Power Quality Affecting Client Billing

Posted on 14th May 20243rd October 2024 by Bertie Bezuidenhout

Peruse this document for a more comprehensive understanding of the subject addressed in this paper.

While power electronics equipment can enhance efficiency and control, they can also cause distortions in the power system, leading to power quality issues. Harmonics, which distort the standard sinusoidal waveform of power, can result in various problems such as equipment overheating, malfunctions, and inefficiencies. Solid-state power meters are often considered a reliable method for power measurement, including harmonic power monitoring. But is this presumption accurate? These devices are expected to deliver precise and instant data, thereby also improving power quality management.

Traditional billing methods may not accurately represent actual power consumption in these situations. Hence, the idea of balanced billing is to be introduced. Balanced billing strives for fair and precise billing by considering the complexities of unbalanced and non-sinusoidal voltage supply.

In a previous blog post, I showed how consumers could face significant financial impacts on their electricity bills due to imbalanced network situations. On the other hand, electricity producers, regardless of whether they use coal-fired power plants, nuclear energy, or renewable sources, might remain unaffected. This indifference stems from the potential profit increase they could gain from the inefficiencies caused by these imbalanced network conditions.

Electronic meters improve the accuracy of active power measurements by including harmonics filtering. As domestic electrical appliances become more sophisticated, they produce higher harmonic levels that need to be considered in the active power measurement. While electromechanical methods can measure harmonic power up to the 5^th harmonic, electronic methods can accurately estimate up to and beyond the 63^rd harmonic.

Including harmonics in active energy calculations improves the accuracy of billing and grid management, especially as the occurrence of non-linear loads in domestic appliances increases. Without a standardized method for measuring harmonic power, a qualitative evaluation of electronic energy meters can help determine if a solution is capable of such measurement. Recent advancements in integrated circuit technology, as indicated by Analog Devices’ ADE product line, now allow energy meter designers to provide low-cost harmonic energy measurements, meeting the changing needs of energy providers.

Utility companies often levy additional charges on medium and large customers with low power factors. However, these charges can be unfair in situations where the installations are subject to voltage imbalance and harmonic distortion. It is crucial to establish the fairest definitions of Power Factor (PF) and their corresponding measurement methods when powering a constant impedance load or an induction motor with unbalanced and non-sinusoidal voltages.

Fairness is defined by the expectation that a meter, built based on a specific definition and measurement method, should produce values under non-ideal supply conditions that are very close to those it would yield under an ideal balanced sinusoidal supply.

To achieve this, both meter manufacturers and power distribution companies need to include a variety of computational simulation methods in their design and production processes. These methods should simulate different scenarios where a balanced customer, represented as a constant impedance load or an induction motor, incurs costs due to a voltage supply that is no longer balanced and sinusoidal. The same methodology should be applied to an induction motor under a wide range of unbalanced, non-sinusoidal supply situations.

It is crucial for utilities to have the confidence to install any meter in any electrical environment (sinusoidal or non-sinusoidal) knowing that they will all produce identical readings for the same load. Anything less is unacceptable.

My personal question is: is this being implemented? Prepaid meters were introduced many years ago when the phenomenon of harmonics, or the distortion of the normal sinusoidal waveform of power, was perhaps completely unknown. However, those prepaid meters have not been replaced, and I question whether the “new smart meters” are constructed based on the principles discussed in this paper.

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Who Gains Advantage from Unbalanced Network Conditions?

Posted on 9th May 20243rd October 2024 by Bertie Bezuidenhout

What could possibly prompt Eskom or any power distribution companies to look into issues of unbalanced power networks? Could it be the threat of legal proceedings?

I understood that a representative from Eskom was notified about potential network imbalances at the Modderbee municipal substation, but it might have been disregarded as unlikely. However, since I was not present, I cannot vouch for the accuracy of the information I received indirectly.

The secondary reason for publishing this article is my effort to reach out to someone who professes to have extensive knowledge about Eskom’s power quality. I did not just send one email, but two. Despite being successfully delivered, the first email went unanswered, and the second was “deleted without being read,” as per the notification I received in my email account.

Consider the recent increase in reported issues with cables and transformers, and then draw your own conclusions: Are Eskom and other power suppliers aware of the network imbalances? Moreover, do they implement sufficient checks to identify these issues in the networks? From what I’ve observed, it doesn’t seem so. They seem to ignore any alerts related to network imbalances.

