Harmonized Power

Power quality problems have persisted for a considerable period. Despite this, awareness of these issues was not widespread in the past, and it seems that the situation remains unchanged today.

It is also important to note that network imbalances are not easily detectable in power supplies. For example, some people might believe that the power supply is operating correctly by examining the phase-to-neutral voltages. Likewise, others might conclude that the power supply is in good working order by measuring the phase-to-phase voltages and finding them satisfactory.

Power system faults are frequently unbalanced, making the analysis complex. However, the use of symmetrical components simplifies this process. By converting the system into these components, engineers can more effectively examine the behavior of faults.

Symmetrical components enable the transformation of intricate three-phase networks into three simpler sequence networks. For balanced three-phase systems, these sequence networks are independent, while for unbalanced systems, they connect only at points of imbalance. This division streamlines the analysis and presents complicated phenomena in a more comprehensible manner.

Instead of duplicating the complete explanation of Symmetrical Component Analysis from the Agulhascorp website, I have opted for a different strategy. I recommend delving deeper into these topics to understand the logic behind this analysis and gain knowledge about Negative Phase Sequencing. This exploration will provide you with the necessary foundation to understand the upcoming discussion.

From my perspective, and many others concur, the only way to identify power quality issues in your locality, city, province, or country is by gathering a multitude of parameters to aid in conducting an exhaustive Symmetrical Component Analysis.

During the installation of the Power Quality Monitor at the Modderbee municipal substation in Springs on August 30, 2023, we observed a phase-to-neutral voltage discrepancy. To validate this, I employed a secondary device and confirmed that the voltage was indeed below 2 volts, whereas it should have been approximately 6.6kV. Nonetheless, the discrepancies between the phase-to-phase voltages were found to be minimal. Our hypothesis was that a blown fuse on the secondary side of the busbar-VT could be the culprit. Despite this, we proceeded with the installation, prioritizing current measurements.

The essential understanding is that conducting a proper Symmetrical Component Analysis to identify any potential problems with power distribution is unfeasible without the correct tools to simultaneously gather all necessary parameters.

The Modderbee municipal substation, which is supplied by two 6.6kV cables from the Eskom substation located approximately 20 meters away, is equipped with two 6.6kV busbars and an open bus-section breaker. Due to that specific arrangement, the busbar-VTs are responsible for measuring the incoming voltages from both 6.6 kV cables.

After analyzing the Power Quality Monitor results, the feeder being measured experiences substantial current and voltage imbalances. Given the significant imbalances, I felt compelled to notify both the senior individuals in the electricity department of the City of Ekurhuleni Metropolitan Municipality and the responsible Eskom officials overseeing the nearby substation. Facing this challenging situation, I recognized the need to change my approach.

Despite my numerous pleas to City Power to probe potential imbalances at the Roosevelt Park substation in Johannesburg, and even offering my assistance to identify if this issue was localized, I took it upon myself to install my own Power Quality Monitor at a nearby three-phase setup. I had a hunch that our area was suffering from unbalanced network conditions, and I was eager to validate this.

On April 12, 2024, I installed my Power Quality Monitor at a house in my neighborhood for approximately 20 hours. After retrieving the device and briefly analyzing the data, I noticed a significant drop in two of the three phases at 04:23:55. At first, I was puzzled as to why only two phases were affected while the third remained stable. However, a thorough examination of the data confirmed that our residential area is indeed susceptible to unbalanced network conditions.

Despite my attempts to get City Power to perform a concurrent assessment for unbalanced network conditions, I am still awaiting the requested results. Nevertheless, I have already shared my data with them.

The question that should have been raised based on my statement “you will notice that the phase-to-phase voltage between phases 2 & 3 is less than 1 volt” is “why?” The voltage recordings were at 21:20:00 on April 12, 2024, between phases 1 & 2 was 414.9-volts and between phases 1 & 3 was 414.82-volts.

If you are under the impression that residing in a different part of the globe shields you from unbalanced network conditions, it might be worth verifying that assumption. As outlined in this newsletter, you might be totally unaware of such occurrences.

Perhaps it is worth noting that it is not the first-time unbalanced network conditions have had a severe impact on consumers. In a blog post how transmission lines with high and extra-high voltage that are untransposed, can cause Negative Phase Sequencing which could lead to production losses. In another blog post how the power factor often decreases to unacceptable levels due to high-powered distributed generation which sits on lightly loaded short distribution lines.

