DNP3 analog input data (Object type 30) is mainly derived from the protection relay’s IEC 61850 measurand object classes MV and CMV. Since the MV and CMV source values are of float32 type, the default setting for the default variation of DNP3 analog data is float32.
If needed, the default variation can be changed to integer 16 or 32 bit types. In such case, re-scaling of the original data has to be applied.
There are four scaling options associated with analog input reporting.
- None: The value is presented as is. None of the configured values in the Communication Management tool columns Min Source Value, Max Source Value, Min Dest Value and Max Dest Value has any effect.
- Multiplication: The process value is multiplied by a constant. An offset is added producing the reported value. In the Communication Management tool the constant is found in the Max Dest Value column and the offset in the Min Dest Value column.
- Division: The process value is divided by a constant. An offset is added by producing the reported value. In the Communication Management tool the constant is found in the Max Dest Value column and the offset in the Min Dest Value column.
- Ratio
- Configuration-time ratio scaling: Find R for new set of {source_min, source_max, Dest_min, Dest_max}
- R = (out_max - out_min)/(in_max - in_min)
- Reported value = (inval - in_min) * R + out_min.
Some DNP3 analog input points, such as CT/VT measurement values, support primary and secondary scaling. This selection can be done in PCM600 by selecting either "Primary value" or "Secondary value" for Representation. If the analog input object does not support primary and secondary scaling, the selection does nothing.
The DNP3 analog input event buffer size is 150.
In case of analog events, the IED system produces changed analog events with a specific sampling rate and deadband. The sampling rate and deadband can be additionally modified for DNP3 AI points through the Communication Management tool in PCM600. If a DNP3 analog input points' additional Deadband value is set to “0.0”, the IED system analog events are propagated as such through the DNP3 protocol. Sampling rate of the DNP3 AI value can also be reduced through the points' Deadband Time setting. This means that the events are transmitted less frequently. If Deadband Time is for example set as “2”, then analog events are not produced more frequently than with two seconds interval from the DNP3 AI object.