DECS-400 Digital Excitation Control System
4
SPECIFICATIONS, continued
IRIG-B Time Sync
Standard:
200-98, Format B002, Demodulated (dc level-shifted digital signal) or NTP via Ethernet
Regulation Accuracy
AVR Mode
Voltage regulation ±0.2% over the load range, at rated power factor and constant generator
frequency. Steady state stability is ±0.1% at constant load and frequency. Temperature
Stability ±0.5% between 0 to 50°C at constant load and frequency. Response Time <1
cycle.
FCR Mode
Field Current Regulation is ±1.% of the nominal value for 10% of the rectifier bridge input
voltage change or 20% of the field resistance change. Otherwise, ±5.0%.
VAR Control Mode
Reactive Power Regulation is ±2.0% of the nominal VA rating at the rated frequency.
PF Control Mode
±0.02 Power Factor for real power between 10 and 100% at rated frequency.
(e.g. set point PF = 0.8, PF regulation is between 0.78 and 0.82)
Metering Accuracy
Generator and Bus Voltage:
±1.0%
Generator and Bus Frequency: ±0.1 Hz
Generator Line Current:
±1.0%
Power Factor:
±0.02 PF
Field Current and Voltage:
±2.0%
Aux. Voltage and Current Input: ±1.0%
Generator Power:
Apparent Power (VA) ±2.0%; Active Power (W) ±2.0%; Reactive Power (var) ±2.0%
Power System Stabilizer (PSS)
Operating Mode:
Generator or Motor, ABC or ACB phase sequence
Sensing Configuration: Power and Speed or Speed only
Power Measurement:
2 wattmeter method
Frequency Range:
Responds to power oscillations from 0.1 to 5 Hz. Low-pass and high-pass
filtering prevents unwanted PSS action outside this range.
Soft Start
Two sets of soft start settings are available when operating in AVR or FCR mode. Bias level is adjust-
able from 0-90% in 1% increments; time to reach nominal value is adjustable from 1-7,200 s in 1 s increments.
Sequence of Events Recording
Events are time- and date-stamped and stored in volatile memory. 127 event
capacity, 50 ms scan interval. SER can be triggered by input/output status changes, alarms, or system operating
status changes.
Data Logging (Oscillography)
Stores 6 records, with up to 6 variables per record. Sampling rate: 600 data
points per record, pre-trigger adjustable from 0 to 599 data points. Record interval adjustable from 4 ms to 10 s.
Trending
Stores 1 record, with up to 6 variables per record. Sampling rate is 1200 data points per record, with
total record duration adjustable from 1 hour to 30 days.
Paralleling/Line Drop Compensation
Can use either reactive droop or reactive differential (cross-current)
compensation. Droop adjustable from 0% to 30% in 0.1% increments. Parallel compensation burden is less than 1
VA. Negative droop settings provide line drop compensation. Adjustable from -30% to 0% in 0.1% increments.
Limiters
Underfrequency Compensation
Choice: Underfrequency compensation with slope adjustable from 0 to 3.00 PU in
.01 PU increments and knee frequency between 15 and 90 Hz, or Volts/Hertz ratio limiter with slope adjustable
from 0 to 3.0 PU in 0.1 PU increments. Provisions for two levels of protection, with duration of high V/Hz limit
adjustable in the range of 0 to 10 s.
Overexcitation
On-line and off-line limiters provided, each a choice between summing point and takeover type
controllers. Dual settings groups. Provisions to scale settings for both type limiters based on an auxiliary analog
input (by others) representing air temperature, hydrogen pressure, etc. Includes a cooldown feature to prohibit
repeated high forcing level operation that could be damaging to the rotor.