A question that often arises is: who benefits from the extra costs that customers incur due to unbalanced network voltage conditions? Let us explore this. Customers need a specific amount of electrical power, also known as real power, to perform certain tasks. However, the unbalanced network conditions result in a significant increase in inefficient powers, leading to a rise in apparent power. As customers’ bills are mainly calculated based on this apparent power, they end up paying more for these inefficient powers. On the generation side, power must be produced to also compensate for the losses. Each unit generated carries a profit margin. Hence, the more units produced, the higher the profits. It is crucial to remember that all power plants, whether they are coal-fired, nuclear, or renewable, do not operate as non-profit organizations.

It’s also important to note that network imbalances are not easily noticeable in power supplies. For example, in Linden, people might believe the power supply is working properly by examining the phase-to-neutral voltages. Likewise, in Modderbee, officials from Eskom and the electricity department might view the network as free of issues when they see that the phase-to-phase voltages are stable.

If you think that living in a different part of the world protects you from unbalanced network conditions, it may be beneficial to reevaluate that belief. As highlighted in this document, you might be completely oblivious to such events.

Read this document.

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Power Networks in Flux – Balancing the Unbalanced

Posted on 6th May 20243rd October 2024 by Bertie Bezuidenhout

Unbalanced network conditions in power supplies can be deceptive because phase-to-neutral voltage measurements might not reveal the full picture. Here are why phase-to-phase voltages might not be close to each other even if phase-to-neutral voltages are:

Unmatched Impedance: If the impedance in the transformer banks is unmatched, it can cause unbalanced conditions that are not apparent in phase-to-neutral measurements but will affect phase-to-phase voltages.
Large Single-Phase Loads: When large single-phase loads are unevenly distributed across a three-phase network, it can create an imbalance that affects phase-to-phase voltages.
Generation Faults: Faults in power generation can lead to unbalanced conditions that might not be detected by measuring phase-to-neutral voltages alone.

In the case of Linden and Modderbee, officials may overlook unbalanced conditions by only considering phase-to-neutral or phase-to-phase voltages. It is crucial to measure both to get an accurate assessment of the power supply’s balance. Unbalanced conditions can lead to equipment damage, increased network losses, and inefficiencies. Therefore, comprehensive measurements and analysis are necessary to ensure the reliability and safety of the power supply.

To determine if you are paying too much for electricity, you can indeed perform a simple check using a clip-on ammeter and a voltmeter to calculate the apparent power in volt-amperes (VA). Here is how you can do it:

Measure the Current (I): Use the clip-on ammeter to measure the current flowing through the circuit.
Measure the Voltage (V): Use the voltmeter to measure the voltage across the circuit.
Calculate Apparent Power (S): Multiply the current by the voltage to get the apparent power in VA.
Determine the Cost: Multiply the apparent power by the tariff rate provided by your electricity supplier.

This method gives you an instantaneous reading of your power usage, which you can compare with your electricity bill to see if there is a significant discrepancy. If you suspect your meter is faulty, having it tested is a good option despite the initial cost which would likely be refunded if the meter is indeed faulty. Regular monitoring of your power usage can help you identify any inconsistencies or potential overcharges on your electricity bill.

To accurately determine if you are being overcharged for electricity, it is essential to consider the following assumptions:

Constant Current and Voltage: The assumption that current and voltage remain constant is a simplification for calculation purposes. These can fluctuate due to various factors such as appliance usage and utility supply stability.
- Perfect Power Supply: Assuming a perfect power supply without any fluctuations is an ideal scenario often used in theoretical calculations but not typically found in residential settings.
Synchronized Timing: Starting the measurement process at the same time as the meter reading ensures that the comparison is based on the same usage period, which is crucial for accuracy.
Meter Accuracy: It’s assumed that the meter is accurately measuring the power consumption without any faults or errors.
No Unauthorized Usage: This assumption implies that there is no electricity theft or unauthorized usage being recorded on your meter.
No Additional Charges: It’s assumed that the bill reflects only the cost of electricity consumed, without any additional fees or charges that could affect the total amount due.

