Basler ElectricDECS-200-1C Digital Excitation Control System

One DECS-200 Digital Excitation Control System can accommodate 32Vdc, 63Vdc, or 125Vdc applications up to 15Adc. This unique flexibility provides precision control of generators of virtually any size. The DECS-200 also incorporates a pulse width modulated power stage, which improves system performances in non-linear load applications.

FEATURES

• Microprocessor-based design

• True RMS sensing, single or three phase

• 32Vdc, 63Vdc, and 125Vdc outputs at 15Adc

• 0.25% Voltage Regulation Accuracy

• Setup from front panel HMI or by PC with Windows® setup software included

• 20 standard stability selections

• User customizable stability selection

• Paralleling compensation

• Underfrequency compensation or V/Hz Ratio Limiter

• Soft start buildup

• Field Current Regulation Mode (Manual Mode)

• Autotracking between operating modes and between DECS-200 units

(optional)

• Minimum Excitation Limiter (Internally generated or customizable)

• On and off-line Maximum Excitation Limiters

• Stator Current Limiter

• Var and Power Factor Controllers

• Exciter Diode Monitoring (EDM)

• Sequence of Events Recording

• Oscillography

FEATURES, continued

• Voltage Matching

• Eight (8) generator protection features

• Programmable output contacts

• Front panel backlit LCD display

• Front panel mounted RS-232 and side RS-485

communications ports

• Modbus™ protocol for RS-485 input allows

communications up to 4000 feet away

• <1% metering accuracy for 12 generator parameters

• Remote set point control via:

- Contact inputs

- Proportional control via ±10Vdc or 4-20mA

- Communications inputs RS-232 (ASCII) or RS-485

 (Modbus™)

• Meets C37.90.1-1989 for Surge Withstand and Fast

Transient

• UL recognized, CSA certified, CE compliant, DNV

certified, GOST-R certified, Byelorussian certified

• U.S. Patent Number 5,294,879

DESCRIPTION

The microprocessor based DECS-200 is a total excitation control system in one enclosure. It contains all the

functionality necessary to limit, control, and protect a

generator from operating outside of the machine's

capability. A feature of DECS-200's sophisticated

design allows the nonactive control mode within the

unit to follow the active mode, permitting bumpless

transfer between modes. The optional external tracking

feature also allows for unit-to-unit communication,

permitting autofollowing and transfer between DECS200 units. It can also communicate to a PC via the front

panel RS-232 port for local programming and metering,

and it can communicate via Modbus™ protocol via the

side RS-485 port for communications up to 4000 feet

away from the DECS-200 unit. The DECS-200 has all

the features, functionality, flexibility and programmability expected from a state-of-the-art microprocessor

based product.

APPLICATIONS

The DECS-200 is an excitation control system used to control the output voltage, vars or power factor of a

synchronous generator by varying or controlling the amount of dc excitation applied to the generator's exciter

field. The DECS-200 is suitable for virtually any size machine

SPECIFICATIONS, continued

Generator Current Sensing Two ac current sensing ranges and two channel (phase) inputs:

• For metering and control: 1A and 5A.

• For cross current compensation: 1A and 5A.

Sensing Burden Voltage: Less than 1VA per phase.

Current: Less than 1VA.

Parallel Compensation: Less than 1VA.

Contact Switching Inputs 11 contact switching inputs are supplied with 24Vdc to accommodate dry

contacts. Contacts are as follows:

• Start • Var/PF Enable

• Stop • Pre-position

• Secondary DECS Enabled (optional) • Raise Switch

• Unit/Parallel Operation • Lower Switch

• AVR Mode • Alarm Rest

• FCR Mode

Remote Set Point Control Two separate analog inputs for remote set point control. Typically used to accept

(Accessory Input) a signal from a Power System Stabilizer. Select one from the configuration menu.

