Frequently asked questions

FAQ000219204

21 October 2021

SUMMARY:
This article explains the setup to configure DNP3 historise analog points at a fixed scan rate regardless of data change using Aveva Telemetry Server and Scadapack RTU

SITUATION: 
Applies to Aveva Telemetry Server 2020 and earlier versions along with Scadapack RTU.

ACTION:
The standard behaviour when an Integrity Poll is triggered is for the DNP3 driver to poll the RTU for all event data and all static (class 0) data.  
If there is event data for a point this will always be sent through to the database and stored.
However static data for a point must have changed since the last poll to trigger an update of the database. Plus by default static data will not be stored historically.
 

• Firstly on the Analog Point user needs to change the 'Historic Data Filter' to 'Static and Event Data': This will log both events and static data historically. But it will only log a static data value if it has changed since it was last updated. So if the value is not changing user will not see an update when the integrity poll goes off.
• To ensure the point updates every hour regardless of whether the value has changed user need to change the 'Scan Group (Confidence Poll) to 'Group 8': There is no need to tick the 'Level 3 Scan' as user have configured the Integrity Poll to go off every hour to get the data.

          
 

• What is 'Group 8'? The Scan Groups are some pre-defined timers which are defined on the Channel that is used by the Outstation:

   

• With these two changes (Historic Data Filter and Scan Group) on the analog point user should be able to get the static value logged historically every hour whether it has changed or not.

Note: the above is fine for a slow integrity poll, but if the polling was done a lot faster (every second) this would create a lot of updates to the database and the historian which might create performance issues. So be cautious of using the above in other situations if the polling is a lot faster.