By carefully considering these assumptions and comparing your actual power usage with the billed amount, you can determine if there is a discrepancy. If you suspect an error, it may be necessary to have your meter tested or to consult with your electricity provider for clarification. Remember, the accuracy of your determination is contingent upon the validity of these assumptions. If any of these assumptions do not hold true, the conclusion drawn about overcharging may not be reliable. These assumptions are necessary for a simplified calculation, but they do not reflect the complexities of actual power usage and supply conditions. For a more accurate assessment, a continuous recording of power consumption over the billing period, accounting for fluctuations, would be required. This data could then be compared with the meter reading on your bill to determine if there is a discrepancy indicating you might be paying too much for electricity. If such a discrepancy is found, it would be advisable to have your meter tested. Remember, the cost of testing the meter is typically refunded if the meter is found to be faulty.

Unbalanced voltage conditions in power supplies can indeed have significant effects, even if they are not immediately obvious. Let us explore why phase-to-phase voltages might not be relatively close to each other, despite phase-to-neutral voltages appearing balanced.

Voltage Imbalance and Its Causes:
- Voltage imbalance occurs when the voltages in a three-phase system are not equal. It can result from various factors:
  - Generation Faults: Issues in the power generation process can lead to voltage imbalances.
  - Unmatched Impedance: Transformer banks with unmatched impedance can cause imbalances.
  - Single-Phase Loads: Unevenly distributed single-phase loads across the three phases can create voltage imbalances. For example:
    - If one phase carries significantly more current due to single-phase motors or heating/cooling loads, the line-to-neutral voltage of that phase will be lower than the other two.
    - Similarly, if most of the load is connected over only two phases, one line-to-neutral voltage will be higher than the other two.
  - Unbalanced voltage affects both induction motors and electronic rectifiers.

Effects on Induction Motors:
- Motor Torque and Speed: Unbalanced voltage negatively impacts motor torque and speed.
- Noise: Motors may produce excessive noise.
- Current Imbalance: Voltage imbalance can lead to increased current imbalance.
- Temperature Rise: The temperature rise due to voltage imbalance can be much greater than the percentage of imbalance itself.
Why Phase-to-Phase Voltages May Differ:
- Even if phase-to-neutral voltages appear balanced, phase-to-phase voltages can differ due to the specific load distribution.
- Consider a scenario where:
  - Phase A has a higher load (more single-phase devices connected).
  - Phase B and C have relatively lower loads.
- In this case:
  - The line-to-neutral voltage of Phase A will be lower.
  - The line-to-line voltages (Phase A-B and Phase A-C) will also differ.
- Thus, phase-to-phase voltages may not be close to each other, even when phase-to-neutral voltages seem balanced.
Practical Implications:
- Unbalanced voltages can lead to equipment damage, motor inefficiencies, and increased network losses.
- Monitoring phase-to-phase voltages is crucial to identify and address voltage imbalances.

Remember that maintaining balanced voltages across all three phases is essential for a stable and efficient power supply. If you encounter unbalanced conditions, further investigation is necessary to ensure the health of your electrical system.

A deep understanding of the complexities involved in electrical power systems and the importance of accurate billing are based on the actual power consumption. Concerns should be raised about the potential discrepancies in power distribution and billing, especially in the context of an unbalanced network where inefficiencies can lead to increased apparent power and potentially higher charges for consumers.

Here is a brief overview of the power types:

Real Power (P): This is the power that performs work in the circuit, such as running appliances or lighting. It is measured in watts (W) and is what consumers ideally should be billed for.
Reactive Power (Q): This power does not perform any real work; instead, it is used to maintain the electric and magnetic fields in inductive and capacitive loads. It is measured in volt-amperes reactive (VAR).
Apparent Power (S): This is the combination of real and reactive power and represents the total power supplied to the circuit. It is measured in volt-amperes (VA).

The relationship between these types of power can be represented by the formula:

In a perfectly balanced system, the real power would equal the apparent power, and there would be no reactive power. However, in practical systems, especially those that are unbalanced, the apparent power is typically higher due to the presence of reactive power.

If you are being billed solely on apparent power, it is possible that you are paying not only for the real power consumed but also for the inefficiencies of the system.

The document attached to this blog post contains a whole lot more detail concerning the unbalanced power network condition in Linden and Modderbee.