• ±10Vdc

• 4 to 20 milliamperes

COMMUNICATION There are three communication ports, two RS-232 and one RS-485: COM0: RS-232, 9 pin, sub-D connector located on front panel and used to communicate with local computers. 1200 to 19200 baud, 8N1 full duplex, ASCII commands COM1: RS-232, 9 pin, sub-D connector located on right side panel and used to connect primary and backup DECS-200 units. Port is only used for optional autotracking. COM2: RS-485, located on left side panel and used to communicate with local or remote computers or other devices. 1200 to 19200 baud, 8N1 half duplex, Modbus™ protocol

SPECIFICATIONS, continued

REGULATION ACCURACY

AVR Mode: Voltage regulation equals ±0.25% over the load range at rated power factor and constant

generator frequency. Steady state stability equals ±0.1% at a constant load and generator frequency.

Temperature drift equals ±0.5% for 0 to 50°C temperature change. Underfrequency (volts/hertz)

characteristic slope from 0 to 3.0 P.U. is adjustable in 0.1 P.U. increments.

FCR Mode: Field current regulation equals ±1.0% of the nominal value for 10% of the bridge input voltage

change or 20% of the field resistance change.

var Mode: ±2.0% of the nominal VA rating at the rated frequency.

PF Mode: ±0.02 PF in the set point PF for the real power between 10 and 100% at the rated frequency.

(e.g. -set point PF=0.80, PF regulation is from 0.78 to 0.82 PF.)

Internal autotracking(optional): ±0.5% of the nominal field voltage change when transferring.

PARALLEL COMPENSATION Can use either reactive droop or reactive differential (cross-current) compensation. Adjustable from 0 to 30% of the rated generator voltage droop with optional 1 ampere or less or 5 amperes

or less input. Line drop compensation uses this same parameter; however, it is adjustable from -30% to 0.

FIELD OVERVOLTAGE PROTECTION Adjustable in increments of 1.0Vdc from 1.0 to 325Vdc rated output

voltage with a 0.2 to a 0.2 to 30 second inverse time delay settable in increments of 0.1 second.

FIELD OVERCURRENT PROTECTION Adjustable in increments of 0.1Adc steps of rated field current from 0 to

16Adc excitation current setting with an inverse time delay (ANSI C50.13).

EXCITER DIODE MONITOR (EDM) The DECS-200's EDM can detect open and shorted diodes on brushless

generators. To do this, the DECS-200 requires the user to input the number of generator poles and the number of

exciter poles (both adjustable from 0 to 20 in increments of 2). The open and shorted diode ripple threshold is

adjustable from 0 to 100% of field current. The open diode protection time delay is adjustable from 10 to 60

seconds, and the shorted diode protection time delay is adjustable from 5 to 30 seconds.

GENERATOR UNDERVOLTAGE PROTECTION Adjustable in increments of 1Vac from 0 to 30kV sensing voltage

setting with a 0.5 to 60 second time delay (ANSI C50.13) settable in increments of 0.1 sec.

GENERATOR OVERVOLTAGE PROTECTION Adjustable in increments of 1Vac from 0 to 30kV sensing voltage

with a 0.1 to 60 second time delay (ANSI C50.13) settable in increments of 0.1 second.

GENERATOR LOSS OF FIELD PROTECTION Adjustable in increments of 1 kVar from 0 to 3,000Mvar, with a

0.1 to 9.9 second delay settable in increments of 0.1 second.

LOSS OF SENSING The loss of sensing setting for both balanced and unbalanced generator voltage is adjustable from 0 to 100% of nominal generator voltage. The protection delay is adjustable from 0 to 30 seconds in 0.1

increments.

SOFT START Functional in AVR and FCR with an adjustable rate of 1 to 7200 seconds in one second increments.

SUMMING POINT and TAKEOVER TYPE

OVEREXCITATION LIMITING Limiter response time is less than three cycles.

SUMMING POINT TYPE:

On-Line High Current Level (instantaneous) set point adjustable from 0 to 30.0Adc in 0.1Adc increments. Limiting occurs for a time period ranging from 0 to 10 sec., settable in 1 sec. increments.

Medium Current Level set point adjustable from 0 to 20Adc in 0.1Adc increments.

Limiting occurs for a time period ranging from 0 to 120 seconds, settable in 1 sec. increments.

