IEC 61850 9-2 Sampled Values - DR Clarification

Dear All,

Requesting clarification on the below subject.

The standard defines the data quality value as good, invalid or questionable. If the data quality is invalid or questionable then the subscribed IED metering and DR analog channels need to indicate the data quality information also, Otherwise user may not know the data is not a good one. If we subscribe the channels from more merging units then one MU data may be invalid, so each channel wise do we need to indicate the data quality values???

Basically I want to know how they handle the data quality in the DR and metering?

Regards

Raghav.