CT accuracy at very low load
CT accuracy at very low load
(OP)
Howdy all,
Does anyone know how an ITI model 780 600:5 CT will perform at very low load - such as 3% of rating? A customer has this CT installed in a metering and overcurrent relaying application and they will not take a bus shutdown to change it to a lower ratio CT. They plan on installing a new Cutler-Hammer IQ Dataplus 4000 meter and they want to know if the meter will read within reasonable accuracy down to about 3% of the CT rating. The ANSI metering accuracy of the CT is 0.3% at 100% of rating and 0.6% at 10% of rating, but what happens at 3% of rating??? I'm trying to tell them that this is not a good idea.
Does anyone know how an ITI model 780 600:5 CT will perform at very low load - such as 3% of rating? A customer has this CT installed in a metering and overcurrent relaying application and they will not take a bus shutdown to change it to a lower ratio CT. They plan on installing a new Cutler-Hammer IQ Dataplus 4000 meter and they want to know if the meter will read within reasonable accuracy down to about 3% of the CT rating. The ANSI metering accuracy of the CT is 0.3% at 100% of rating and 0.6% at 10% of rating, but what happens at 3% of rating??? I'm trying to tell them that this is not a good idea.






RE: CT accuracy at very low load
RE: CT accuracy at very low load
If this was being used for billing or revenue metering, that's another story.
For relaying, we'd be more concerned about how the CT performed at 500% or 2000% current.
The thing that helps you is that the newer digital meters have very low burdens compared with old electro-mechanical meters.
RE: CT accuracy at very low load