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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...

fb599 - Is your REF545 an SCU (Switchbay Control Unit)? We have ABB's REF542 which is an SCU and have had one such incident in the past. Please give more details of REF545.

bigamp - You were absolutely right. We did a thorough check of the CT wiring and discovered that the complete wiring had been chaotically changed by the contractor. It took us a lot of time and effort to correct the same, after which we checked the phase angle displacement. The phase angle...

Thanks everyone for their valuable inputs. A small correction, the relay is 7UT512, not 7UT513 (it was a typing error). I am giving below the details of tests conducted. The relay has the provision to do commissioning tests and can give out phase displacement and phase angle measurements of...

Thanks everyone for the response. RajT - The transformer is 25 MVA, %z = 12.38. All the parameters required by the Siemens relay have been entered properly. Which particular setting do you need? DanDel - I agree with you, but this particular relay is not a conventional relay. It is...

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...

Dandel, Each of the outgoing feeders from the switchgear has one of these SCUs installed and there over 200 such outgoing feeders from various switchboards. You are right, we are seriously considering blacklisting the manufacturer. But for the moment we are stuck with this problem.

We have been replacing the entire card with spare ones (supplied by ABB), but we have now ran out of all spares and have reached a critical stage. We have lost about 7 SCUs until now, all of them with the same problem. (This is a big company with about 200 such SCUs installed all over the...

Dandel, We already contacted the manufacturer, but the response from them is not so encouraging as it is well-past the warranty period. So, we are left to fend for ourselves. The installation is 5 years old. The manufacturer's catalog specifically says that the average life of the capacitor is...

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...

appunni, Beyond 120% of the rated current, metering CTs must saturate at a specific multiple of rated current (generally 5 or 10 times rated current) so that the instrument can be protected. The phase displacement limits and ratio error are also totally different between a protection and a...

kantor, Can you explain more about the modification you have done? Also, what are the relays connected on the secondary side?

Suggestion: Rather than an underfrequency relay, try using df/dt relay (rate of change of frequency) if possible.

Is there a restricted earth fault protection on both primary and secondary sides?