CCVT Accuracy

[mesutphen]

In our switchyard, we have 1 CCVT for each autotransformers, on B-phase. These CCVT's are called "Bus CCVT's" and are of "metering accuracy." The output from these goes to an autotransformer energized indication, and is also used in synchronization.

One of these CCVT's needs to be replaced, but we don't have a "metering accuracy" replacement. We do, however, have a "Relaying accuracy" replacement (which we also use in the switchyard for transmission lines). Since the autotransformer CCVT's are not used for metering, would it be wrong to replace it with a "Relaying accuracy" instead?

I looked in the original documentation, but could not find a reason why they chose a higher-accuracy CCVT.

 

[scottf]

I see metering accuracy CCVTs/VTs often used for synch check due to the tighter phase-angle error limits over relay class units. However, I'm not really sure that rationale is correct.

Of course, I see plenty of relay accuracy CCVTs used for that purpose too and I've never heard of an issue.

The transient response for synchronization COULD be an issue, but I doubt it (meter accuracy CCVT would typically have faster/better transient response than a relay accuracy unit...but at the low applied burdens, there wouldn't be much performance difference).

Is there power-line carrier being used at these points (e.g. CCVT being used as coupling capacitor too)? What is the voltage class?

 

[mesutphen]

Thanks, scottf. We actually use relay accuracy CCVTs for synchronization in other areas.

These CCVTs are not using power-line carrier, and they are 138KV voltage class.