These are just a few articles I have published concerning power quality issues but there is a few more worth perusing.

In September 2023, I resumed my newsletters, incorporating excerpts from my findings. My goal is that someone connected to Eskom’s power quality team, the distributors, or South Africa’s AMEU members will take notice and investigate whether this issue is localized or more widespread.

Also starting in September 2023, I have consistently provided insights on Symmetrical Component Analysis through the Agulhas Utilities Corporation’s website, blog, LinkedIn, and Facebook. My intention was to catch the attention of Eskom employees who might find my posts informative and share them with their colleagues responsible for power quality. However, my efforts have yet to yield the desired results, leaving me to wonder if anyone from Eskom will ever take notice. Moreover, my email to the Group Executive (Distribution) appears to have been disregarded without being read. My attempts to connect with senior officials in the City of Ekurhuleni Metropolitan Municipality’s electricity department via email have also been unsuccessful.

Upon reviewing the “Power Quality Data Linden” spreadsheet that I sent to City Power officials on March 15, 2024, they should have immediately asked: What is the impact of voltage imbalance on electric motors, generators, transformers, and power supply cables?

Motor performance is dependent on voltage. A 1 percent voltage imbalance at a fully loaded motor’s terminals can result in a 6 to 10 percent phase current imbalance. This imbalance increases the motor’s operating temperature, reduces its energy efficiency, and shortens its lifespan. Moreover, unbalanced voltage changes the motor’s speed and torque characteristics. It leads to an unbalanced stator current, increasing losses and net torque. The negative sequence current creates a backward-rotating magnetic field and a torque opposite to the positive sequence component. As a result, the torque from the negative sequence current tries to slow down the motor by applying counter torque.

Recently, I have been discussing the financial impact of unbalanced networks on customers’ bills in a blog post. These unbalanced networks result in customers paying significantly more for their electricity. I have also written articles highlighting how unbalanced networks lead to additional charges for customers.

The document incorporated with the blog post provides a succinct explanation of the principles of balanced and unbalanced power networks. It uses real-world data to illustrate the differences between balanced and unbalanced network scenarios.

The question I am addressing is whether Eskom and other power distributors are aware of unbalanced network conditions and what actions they are taking to rectify them.

Despite my numerous appeals to City Power to investigate potential imbalances in the network at the Roosevelt Park substation in Johannesburg, and even offering my services to help determine if this issue was localized, I took it upon myself to set up my own Power Quality Monitor at a nearby three-phase installation. I suspected that our area was experiencing unbalanced network conditions, and I wanted to confirm this.

Significantly, in a recent blog post, I have shown how consumers, who are subjected to imbalanced network conditions, carry a substantial financial load via their electricity bills. On the other hand, those producing electricity — be it through coal-fired power plants, nuclear, or renewable energy — might remain unaffected. This is because the inefficiencies stemming from these imbalanced network conditions could potentially enhance their earnings.

In the evolving landscape of power systems, the role of power electronics equipment has become increasingly significant. However, this advancement brings with it a set of challenges, particularly in terms of power quality. Power electronics equipment, while offering improved efficiency and control, can introduce distortions in the power system, leading to power quality concerns.

One of the key aspects of power quality is the level of harmonic content in the overall power supply. Harmonics, or the distortion of the normal sinusoidal waveform of power, can lead to a variety of issues, including equipment overheating, malfunctions, and inefficiencies. Solid-state power meters are frequently viewed as a dependable technique for power measurement, encompassing the monitoring of harmonic power. However, is this assumption valid? It is anticipated that these devices will provide accurate and immediate data, thereby enhancing the management of power quality.

In my blog post titled “Power Quality Affecting Client Billing,” I delve into the unique billing challenges posed by unbalanced and non-sinusoidal voltage supply. I also explore the idea of balanced billing, a method that ensures fair and accurate billing by considering the intricacies of unbalanced and non-sinusoidal voltage supply.

It is essential for utility companies to be confident in their ability to install any meter in any electrical environment, whether sinusoidal or non-sinusoidal, with the assurance that all meters will yield identical readings for the same load. Anything short of this is not acceptable.

I am left wondering: is this principle being put into practice? Prepaid meters, which were introduced at a time when the phenomenon of harmonics — the distortion of the normal sinusoidal waveform of power — was likely not fully understood, have not been replaced. I question whether the “new smart meters” are designed in accordance with the principles I have discussed in this blog post.

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