Hi,
I just had the time to read the datasheet.
The first I found (icecomponents CT07-1000"), dated "9/11" talked about 40Hz ... 200,000Hz. I was surprised.
Then I went to icecomponents.com and downloaded their datasheet, dated 11/17. Now they talk about 47Hz ... 2500Hz.
Without any change notice. The datasheet now is reduced from 2 pages to a single page.
None of the datasheets talks how they measure the frequency range. None talks about accuracy, precision, distortion....
Let´s say they used the -3db limit. But -3dB still means 30% error.
This is a classical transformer style CT. Depending on the core they use you may have additional measurement errors.
* typical amplitude loss
* but also additional distortions due to hysteresis and saturation effects.
If you want to use them, a simple "try if 450 Hz goes through somehow" may not be sufficient for your (good quality) THD measurement tool.
You need to measure all the THD effects that are caused by the CT itself. And - worst of all - I guess it is not linear.
If I had to build a THD measuremnt tool, then I´d ensure that the measurement does not add significant THD to the input signal.
Neither with low currents nor with high currents.
Thus my way: either a resistive current measurement, or an active CT with field compensation. (like many LEM current sensors)
You may also check whether hall sensors are good enough.
For sure you don´t need to go my way.
Klaus