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 ClearSCADA).
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 (ClearSCADA).
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 ClearSCADA, you then need to specify the counter interrogation requests that ClearSCADA 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 ClearSCADA 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 ClearSCADA 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 ClearSCADA 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 ClearSCADA’s Intervals and Offsets are set appropriately (for any counter requests that ClearSCADA 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 ClearSCADA 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 ClearSCADA.
Use the information in the table below to help you decide which counter interrogation requests ClearSCADA 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 ClearSCADA (Yes) and which are clear (---).
ClearSCADA performs the selected activities at the times and frequency specified by the corresponding Interval and Offset fields (see Configure the Counter Interrogation Intervals).
| Mode | Request | Freeze | Reset | Description |
|---|---|---|---|---|
|
A—Local Freeze with Spontaneous Transmission |
--- |
--- |
--- |
The outstation performs the required counter operations automatically. No counter operation activity is triggered by ClearSCADA. |
|
--- |
--- |
Yes |
The outstation automatically freezes its counters and transmits those frozen counter values to ClearSCADA. ClearSCADA periodically sends requests to the outstation to reset the counter values. |
|
|
B—Local Freeze with Counter Interrogation |
Yes |
--- |
--- |
The outstation freezes its counter values automatically. ClearSCADA periodically sends a request for frozen counter values to the outstation. |
|
Yes |
--- |
Yes |
The outstation freezes its counter values automatically. ClearSCADA periodically requests that the outstation resets it counters and sends the frozen counter values to ClearSCADA. |
|
|
C—Freeze and Transmit by Counter Interrogation Commands |
Yes |
Yes |
--- |
The outstation only performs counter operations upon request from its master. ClearSCADA periodically requests that the outstation freezes its counter values and then transmits those frozen values to ClearSCADA. |
|
Yes |
Yes |
Yes |
The outstation only performs counter operations upon request from its master. ClearSCADA periodically requests that the outstation freezes and resets its counter values, and then transmits those frozen values to ClearSCADA. |
|
|
D—Freeze by Counter Interrogation Command, Frozen Values Reported Spontaneously |
--- |
Yes |
--- |
ClearSCADA periodically requests that the outstation freezes its counter values. The outstation automatically transmits the frozen counter values to ClearSCADA. |
|
--- |
Yes |
Yes |
ClearSCADA periodically requests that the outstation freezes and resets its counter values. The outstation automatically transmits the frozen counter values to ClearSCADA. |