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Contravention of Fiduciary Duties

Posted on 8th April 20243rd October 2024 by Bertie Bezuidenhout

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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Compensating For Power Quality Issues Caused by Power Electronics Devices

Posted on 2nd April 20242nd June 2024 by Bertie Bezuidenhout

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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Unfazed Attitude Towards Power Quality Issues

Posted on 30th January 20242nd June 2024 by Bertie Bezuidenhout

On September 24, 2023, I posed an article in which I explained how poorly maintained switchgear could lead to long-lasting power quality issues. In that article, which was based on an actual incident in Benoni, Gauteng, South Africa, I mentioned that the voltages of two of the three phases increased by more than 51% while the third phase dropped to a value which was almost zero. I also stated that further investigation was needed “to determine the cause of the voltage discrepancy”. The content of this article was also posted on other media with links sent to several people I believed should be made aware of what could be happening without anyone knowing about it. Amongst them was someone who, from what I was told, sent the information to the municipality. I even placed the pertinent parts of the article in a newsletter that was sent to those on a mailing list, including people at Eskom.

In that same article, I commented that I am not sure whether an investigation will be done. Almost five months later and numerous more attempts from my side to “escalate” this kind of issue, and I have not been contacted. So, I am beginning that believe that the municipalities and/or Eskom is unperturbed about issues of poor Power Quality.

On October 2, 2023, I posted another article in which I stated that “In many cases operators and maintenance crews are unaware of the negative consequences that phase imbalances can have on LV networks and electrical equipment. Current imbalances would lead to a reduction in the serviceable loading capacity of LV cables and distribution transformers. Because of the imbalances, some of the phases could carry higher loads while the remaining phase or phases could be lightly loaded but, the limiting factor for the addition of three-phase loads is the current on the highest loaded phase or phases.

“Current imbalances can also cause additional heat losses in distribution transformers and LV cables in both the phase and neutral conductors. These types of losses represent a signiﬁcant part of the total losses occurring in LV networks.

“When end users, such as municipalities, are supplied by unbalanced voltages, induction machines and power converters face adverse effects such as reduced efﬁciency, increased losses, potentially dangerous overheating and, in some situations, premature failures. At severe voltage or current imbalance levels, some types of protection relays could malfunction, leading to miscoordination, nuisance tripping and lack of selectivity.”

In that same article, I also said that such issues are usually not restricted to just the one substation. Often it may affect an entire region, depending on where the fault is located. There be many such issues going unnoticed.

Late December 2023, I learned that people in the Magaliesburg area are having to replace electric motors and other electronic equipment quite frequently. Earlier this week, while in the Magaliesburg area, I noticed the signs of an Unbalanced Network. This has probably been going on for many years, listening to those living and running businesses in that area.

On November 7, 2023, I posted an article in which I pointed out how unbalanced voltages, phase-shift variations, and harmonics disturbances would result in enormous economic losses. This was aimed at accountants and financial officers to make them sit up and start to notice how some financial losses at their businesses are preventable. I mentioned how “customers on that feeder [the one in Benoni], are most likely paying around 237.27% more than they ought to”.

Now, the question is: is there an Unfazed Attitude Towards Power Quality Issues?

Judging by the lack of action from all those who have or must have seen these articles, I would say YES, there certainly is Unfazed Attitude Towards Power Quality Issues.

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Cost of Complacency

Posted on 7th November 20232nd June 2024 by Bertie Bezuidenhout

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 believes 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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Consequence of Weaknesses in Power Quality

Posted on 23rd October 20232nd June 2024 by Bertie Bezuidenhout

In the mid-eighties, as part of my function, I was asked to help and solve a problem of one of our client’s constant complaints about “power failures”. This client was the National Accelerator Centre (NAC) in Faure, Western Cape. Today it is called the iThemba LABS. According to their website, this is the largest accelerator facility in the Southern Hemisphere and the only Cyclotron facility on the African continent.

When I contacted them to find out what the issues were, I was invited to visit them and given several private tours throughout the facility so that I could understand the intricacies of their operation. On more than one occasion, I was taken all the way through to the operating room so I could understand the consequences of power interruptions. I was also shown the damages that was caused every time there was a “power interruption” and explained how long it took them to repair the damages. However, after my first visit, I pulled all the daily incident reports and could not find any power interruptions that occurred on the corresponding dates.