Low Current Level set point adjustable from 0 to 15Adc in 0.1Adc increments. Limiting occurs

SPECIFICATIONS, continued

Off-Line High Current Level (instantaneous) set point adjustable from 0 to 30Adc in 0.1Adc increments.

Limiting occurs for a time period ranging from 0 to 10 seconds, settable in 1 second increments.

Low Current Level set point adjustable from 0 to 15Adc in 0.1Adc increments. Limiting occurs indefinitely.

TAKEOVER TYPE OEL: The Takeover OEL uses an I2

t characteristic.

On-Line High Level: High Current Level (instantaneous) set point is adjustable from 0 to 30.0Adc in 0.1

Adc increments.

Low Level: Low Current set point is adjustable from 0 to 15.0Adc in 0.1Adc increments. Limint

occurs indefinitely.

Time Dial - This setting determines the inverse time curve selected.

Off-Line High Level - High current level (instantaneous) set point is adjustable from 0 to 30.0Adc in

0.1Adc increments.

Low Level - Low current set point is adjustable from 0 to 15.0Adc in 0.1Adc increments. Limiting

occurs indefinitely.

Time Dial - This setting determines the inverse time curve selected.

UNDEREXCITATION LIMITING Adjustments based on generator ratings.

STATOR CURRENT LIMITING

High Level - High current level set point adjustable from 0 to 60,000Aac in 0.1Aac increments.

Limiting occurs for a time period ranging from 0 to 60 seconds, settable in 0.1 sec. increments.

Low Level - Low current level set point adjustable from 0 to 60,000Aac in 0.1Aac increments.

Limiting occurs indefinitely.

SEQUENCE OF EVENT RECORDING (SER) 127 event reports stored in volatile memory (retrievable via

BESTCOMS). SER triggered by: Input/Output status changes, system operating status changes, and alarm annunciations.

OSCILLOGRAPHY Stores 8 records. Up to 6 variables can be logged in a record. Sampling rate: 600 data points

per log, pre-trigger adjustable from 0 to 599 data points, 4ms to 10sec intervals between data points (2.4sec to

6000sec. total log duration)

MANUAL EXCITATION CONTROL Regulates field current from 0 to 15.0A in increments of 0.1Adc.

VOLTAGE MATCHING Matches utility bus RMS voltage with generator output RMS voltage within ±0.15% of

the generator voltage

REAL TIME CLOCK Time displayed in either 12 hour or 24 hour format and can be selected to allow for daylight

savings timer. The date is selectable for two formats: d-m-y or m/d/y. Requires control power to operate. If power is

lost, the clock will need to be reset.

SURGE WITHSTAND CAPABILITY (SWC) IEEE C37.90.1-1989

FAST TRANSIENT IEEE C37.90.1-1989

HIGH POT. IEEE 421.3

ENVIRONMENTAL

Operating temperature: -40°C to +60°C (-40°F to +140°F) Storage temperature: -40°C to +85°C (-40°F to +185°F)

Salt Fog Per MIL-STD-810E, Method 509.3 (100 hrs. of salt fog, 100 hours of drying time)

Shock 15 Gs in each of three mutually perpendicular planes

Vibration 5-26Hz: 1.2Gs; 27-52Hz: 0.914mm (.036 inch) double amplitude; 53-500Hz: 5.0Gs

Size 8.08" (205mm) wide x 6.76" (171mm) deep x 12.0" (304mm) high

Weight 14 lbs. (6.35kg)

AGENCY UL recognized per Std. 508; UL file number E97035; CSA certified per Std. CAN/CSA-C22.2,

Number 14, CSA file number LR23131; CE compliant, EMC and LVD; Certified per DNV

FEATURES/FUNCTIONS

Voltage Regulation

The DECS-200 regulates the generator RMS voltage to within

0.25% from no-load to full-load. It does this by utilizing digital

signal processing and precise regulation algorithms developed

by Basler Electric, utilizing the experience gained in many years

of manufacturing tens of thousands of digital voltage regulators.

