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[Speed Daemon]

In India 240V will be L-N-E supply i.e. live and neutral with a protective earth, IIRC the standard socket is the olders BS546 standard similar to the modern BS1363 but with round pins, no fuse and there is separate 6A and 16A plugs (the original British standard being 5/15A). The larger of these plugs being used as the standard plug for stage lighting in Britain.

The Suko type plugs originally mentioned were probably referring to Schuko (CEE7/3 & 7/4) which whilst they may fit in an Indian socket there will be no earth connection.

Thanks for the lesson, Levi.  I've used residential power in Europe where there are two hots (balanced line) and a ground, with no voltage divider like for US home service.  Never had to deal with more industrial venues though.  IIRC they split 480 single phase over there.

I can't say that I've ever had to deal with a mixed power situation where the control room has 3-phase inverter power (left over from cinema projectors?), but FOH has only the mains.  Worked in plenty of data centers and other critical facilities where every outlet was fed by regenerated 3-phase UPS power, so there was uniformity in power quality and grounding methods.  I can only imagine that a split system can't just tie the 3-phase inverter neutral to the mains neutral, and that the potential for spurious voltages and ground loops would be high.

Best of luck to Sidhu, who has a not insubstantial power engineering challenge!

[Nitin Sidhu]

Thank you all so much for the time and effort.
I am attaching a diagram to illustrate the connections to the best of my knowledge. I hope it provides clarity.

@Daniel, CEE7/3 is correct. A lot of equipment here is sold with this AC Power plug, and I am aghast how it is legally possible. The L and N
pins will fit Indian sockets, but offer no ground protection. Additionally, there is a gauranteed 50% chance that the user will plug it in reversed.

I long ago saw that if we have a 3 core power cable connected to a 2 core outlet (hence no ground connected), the ground cable will have some voltage induced in it. As an experiment, I took a short strand of 1mm wire, and placed it next to a live wire, sure enough, a simple Voltage tester lit up when connected to the end of this free strand. This voltage is then perceptible on the chassis of, for example, a mixer.

If something else is critical to the diagnosis, I am willing to visit the center again and measure everything.  This will take time and permits etc. But well worth it I would think. I am also going to do a thorough inspection of all our power supplies.

Thank you all once again!

Regards,
Sidhu

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