CT selection for commercial facility

[tmaly1]

We're working on new installation for an airport facility in northern Virginia. The load current for the facility is about 400 amps, the line-line voltage is 208 volts, and the CTs will be used for metering purposes only. I was wondering what is the accuracy class for availble CTs that fit into this application so I can calculate the secondary voltage equivalent to the magnitude of max. %error current (at 20 times rated). Di I have to calculate the CT secondary burden as well or it's not significant??!
Any advise or tip will be much appreciated. Thank you all in advance.

 

[busbar]

Accuracy rating for metering and relaying are being mixed in the posted description. For metering, {ratio and phase-angle} accuracy is of concern over the range of 10% of rated up the CT rating factor, which usually tops out at 4 per-unit {400%.} The “20X” reference refers to performance under fault conditions, which is usually not for concern in metering applications.

In revenue metering, burden [typically expressed in ohms] is still very much of concern for accurate performance. A reference is IEEE Std C57.13-1993 §6. Some manufacturer’s literature references C57.13.

 

[dpc]

If this is revenue metering, the utility will generally provide the CTs.