ClearSCADA raises an interrogation alarm of the appropriate type (see IEC 60870-5 Outstation Status Attributes) when it either:
- Does not receive a valid termination message for an interrogation request that it has sent to an IEC 60870-5 outstation. (For instance, in response to a station interrogation request, group interrogation request, or a request for station or group counter data.)
- Does not receive an activation confirmation, in response to a station or group counter Reset or Freeze request.
Not receiving such a termination or confirmation message from the outstation may occur for one of several reasons, including:
- The outstation not supporting the interrogation command that ClearSCADA has sent.
Each IEC 60870-5 device has an interoperability Profile document that describes what functionality is provided. If the interrogation command is not supported, disable ClearSCADA from sending that type of interrogation request.
- ClearSCADA timing out the request, because the outstation is taking longer than the expected time to return the data that ClearSCADA has requested. To rectify this, either:
- Reduce the amount of data that the outstation is generating.
- Increase the driver timeouts, in order to give the outstation longer to return its data.
- ClearSCADA not receiving the expected sequence of events, due to an unusual network condition.
This should clear automatically the next time that the interrogation interval expires.
Further Information
Configure the Station and Group Interrogation Intervals.
Counter Operation Modes and Interrogation Requests.
Configure the Counter Interrogation Intervals.
Driver timeouts are configured using the ClearSCADA Server Configuration Tool (specifically the fields within the Timeouts part of the Drivers section—see Driver Settings in the ClearSCADA Guide to Server Administration).