Counter Operation Modes and Interrogation Requests

Counters on outstations that communicate using the IEC 60870-5 protocol are periodically ‘frozen’ at the outstation, either automatically (‘spontaneously’) by the outstation, or in response to a request from the SCADA master (for instance Geo SCADA Expert).

The outstations transmit the frozen counter values to the master, either automatically and/or in response to a request for those values. (A request for a counter value in between ‘freezes’ results in the server being sent the last frozen value for that counter.)

Frozen counter values can be reset at the outstation automatically and/or upon request, or the counter values can continue to increment in order to provide, for instance, a total runtime value.

The counter activity at each outstation depends on what counter operation modes that outstation supports and uses, and what functionality is configured in the master (Geo SCADA Expert).

You need to refer to the outstation’s interoperability Profile document to ascertain which counter operation modes a particular outstation supports. You also need to be aware of what counter functions are set at the outstation. Within Geo SCADA Expert, you then need to specify the counter interrogation requests that Geo SCADA Expert is to perform—the properties for these requests are displayed within Counter Interrogation Intervals section of the Outstation Form (see Configure the Counter Interrogation Intervals).

The Counter Interrogation Intervals section includes check boxes that allow you to define whether Geo SCADA Expert is to send messages to the outstation in order to:

• Request the latest frozen counter values from the outstation
• Freeze the counter values at the outstation
• Reset the counter values at the outstation.

You need to select those check boxes for which Geo SCADA Expert is to send requests to the outstation. Leave the check boxes clear for those functions for which the outstation is set to perform automatically, or which are not required.

Use the corresponding Interval and Offset fields to define when Geo SCADA Expert sends the selected request(s) to the outstation (see Configure the Counter Interrogation Intervals).

If an outstation performs any counter interrogation activities automatically, you need to be aware of when the outstation performs those activities. You can then use this information to determine whether Geo SCADA Expert’s Intervals and Offsets are set appropriately (for any counter requests that Geo SCADA Expert sends to that outstation). For instance, an outstation might support automatic freezing and/or resetting of counter values, but might only transmit the frozen values to Geo SCADA Expert on request. You would therefore need to be aware of when the outstation freezes and/or resets those values, so that you can specify appropriate counter Request intervals within Geo SCADA Expert.

Use the information in the table below to help you decide which counter interrogation requests Geo SCADA Expert needs to send to an outstation. The Mode column lists the various counter operation modes that might be supported by an outstation (as indicated in each outstation’s interoperability Profile document). The Request, Freeze, and Reset columns indicate which check boxes are selected in Geo SCADA Expert (Yes) and which are clear (---).

Geo SCADA Expert performs the selected activities at the times and frequency specified by the corresponding Interval and Offset fields (see Configure the Counter Interrogation Intervals).