Power Quality Unmasked: Protecting Your Operations and Bottom Line

SUMMARY KEYWORDS

Power quality, harmonic distortion, VFDs, non-linear loads, voltage distortion, power electronics, transformer connections, characteristic harmonics, triplen harmonics, protective devices, equipment failure, real-time simulation, power quality meters, operational interruptions, safety risks.

SPEAKERS

Speaker 1, Speaker 2

Speaker 1  00:00

Welcome to the deep dive, where we take a stack of information and find the most important insights for you. Today, we’re diving into a challenge that’s probably buzzing quite literally, I suppose, in many of your facilities, power quality. Specifically, we’re looking at harmonic distortion caused by modern equipment, things like VFDs.

Speaker 2  00:17

Yes, this is absolutely a critical topic if you’re managing operations, safety or electrical systems in, say, industrial plants, mining or even data centres. Well, you need to be across this as our sources really highlight, poor power quality isn’t just some technical glitch, it carries some pretty heavy operational and financial consequences, right?

Speaker 1  00:36

And our source material for this deep dive comes from some really compelling research out of the Durban University of Technology (DUT). They focused on power quality in an island network, which actually has a lot of parallels to complex industrial sites. And we’re also drawing insights from an article discussing common power quality disturbances in heavy industry.

So our mission today is to unpack what these sources tell us about where harmonics come from why they’re a problem for your specific operation, and what understanding them, you know, at a detailed level really means, okay, let’s dive in.

You know, often when there’s a power issue in a facility, the first instinct is maybe to point fingers at the utility provider. That’s a very common reaction, yeah. But what the sources make really clear is that many significant problems actually originate within your own four walls. They stem from the dynamic conditions of your internal network.

Speaker 2  01:27

That’s such a crucial point. Issues like sudden voltage swells, those frustrating undervoltage sags, total interruptions, and yes, our focus today, harmonic distortion. They’re frequently generated internally by the equipment right there in your plant.

One of the sources explicitly notes that in complex systems like you find in mining or big industrial plants, blaming the utility is often, well, simply inaccurate, and the costs of these internal disturbances, they’re not trivial at all. Are they? The sources list a whole range of expensive outcomes. We’re talking operational interruptions that halt production?

Speaker 3  02:02

Yeah, lost data, which can cause real ethics, damaged equipment, leading to expensive repairs or even replacements. Energy inefficiency, driving up your bills potential, utility fines, reduced overall productivity, and crucially, even worker safety.

Speaker 1  02:15

Risks for a facility like a Hein, you know, unexpected downtime linked to power quality could be massive production losses?

Speaker 2  02:23

Exactly, and because the disturbances are so variable and often interconnected, the sources suggest that relying on a single, simple power quality solution is rarely going to cut it. It requires a more comprehensive, sort of multi tiered approach, and they indicate this process really begins by identifying specific devices that are the primary offenders, things like drives, motors, pumps, the kind of stuff that’s everywhere in heavy industry.

Speaker 1  02:50

Okay, so let’s focus on those offenders. Then, where exactly do these disruptive harmonics come from? Especially in today’s facilities packed as they are, with modern control electronics and variable frequency drives VFDs?

Speaker 2  03:01

Well, the main culprits are what we call non linear loads. If you think back to older industrial equipment, the loads were mostly linear. They drew current smoothly, you know, in sync with the voltage, sine wave, yes, and clean, pretty much. But modern equipment, especially power electronics, like the rectifiers used in VFDs, doesn’t do that. They draw current in these short, abrupt pulses, and this fundamentally distorts the current waveform. It’s no longer that clean sine wave flowing into the device. One of the sources specifically highlights how this non sinusoidal current effectively pollutes the network.

Speaker 1  03:34

So it’s those rectifiers inside the VFDs, the ones converting AC to DC, that are the source of the trouble here. How does that pulsing actually create the distortion, right?

Speaker 2  03:43

So the VFDs rectifier charges up a DC bus which has capacitors on it. Once those capacitors are charged, current from the incoming AC supply only needs to flow into the VFD when the instantaneous AC voltage is actually higher than the voltage already sitting on that DC bus.

Okay, so only at the peaks?

Exactly. It only happens for brief periods near the peak of the AC sine wave. So instead of a smooth, continuous flow, you get these pulses of current being drawn. This pulsed non sinusoidal current is what creates the harmonic distortion and injects it back onto your AC network.

Speaker 1  04:19

And this distortion on the current side doesn’t just stay there, does it? It then impacts the voltage wave form across the system, potentially affecting other sensitive equipment connected to the same supply.

