Basler Electric DECS-400 - Manual (Page 15)

9369700990 Rev R 3
Power System Stabilizer (Style 1XXX)
An optional, integrated PSS duplicates the excellent performance of the Basler PSS-100 power system
stabilizer without the complications of an additional control device. The PSS provides damping for local
mode, inter-area, and inter-unit oscillations in the 0.1 to 5.0 hertz range. The PSS incorporated in the
DECS-400 is a dual-input, IEEE type PSS2A stabilizer that utilizes the “integral of accelerating power”
algorithm. The PSS can also be set up to respond only to frequency if required for unusual applications.
Inputs required for PSS operation include three phase voltages and two or three phase line currents.
Underfrequency Limiter or Volts per Hertz Limiter
An underfrequency limiter or a V/Hz ratio limiter can be selected to avoid overfluxing the generator or
other connected magnetic devices.
The underfrequency limiter slope can be set from 0 to 3 PU V/Hz in 0.1 hertz increments. The frequency
roll-off knee-point can be set across a range of 15 to 90 hertz in 0.1 hertz increments.
The V/Hz ratio limiter regulates voltage based on a user-defined V/Hz slope that is adjustable between
zero and 3.0 PU. The V/Hz ratio limiter includes two limiting levels to permit operation above the primary
V/Hz range for a user-adjustable time limit to inhibit limiter response during transient frequency or voltage
excursions.
Soft-Start Voltage Buildup
A user-adjustable voltage soft-start feature controls the rate of generator voltage buildup and prevents
voltage overshoot during generator system startup. The soft-start feature is active in both AVR and
Manual operating modes.
Reactive Droop and Line Drop Compensation
The DECS-400 has provisions for paralleling two or more generators by using reactive droop. Reactive
differential compensation can be used with the addition of an external current transformer (CT) with a
nominal secondary rating of 1 Aac or 5 Aac. The current input burden is less than 1 VA, so existing
metering CTs can be used. A Line Drop Compensation setting allows the DECS-400 to compensate for
line drop between parallel generators.
Setpoint Control
External adjustment of the active DECS-400 setpoint is possible through:
•
Raise and lower contact inputs
•
An auxiliary analog control input of 4 to 20 mAdc or
±10 Vdc
•
A PC operating BESTCOMS software (provided with the DECS-400) and connected to the RS-
232 communication port
•
A controller using Modbus™ protocol and connected to the RS-485 port
The traverse rates of all operating modes are independently adjustable, so the operator can customize
the rate of adjustment and “feel” to meet his or her needs.
Dual Pre-Position Inputs
Two user-adjustable sets of predetermined operating points are provided for each mode of operation. At
startup, and with the appropriate contact inputs applied to the DECS-400, the operating mode is driven to
one of two preset operating or regulation levels (depending on the configuration of the system). An
adjustable traverse rate setting can be used to control the rate at which the setpoint is driven toward the
pre-position operating point. This feature allows the DECS-400 to be configured for multiple system and
application needs.
Manual Operating Modes
The DECS-400 has two manual modes of operation: Field Current Regulation (FCR) and Field Voltage
Regulation (FVR).
DECS-400 General Information