We recently conducted an infrared thermography test on our outdoor cable sealing ends. In one of the phases, the temperature was found to be 7.2 degrees Centigrade more than the corresponding phase in an adjacent cable sealing end. Currents in both the CSEs were found to be the same, but I would...
As per VDE0410, the measuring class of measuring instruments has to be Class 1. Does it mean that the CT secondary which feeds such instruments has to be Class 1? The CT secondaries of all measuring CTs which I have seen are all of 1 ampere. Do we also have measuring CTs of Class 1 but with 5...
I have heard that there is an empirical method of finding the approximate location of a fault in a cable in the absence of a fault locator (some call it as null point method and others as 'loop method'). Would appreciate if someone who knows the procedure / empirical formula can share the same.
We installed a new ABB-make induction motor just 3 days back. The motor details are 460V, 60 Hz, 179 kW, 278 amperes, 1787 rpm.We did the usual commissioning checks. Winding resistance was found balanced and IR value was 500 Mega Ohms. Yesterday, the motor got flashed over. The motor was very...
We have a problem with one of our transformers. As soon as the load crosses 15% of the rated current, the transformer trips on differential protection. The transformer is Dyn11, 13.8/4.16 kv. Primary CTs are connected in star (1000/1A). The secondary CTs are also star connected (3000/1A). The...
We have ABB's Switchbay Control Units (SCUs) installed in 4.16 kV and 34.5 kV switchgear. Since the past 7 months, we have had a series of failures on some of these SCUs. The display becomes totally blank. Upon inspection, we found that the capacitor in the power supply card had failed. The...