Stability

The DECS-200 utilizes proportional (P), integral (I) and derivative

(D) stability control. DECS-200 has 20 preprogrammed stability

(PID) settings for exciter field applications. This means that a

standard stability setting is already available for most applications/machines. The DECS-200 has a stability range that allows

for customizing the stability settings to fine tune the stability to

provide optimum customized generator transient performance.

Setup software contains PID selection program to assist in

determining the correct PID settings. The DECS-200 provides for

customizing the stability and transient performance of the Min/

Max Excitation Limiter and var/PF controllers by providing

additional stability adjustments.

Underfrequency Limiter or V/Hz Ratio Limiter

DECS-200 is selectable for either Underfrequency Limiter or a

V/Hz Ratio Limiter function. The underfrequency limiter slope can

be tuned to have 0 to 3 times p.u. Volts/Hz, in 0.1Hz increments,

and the corner frequency roll-off point can be set across a range

of 45 to 65Hz, in 0.1Hz increments. This adjustability allows the

DECS-200 to precisely match the operating characteristics of the

prime mover and the loads being applied to the generator. The

Volts/Hz Ratio Limiter clamps the regulation set point to prevent

operation above a V/Hz level that is prescribed by the slope of the

DECS-200. This feature is also useful for other potentially

damaging system conditions such as a change in system voltage

and re-duced frequency situations that exceed the V/Hz ratio.

Soft Start Voltage Buildup

Generator voltage overshoot can be harmful to the generator's

insulation system if not controlled. DECS-200 has a soft start

feature with a user-adjustable setting to govern the rate at which

the generator voltage is allowed to build up. This reduces the

amount of generator voltage overshoot form nominal operating

voltage during start-up of the generator system.

Paralleling Compensation

DECS-200 has provisions to parallel two or more generators

using reactive droop or reactive differential compensation with

the addition of an external current transformer with secondary

currents of 1 or 5Aac. The current input is rated at less than 1VA.

This low burden means that existing metering CTs can be used

and dedicated CTs are not required.

Set Point Control

DECS-200 has means for external set point adjustment of the

controlling mode of operation. This eliminates the need for

additional equipment like motor operated potentiometers for

remote control or multiple point control for the excitation system.

The operating mode's set point may be directly controlled by

raise/lower contact inputs or auxiliary inputs of 4-20mA or

±10Vdc. The auxiliary input adjusts the operating mode across its

predetermined adjustment range. The auxiliary input can be

provided from other controlling devices such as a power

system stabilizer. These devices modify the operation of the

DECS-200 to meet specific operating characteristics and requirements for the machine under DECS-200 control. Two more

methods of set point control may be achieved via the RS-232

communication port by using the Windows® based PC software

or by the RS-485 port using Modbus™ protocol. Regardless of

which method of set point is used (contact inputs, auxiliary input

or communications with a PC or PLC), traverse rates of all modes

of operation are independently adjustable. This means an

operator can customize the rate of adjustment and "feel" to meet

his/her needs.

Pre-position Inputs

DECS-200 provides the added flexibility of allowing a predetermined operating point for each mode of operation. With a contact

input to the DECS-200, the operating mode is driven to an

operating or regulation level assigned to that operation mode by

the operator or user. The pre-position inputs operate in one of two

modes, Maintain or Release. The Maintain mode prevents

adjustment of the setpoint as long as the pre-position contact is

closed. The release mode allows adjustment of the setpoint even

though the pre-position is closed. This feature allows the DECS200 to be configured for specific system and application needs.

Field Current Regulation Operating Mode

DECS-200 provides a manual channel of operation called Field

Current Regulation, or FCR, Mode. In this mode, DECS-200

regulates the field current generated by the internal PWM power

stage. It does not rely on the sensing input to DECS-200 and is,

therefore, a good source of backup excitation control when loss

of sensing is detected. In this mode, control of the generator is

totally dependent upon the operator to maintain nominal generator voltage as the load varies on the generator.

Var/Power Factor Controller Operating Mode

DECS-200 has, as another standard feature, two modes of

operation when the generator is in parallel with the utility power

grid. The DECS-200 has both var and PF modes of operation.

