................................33
Auxiliary Control Input Type ....................................................................................................................33
Auxiliary Control Input Function ..............................................................................................................33
PSS Test Input.....................................................................................................................................33
Limiter Scaling .....................................................................................................................................33
Setpoint Limits .....................................................................................................................................33
Auxiliary Control Gains............................................................................................................................33
AVR Mode............................................................................................................................................34
FCR Mode............................................................................................................................................34
FVR Mode............................................................................................................................................34
Var Mode .............................................................................................................................................34
Power Factor Mode..............................................................................................................................34
Summing Type ........................................................................................................................................34
Contact Inputs and Outputs.....................................................................................................................37
Contact Inputs .........................................................................................................................................37
Start and Stop Inputs...........................................................................................................................37
Programmable Inputs ..........................................................................................................................37
Contact Outputs.......................................................................................................................................38
Watchdog Output.................................................................................................................................38
Programmable Outputs........................................................................................................................38
Protection...................................................................................................................................................41
Voltage Protection ...................................................................................................................................41
Overexcitation (Volts per Hertz)...........................................................................................................41
Generator Undervoltage ......................................................................................................................43
Generator Overvoltage ........................................................................................................................44
Loss of Sensing ...................................................................................................................................44
Frequency Protection ..............................................................................................................................45
Overfrequency .....................................................................................................................................45
Underfrequency ...................................................................................................................................46
Power Protection.....................................................................................................................................46
Reverse Power ....................................................................................................................................46
Loss of Excitation.................................................................................................................................47
Field Protection........................................................................................................................................48
Field Overvoltage.................................................................................................................................49
Field Overcurrent.................................................................................................................................49
Exciter Diode Monitor ..........................................................................................................................50
Power Input Failure..............................................................................................................................52
Sync-Check Protection............................................................................................................................53
Generator Frequency Less Than 10 Hertz..............................................................................................54
Configurable Protection...........................................................................................................................54
Limiters ......................................................................................................................................................57
Overexcitation Limiter..............................................................................................................................57
Summing Point OEL ............................................................................................................................57
Takeover OEL......................................................................................................................................59
Underexcitation Limiter............................................................................................................................61

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DECS-250 Contents
Stator Current Limiter..............................................................................................................................63
Low-Level Limiting...............................................................................................................................63
High-Level Limiting ..............................................................................................................................63
Initial Delay ..........................................................................................................................................63
Var Limiter ...............................................................................................................................................64
Limiter Scaling.........................................................................................................................................64
Underfrequency Limiter...........................................................................................................................65
Volts per Hertz.....................................................................................................................................66
Metering .....................................................................................................................................................69
Metering Explorer....................................................................................................................................69
HMI ......................................................................................................................................................69
BESTCOMSPlus®................................................................................................................................69
Metered Parameters................................................................................................................................70
Generator.............................................................................................................................................70
Power...................................................................................................................................................70
Bus.......................................................................................................................................................71
Field .....................................................................................................................................................72
PSS......................................................................................................................................................72
Synchronization ...................................................................................................................................73
Auxiliary Control Input..........................................................................................................................73
Tracking...............................................................................................................................................73
Control Panel.......................................................................................................................................74
Metering Summary...............................................................................................................................75
Status Indication......................................................................................................................................76
System Status......................................................................................................................................76
Inputs ...................................................................................................................................................77
Outputs ................................................................................................................................................78
Network Load Share............................................................................................................................79
Configurable Protection .......................................................................................................................79
Alarms..................................................................................................................................................80
Real-Time Clock ..................................................................................................................................83
Auto Export Metering...............................................................................................................................84
Event Recorder..........................................................................................................................................85
Sequence-of-Events Recording ..............................................................................................................85
Data Logging...........................................................................................................................................85
Setup....................................................................................................................................................86
Triggers................................................................................................................................................86
Trending ..................................................................................................................................................89
Power System Stabilizer...........................................................................................................................91
Supervisory Function and Setting Groups...............................................................................................91
Supervisory Function...........................................................................................................................91
Setting Groups.....................................................................................................................................91
Theory of Operation.................................................................................................................................91
Speed Signal........................................................................................................................................93
Rotor Frequency Calculation...............................................................................................................93
Generator Electrical Power Signal.......................................................................................................93
Derived Mechanical Power Signal.......................................................................................................94
Stabilizing Signal Selection..................................................................................................................94
Torsional Filters ...................................................................................................................................95
Phase Compensation ..........................................................................................................................95
Washout Filter and Logic Limiter.........................................................................................................95
Output Stage........................................................................................................................................96
Terminal Voltage Limiter......................................................................................................................96
Stability Tuning .......................................................................................................................................101
AVR Mode .............................................................................................................................................101
Predefined Stability Settings..............................................................................................................101

