What is the legislated voltage range for end users in South Africa?

Of late I've had issues with my business solar system as mains voltage had dropped to 211V. Conversely at my home at night we are getting up to 250V.

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Hi Gerald

Spoke to an Eskom friend.  They need to be as close to 240V as possible with a 10% deviation allowed.

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.

The grid is not stable. It is all over the place. 

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.

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.

On 12/11/2016 at 8:13 AM, Mark said:

Hi Gerald

Spoke to an Eskom friend.  They need to be as close to 240V as possible with a 10% deviation allowed.

Yes and then it may not drop by more than 5% of the stated value when on full load

According to SANS 10142 the standard voltage for single phase is supposed to be 230V +- 10%. 

That is actually a 47V range.

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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 :-)

I have just checked and receiving 217/218 volts 

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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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.

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. 

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. 
 

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. 

I have had my solar system for just over four years. Since Sunday last week, my grid supply has been stopped due to serious overvoltage. This has been happening every evening, and it was an absolute mess most of yesterday, with no industries operational. Voltages go up to 272V.

I have been reporting this to Tshwane, but I get the feeling that thanks for reporting, but no feedback.

What can be done to get the voltages back to normal?

 

46 minutes ago, Speedy said:

I have had my solar system for just over four years. Since Sunday last week, my grid supply has been stopped due to serious overvoltage. This has been happening every evening, and it was an absolute mess most of yesterday, with no industries operational. Voltages go up to 272V.

I have been reporting this to Tshwane, but I get the feeling that thanks for reporting, but no feedback.

What can be done to get the voltages back to normal?

 

It seems your supply voltage is the transformer tap change is set to the upper limit 250v for load conditions and during lower demand from the transformer the voltage rises to 272v. The council must change the transformer tap down to 220v~230v then during reductions in load on the transformer it should not exceed 230v~240v that is acceptable voltage. You need to report this until you get it resolved as 272v could damage appliances. I will see what i can do from my side i know a few council electricians in Tshwane.

If your supply is single phase an increase in supply voltage could also indicate a failing neutral-earth bond somewhere in the supply cabling before it arrives at your property. When this happens the voltage between neutral and live as well as neutral and earth can rise dangerously high and destroy appliances. The easiest way to test for this is to use a multimeter and test the voltage difference between the incoming neutral and live and also between the incoming neutral and a known good earth with the main breaker switched off. Then put your DB under load ie switch on several high current appliances and make the same tests again. If the difference in results is more than a few volts there's a high liklihood of a supply issue that should be reported.

Just an update: I just received a mail from the call centre to enquire whether the issue has been resolved. There is no electrician on site, and the voltages remain the same. I wish they would give you at least the name and number of the person dealing with the matter, but I feel that the City of Tshwane hopes the matter will go away on its own.

As @TaliaB indicated the voltage is too high and needs to be corrected. 

Even the voltage during the highest load during peak can be 25V lower to prevent the high level during the after 22h00 period. This shows a different tap must be used. 

If a sparky from Tshwane would come out they can easily just compare the voltage of a transformer close to this one in the same residential area at the same time of day. 

On 2016/12/11 at 8:13 AM, Mark said:

Hi Gerald

Spoke to an Eskom friend.  They need to be as close to 240V as possible with a 10% deviation allowed.

Last time I checked SA is on 230V

Yes agreed with @HendrikBigChiefthe standard for single phase supply voltage is 230v derived from 3ph 4 wire supply square root of 400v(3ph voltage) = 230v. Under and over voltage should be investigated as to the actual cause.

Delta/star transformers, also known as delta-wye transformers, are commonly used in electrical power distribution systems. They are designed to handle both balanced and unbalanced loads effectively.
In a delta connection, the primary and secondary windings are connected in a triangular shape. This configuration allows the transformer to handle unbalanced loads efficiently. The delta connection provides three independent paths for current flow, which makes it suitable for unbalanced loads. In Delta Star transformers if  unbalanced loads occur within the star winding the neutral current increases dramatically and voltdrop occurs within that winding resulting in temprature rise and inefficiency in the transformer. It is thus imperative that regular load balancing needs to be done as single phase loads is added( new primises ).

By changing taps on a supply transformer high or low supply voltages could be mitigated unless there is huge unbalance on one of the phases or the transformer capability is exceeded as a unit where transformer failure will occur within time. Checks and balances needs to be done regulary to ensure quality of supply at consumer level especially single phase customers that affect the balance of the 3ph 4 wire transformer.

 

Edited November 6, 20241 yr by TaliaB

The City of Tshwane just closed the case with the comment that they "checked, and there is power on the meter". I cannot beleive that a METRO have this level of skill in its team, any suggestion as to what I can do next.

13 minutes ago, Speedy said:

The City of Tshwane just closed the case with the comment that they "checked, and there is power on the meter". I cannot beleive that a METRO have this level of skill in its team, any suggestion as to what I can do next.

OK, I don't live in Thswane, but we have had voltage problems in my neck of the woods (under rather than your over). The way we eventually got it sorted was to get everybody in the area who had the means to check their supply voltage. Then everybody finding voltage regularly outside of the tolerance (10% either way) had to log a call, then we worked with our councillor to consolidate all the data and the call references. What this did was allow City Power to see if there was a pattern of under voltage or if it was just one or two properties, and the addresses (included in the consolidated data) helped them decide which substations had to be adjusted. 

You won't get this done by yourself, and your councillor will have to put in some hard yards. But speak to your neighbours or put a query on street/suburb social media. 

The problem I've just described was narrowed down to a certain number of neighbouring streets. Then one day our power goes down, then about 10 minutes later came back on, but at a better voltage. 

The 2nd chapter is that later three houses in my street with consecutive numbers (and possibly a 4th, but that person is reclusive and shares no information) found their supply voltage dropping again. City Power sent a technician out, but he needed to test. What he did was similar to what is described earlier in this thread. He asked us to bypass or unplug any inverters. One house refused him entry, but he asked the other two of us in turn to turn on everything we could and he measured the voltages at the top of the street pole. Then he did these tests a second time, but now measuring at the meter. He finds no difference between the meter and the pole. So now it's process of elimination.

So he checks the overhead cables for damage or for intrusion by trees. Finds a birds nest in the box on top of the next pole in the street. No difference. Then he tells us he is going to look at the sub supplying the street. Before he returned about 10 minutes later I had seen the voltage improve. But no, we had to test again (which I was OK with - he's taking us seriously and he's being rigorous). Now he doesn't see the same drop (at the properties that granted him access) and he's happy.