When the generator is in parallel with the utility grid, the DECS200 can regulate the var output of the generator to a specific var

level magnitude or it can vary the var output of the generator to

maintain a specific power factor as the kW load varies on the

generator.

Maximum Excitation Limiters

Overexcitation limiting (OEL) operates in all modes except FCR

mode. OEL senses the field current output of the voltage regulator or static exciter and limits the field current to prevent field

overheating. In FCR mode, the DECS-200 only announces that all

conditions for OEL are fulfilled and does not provide limiting. The

DECS-200 provides two types of overexcitation: Summing Point

and Takeover.

Summing Point Type OEL

Three OEL current levels are defined for on-line operation. They

are high, medium, and low. The generator can operate continuously at the low OEL current level and for programmed times at

the high and medium OEL current levels. Two OEL current levels

are defined for off-line (main breaker open) operation. They are

high and low. The generator can operate continuously at the low

OEL current level and for a programmed time at the high OEL

current level.

FEATURES/FUNCTIONS, continued

Takeover Type OEL

The field current level at which limiting occurs is determined by an

inverse time characteristic. Two current levels and a time dial

setting are defined for the takeover-style OEL limiter. Separate

curves may be selected for on-line and off-line operation. If the

system enters an overexcitation condition, the field current is

limited and made to follow the selected curve. The selection of

on-line or off-line OEL levels/curves is determined by an OEL

option selection.

Minimum Excitation Limiter

The minimum excitation limiter limits the amount of excitation

supplied to the field of the generator from dropping below unsafe

operating levels. This prevents the machine from possibly slipping

poles and from damaging the machine. It limits the amount of

vars being absorbed by the machine, based on user-definable

settings. An internally generated Underexcitation Limiting (UEL)

curve can be utilized based on a var level at 0kW, or a

customizable 5 point UEL curve can be selected to match specific

generator characteristics.

Stator Current Limiter

The stator current limiter (SCL) senses the level of stator current

and limits it to prevent stator overheating. The SCL operates in all

modes except FCR. In FCR mode, the DECS-200 only announces

that a stator overcurrent condition exists; it does not provide

current limiting. Two SCL current levels are provided: high and

low. The generator can operate continuously at the low SCL level

but only for a programmed time at the high SCL level.

Internal Autotracking Between DECS-200 Operating

Modes

DECS-200 is an intelligent device that can provide autotracking

(autofollowing) of the controlling mode by the non-controlling

modes. This allows the operator to initiate a controlled, bumpless

transfer of the DECS-200 operating modes, causing minimum

amounts of line disturbance for the power system. This feature

can be used in conjunction with a set of protective relays to

initiate a transfer to a backup mode of operation, such as FCR

mode, upon the detection of a system failure or fault, i.e., loss of

sensing.

External Autotracking between Dual DECS-200 Units

(Optional)

A DECS-200 can also follow (autotrack) a second DECS-200 unit.

The second DECS-200 is put into a specific operating mode and

follows the excitation level of the first. In the unlikely event of a

failure of the first DECS-200, protective relays can initiate a

transfer of control from the first to the second DECS-200.

Protective Functions

There are several protection functions built into the DECS-200

unit. These functions may be used as backup to the primary

protection relays and can be assigned programmable output

contacts via the PC software. The protection features offer fully

adjustable tripping levels and time delays. The protective features

are as follows:

• Generator Overvoltage • Watchdog Timer

• Generator Undervoltage • Loss of Sensing

• Field Overvoltage • Loss of field

• Field Overcurrent • EDM Exciter Diode Monitor

Sequence of Events Recording (SER)

A sequence of event report (SER) is a very powerful tool when

reconstructing the exact timing of an event or disturbance. The

DECS-200 monitors its contact inputs and outputs for a change of

state, system operation changes, and alarm conditions. If any of

these events occurs, the DECS-200 will log that event with a date

and time stamp. Date and time stamping of the event allows the

user to recreate a chain of events in the sequence in which they

occurred. The DECS-200 can store 127 events in volatile

memory, and those events are retrievable using BESTCOMS.