I could not argue that there were no “power interruptions” since I saw the damage. I then enlisted the services of our specialist department. At this point, I must stress, that the kind of instrumentation that is currently available on the market, did not exist. Most of it had to specially build and for a particular function.

Approximately a month later, the specialists came back with, what people may describe today, as rudimentary instrumentation. This was installed at the substation with clear instructions that no-one else were allowed to enter that substation without my presence. Wire was strewed all over the floor. Essentially, the main instrument was a high-speed analogue-to-digital converter that could be trigger by set parameters which then records everything on a computer that we bought specifically for this exercise. When an event occurred, everything before and after an event was recorded. Today, this is a built-in standard function of my Power Quality Monitor. The purpose of that instrumentation was to give us a set of data that we could analyze to determine the cause of power distortions.

After collecting the data, I spend a considerable amount of time to find a correlation between the event recorded at that substation, and anything that happened on the entire network which could have been related. This was a mammoth task and I spent long hours going through daily incident reports obtained from both the local and national control centers.

During this exercise, I found that some of the incidents related to the tripping of 400- and 132kV circuit breakers over a thousand kilometers away.

With this information, I went back to the executive of National Accelerator Centre. I told them that my news was not good and there was nothing we could do about the problem. Whatever caused the “power distortions” was within the power supply limits at that time. I did, however, undertook to help wherever I could, and it was then that I contacted a friend at a European company with presence in South Africa, to come up with one or more solutions. One of those solutions was a motor-generator set with a massive sized flywheel. Whether that was implemented, I am not sure since I was promoted shortly afterwards and move to a different part of the country.

The primary reason for this blog is that, at that time, I was supported by all my seniors all the way up the ranks, and they often visited the site to find out how they can be of assistance. Judging by what I see and experience now, I doubt if this will happen today or anytime soon.

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Power Network Disturbances

Posted on 13th October 202323rd March 2024 by Bertie Bezuidenhout

Throughout my time in the power transmission and distribution industry I have probably had experiences that many others may never have. In a previous post, I talked about the current and voltage unbalances and how a large factory in the Western Cape in South Africa was severely affected by negative phase sequencing. In this post I want to touch on another incident we have had around that same time.
Without being directly involved, I learnt about a 500kW electric water-pump motor that was ripped out of its foundation, breaking the water pump, and causing major havoc in the pump station leaving a large urban area without water.

The question that should be asked: are those responsible for looking after the factory or mine aware of the influences of voltage / current harmonics and phase unbalances among several other similar negative effect on their plant? Most probably not since many think that if the lights are burning, everything is hunky-dory, and they should not worry about anything. Fact is, it is not and it is worthwhile to read the other blogs.

If you think that this only applies to South Africa, think again. It is happening in Ireland and the USA or wherever you are from: those reading my blogs.

A second topic I want to discuss is how something unexplained is later contributed to something someone think is “fact”. Many years ago, the loss of power transformers connected to overhead power lines were all contributed to lightning damage. When I worked at Eskom Western Cape in the eighties, I used to receive a daily incident report for the entire region. One day, I noticed that twelve 22kV/380V transformers were lost due to lightning in the Calvinia and Williston areas. I would not except what was stated in the reports and instructed the depot to dispatch all those transformers back to the main workshop in Brackenfell. I also instructed the head of the transformer workshop to cut those transformers open as soon as they arrived and let me when it is done. After the top lid of the transformers were cut open, we found that the core of the transformers was “standing” in water that penetrated over time. We would have spent vast amounts of money on additional lightning protection for something that had nothing to do with lightning.

Then, a few years later, I asked one of my subordinates why there was such a large maintenance backlog. His explanation was that the maintenance crews are not maintaining the 22kV/380V transformers. I immediately instructed him and the person reporting to me to remove all those transformers from the maintenance schedule. I then had to explain that one of the maintenance strategies that should be employed is run-to-failure. It cost less to replace those transformers than to maintain them on a regular basis. Obviously, the cost includes all the associated costs.

Now, I am an independent consultant and working for myself, I can do these types of investigations. That means proper Power Quality Investigations and many more similar types of analytical work.

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Power Quality Issues Caused by Distributed Generation

Posted on 11th October 20232nd June 2024 by Bertie Bezuidenhout

To mitigate the effects of Load-Shedding, many homeowners have decided to install PV Solar Energy systems. And, as I said before, they are more worried about how much it would cost than the quality of the products. If they can pay the lowest possible price for the entire installation, they are happy and do not care so much about what they get.

