It is important to realize that unbalanced networks are not easily manifested in power supplies.

In this document, I am highlighting two cases in which unbalanced networks are perhaps not easily noticeable. In the case of Linden, people may think that the power supply is normal by measuring the phase-to-neutral voltages. In the case of Modderbee, Eskom and officials from the electricity department may think that there is nothing wrong with network when they select the phase-to-phase voltages and notice that it is almost the same.

Perhaps an even more important question is: do the unbalanced networks affect the customers’ electricity bills? The short and simple answer is yes, it does!

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On the 2^nd of October 2023, I published an article with the heading “Phase Imbalance in Distribution Networks” in which I stated that “In a recent unrelated “survey”, I came across a 10-minute averaged voltage unbalance of 327% between Phase 2 and Phase 1”. I also asked the question: is Eskom aware what is happening on the Distribution and Reticulation Networks? I also stated that, since the medium-voltage supply comes directly from an Eskom substation which is probably about 20-metres away, one wonders what is going on at the Eskom substation since it is highly unlikely that the voltage unbalance is as a result faulty equipment at the municipal substation. It is as if one phase is completely missing. The same “missing” phase also show an abnormal high current. The neutral current which is supposed to be at or close to zero is also very high.

In a recent webinar, I posted a question about power quality disturbances. I was then told about the large number of Quality of Supply Instrument that Eskom have installed, assuming that it is regularly maintained and monitored so that poor power quality issues will be detected almost immediately, and action taken to rectify whatever may be causing the issue or issues.

Last week, I reached out to someone at Eskom I believe may be able to help me to have this situation investigated or refer me to someone who can assist me, but that email remained unanswered and the email I sent this morning, “was deleted without being read”. This person’s name appears to be involved in this type of work on the behalf of Eskom, and that is why I reached out to him. So, my question now is: do Eskom or any of the Power Distributors care about Poor Quality of Supply?

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It is a known fact that there is a growing shift towards renewable energy sources as well as buying and selling electrical power which most often necessitates the use of HVDC transmission systems.

Both the solar power generation and HVDC transmission systems make extensive use of power electronics devices.

In future, more-and-more grid-forming converters (GFMCs) will be introduced as the scale of microgrids also increase. These structural changes would undoubtedly change the system operation paradigms, which in turn, necessitating a deeper understanding how these new devices function and how it would affect network stability and particularly, power quality.

In many studies, it has been found that an extensive use of power electronics devices plays a major role in power quality issues, specifically voltage sags and swells.

The trend of retiring rotating generation plants could lead to grid instability if it is not carefully monitored and actioned well ahead of time before major issues develop. Currently, gas and steam turbine power generation play a vital role in terms of grid inertia and stability.

Thus, with the shift towards renewable energy sources and the trend of retiring rotating generation plants, national grid companies need to consider other alternatives to help compensate for power quality issues caused by power electronics devices. This includes capacitors, static VAR compensators, and static compensators.

The installations of capacitor banks at substations are not new. It is relatively cheap, reliable, and easy to install but it takes up a lot of space and require special controlling devices. An ordinary circuit breaker simply does not work with capacitor banks. Another disadvantage is that they can only supply reactive power and not absorb it. When load rapidly increases and voltage drops, the effectiveness of capacitors diminishes.

Static VAR Compensators (SVCs) consisting of shunt capacitors and reactors and may offer a greater degree of voltage control, but it is of little use for rapid voltage changes.

Although static synchronous compensators (StatComs) with its use of sophisticated power electronics is a far better option, it has a major drawback; it is far pricier than the more basic equipment.

A synchronous compensator is a large piece of machinery. It is spinning generator and flywheel combination. Having it connected to the high-voltage transmission network via a step-up transformer it is kept in sync with grid frequency and thus contributes to network stability, dampening any fluctuations in frequency. Again, this concept is “not new”. In the late 1970s Eskom installed several Synchronous Condensers.

The intermittency of wind energy and the extensive use of power electronics devices, such as found in HVDC transmission systems and solar power generation equipment, emphasizes that grid stabilization and equipped with AC filters to avoid the harmonic impact on the AC network performance, have an increasingly important role in a successful energy transition.

Coal-fired power stations can be repurposed whereby the steam turbine is removed and replaced with a large-mass flywheel and Synchro-Self-Shifting (SSS) clutch. The electrical rotating equipment, such as the existing generators, is then reconfigured to become synchronous condensers. Since it is already connected to the high-voltage transmission network via a step-up transformer, it will become a stabilizing device.

With the rapid shift towards renewable energy sources, we should have started thinking about ways to stabilize the network by installing more synchronous condensers and AC filters to avoid the harmonic impact on the AC network performance. In an article published in the Engineering News of 20 November 2023, it is stated that “Eskom is preparing to introduce 11 synchronous condensers – seven new and four repurposed – across its transmission system to support grid stability as the penetration of variable renewable-energy generators rises”. On 22 June 2023, the Australian Renewable Energy Agency (ARENA) published and supported a report in which the installation of synchronous condensers is also addressed.

A timely commitment to install synchronous condensers is needed because “long queue for new SCs is already forming” [my interpretation based on what I have read about this topic]. Considering that there is already a significant rise in reports about poor power quality issues, my question is: Was this unforeseen by the industry? The large-scale use of power electronics in solar power generation and HVDC power transmission has been around for many years.

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In the latest newsletter which would be published on November 14, 2023, I am making another attempt, this time, to catch the attention of accountants and financial officers explaining to them how unbalanced voltages, phase-shift variations, and harmonics disturbances would result in enormous economic losses.

But first, I must go back to a previous blog posted September 24, 2023, in which I referred to unbalanced voltages and currents I “accidently” came across when I analyzed the measurements, I took for a consulting engineer who wanted to know what the maximum loading on a 6.6kV cable feeder is.

On our website, there are two pages which are particularly relevant to understand the consequences of unbalanced voltages, phase-shift variations, and harmonics disturbances. The most recent one explains how unbalanced three-phase quantities are decomposed into their symmetrical components to understand what happens “almost undetected” but have an enormous impact on the power system. In an earlier published, Negative Phase Sequences have a harmful effect on power system equipment and operation.

In the latest newsletter mentioned above and called Financial Losses Resulting from an Unbalanced Network which would be published on November 14, 2023, under the heading Cost of Sales Losses, I explain how some large power users – industrial and commercial – are paying for Apparent Power (kVA) while they can only effectively use the Real Power (kW). In the incident referred to in the blog posted September 24, 2023, the customers on that feeder, are most likely paying around 237.27% more than they ought to. The ratio of kVA to kW is 3.37:1.

The question is: is that restricted only to large power users – industrial and commercial – or do single-phase power users also get charged so much more. The answer is a little more complex and not that straightforward, but the simpler answer is yes, they do. Everyone, single-and three-phase power users is charged per unit and that unit is kVAh and not kWh. So, those power users fed from that feeder are paying approximately 3.37 times for what they are getting.

When you do go and lay a complaint with the power utility company, they will make you pay to have the electricity meter tested, and I can tell you beforehand, there will be nothing wrong with the meter. What happens next is also not going to solve the problem. Someone will be sent out to check the voltages and currents at the substation, and even that will show that there is “nothing wrong”. Why, they check the voltages between phases with a panel meter which is grossly inaccurate. That would then finally “prove” that there is “nothing wrong”.

If anyone believe that this is only restricted to one area, think again. I have had a discussion with someone from Middelburg, Mpumalanga, South Africa since the incident I referred to previously, who also complaint that their account is mysteriously double than it used to be.

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