Basler Electric DECS-250N - Manual (Page 60)

44 9440500990 Rev D
Protection DECS-250N
Generator Overvoltage
An overvoltage pickup condition occurs when the sensed generator terminal voltage increases above the
pickup setting
A . An overvoltage trip condition occurs if the generator voltage remains above the pickup
threshold for the duration of the time delay setting B . Generator overvoltage protection can be enabled and
disabled C without altering the pickup and time delay settings. Overvoltage pickup and trip elements in
BESTlogicPlus can be used in a logic scheme to initiate corrective action in response to the condition.
BESTCOMSPlus generator overvoltage settings are illustrated in Figure 29.
Figure 29. Generator Overvoltage Protection Settings
A Generator Overvoltage Pickup (V): Adjustable from 0 to 600,000 Vac in 1 Vac increments.
B Generator Overvoltage Time Delay (s): Adjustable from 0.1 to 60 seconds in 0.1 second increments.
C Generator Overvoltage Enable/Disable: Select Enabled or Disabled.
Loss of Sensing
The generator voltage is monitored for a loss of sensing (LOS) condition. LOS protection settings are
illustrated in Figure 30.
In the DECS-250N, a loss of sensing event is calculated using sequence components. A loss of sensing
event occurs when the positive sequence voltage drops below the balanced
A setting percentage of the
AVR setpoint, or when the negative sequence voltage increases above the unbalanced B setting
percentage of the positive sequence voltage. A delay timer C is started when the event occurs, delaying
the alarm by a predetermined time
A LOS condition can be used to initiate a transfer to manual (FCR) control mode D . It also can be
configured in BESTlogicPlus to initiate other actions. Protection can be enabled and disabled E without
altering the individual loss of sensing settings.
LOS protection is automatically disabled when a short circuit exists. A short circuit is detected when the
measured current is greater than twice the rated current for a single-phase CT connection and when the
positive sequence current is greater than twice the rated current for a three-phase CT connection.
Figure 30. Loss of Sensing Protection Settings