Speaker 2  04:29

Precisely that distorted current flowing through the network’s impedance causes voltage distortion, and this can absolutely create power quality issues for other connected loads. Think about your critical control systems, protective relays, all the sensitive electronics you find in data centres or modern plant automation. It increases the rms current, which leads to extra heating and conductors and equipment. Not good, no It stresses electrical and mechanical components, and it increases the risk of potentially harmful systems. System resonances plus harmonics also have a negative impact on your facility’s Power Factor.

Speaker 1  05:05

Okay, let’s get a bit more technical, as the sources certainly do. They talk about characteristic harmonics.

1. What does that term mean?
2. And does the research indicate certain harmonics are more problematic than others?

Speaker 2  05:16

Yeah, characteristic harmonics, basically, these are the specific harmonic frequencies you’d expect to see based on the design of the power electronic device, specifically the pulse number of its rectifier, often denoted by q.

So for a common six pulse rectifier, which you find in loads of VFDs, the characteristic harmonics are theoretically of the order k, Q, the other 1k, Q, anyone. Okay, right? Where k is just any integer, 123, and so on. So for k1 you get six times one plus or minus one, giving you the fifth and seventh harmonics. Ah, okay, fifth and seven. And for k2 you get the 11th and 13th. And it continues like that.

The sources point out that these orders, fifth, seventh, 11th, 13th, are the dominant harmonics theoretically expected to be generated by a standard six pulse drive and pushed back into the network.

Speaker 1  06:00

I see, the sources also mention that how transformers are connected can play a role in which harmonics actually appear on the network side.

Speaker 2  06:07

Then do transformer winding connections significantly influence how these harmonics propagate, or if they get cancelled out, to some extent?

For instance, the sources explain how combining, say, star star and star delta transformer connections to feed two separate six pulse rectifiers, operating in parallel, effectively creates what looks like a 12 pulse configuration from the perspective of the primary supply.

Okay, so it acts like a 12 Pulse Drive from the supplies point of view. Yes. And theoretically, this 12 pulse arrangement cancels out or eliminates those lower order characteristic harmonics the fifth and seventh on the supply side. This leaves the dominant harmonics at higher orders, the 12k, 9, type like the 11th and 13th. That’s why 12 pole systems are often considered theoretically cleaner in terms of the harmonics they inject back into the main supply.

Speaker 1  06:54

So a 12 pole setup is, in theory, better at cleaning up the network. But what about those tricky triplin harmonics, you know, the third, ninth, 15th and so on. Are they always eliminated like the theory might suggest?

Speaker 2  07:05

Ah, the triplins, theoretically, a balanced six pulse rectifier feeding a balanced load should also eliminate triple harmonics in the line currents on the AC supply side, they should sum to zero at the connection point, however, and this is a really crucial real world insight highlighted by that DUT study, their actual field measurements showed that triplet harmonics were significantly present, particularly on the star connected winding of a transformer supplying the

Speaker 1  07:28

VFDs. So theory said no, but reality said.

Speaker 2  07:32

Yes, pretty much. And the research links this presence, at least in part, to the star point of that winding being grounded. This is a perfect example of where the complexities of a real plant network, things like system grounding, can cause significant deviations from the simplified theory. And these triplins, they can cause serious issues like overheating neutral conductors or interfering with ground fault protection systems.

Speaker 1  07:57

Okay, so we’ve got these distorted currents and voltages flowing around and sometimes even unexpected harmonics, like trip lens popping up in practice. What does all of this distortion actually do to the equipment and the overall operation in, say, a plant or a data centre?

Speaker 2  08:12

Well, one major impact the sources discuss is nuisance tripping of protective devices.

Harmonics can essentially fool relays and breakers into thinking there’s a fault condition when there isn’t, leading to shutdowns, exactly unexpected and costly shutdowns or operational interruptions that ties directly back to those financial consequences we mentioned earlier.

Harmonics also cause additional heating in Transformers. That’s why the K factor, which is a parameter quantifying a Transformers ability to handle harmonic currents without overheating is highlighted as important the sources you need Transformers rated for the harmonic load.

Speaker 1  08:46

I remember the sources also specifically mentioned premature equipment failure and malfunction, even linking poor power quality to potentially disastrous events.

Speaker 2  08:57

Absolutely poor power quality, especially the combination of harmonics and things like voltage sags, significantly reduces the lifespan of equipment and can cause malfunctions.

The drill ship case study, for instance, references data from their computerised maintenance management system, their CMMS to help illustrate the link between power quality issues and equipment damage or reduced reliability.

So there’s data showing this connection, yes, and this directly translates to costly downtime and decreased plant productivity. Sensitive electronics in modern control systems or even your backup generation units in islanded networks or data centres, they’re particularly vulnerable to these distortions. It can impact their stability and definitely their longevity and safety.

Speaker 1  09:38

Is a concern that comes up repeatedly in the sources, isn’t it? It’s not just about cost. Just about cost and uptime?

