User manual 09/2009 - Schneider Electric

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User manual 09/2009 - Schneider Electric

AlarmsAlarm on Equality ConditionThe alarm is activated when the associated monitored quantity equals the pick-up threshold. The alarmis deactivated when the associated monitored quantity is different from the pick-up threshold.Alarm activation is determined using the pick-up/drop-out thresholds.The figure below illustrates activation of an alarm on an equality condition (monitoring of quadrant4):SA Pick-up thresholdSD Drop-out thresholds1 Quadrant 4 alarm: pick-up zone (in green)Management of Time Delays (Superiority or Inferiority Conditions)The alarm time delays are managed by 2 counters that are normally at 0.For the pick-up threshold, the time delay counter is:• Incremented when the activation condition is fulfilled• Decremented if the activation condition is no longer fulfilled (before the end of the pick-up time delay)If the deactivation condition is reached, the pick-up time delay counter is reset and the drop-out timedelay counter is incremented.For the drop-out threshold, the same principle is used.Example:Management of the time delay on an overvoltage alarm (code 79, see Detailed Tables of Alarms,page 110)5 s2 s1 Evolution of the voltage2 Pick-up time delay counter at 5 s3 Drop-out time delay counter at 2 s4 Overvoltage alarm: pick-up zone (in green)The alarm pick-up time delay counter trips when the 500 V threshold is crossed by the voltage. It isincremented or decremented according to the value of the voltage in relation to the threshold.The alarm drop-out time delay counter trips when the voltage drops back below the 420 V threshold.108 LV434104 09/2009

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