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Contents DECS-250
Custom Stability Settings...................................................................................................................101
Auto Tuning........................................................................................................................................103
FCR and FVR Modes............................................................................................................................104
FCR Mode Stability Settings..............................................................................................................104
FVR Mode Stability Settings..............................................................................................................105
Other Modes and Functions..................................................................................................................106
Var Mode ...........................................................................................................................................106
Power Factor Mode............................................................................................................................106
Overexcitation Limiter (OEL) .............................................................................................................106
Underexcitation Limiter (UEL)............................................................................................................106
Stator Current Limiter (SCL)..............................................................................................................106
Var Limiter..........................................................................................................................................106
Voltage Matching...............................................................................................................................106
Mounting..................................................................................................................................................109
Mounting Considerations.......................................................................................................................109
Projection Mounting...............................................................................................................................109
Behind-the-Panel Mounting...................................................................................................................109
Terminals and Connectors.....................................................................................................................113
Overview................................................................................................................................................113
Terminal Types......................................................................................................................................117
Typical Connections...............................................................................................................................119
BESTCOMSPlus®Software.....................................................................................................................123
General Description...............................................................................................................................123
Installation .............................................................................................................................................124
Install BESTCOMSPlus®....................................................................................................................124
Activation of the DECS-250 Plugin for BESTCOMSPlus®.....................................................................124
Connect a USB Cable........................................................................................................................125
Start BESTCOMSPlus®and Activate DECS-250 Plugin Automatically.............................................125
Manual Activation of the DECS-250 Plugin.......................................................................................127
Establishing Communication .............................................................................................................128
Menu Bars .............................................................................................................................................128
Upper Menu Bar (BESTCOMSPlus®Shell) .......................................................................................128
Lower Menu Bar (DECS-250 Plugin).................................................................................................130
Settings Explorer...................................................................................................................................130
Metering Explorer..................................................................................................................................130
Settings File Management.....................................................................................................................131
Opening a Settings File .....................................................................................................................131
Saving a Settings File........................................................................................................................131
Upload Settings and/or Logic to Device ............................................................................................131
Download Settings and Logic from Device........................................................................................131
Printing a Settings File.......................................................................................................................131
Comparing Settings Files...................................................................................................................131
Automatic Metering Export....................................................................................................................133
Firmware Updates.................................................................................................................................133
Upgrading Firmware in Expansion Modules......................................................................................134
Upgrading Firmware in the DECS-250..............................................................................................135
BESTCOMSPlus®Updates....................................................................................................................136
BESTlogic™Plus.....................................................................................................................................137
Introduction............................................................................................................................................137
Overview of BESTlogic™Plus...............................................................................................................137
BESTlogic™Plus Composition ..........................................................................................................138
Logic Schemes......................................................................................................................................152
The Active Logic Scheme..................................................................................................................152
Sending and Retrieving Logic Schemes............................................................................................152
Default Logic Schemes......................................................................................................................153
Programming BESTlogic™Plus ............................................................................................................156

