There is a field available in the Event Journal that records the time that an alarm or event was received by ClearSCADA. This field is not displayed by default when installing ClearSCADA, however ClearSCADA will record this information at all times for use when required.
When enabled, two fields will then become available in the Event Journal. The first field shows the time that the alarm condition was activated. In a PLC polling architecture, this time will be generated by ClearSCADA as it performs a read of the device and determines that the point is in an alarm condition. For RTU protocols such as DNP3 that support time-stamping of data, this timestamp will typically be derived by the RTU. In some cases this information will then be buffered by the RTU until the next time it communicates with ClearSCADA and is able to upload this information.
The second field is the time that ClearSCADA received the alarm or event condition. In the PLC polling architecture, the received time will be the same as the actual time since ClearSCADA generates both timestamps. For the time-stamped protocols, the received time is the time that ClearSCADA actually received that time-stamped event. There may be a long delay between these times depending on the type of data, the polling mechanisms used, communications network traffic and sbsequent delays etc.
Using these two fields in the Event Journal, it is thus possible to determine exactly when the condition was raised in ClearSCADA and therefore how long it was active before it was actioned.
For detailed information on how to configure the event list to display both columns, refer to the section "Define which Columns are shown on the Event List" in the online help. The columns of interest are RecordTime (for activated time) and ReceiptTime (for the time it was received by ClearSCADA).
ClearSCADA also provides functionality to allow alarm analysis to take place. These functions allow the following things to be checked:
Maximum period between alarm occurring and being received
Maximum period between alarm being received and acknowledged (accepted)
Maximum period between alarm occurring and being cleared
The period between the alarm occurring and being received will generate an event in the event journal if the alarm was not received by ClearSCADA within the configured time interval after it was first generated. This obviously relates only to protocols such as DNP3 which are capable of producing data time stamps at the RTU.
The period between the alarm being received and acknowledged (accepted for users with locale of English (United Kingdom)) will generate an event on acknowledgement of the alarm if it was active in ClearSCADA for longer than this time interval before it was acknowledged.
The period between the alarm occurring and being cleared will generate an event on the clearance of the alarm condition if the alarm was active for longer than this time.
Each of these events will be added into the Event Journal with a category of Alarm Analysis and so can be searched simply and quickly to obtain a picture of the alarm behavior of the system.