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Majesus, I might be wrong, but I think that the contributionof motors (LV and MV) is dur to the fact, that you have stored mechanical (rotation) energy; so the motor acts as a generator driven by the inertia of the driven machine. That's how I understood it.

Davrom, thanks for giving the link to the IEC concerning the definition of Icm. I also appreciate your description of the Icm - could not do it better. Maybe it was not fully clear to what I was referring with mechanical stress and thermal stress, but it is exactly what you wrote: Mechanical...

Uno, sorry for the late reply, but I saw your post just today. It has allready been perfectly tackled by davrom, theefore just my understanding as additional information as I had the same problem in the past: the result of your ETAP program should be: - Ik": Initial short circuit current...

Imok2, it should be 5..10 times the current rating (C-characteristic, not D-characteristic. See also page 10 for the trip curve (upper left picture). Good link imok2.

As described above, MCCBs are very fast. Therefore they limit the (peak) short circuit current (as also fuses do). In opposite to this, ACBs do not limit the (peak) short circuit current. That means, that a switchgear that is connect to a transformer via an ACB has to be rated for the full short...

In any case, you need a complete short circuit calculation of your network. The how to do is described in the IEC 60909-1. Do not only consider the symmetrical velue of the short circuit (Ik" in kA rms) but also the initial peak value (ip in kA peak) of the short circuit, where Ik" is...

Dear all, sorry for the late reply, but I was out off the office for some days and did not have the possibility to check the internet. Special thanks to stevenal for all the bothering, I really appreciate it. Sorry again for the late reply. Hope I can answer all your questions so far: To...

Dear all, I have an interesting problem, that I cannot explain: We have three transformers vector group DYN11, 10/0.4kV. All three transformers are supplied from the same medium voltage substation and each of them feeds one low voltage distribution. The star points of the transformers are...

Dear all, can anyone give an explanation of ICC? I found it very often in technical documentation of electrical equipment but nobody (also not the vendors of the equipment) could give me a reasonable explanation. Very often, they get confused with other abbreviations like ICM, ICU, ICW. For...