Digital Excitation Control System (DECS-400)

The DECS-400 is a microprocessor-based controller that provides excitation control, flexible logic control, and optional power system stabilization for synchronous machines in an integrated package. The controller provides an analog output to control the firing of external bridge(s) and monitors machine parameters to control, limit, and protect the synchronous machine from operating beyond its capability limitations.

The optional power system stabilizer function is an IEEE-type PSS2A, dual input, "integral of accelerating power" stabilizer that provides supplementary damping for low-frequency local mode, inter area, and inter unit power system oscillations.

Other features include:

• Five Control Modes, with autotracking between modes
  - Automatic Voltage Regulation (AVR)
  - Field Current Regulation (FCR)
  - Power Factor (PF)
  - Field Voltage Regulation (FVR)
  - Var Control
• 0.20% Voltage Regulation Accuracy
• Two pre-position set points for each mode
• Two Programmable Analog Outputs
• Setup from Front Panel HMI or by PC (local or remote)
• 40 Standard Stability Settings
• Time synchronization using IRIG or NTP (via Ethernet)
• Optional Integral Power System Stabilizer
  - Dual input, integral of accelerating power (IEEE PSS2A/2B)
  - Customer selectable speed-only sensing
  - Two wattmeter power measurement
  - Optional Frequency Based Operation
  - Generator or Motor control modes
• Customizable Stability Setting with two PID setting groups
• Reactive Droop, Line Drop Compensation
• Generator Voltage Soft-Start during Buildup
• Real Time Metering for 19 Generator Parameters
• Voltage Matching
• Autotracking with Optional Backup DECS-400
• Flexible Remote Set point Control
  - Contact inputs
  - Proportional Analog input, 10 Vdc or 4-20 mA
  - Digital Communications
• Local RS-232, ASCII, Modem Capabilities
• RS-485, Modbus™, RJ-45 Ethernet
• Built-in limiting functions
  - Overexcitation Limiters - Summing Point or Takeover Type
  - Underexcitation Limiters - 5 point user programmable or internally generated, summing point or takeover
  - Dual Slope Voltz/Hz Ratio or Underfrequency Limiter
  - Stator Current Limiter (single phase or three phase)
• Built-in Protective Functions
  - Field Overvoltage and Overcurrent
  - Generator Undervoltage and Overvoltage
  - Loss of Sensing Voltage
  - Loss of Field (40Q)
  - Field Overtemperature (for main field)
  - Dual Slope Volts/Hertz (24)
  - Exciter Diode Failure (for brushless exciters)
  - Generator Frequency less than 10 Hz
• Setup and initial operation are facilitated by BESTCOMS, which offers:
  -real time monitoring test analysis
  -flexible oscillography, trending
  -expanded testing capabilities, including means for performing frequency response tests
• Sixteen Contact inputs - 10 user-programmable
• Eight Contact Outputs - 6 user-programmable
• Metering - Two 4-20mA meter drivers, customer programmable
• Four Communication Ports
• Data Logging, Sequence of Events Recording, Trending, real time monitoring test analysis, and built-in frequency response test capabilities
• UL Recognized, CSA certified, CE Compliant, GOST-R certified per the relevant standards of Gosstandart of Russia, Byelorussian certified

Download Bulletin SZF for more information.