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SA Mains Voltage Range


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I have done installations where the systems work 100% until winter starts.  In some areas of CPT for example Camps Bay, Rondebosch, Constantia and Oranjezicht  the grid voltage tends to drop due to heavy loads from underfloor heating and heaters being used.  I have seen the voltage drop as low as 195v, with some very upset clients because their systems aren't working.  Some suppliers will help with adjusting the tolerance on the inverter to accept a lower grid voltage before shutting down, but then the inverter is not NRS compliant anymore.

I have had some clients where their electronic appliances got damaged due to high voltage and they where blaming the inverter.  On two occasions we found that the municipality did maintenance on the sub station and used higher tappings on the transformer, pushing the grid voltage up to 260v.  Another problem was with a faulty/floating neutral in the substation.  When testing between Live and Neutral the voltage was as high as 302v.

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Jip, it is not new. Since the first round of power failures in Cpt, before Government admitted there was an issue, it was picked up by some astute folks. Volts hitting 380 in Gordon's Bay. Insurance claims skyrocketed at one stage.

Therefor I have a online UPS powering all my Pc's and other stuff that I do not need damaged. They are inefficient as can be but when my when solar system uses Eskom, the inverter passes what they get straight through. They do not "clean" Eskom power. Wished solar Inverters, where possible, had the same protections built in as what are in UPS'es.

Things like lights and fridge / freezer I went off-grid very slowly. For the rest, tough, insurance claim if it can be proven it was Eskom.

Ps. Must say, now that I think of it, I cannot recall when last I had to change a bulb. Wonder if Eskom had an effect on the bulbs lifetime.

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6 hours ago, DownTime said:

faulty/floating neutral in the substation

Just as scary as a broken neutral/earth on a TN-C-S setup.

My voltage at home is pretty stable. It ranges from 237V to 240V. Never seen it outside that range. With the little Ziehl sitting in the DB and cycling through the various stats with its little LED display, and the semi-clear front cover, I can see it every time I go into the garage.

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10% is 23V, so it could be as low as 207V and still be in spec. If you then allow another 5% under load, you're a tad under 200V. You could also be 10% over or 253V. So the full range then is almost 60V. Just doing the math here... I have no real experience with actual installations :-)

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  • 6 years later...

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