9440300990 10-15
DECS-250 Protection
• Positive Sequence Current
• Positive Sequence Voltage
• Power Input
• PSS Output
• RTD Input 1, 2, 3, 4, 5, 6, 7, 8
• Setpoint Position
• Thermocouple 1, 2
• Total kVA
• Total kvar
• Total kW
• Tracking Error
If an optional Analog Expansion Module (AEM-2020) is used, any one of the following analog, RTD, and
thermocouple inputs may be selected.
• Analog Input 1, 2, 3, 4, 5, 6, 7, or 8
• RTD Input 1, 2, 3, 4, 5, 6, 7, or 8
• Thermocouple 1 or 2
Protection can be always enabled or enabled only when the DECS-250 is enabled and supplying
excitation. When protection is enabled only in Start mode, an arming time delay can be used to delay
protection following the start of excitation.
A hysteresis function holds the protection function active for a user-defined percentage above/below the
pickup threshold. This prevents repeated pickups and dropouts where the monitored parameter is
hovering around the pickup threshold. For example, with a hysteresis setting of 5% on a protection
element configured to pick up at 100 Aac of A-phase generator overcurrent, the protection element would
pick up when the current rises above 100 Aac and remain picked up until the current decreases below 95
Aac.
Each of the eight configurable protection elements has four individually-adjustable thresholds. Each
threshold can be set for pickup when the monitored parameter increases above the pickup setting (Over),
pickup when the monitored parameter decreases below the pickup setting (Under), or no pickup
(Disabled). The pickup level for the monitored parameter is defined by a threshold setting. While the
threshold setting range is broad, you must use a value within the setting range limits for the monitored
parameter. Using an out-of-limits threshold will prevent the protection element from functioning. An
activation delay serves to delay a protective trip after the threshold (pickup) level is exceeded.
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