Oscillography (See Figure 6)

The data recording feature can record up to eight (8) oscillographic records stored in volatile memory. The user can select up

to six (6) variables to be monitored when triggered by the DECS200 BESTCOMS, a Logic Trigger, or a Level Trigger. Variables

that can be selected are: generator voltage, current (single

phase), frequency, kW, Power Factor, exciter field voltage, and

current.

The user can utilize the DECS-200 BESTCOMS to trigger and

save a record of a voltage step response during commissioning.

Once commissioned, a logic trigger or level trigger can be used

to activate the data recorder to capture the occurrence for review

at a later time. DECS-200 alarms can also be used to start the

data recorder. When an alarm condition occurs, an oscillographic

record can be stored. A level trigger will initiate a record to be

saved when a variable exceeds a predetermined setting. An

example of this is when the exciter field current exceeds a

predetermined setting.

The oscillographic records are recorded in accordance with the

IEEE Standard Common Format for Transient Data Exchange

(COMTRADE). Basler Electric can provide BESTWAVE, a

COMTRADE viewer, which is a program that will allow the user to

view the oscillography records saved by the DECS-200.

Communications

DECS-200 comes complete with Windows® based PC software.

This software makes the programming and customization of the

DECS-200 easy and fast. The software comes with a PID

selection program that allows the user to select stability settings

quickly and easily in a user-friendly format. The PC software has a

special monitoring function that allows the user to view all

settings, a metering screen for viewing all machine parameters,

and a control screen for remote control of the excitation system.

The RS-485 port supports Modbus™ communications protocol.

This is an open protocol with all registers and operating instructions available in the instruction manual, to make it simple for the

user to develop custom communications-based interface.

Password Protection

All DECS-200 parameters are viewable via the front panel LCD

display, the PC software or via Modbus™ without the need of a

password. If the user wishes to change a setting, the proper

password must be entered to allow access to the parameter. Two

levels of password protection exist, one for global access of all

parameters and one for a limited amount of access to parameters

normally associated with operator control.

FRONT and SIDE PANEL VIEWS

The front panel HMI (Human Machine Interface) is composed of several elements, including a backlit LCD screen, six (6) pushbuttons and six (6) LEDs. The LCD is the primary interface because it conveys the majority of the information between the DECS-200 and the user/operator. Front panel pushbuttons allow the user to view menu screens and modify the various screen settings and operating conditions. The LEDs annunciate their respective states.

A) 64x128 pixel graphic LCD with backlighting. Primary source for receiving information from the DECS or when locally programming settings. Displays operations, set points, loop gains, metering, protection functions, system parameters and general settings. B) Pre-Position LED – Turns ON at the predefined setting (within the limits of the setpoints) of the current mode. C) Lower Limit LED – Turns ON at the minimum set point value of the current (active) mode. D) Upper Limit LED – Turns ON at the maximum set point value of the current mode. E) Scrolling Pushbuttons – Scrolls UP/DOWN/LEFT/RIGHT through the menu tree or when in the EDIT mode, the LEFT/RIGHT scrolling pushbuttons select the variable to change and the UP/DOWN scrolling pushbuttons change the variable. F) Reset Pushbutton – Cancels editing sessions and can be used as a quick-access to the metering screen. G) Serial Port COM0 – D-type 9 pin connector. This port is dedicated to RS-232 (ASCII commands) communication with a computer terminal or PC running a terminal emulation program such as BESTCOMS™. H) Edit Pushbutton – Enables settings changes. When the EDIT pushbutton is first pushed, an LED on the pushbutton turns ON to indicate the edit mode is active. When changes are complete (using the scrolling pushbuttons) and the EDIT pushbutton is pushed again, the LED turns OFF, indicating the changes are saved. If changes are not completed and saved within five minutes, the edit mode is exited without saving changes. I) Null Balance LED – Turns ON when the inactive modes (AVR, FCR, var, or PF) match the active mode. J) Internal tracking LED – All inactive modes (AVR, FCR, var, or PF) track the active mode to accomplish the bumpless transfer when changing active modes.