Basler Electric DECS-400 - Manual (Page 17)

9369700990 Rev R 5
52 L/M contact inputs are closed). In FCR mode, the DECS-400 provides indication that a stator
overcurrent condition exists, but limiter action is inhibited.
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.
Reactive Power Limiter
The var limiter accommodates applications where the prime mover (turbine) has been uprated but the
generator ratings are unchanged. In this case, the generator power factor is increased and the generator
is var limited. The var limiter is available for these applications to limit reactive power flow out of the
generator to a safe level.
Autotracking Between DECS-400 Operating Modes
The DECS-400 can provide autotracking (automatic following) of the controlling mode by the non-
controlling modes. This allows the operator to initiate a controlled, bumpless transfer of the DECS-400
between operating modes with minimal disturbance to 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 (such as loss of sensing).
Autotracking Between DECS-400 Units
The DECS-400 is also designed to automatically track a second DECS-400 unit using dedicated
communication ports on the two units. A backup DECS-400 controller can be placed in service and
programmed to track the control output of the primary DECS-400. In the unlikely event of a failure of the
first DECS-400, protective relays can initiate a transfer of control from the first to the second DECS-400
with minimal system disturbance.
Protective Functions
Protective functions built into the DECS-400 may be used as a backup to the primary protection relays
and can be assigned to as many as six programmable output contacts via BESTCOMS software. The
protective functions offer fully adjustable tripping levels and time delays. DECS-400 protective functions
are listed below. Functions marked with an asterisk (
∗) have dual setting groups.
•
Field overcurrent
∗
•
Field overtemperature
∗
•
Field overvoltage
∗
•
Generator overvoltage
∗
•
Generator undervoltage
∗
•
Loss of field
∗
•
Loss of Field Isolation Module
•
Loss of sensing voltage
•
Microprocessor watchdog
•
Open exciter diode (brushless application)
•
Shorted exciter diode (brushless application)
•
Volts per hertz protection
Programmable Logic
The DECS-400 utilizes programmable logic functionality in the form of multiplexors, AND gates, OR
gates, NOT gates, and timer gates. Inputs to the logic are in the form of discrete information including
switching inputs, system status data, protection status data, limiter status data, alarm status data, and
PSS status data. The outputs of the programmable logic module can be used to control the relay outputs
as well as various other functions inside the DECS-400 such as control functions (start/stop, mode select,
etc.), protection functions (Field Overvoltage Enable, Field Overcurrent Enable, etc.), limiter functions
(OEL enable, UEL enable, etc.), and PSS functions. BESTCOMS provides a tool for customizing the
system control logic for specific applications.
DECS-400 General Information