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High 3rd harmonic on the neutral

MS01
Afternoon,

I was wondering if anyone has nay experiences of having issues with high 3rd harmonic currents on the neutral on high-rised residential schemes? I appreciate  non-linear single phase loads will impact the 3rd harmonic and even on a balanced system harmonics are an issue but we are measuring it at 300% but I can’t think why this may be the case on a residential building.

Does anyone have any ideas?



M
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  • 0
    I would not expect this in a block of flats, a data centre yes.

    I wonder. If the flat's don't have a large resistive load (e.g. space/water heating is by gas or communal heating system) - what's left? Much of the stuff that's left on standby these days will have electronic PSUs (most likely switchmode) the washing machine's motor is likely got the domestic equivalent of a VSD in front of it, probably the vacuum cleaner too (or is battery powered with an electronic PSU to recharge it). Even the simple oven I installed recently demanded an A-type RCD as presumably it temperature controls via power electronics rather than the old clunk-on-clunk-off thermostats. Lighting is now CFL or LED with electronic ballasts/drivers. So maybe it's only the kettle and toaster left as nice clean resistive loads, maybe a tumble dryer - but they're not on very often. Maybe we are drifting towards domestic being as troublesome as datacentres.

       - Andy.
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  • 0
    I would not expect this in a block of flats, a data centre yes.

    I wonder. If the flat's don't have a large resistive load (e.g. space/water heating is by gas or communal heating system) - what's left? Much of the stuff that's left on standby these days will have electronic PSUs (most likely switchmode) the washing machine's motor is likely got the domestic equivalent of a VSD in front of it, probably the vacuum cleaner too (or is battery powered with an electronic PSU to recharge it). Even the simple oven I installed recently demanded an A-type RCD as presumably it temperature controls via power electronics rather than the old clunk-on-clunk-off thermostats. Lighting is now CFL or LED with electronic ballasts/drivers. So maybe it's only the kettle and toaster left as nice clean resistive loads, maybe a tumble dryer - but they're not on very often. Maybe we are drifting towards domestic being as troublesome as datacentres.

       - Andy.
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