WHM Re-calibration for changing CT ratio
WHM Re-calibration for changing CT ratio
(OP)
I am changing a MV feeder which has existing GE type DS WHM presently fed from 400/5 CTs, I am changing the CTs to 600/5. Is it sufficient to change the meter multiplier by a new multiplier 1.5 multiple (6/4) of existing multiplier or a more elobrate recalibration is required? The meter is not used for revenue metering.






RE: WHM Re-calibration for changing CT ratio
An old electrician trick is to open the CT test switch or insert the shorting screws at the CT terminal strip one at a time. The meter should slow down when a phase current is cut out. If it speeds up something is wrong. If it slows down, it might be correct because the test does not find all errors.
RE: WHM Re-calibration for changing CT ratio
RE: WHM Re-calibration for changing CT ratio
You do need to ensure that you do not exceed the maximum pulse rate for the meter, you will be able to find this in the meter technical data sheet. If this rate is exceeded there won't be sufficient discrimiation between pulses and the system won't work correctly.