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DECS-250 Contents
Pickup and Dropout Timers ...............................................................................................................157
Offline Logic Simulator ..........................................................................................................................158
BESTlogic™Plus File Management ......................................................................................................158
Saving a BESTlogicPlus File.............................................................................................................159
Opening a BESTlogicPlus File...........................................................................................................159
Protecting a BESTlogicPlus File........................................................................................................159
Uploading a BESTlogicPlus File........................................................................................................159
Downloading a BESTlogicPlus File ...................................................................................................159
Copying and Renaming Preprogrammed Logic Schemes ................................................................159
Printing a BESTlogicPlus File............................................................................................................159
Clearing the On-Screen Logic Diagram.............................................................................................160
BESTlogic™Plus Examples ..................................................................................................................160
Example 1 - GOVR Logic Block Connections ...................................................................................160
Example 2 - AND Gate Connections.................................................................................................160
Communication.......................................................................................................................................161
Local Communication............................................................................................................................161
Communication with a Second DECS...................................................................................................161
Modbus™Communication.....................................................................................................................162
RS-485 Port .......................................................................................................................................162
Ethernet Port......................................................................................................................................163
CAN Communication.............................................................................................................................163
Connections.......................................................................................................................................164
Port Configuration..............................................................................................................................164
Remote Module Setup.......................................................................................................................164
Ethernet Communication.......................................................................................................................165
Ethernet Connection..........................................................................................................................165
PROFIBUS Communication..................................................................................................................168
Configuration...........................................................................................................................................169
Generator, Field, and Bus Ratings........................................................................................................169
Bridge ....................................................................................................................................................170
Sensing Transformer Ratings and Configuration..................................................................................170
Generator PT.....................................................................................................................................171
Generator CTs ...................................................................................................................................171
Bus PT ...............................................................................................................................................171
Startup Functions ..................................................................................................................................171
Soft Start............................................................................................................................................172
Field Flashing.....................................................................................................................................172
Device Information.................................................................................................................................172
Firmware and Product Information ....................................................................................................173
Device Identification...........................................................................................................................173
Display Units..........................................................................................................................................174
Security....................................................................................................................................................175
Password Access..................................................................................................................................175
Password Creation and Configuration...............................................................................................175
Port Security..........................................................................................................................................176
Port Access Configuration .................................................................................................................176
Login and Access Controls....................................................................................................................177
Access Timeout .................................................................................................................................177
Login Failure......................................................................................................................................177
Timekeeping ............................................................................................................................................179
Time and Date Format...........................................................................................................................179
Daylight Saving Time Adjustments........................................................................................................179
Network Time Protocol (NTP) ...............................................................................................................179
NTP Settings......................................................................................................................................179
IRIG .......................................................................................................................................................179

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Contents DECS-250
Testing......................................................................................................................................................183
Real-Time Metering Analysis ................................................................................................................183
Graph Parameters .............................................................................................................................184
Frequency Response ............................................................................................................................185
Test Mode..........................................................................................................................................185
Bode Plotting......................................................................................................................................185
Transfer Function...............................................................................................................................185
Frequency Response.........................................................................................................................186
Time Response .....................................................................................................................................186
Signal Input........................................................................................................................................187
Test Signal Characteristics................................................................................................................187
Step Response Analysis........................................................................................................................188
AVR, FCR, and FVR Tabs.................................................................................................................188
Var and PF Tabs................................................................................................................................189
Analysis Options....................................................................................................................................189
Layout Tab.........................................................................................................................................189
Graph Display Tab.............................................................................................................................190
CAN Communication..............................................................................................................................191
Introduction............................................................................................................................................191
CAN Parameters ...................................................................................................................................191
Diagnostic Trouble Codes (DTCs).....................................................................................................193
Modbus™Communication......................................................................................................................195
Introduction............................................................................................................................................195
Message Structure.............................................................................................................................195
Modbus Modes of Operation.................................................................................................................196
Modbus™Over Serial Line.................................................................................................................196
Modbus on TCP/IP.............................................................................................................................197
Error Handling and Exception Responses.........................................................................................198
DECS-250 Modbus™via Ethernet.....................................................................................................198
Detailed Message Query and Response for RTU Transmission Mode ................................................199
Read Holding Registers.....................................................................................................................199
Return Query Data.............................................................................................................................199
Restart Communications Option........................................................................................................200
Listen Only Mode...............................................................................................................................200
Preset Multiple Registers...................................................................................................................200
Preset Single Register.......................................................................................................................201
Data Formats.........................................................................................................................................202
Floating Point Data Format (Float) ....................................................................................................202
Long Integer Data Format (Uint32)....................................................................................................202
Integer Data Format (Uint16) or Bit-Mapped Variables in Uint16 Format.........................................203
Short Integer Data Format/Byte Character Data Format (Uint8).......................................................203
String Data Format (String)................................................................................................................203
CRC Error Check...............................................................................................................................204
Secure DECS-250 Login via Modbus....................................................................................................204
Modbus Parameters..............................................................................................................................204
General ..............................................................................................................................................204
Security..............................................................................................................................................205
Binary Points......................................................................................................................................205
Metering.............................................................................................................................................214
Limiters ..............................................................................................................................................219
Setpoints............................................................................................................................................222
Global Settings...................................................................................................................................223
Relay Settings....................................................................................................................................225
Protection Settings.............................................................................................................................226
Gains Settings....................................................................................................................................228
Legacy Modbus..................................................................................................................................229

