CT selection for commercial facility
CT selection for commercial facility
(OP)
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.
Any advise or tip will be much appreciated. Thank you all in advance.






RE: CT selection for commercial facility
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.
RE: CT selection for commercial facility