Speaker 2  09:44

It is one of the sources explicitly states there are safety concerns associated with poor power quality.

This could manifest in several ways, maybe equipment behaving unexpectedly or overheating components becoming a fire risk, or think about critical process safety systems malfunctioning because of. Voltage disturbances.

The DUT study actually beyond just harmonics, showed how large voltage sags caused by starting big motors directly online, all starting could degrade voltage quality, not just locally, but even upstream, on the 11KV bus, bar, wow. That far upstream, yes, and such disturbances as the sources imply, would potentially impact critical safety related systems or control services. Control circuits if they’re not adequately addressed or accounted for in the design and operation.

Speaker 1  10:26

Given all these potential issues, the costs, the failures, the safety risks, it really sounds like you can’t manage these problems if you don’t measure them first. How do we go about actually identifying these power quality issues in a practical setting like in your plant.

Speaker 2  10:41

Measurement is absolutely essential. You need to measure voltage and current harmonics to understand the actual power quality conditions on your network and ensure reliability. The sources talk about using specialised power quality metres or analysers.

These metres need to be capable of accurately measuring and recording, not just summary parameters like THD total harmonic distortion, which gives you an overall picture exactly, but you need more detail. They need to measure individual harmonic components, often up to the 50th harmonic, and calculate metrics like the K factor for transformers. The ability to accurately separate these harmonic components across different frequencies is key, and ideally your measurements should adhere to standards like IEEE Standard 519-2022 for consistency,

Speaker 1  11:23

The DUT study also relied heavily on simulation too, didn’t it not just measurement?

Speaker 2  11:27

Yes, that’s right. Simulation is highlighted as a really proven tool for identifying potential power quality issues and predicting how a network will behave under various conditions like starting a large motor or adding more VFDs. The dissertation specifically points to real time simulation as gaining widespread usage because it offers, and I quote, superior capabilities compared to traditional offline simulation methods.

11:52

Real time simulation, how does that work?

Speaker 2  11:55

fIt allows for dynamic mathematical models of your network to predict behaviour, literally in real time, interfacing, perhaps with actual control hardware. This is incredibly valuable for analysing complex, constantly changing systems, like those in heavy industry or islanded networks. It lets engineers test mitigation strategies virtually before implementing them physically.

Speaker 1  12:15

Let’s dig into that case study from the DUT research, the one on the drill ship. Yeah, it’s an island network, maybe simpler in scale than a huge plant, but similar in its dynamic, complexity, right? It had generators, transformers, motors, VFDs.

Speaker 2  12:26

Yes, and it provides a really strong practical example of the challenges faced in these complex Island or industrial networks. The simulations they ran confirmed that transient events like those voltage sags caused by direct online starting of large pump motors significantly impacted voltage quality for other loads on the same bus bar, and as we mentioned, it even affected voltages upstream on the 11 KV system. This kind of disturbance can really ripple throughout a facility.

Speaker 1  12:54

Okay, so sags were an issue, and what about the harmonics from the VFDs? What did the actual field measurements show there.

Speaker 2  13:01

This was one of the most impactful findings. I think. The field measurements were taken on the transformer supplying the main drilling drive system. Now, this system used parallel six pulse rectifiers configured to behave like a 12 pulse system from the primary side. So theoretically it should have been cleaner,

Speaker 1  13:16

right? The 12 pulse configuration we talked about, exactly.

Speaker 2  13:20

But despite this theoretically cleaner setup, the measurements taken on the secondary winding supplying the rectifiers showed well very significant harmonic distortion the source. Compared these measured current harmonics to international standards, specifically IE, 519, which sets a limit of 12% total harmonic distortion, or THD, for this part of the system, 12% is the limit. What did they find on the Delta connected secondary winding, the measured THD was, wait for it, 135.2%

Speaker 1  13:48

Wow. 135% that’s almost 12 times the standard limit,

Speaker 2  13:52

Exactly. And on the star connected winding, the measured THD was even higher, 137.8% incredible. Both vastly exceeding the IEEE Standard 519-2022, limit.

This data coming directly from the sources field measurements makes it undeniably clear that the actual harmonic levels in real world complex systems can be dramatically higher than theoretical expectations and can far exceed accepted standards. This poses a very real threat to equipment and operations,

Speaker 1  14:17

and you mentioned earlier those tricky triplin harmonics showed up in the measurements too, even though theoretically they should have been eliminated by the six pulse rectifiers on the line side, or certainly minimised in a 12 pulse setup.

Speaker 2  14:30

Yes, that was another key finding from the DUT study. The field measurements on that star connected winding showed a high presence of triplen harmonics, the third, the ninth, and so on in the current spectrum, and the source directly attributes this at least partly to the Transformers grounded Star Point Configuration.

14:48

So the way the system was grounded played a big role, it seems.