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DECS-250 Contents
PROFIBUS Communication ...................................................................................................................237
Data Types ............................................................................................................................................237
Float/UINT32......................................................................................................................................237
UINT8.................................................................................................................................................237
Setup .....................................................................................................................................................239
PROFIBUS Parameters.........................................................................................................................240
Maintenance ............................................................................................................................................285
Storage..................................................................................................................................................285
Preventive Maintenance........................................................................................................................285
Connections.......................................................................................................................................285
Electrolytic Capacitors .......................................................................................................................285
Cleaning the Front Panel.......................................................................................................................286
Troubleshooting.....................................................................................................................................286
DECS-250 Appears Inoperative ........................................................................................................286
Display Blank or Frozen.....................................................................................................................286
Generator Voltage Does Not Build ....................................................................................................286
Low Generator Voltage in AVR Mode................................................................................................286
High Generator Voltage in AVR Mode...............................................................................................287
Generator Voltage Unstable (Hunting) ..............................................................................................287
Protection or Limit Annunciation........................................................................................................287
HMI Meter Readings Incorrect...........................................................................................................287
No Communication ............................................................................................................................287
DECS-250 Reboots Frequently .........................................................................................................287
Support..................................................................................................................................................287
Specifications..........................................................................................................................................289
Operating Power....................................................................................................................................289
Control Power........................................................................................................................................289
Style LXXXXXX..................................................................................................................................289
Style CXXXXXX.................................................................................................................................290
Terminals ...........................................................................................................................................290
Generator and Bus Voltage Sensing.....................................................................................................290
Terminals ...........................................................................................................................................290
50 Hz Sensing Voltage Nominal Input, Range ..................................................................................290
60 Hz Sensing Voltage Nominal Input, Range ..................................................................................290
Generator Current Sensing ...................................................................................................................290
Terminals ...........................................................................................................................................290
Accessory Inputs...................................................................................................................................291
Current Input......................................................................................................................................291
Voltage Input......................................................................................................................................291
Contact Inputs .......................................................................................................................................291
Terminals ...........................................................................................................................................291
Communication Ports............................................................................................................................291
Universal Serial Bus (USB)................................................................................................................291
RS-232...............................................................................................................................................291
RS-485...............................................................................................................................................292
Ethernet .............................................................................................................................................292
Controller Area Network (CAN) .........................................................................................................292
IRIG Time Synchronization Input ..........................................................................................................292
Contact Outputs.....................................................................................................................................292
Field Power Output................................................................................................................................293
Minimum 10-Second Forcing Output Rating .....................................................................................293
Minimum Field Resistance.................................................................................................................293
Regulation .............................................................................................................................................293
FCR Operating Mode.........................................................................................................................293
FVR Operating Mode.........................................................................................................................293
AVR Operating Mode.........................................................................................................................293
Var Operating Mode...........................................................................................................................293

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Contents DECS-250
Power Factor Operating Mode...........................................................................................................293
Parallel Compensation ..........................................................................................................................294
Setpoint Range..................................................................................................................................294
Generator Protection Functions ............................................................................................................294
Overvoltage (59) and Undervoltage (27)...........................................................................................294
Loss of Sensing .................................................................................................................................294
Overfrequency (81O) and Underfrequency (81U).............................................................................294
Reverse Power (32R) ........................................................................................................................295
Loss of Excitation (40Q) ....................................................................................................................295
Field Protection Functions.....................................................................................................................295
Field Overvoltage...............................................................................................................................295
Field Overcurrent...............................................................................................................................295
Loss of PMG ......................................................................................................................................295
Exciter Diode Monitor (EDM).............................................................................................................295
Synchronism Check (25) Protection......................................................................................................296
Voltage Difference .............................................................................................................................296
Slip Angle...........................................................................................................................................296
Slip Frequency...................................................................................................................................296
Startup...................................................................................................................................................296
Soft Start Level ..................................................................................................................................296
Soft Start Time...................................................................................................................................296
Field Flash Dropout Level..................................................................................................................296
Maximum Field Flash Time................................................................................................................296
Voltage Matching...................................................................................................................................296
On-Line Overexcitation Limiting............................................................................................................297
High Current Level.............................................................................................................................297
Medium Current Level .......................................................................................................................297
Low Current Level..............................................................................................................................297
Off-Line Overexcitation Limiting ............................................................................................................297
High Current Level.............................................................................................................................297
Low Current Level..............................................................................................................................297
Sequence of Events Recording (SER)..................................................................................................297
Data Logging (Oscillography)................................................................................................................297
Environment ..........................................................................................................................................298
Temperature ......................................................................................................................................298
Humidity.............................................................................................................................................298
Salt Fog..............................................................................................................................................298
Type Tests.............................................................................................................................................298
Shock.................................................................................................................................................298
Vibration.............................................................................................................................................298
Impulse ..............................................................................................................................................298
Transients ..........................................................................................................................................298
Static Discharge.................................................................................................................................298
Radio Interference .............................................................................................................................298
HALT (Highly Accelerated Life Testing) ............................................................................................298
Patent ....................................................................................................................................................298
Physical .................................................................................................................................................299
Regulatory Standards............................................................................................................................299
Maritime Recognition.........................................................................................................................299
UL Approval.......................................................................................................................................299
CSA Certification................................................................................................................................299
CE Compliance..................................................................................................................................299
EAC Mark (Eurasian Conformity) ......................................................................................................299
Analog Expansion Module.....................................................................................................................301
General Information...............................................................................................................................301
Features ................................................................................................................................................301
Specifications ........................................................................................................................................301
Operating Power................................................................................................................................301

