DECS-400 Digital Excitation Control System
5
Off-Line
Level One – Highest current level set point adjustable from 0 to 11,999Adc in 0.1% increments of
the rated field current. Limiting occurs for a time period ranging from 0 to 60 seconds, settable in
1 second increments.
Level Two – Lowest current level set point adjustable from 0 to 11,999Adc in 0.1% increments of
the rated field current. Limiting occurs indefinitely.
Takeover Type OEL
The Takeover OEL uses an I
2
t characteristic. Limiter response time is less than three
cycles.
On-Line
High Level – High current level (instantaneous) set point is adjustable from 0 to 11,999 Adc in 0.1
Adc increments.
Low Level – Low current set point is adjustable from 0 to11,999 Adc in 0.1 Adc increments.
Limiting 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 11,999 Adc in 0.1
Adc increments.
Low Level – Low current set point is adjustable from 0 to 11,999 Adc in 0.1 Adc increments.
Limiting occurs indefinitely.
Time Dial – This setting determines the inverse time curve selected.
Underexcitation
Customer selectable summing point type of takeover type limiter. The UEL curve can be se-
lected either by specifying acceptable reactive power level at zero active power output, or by
entering a five point UEL characteristic. Dual settings groups available. UEL limiter adjusts
characteristics with changes in terminal voltage.
Stator Current
Single or three phase stator current limiter, adjustable between 100% and 300% of nominal
generator output current. Includes a two-step limiter with a definite time delay for the higher limit
level, adjustable between 0 and 60 s. Summing point type limiter with PI control loop.
Protection Functions
Field Overvoltage
Range 1 to 2000 Vdc, time delay 0.2 to 30 s, dual setting groups
Field Overcurrent
Range from 0.1 to 9,999 Adc, time delay 0.1 to 20 s, dual setting groups
Generator Undervoltage
Range from 0 to 34,500 Vac, time delay 0.5 to 60 s, dual setting groups
Generator Overvoltage
Range from 0 to 34,500 Vac, time delay 0.1 to 60 s, dual setting groups
Loss of Sensing Voltage
Pickup level 0 to 100% with balanced or unbalanced conditions; time delay 0 to 30s
Generator Frequency
<10 Hertz
Loss of Field (40Q)
Range 0 to 3000 Mvar, time delay 0 to 9.9 s
Field Overtemperature
Calculated from field voltage and current. Setting range from 0 to 572°C, time delay from
0.1 to 60s
Volts per Hertz (24)
Range from 0.5 to 6 V/Hz, integrating reset range 0 to 9.9 V/Hz
Exciter Diode Failure
Shorted and/or Open; Exciter to Stator Poles Ratio less than or equal to 10, generator
frequency range 40 to 70 Hz (for brushless exciter applications)
SPECIFICATIONS, continued
Summing Point Type OEL
Limiter response time is less than three cycles.
On-Line
Level One – Highest current level (instantaneous) set point adjustable from 0 to 11,999Adc in
0.1% increments of the rated field current. Limiting occurs for a time period ranging from 0 to 60
seconds, settable in 1 second increments.
Level Two – Medium current level set point adjustable from 0 to 11,999Adc in 0.1% increments of
the rated field current. Limiting occurs for a time period ranging from 0 to 120 seconds, settable
in 1 second increments.
Level Three – Lowest current level set point adjustable from 0 to 11,999Adc in 0.1% increments
of the rated field current. Limiting occurs indefinitely.
