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SA Mains Voltage Range


Gerald_db

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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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10 hours ago, Mariana Crompton said:

Would a voltage regulator switch off the main board into the house when the voltage is higher than 250.? I have an inverter but that keeps running out when the electricity goes higher, it seems to come on when it drops below to 248.

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We would like to help but  your explanation is a bit vague. 

• Do you have some sort of device connected on the incomer side of your db. Picture please.

• You say inverter running out do you mean above 248v does it go to the battery, switching over from utility to inverting mode? Make and model of your inverter.

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11 hours ago, Mariana Crompton said:

Would a voltage regulator switch off the main board into the house when the voltage is higher than 250.? I have an inverter but that keeps running out when the electricity goes higher, it seems to come on when it drops below to 248.

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My 1st call would be to try and get the supply authority to lower the tap on the transformer to below 250V. Inverter dependent the "normal" grid supply might be increased to say 255V on the upper level. Mentioning it with reluctance as a test. 

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11 hours ago, Mariana Crompton said:

Would a voltage regulator switch off the main board into the house when the voltage is higher than 250.? I have an inverter but that keeps running out when the electricity goes higher, it seems to come on when it drops below to 248.

We don't have a lot of detail here. If by inverter you mean a hybrid inverter such as a Voltronics, Sunsynk, Victron etc then they will usually have a setting for safety code as they are sold in different countrie with different requirements.

My inverter (Goodwe) is set to "South Africa 230V". It expects 230V at 50Hz. It allows some over or under voltage, and it allows a small variation on frequency. When the grid is up (disquitetingly common lately) it will mimic the grid (EG if grid is 238V at 50.1Hz, then that's what the inverter tries to put out). I've never had to deal with a problem of too high a voltage, but we have had low voltage problems, and at about 185 the inverter will disconnect from the grid (it carries on monitoring it). 

Or I can just set it to "230V default" at which point it accepts nearly anything, which isn't necessarily what you want.

Now (TLDR) all of this behaviour is controllable by changing settings on the inverter.

If you're referring to the "trolley" style of inverter, you might find there's a range setting switch (won't be very granular), or there may be jumpers inside on the PCB that a suitably skilled person could manipulate (if that won't invalidate the warranty).

So what inverter do you have? Do you have a manual for it?

The standard for SA is 230V + or - 10%. An inverter set up for the South African code should still accept 250, certainly should go on past 248 to 253, then start thinking about things (and should also tolerate a drop down to at least 207).

225 plus 10% gives 247.5

I think this is a settings problem. Though if you are getting over voltages according to our standard, IE the voltage is going > 253, then, as @Scorp007 has said, you should have a chat with the municipality. 
 

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2 minutes ago, Bobster. said:

We don't have a lot of detail here. If by inverter you mean a hybrid inverter such as a Voltronics, Sunsynk, Victron etc then they will usually have a setting for safety code as they are sold in different countrie with different requirements.

My inverter (Goodwe) is set to "South Africa 230V". It expects 230V at 50Hz. It allows some over or under voltage, and it allows a small variation on frequency. When the grid is up (disquitetingly common lately) it will mimic the grid (EG if grid is 238V at 50.1Hz

Or I can just set it to "230V default" at which point it accepts nearly anything, which isn't necessarily what you want.

So what inverter do you have? Do you have a manual for it?

The standard for SA is 230V + or - 10%. An inverter set up for the South African code should still accept 250, certainly should go on past 248 to 253, then start thinking about things (and should also tolerate a drop down to at least 207).

225 plus 10% gives 247.5

I think this is a settings problem. Though if you are getting over voltages according to our standard, IE the voltage is going > 253, then, as @Scorp007 has said, you should have a chat with the municipality. 
 

Although you choose 230V the grid code for ZA implies up to 260V but nothing higher and the inverter must switch off. But again although the ZA grid code is selected there could be a setting where one can adjust but I would not set to higher than 260V. That level is there for a very good reason. 

Here we not just talking of hybrids but any inverter that is connected to the grid and can in fact export. Also known as string inverters or grid tied. 

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