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DECS-250 Contents
Analog Inputs.....................................................................................................................................301
RTD Inputs.........................................................................................................................................301
Thermocouple Inputs.........................................................................................................................301
Analog Outputs..................................................................................................................................301
Communication Interface...................................................................................................................302
Type Tests.........................................................................................................................................302
Environment.......................................................................................................................................302
UL Approval.......................................................................................................................................302
CSA Certification................................................................................................................................302
CE Compliance..................................................................................................................................303
Physical..............................................................................................................................................303
Installation .............................................................................................................................................303
Mounting ............................................................................................................................................303
Connections.......................................................................................................................................304
Communications....................................................................................................................................310
Functional Description...........................................................................................................................310
Analog Inputs.....................................................................................................................................310
RTD Inputs.........................................................................................................................................311
Thermocouple Inputs.........................................................................................................................312
Analog Outputs..................................................................................................................................313
Metering.................................................................................................................................................314
Analog Inputs.....................................................................................................................................314
RTD Inputs.........................................................................................................................................315
Thermocouple Inputs.........................................................................................................................315
Analog Input Values...........................................................................................................................315
Analog Outputs..................................................................................................................................317
Maintenance..........................................................................................................................................317
Firmware Updates.................................................................................................................................317
Contact Expansion Module....................................................................................................................319
General Information...............................................................................................................................319
Features ................................................................................................................................................319
Specifications ........................................................................................................................................319
Operating Power................................................................................................................................319
Contact Inputs....................................................................................................................................319
Contact Outputs.................................................................................................................................319
Communication Interface...................................................................................................................319
Type Tests.........................................................................................................................................319
Environment.......................................................................................................................................320
UL Approval (CEM-2020 and CEM-2020H) ......................................................................................320
CSA Certification................................................................................................................................320
CE Compliance..................................................................................................................................320
Physical..............................................................................................................................................321
Installation .............................................................................................................................................321
Mounting ............................................................................................................................................321
Connections.......................................................................................................................................323
Communications....................................................................................................................................328
Functional Description...........................................................................................................................328
Contact Inputs....................................................................................................................................328
Contact Outputs.................................................................................................................................329
Metering.................................................................................................................................................330
Contact Inputs....................................................................................................................................330
Contact Outputs.................................................................................................................................330
Maintenance..........................................................................................................................................330
Firmware Updates.................................................................................................................................330
Revision History......................................................................................................................................331

