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AVEVA Enterprise SCADA

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Configure alternative alarm limits

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  • Last UpdatedApr 24, 2025
  • 4 minute read

Follow this procedure to enable, disable, and modify the alternative alarm limits currently configured for a record appearing on the Alternate Alarm Limits Summary window.

Before you begin

Complete the steps in View the attributes of active alternative limits.

To configure alternative alarm limits

  1. On the Alternate Alarm Limits Summary window, select the row header of the record whose limits you want to modify.

    The Alternate Alarm Limits Control Panel dialog box opens.

    If the selected record represents the active set of alarm limits, the dynamic text Active appears at the top of the dialog box in green font. If the selected record is not the active set of alarm limits, the text reads Inactive and appears in red font.

  2. Use the table at the bottom of this section as a guide to modifying the items on the Alternate Alarm Limits Control Panel dialog box.

  3. When finished, select Submit.

    A message appears.

  4. To proceed with the indicated change, select Yes.

    Item

    Description

    High/Low

    Select the left Enabled checkbox to enable and configure the High alarm limits.

    Select the right Enabled checkbox to enable and configure the Low alarm limits.

    For further information, refer to the AVEVA Enterprise SCADA HMI Controller documentation.

    HighHigh/LowLow

    Select the left Enabled checkbox to enable and configure the HighHigh alarm limits.

    Select the right Enabled checkbox to enable and configure the LowLow alarm limits.

    For further information, refer to the AVEVA Enterprise SCADA HMI Controller documentation.

    Analog Setpoint Limit

    Enter the highest and lowest setpoint that can be issued.

    Rate Of Change Alarming Enabled

    Select Enabled to enable the Rate Of Change (ROC) alarm. If the ROC exceeds the configured ROC limits, the system generates an alarm.

    Select the method to use in calculating the ROC.

    Options:

    • baseline method โ€“ use the baseline method

    • custom method โ€“ use the baseline method with the additional fields below:

      • Negative Rate of change limit (Units/Sec)

      • Time Interval for ROC (sec)

        In the baseline method, the system calculates the ROC as the difference between the current and previous poll, divided by the difference in time between these consecutive polls. This yields a rate in Engineering Units (EGUs) per second, which the system then compares against the ROC limit. The system generates an alarm if either positive or negative rate of change occurs.

        The custom method works to reduce nuisance alarms by allowing you to specify the delta time between values, as opposed to the system calculating the ROC between consecutive polls. In addition, the custom method allows for different rate of change limits for positive and negative ROC.

        The system calculates custom ROC by recording multiple poll cycles (up to 30) and calculating the ROC between values that are separated in time by at least the delta time value that you specify (Time Interval for ROC (sec)):

        ROC = (Current Value - Value at Delta Time ago) / Delta Time

        Where:

        "Delta Time" = Time Interval for ROC (sec).

        It is best to set the Delta Time to a multiple of the poll cycle time. For example, if poll cycles are 10 seconds, set the Delta Time to a value divisible by 10.

        Note: Baseline alarms are not persistent. However, Custom ROC alarms are persistent. Subsequent to a Custom ROC alarm, the system continues to calculate the ROC each poll using the above method, and maintains the alarm state so long as the ROC over the Delta Time exceeds limits. For custom ROC alarms, once the limit is no longer exceeded, a return-to-normal alarm will be generated.

        For further information, refer to the AVEVA Enterprise SCADA HMI Controller documentation.

    Rate of Change (Units/Sec)

    Enter the maximum, positive allowable ROC (EGUs per second).

    Negative Rate Of Change (Units/Sec)

    Enter the maximum, negative allowable ROC (EGUs per second).

    Time Interval for ROC (sec)

    Enter the time interval over which the system should calculate the ROC.

    Analog Setpoint Limit

    Enter the highest and lowest setpoint that can be issued.

    Analog Setpoint Creep

    Select Enabled to enable the Setpoint Creep alarm. When the current value of an analog point deviates this much (Spt Creep) beyond the commanded setpoint, the system generates an alarm.

    Flatline

    Select Enabled to enable Flatline Alarming. If an analog, a rate, or a flowTotalConfig value does not change within the Timeout value (in minutes), the system generates an alarm.

    Creep

    Select Enabled to enable the Creep Detection alarm. If the almlimit value creeps out of its calibrated state by a value that exceeds the Creep value, the system generates an alarm.

    For further information, refer to the AVEVA Enterprise SCADA HMI Controller documentation.