Speaker 2  14:50

So this is a critical takeaway. The specific system configuration and grounding choices in a complex network are just as important as the design. The VFD itself, they can introduce unexpected harmonic content, including potentially harmful triplins, even in systems that are designed for lower theoretical harmonic levels.

Speaker 1  15:10

The study also found significant current unbalance on the 440 V system too. Is that right?

Speaker 2  15:14

Correct? The field measurements revealed high current unbalance on a 440 V system transformer, and the source concluded this was likely due to its applying significant single phase loads, which is common but can exacerbate issues. So all these combined findings from the drill ship case study really underscore the complexity of real industrial networks.

They show the significant potential for performance to deviate dramatically from theoretical models under dynamic operating conditions. It highlights why. Simply knowing the type of VFD you have isn’t enough. You really need to understand what’s actually happening on your specific network.

Speaker 1  15:48

Okay, so let’s bring this all back home for the the operations managers, safety officers, power engineers, maybe the consultants and data centre managers listening right now, given everything we’ve heard, especially those real world findings from the DT study and the other sources.

• Why is continuous real time, power quality monitoring, more than just, you know, a technical best practice?
• Why is it really a strategic imperative for your plant, your mine or your data centre?

Speaker 2  16:13

Well, based on everything, these sources are telling us, continuous monitoring and that detailed waveform level analysis are absolutely crucial. They enable the early detection and, importantly, the prevention of operational disruptions. You’re essentially identifying the sources and the severity of power quality issues before they escalate into failures, malfunctions or potentially safety incidents. It’s about being proactive, not reactive. So

Speaker 1  16:37

you’re not just waiting for the equipment to overheat or trip unexpectedly or fail completely before you do something precisely

Speaker 2  16:43

real time, data gives you detailed insight into the dynamic conditions of your network. You can see exactly how different loads, including those VFDs, large motor starts, maybe even capacitor bank switching, are impacting power quality throughout the entire system. Even looking at upstream voltage impacts. This detailed data empowers much more informed decision making regarding necessary mitigation strategies. Do you need filters, where, what type, or maybe you need operational adjustments, or perhaps it points to needing equipment upgrades. You have the data to justify those decisions, and

Speaker 1  17:15

this directly ties back to the business case and the safety aspects, which the sources consistently emphasise as costly consequences of poor power quality,

Speaker 2  17:23

yes, absolutely, by preventing unexpected downtime, by avoiding premature equipment damage, which means extending asset life, by reducing energy inefficiency caused by harmonic losses, and by ensuring compliance with standards like IEEE Standard 519-2022 which is an important benchmark internationally and often referenced here in South Africa, you achieve measurable financial returns. The sources make a very clear connection between poor power quality and tangible costs. Furthermore, as the sources explicitly note, identifying and mitigating these power quality issues directly reduces the significant safety risks associated with equipment malfunction, unexpected shutdowns that might disrupt hazardous processes or the fire risk from overheating electrical components. So understanding your power quality with detailed, continuous real time data is fundamental. It translates directly into improved operational reliability, reduced risk, and ultimately a stronger bottom line.

Speaker 1  18:16

We’ve certainly taken a deep dive into the world of harmonics today. We trace their origin in VFD, ES and modern power electronics, and really explored their real world impact on operational reliability, equipment, longevity, safety and compliance, drawing heavily on those specific findings from the DUT research and other industry sources, yeah, and

Speaker 2  18:35

we’ve seen quite clearly that even systems designed to be theoretically cleaner, like 12 pulse configurations can exhibit significant even standards violating harmonic distortion. In practice, this is often influenced by things like system configuration and grounding. And we also saw that common operations like just starting a large motor can cause voltage disturbances that ripple through the entire network, potentially impacting sensitive loads far away.

Speaker 1  19:00

So understanding these dynamic conditions through proper measurement and maybe simulation, as highlighted in the sources, it really isn’t merely a technical curiosity, is it? It seems fundamental to protecting your assets, ensuring safety, maintaining efficiency, and really moving from reactive problem solving to proactive network management, especially in these complex industrial and data centre environments.

Speaker 2  19:22

Harmonics are well, putting it simply, they’re unhealthy for any power network. They absolutely need to be understood and managed proactively. The increasing complexity of industrial electrical networks, especially with the prevalence of all these modern non linear loads, presents ongoing challenges that demand. Really demand proactive identification and detailed understanding.

Speaker 1  19:43

So here’s something for you our listeners to consider, if a relatively simplified Island network like that drill ship example, studied by a local university revealed such significant standards violating harmonic distortion and voltage disturbances under its dynamic operating conditions.

What Power quality issues might be silently impacting the reliability, the lifespan, and perhaps even the safety of equipment in your complex plant, mine or data centre right now, especially if you’re not monitoring it continuously, right down to the waveform level?