xiv 9440300990 Rev J
Contents DECS-250

9440300990 Rev J 1
DECS-250 Introduction
Introduction
DECS-250 Digital Excitation Control Systems offer precise excitation control and machine protection in a
compact package. DECS-250 adaptability to many applications is assured through configurable contact
inputs and outputs, flexible communication capabilities, and programmable logic implemented with the
provided BESTCOMSPlus®software.
Features and Functions
DECS-250 features and functions include:
•Precise excitation control for synchronous generator or synchronous motor applications
oPower factor and var metering values will be opposite in motor mode
•Five excitation control modes:
oAutomatic Voltage Regulation (AVR)
oField Current Regulation (FCR)
oField Voltage Regulation (FVR)
oPower Factor Regulation (PF)
oVar Regulation (var)
•Three pre-position setpoints for each excitation control mode
•Internal tracking between operating mode setpoints and external tracking of a second DECS
excitation setpoint
•Two PID stability groups with Auto Tune feature
•Remote setpoint control input accepts analog voltage or current control signal
•Real-time metering
•Optional automatic synchronizer
•Optional integrated power system stabilizer (PSS)
oGenerator or motor control modes, accommodates phase rotation changes between
modes
oSpeed and power sensing or speed-only sensing
oTwo wattmeter or three-wattmeter methods of power measurement
•Soft start and voltage buildup control
•Five limiting functions:
oOverexcitation: summing point and takeover
oUnderexcitation
oStator current
oReactive power (var)
oUnderfrequency
•Twenty protection functions:
oGenerator undervoltage (27)
oGenerator overvoltage (59)
oLoss of sensing (LOS)
oOverfrequency (81O)
oUnderfrequency (81U)
oReverse power (32R)
oLoss of excitation (40Q)
oField overvoltage
oField overcurrent
oLoss of PMG
oExciter diode failure
oSync-check (25)
oEight configurable protection elements
•IRIG or network time synchronization
•Sixteen contact sensing inputs
oTwo fixed-function inputs: Start and Stop
oFourteen programmable inputs

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Introduction DECS-250
•Twelve contact outputs
oOne, fixed-function output: Watchdog (SPDT configuration)
oEleven programmable outputs
•Flexible communication
oSerial communication through front-panel USB port
oModbus communication through RS-485 port or Modbus TCP
oEthernet communication through an optional copper or fiber optic port
oCAN communication with an ECU (engine control unit), optional AEM-2020 Analog
Expansion Module, or optional CEM-2020 Contact Expansion Module
oOptional PROFIBUS communication protocol
•Data logging, sequence of events recording, and trending
•Optional CEM-2020 Contact Expansion Module provides:
oTen contact inputs
oEighteen contact outputs (CEM-2020H) or 24 contact outputs (CEM-2020)
oCustomizable input and output functions assigned through BESTlogic™Plus
programmable logic
oCommunication via CAN protocol
•Optional AEM-2020 Analog Expansion Module provides:
oEight analog inputs
oEight resistive thermocouple device (RTD) inputs
oTwo thermocouple inputs
oFour analog outputs
oCustomizable input and output functions assigned through BESTlogicPlus programmable
logic
oCommunication via CAN protocol
Applications
The DECS-250 is intended for synchronous generator or synchronous motor applications. The DECS-250
controls the machine output through the application of regulated DC excitation power to the exciter field.
The level of excitation power is based on the monitored voltage and current, and a regulation setpoint
established by the user. The operating mode, generator or motor, is changed on the Operating Mode
settings screen. Power factor and var metering values will be opposite in motor mode.
Excitation power is supplied from the DECS-250 by means of a filtered, switching power module that uses
pulse-width modulation. It is capable of supplying 15 Adc continuously at a nominal voltage of 32, 63, or
125 Vdc. With nominal operating power applied, it has a forcing capability of 30 Adc for 10 seconds.
Package
A single, compact package contains all excitation control and power components.
A front panel HMI provides local annunciation and control through a backlit liquid crystal display (LCD),
light-emitting diodes (LEDs), and pushbuttons. Remote annunciation and control is provided through a
flexible communication interface which accommodates Ethernet, Modbus, optional PROFIBUS, and the
optional Interactive Display Panel (IDP-800).
Optional Features and Capabilities
DECS-250 optional features and capabilities are defined by a combination of letters and numbers that
make up the style number. The model number and style number describe options and characteristics in a
specific device and appear on a label affixed to the device.

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DECS-250 Introduction
Style Number
The style number identification chart in Figure 1 defines the electrical characteristics and operational
features available in the DECS-250.
Figure 1. DECS-250 Style Chart
Storage
If a DECS-250 will not be placed in service right away, store it in the original shipping carton in a
moisture- and dust-free environment. The temperature of the storage environment must be within the
range of –40 to 85°C (–40 to 185°F).
Electrolytic Capacitor Considerations
The DECS-250 contains long-life aluminum electrolytic capacitors. For a DECS-250 kept in storage as a
spare, the life of these capacitors can be maximized by energizing the device for 30 minutes once per
year. Refer to the energizing procedures provided in Maintenance.
When energizing the DECS-250 from a low impedance source (such as a wall outlet), use of an Inrush
Current Reduction Module (ICRM) is recommended to prevent damage to the DECS-250. For a detailed
description of the Inrush Current Reduction Module, refer to Basler publication 9387900990. ICRM
connections are illustrated in Typical Connections.

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Introduction DECS-250