During the early stages of Load-Shedding, someone from our neighborhood asked me for advice regarding a PV system, but when I gave him a rough estimate of what it would cost, including the cost of a well-engineered design, I could see that the price was far more important than the quality of the system. Those advertising in the newspaper say that something the with same output would cost far less. Not long after he had his PV system installed, he told me that their washing machine had broken down and that they were compelled to replace it. I did respond since I knew what the cause of it was.

As in many other countries, PV systems with microgrids has become an unavoidable choice. This, in turn, bring along new challenges for utility companies. Naturally, if those employed by the utility companies are awake, knowledgeable, and experienced, they can proactively conduct power quality monitoring exercises. With the ever-increasing expansion of renewable energy systems, the most important power quality challenges that is brought about, is the harmonic distortion which affect the voltage and current quality at the point of common coupling (PCC), and negatively affects the loads.

We are all aware that there is a wide variety of inverter models are available on the market with new ones added constantly. Consequently, the harmonics delivered to the main power grid will thus vary according to inverter types and their control strategies. Utility companies therefore must have the knowledge, skills, and instrumentation to investigate the impact of these components that accompany the renewable (embedded / distributed) generation.

The technical consequences of distributed generation are dependent on the size of the system and its location in relation to the main power generation grid. These influences are reverse power flow, overvoltage along distribution feeders, voltage / current harmonics, phase unbalances, power losses, voltage control disturbances, low power factor, and Electromagnetic interference problem.

To overcome these effects, grid measurements, data analysis, and system modelling are needed for different parameters of grid and electricity generated by the renewable energy suppliers to find solutions and to make this resource more reliable.

Power quality parameters such as inrush current, power factor, total harmonic disturbance (THD), and frequency fluctuation should be recorded and studied regularly.

Inrush Current is a small predictable difference between distributed generating station’s voltage and utility grid voltage which can produce transient inrush currents. This can cause a temporary voltage sag at the neighboring buses, nuisance trips, thermal stress of the power components and several other problems.

With Under Voltage / Overvoltage, the grid connected distributed generating systems only inject active power into the utility grid, which may change the value of reactive power that flow in the system.

Output power fluctuation is one of the main factors that may cause severe operating problems for the utility network. This occurs because of variations in solar irradiance caused by the movement of clouds and may continue for minutes or hours. This may cause power swings, voltage flickers and fluctuations of over / under voltage.

Power factor often decreases to unacceptable levels due to high-powered distributed generation which sits on lightly loaded short distribution lines.

Current and voltage harmonic distortion, voltage and current distortions is generated by nonlinear loads such as power inverters that are used in solar systems where the currents flowing through the impedances of the grid affecting the voltage nodes. Harmonics produced under such circumstances can cause series and parallel resonances, overheating in transformers and capacitor banks, and false operation of protection devices that may reduce the reliability of power systems. A total harmonic distortion voltage (THDu) value of between 5% and 8% indicates significant harmonic distortion. Some equipment malfunctions may thus occur. The acceptable current and voltage harmonic level generated in the microgrid was specified by the IEEE standards 519 and 1547 and IEC-61000-3 standard, and this should not exceed a THDu of more than 8%.

Frequency fluctuation is an important factor in power quality. Any change between the produced and the consumed power may lead to frequency fluctuation. Small sized solar systems may cause frequency fluctuation to be insignificant compared with other renewable energy-based resources. However, this issue may become more severe by increasing the penetration levels of solar systems. Large enough frequency fluctuation may change the winding speed in motors and may damage generators.

Although there may be more solution available to moderate the impact caused by distributed generation, one suggestion is to switch off some or all the PV panels when flowing current is under the critical value, or rather divert the power to charging a battery bank. A second suggestion is the use of passive or active filters.

When new solar farms are proposed for connection to the municipal distribution network where this is perhaps far more critical, neither solution are compulsory, as far as I understand. I recently saw a proposal for a grid-tie solar farm without batteries nor active passive or active filters. But, as I said earlier on, utility companies need employees who are awake, knowledgeable, and experienced to know what to look for. Alternatively, utility companies can contract a company, us, to regularly conduct power quality monitoring exercises on their behalf.

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