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Could anybody suggest solution for a situation where, In a 3-phase, 4-wire system, phase and neutral are getting interchanged. How can I prevent this situation and what is it exactly called!?

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    \$\begingroup\$ Usually you can avoid that by proper training of the persons dealing with it. When it happens, I usually call it incompetence. \$\endgroup\$ – PlasmaHH Feb 16 '17 at 9:35
  • \$\begingroup\$ Please elaborate on the affected appliance (household, industrial). "Getting interchanged" and "How [to] prevent" sound like it's happening right now? Do you expect us to make those electricians stop what they're doing or do you just want why that is and how to correct the installation? I think this is an interesting situation, though I don't know what you expect the community to answer (answers could be quite broad). \$\endgroup\$ – try-catch-finally Jan 1 at 8:39
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You can use color codes if your installation uses it. However, I'd rather use a multimeter to be sure because -from my short experience- you're not sure if the technician did actually use color codes. I've seen a phase conductor connected to a socket through an earth color coded conductor (Yellow/Green) because the technician ran out maybe of other colors :)

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  • \$\begingroup\$ Any electrician who uses "earth-colored" wires for phase should be fried, or at least fired, but preferrably fried. \$\endgroup\$ – Oskar Skog Jan 1 at 9:21
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In EU we have black color for phase wires, blue for neutral and yellow/green for earth wire. You can't swap the neutral with line, this can be a deadly mistake. You'd better hire somebody or stop doing this, please.

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    \$\begingroup\$ We also use brown for phase. \$\endgroup\$ – FarO Feb 16 '17 at 12:27
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The old EU system was Black or brown for 3 phase lines. To prevent wiring errors, the new standard is Brown, Black, Grey for L1,L2,L3 and in America, Red, Yellow, Blue colours are used. (RYB)

In applications where reverse rotating machines are hazardous to people or equipment, one will include a three-phase monitor relay. enter image description here This protection consists of different RC passive filters that use phase shifting currents to activate a relay which in turn powers the 3 phase contactors when in the proper sequence or activates a light indicator if faulty.

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