Alert filtering
With the help of the Alert filtering you can set a limit value that specifies after how many individual alarms only the sum alert instead of the individual alarms is shown in the alarm screen. If you would, for example, define the limit value 4 and there would be 4 alarms of this sum alert, only the sum alert would be shown in the alert screen.
To activate the WinCC OA alarm filtering, proceed as follows:
- As of the WinCC OA version 3.7, the alarm filtering is activated by default (set the config entry activateAlertFiltering = 0 in the [general] section of the config file to disable the alarm reduction).
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Choose the option "Threshold filter" for the alarm filtering on the "Filter types" tab of the panel "Properties of alert panel" that is opened through the alarm screen.
CAUTION:The alert filtering (Threshold filter) option can be used in the current mode. It cannot be used in the open mode of the alert screen.
Figure 1. "Filter Types" Tab of the Panel Properties of "Alert Panel" 
- Specify the threshold filter (value limit) in the alert handling of a sum alert in the PARA module. The threshold filter parameter can only be specified for deactivated sum alerts.
In the PARA module you can additionally specify that a sum alert is shown although the limit value has not been exceeded (individual alerts are hidden in the alert screen). For this, activate the filter check box (see figure above) of a sum alert handling. If the "Filter" is used, the DP list is not being used.
Example of alert filtering
For a sum alert an alert class can be specified. The sum alert is only triggered when the single alert has the same alert class as the sum alert.
The alert filtering can also be used if an alert class was not specified for a sum alert.
- In this case two sum alerts are created w1_turbine1.sumalert1 and w2_turbine1.sumalert2.
Below you can find the sum alert handling for the two sum alerts.
- A single alert w1_turbine1.inOperation is triggered with the alert class A.
- The both sum alerts are triggered.
- A single alert w2_turbine1.inOperation is triggered with the alert class B.
- For Sum alert w1_turbine1.sumalert1 the filter criterion (threshold) is now used. (2 alerts).
- Sum alert w2_turbine1.sumalert2 does not use the filter criterion (only one alert exists with the alert class "A").
- A single alert w2_turbine1.current with alert class A is triggered.
- For the sum alert w2_turbine1.sumalert2. the filter criterion is now used (2 alerts with alert class A).
Sum alert in Sum Alert (Cascaded Sum Alerts)
WinCC OA supports the configuration of sum alerts in sum alerts with the same threshold without showing them in the alert screen multiple times. In this case there is talk of cascaded sum alerts, which means that alert reduction works in hierarchies (of more than one level).
The following rules have to be considered:
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A sum alert with a threshold counts only its subordinated active (sum) alerts. An alert is active, if a warning or an alarm is triggered (see A, B, D in figure below). A sum alert is active when it has reached its threshold (see S2 in figure below).
- Once the threshold of a sum alert is reached, the summary alert filters the active alerts of their subordinated sum alerts and shows itself instead (alerts are triggered as hitherto). According to the figure above S2 and D are shown.
- For the filtering only the active subordinated alerts of a sum alert with a threshold are counted. From the figure above for the sum alert S2 these alerts are A, B and C and for the sum alert S3 these alerts are D, E and F.
- Alerts, which are subordinated to a sum alert, are not counted/filtered by the sum alerts, which are superordinated to this sum alert. From the figure above S1 does not count the alerts A, B, C, D, E and F.
The sum alarm S1 contains the sum alarms S2 and S3.
All sum alarms have the same threshold (=2).
A, B and U are active alarms.
S2 and U are shown.
S2: Threshold reached => children are filtered.
U: Its father has not reached the threshold, yet.
S1 is also not shown, because its threshold is not reached. Although the S3 sum alarm is active, since U is active, however, it is not counted by S1, because its threshold has not been reached, yet.
A, B, U and V are active alarms.
S1 is shown.
S1: threshold reached => children S2 and S3 are filtered.
S2: filters its children, but is not shown, since it is also filtered by its father S1.
S3: filters its children, but is not shown, since it is also filtered by its father S1.
Sum alert details
The sum alert details panel opens by right-clicking on a sum alarm in the alert screen.
The column "Filtered" shows if an alarm has been filtered, meaning whether the "alarm filtering" has been used. As shown before, you can set athreshold filter parameterfor the sum alerts on the "Alerts" tab of a sum alert handling (in the PARA module). The filter can be used to specify after how many individual alarms only the sum alert should be shown (alarm filtering). Thesumalertdetailspanel, however, shows the individual alarms and whether the alarms were filtered. That is, whether the threshold parameter has been used or not.
The checkbox "Filter" of a sum alert handling (in the PARA module) can be used to hide individual alarms of an active alarm (to force a single alarm to be filtered). In this way, only the sum alert would be shown although the threshold has not been exceeded. Whether the Filtering has been used or not is indicated by the check box "Force filtered".
