CT Accuracy and Reverse Power

[Lifetimelearner]

Here are the parameters of a question recently asked to me.

The CT's we are implementing for a reverse power relay are 1200:5 A CT's with an accuracy range of +/- 1% Full Scale Error.
Because of the nature of our load we need to be able to measure this full range.
The CT's are installed at the PCC.

We have an inverter operating in parallel to the grid for load displacement and utility bill decreasing purposes downstream of the PCC.

The question is when we are operating the inverter and the incoming CT's are measuring around 10A on the lowest leg, will the 12A accuracy (1%x1200A) possibly trip the reverse power relay?

My answer was that the reverse power relay relies more on the phase angles then the magnitude but I wasn't 100% sure.

Cheers,
Lifetimelearner

 

[GoldDigger]

Unlike a Hall Effect DC current sensor, the AC current transformer cannot by its nature have a zero offset.
As a result the accuracy of the CT itself will improve proportionally (in absolute error) the lower the imposed current.
Do not worry about the CT as a source of error at low currents.
The sensor in the reverse power relay is the only place that any kind of absolute scale error (e.g.+- one digit if digital) might occur.
So your question needs to be addressed by the specifications of the reverse power relay, not the CTs.

JMO

 

[Lifetimelearner]

Unlike a Hall Effect DC current sensor, the AC current transformer cannot by its nature have a zero offset.
As a result the accuracy of the CT itself will improve proportionally (in absolute error) the lower the imposed current.
Do not worry about the CT as a source of error at low currents.
The sensor in the reverse power relay is the only place that any kind of absolute scale error (e.g.+- one digit if digital) might occur.
So your question needs to be addressed by the specifications of the reverse power relay, not the CTs.

JMO

Thanks GoldDigger!

As always your answer is informative and friendly.:thumbsup: