If your site experiences unexplained equipment faults, nuisance tripping, or overheating transformers, the cause might not be your machinery at all; it could be your power quality. Harmonic distortion and poor electrical balance are among the most common yet least understood issues affecting industrial and commercial facilities.
At Johnson & Phillips, we’ve helped countless businesses across manufacturing, healthcare, and data-centre environments to identify, correct, and prevent these problems. Our power quality surveys and harmonic mitigation solutions are designed to protect sensitive equipment, improve reliability, and ultimately save money.
What Are Harmonics?
In a perfect world, your electrical supply would be a smooth sine wave. But modern equipment doesn’t always play by those rules. Non-linear loads, such as variable speed drives, UPS systems, LED lighting, computers, and welders, distort that wave, creating what’s known as harmonics.
These harmonic currents combine with the fundamental frequency and cause voltage distortion throughout the system. The higher the Total Harmonic Distortion (THD), the greater the risk to equipment performance and efficiency.
The problem has grown sharply in recent years. As facilities upgrade to more energy-efficient, electronically controlled systems, the amount of non-linear equipment increases, and so does the potential for harmonic distortion.
Why Power Quality Matters For Sensitive Equipment
Poor power quality doesn’t always announce itself with spectacular failures. More often, it appears as small but persistent issues, such as circuit breakers that trip without reason, overheated neutral conductors, erratic PLCs, or sensitive instruments that mysteriously reset.
Over time, these symptoms add up. Transformers run hotter, cables age faster, and production uptime begins to suffer. In precision environments such as hospitals or data centres, even minor voltage distortion can lead to lost data or compromised equipment.
Aside from the operational impact, there’s also the financial one. A system operating under harmonic stress consumes more power and requires more frequent maintenance. Left unchecked, it shortens asset life and increases the total cost of ownership.
Therefore, maintaining good power quality isn’t just about reliability; it’s about protecting the investment in your infrastructure.
Identifying The Problem: The Power Quality Survey
The first step in solving power quality issues is to understand them. That’s where our power quality survey comes in.
Our engineers carry out detailed on-site monitoring over a representative period, usually one to two weeks. Using high-accuracy analysers, we log voltage and current waveforms, harmonic levels, transients, dips, and swells. The resulting data paints a clear picture of how your electrical network behaves under real-world conditions.
Each survey concludes with a technical report written in plain English, highlighting the causes of distortion, identifying vulnerable equipment, and outlining precise recommendations for mitigation. It’s the evidence you need to make informed decisions, supported by clear financial and operational benefits.
In many cases, we also combine surveys with critical power testing to validate the performance of UPS, generators, and switchgear under load.
Proven Solutions For Harmonic Mitigation
Every site is different, which is why we don’t believe in one-size-fits-all fixes. Our engineers design tailored solutions based on the measured data from your survey, integrating seamlessly with your existing infrastructure.
1. Active Harmonic Filters
These intelligent systems use real-time monitoring to inject counter-currents, effectively cancelling out unwanted harmonics. They’re ideal for sites with variable or unpredictable loads, such as manufacturing plants or data centres, where flexibility is key.
2. Passive Filters
For more stable installations, passive or tuned filters offer a robust and cost-effective option. They’re designed to target specific harmonic frequencies and are often installed at the supply of major non-linear loads.
3. Detuned Power Factor Correction (PFC)
Standard capacitor banks can actually amplify harmonics if not properly designed. That’s why we often use detuned PFC systems in the form of capacitor banks fitted with series reactors that prevent resonance and safely improve the power factor. You can read more about this on our power factor correction page.
4. Line Reactors & Isolation Transformers
Reactors smooth out current waveforms, reducing inrush and protecting equipment from transient spikes. Isolation transformers, meanwhile, create separation between ‘clean’ and ‘dirty’ supplies, ensuring sensitive electronics receive a stable feed. Our in-house transformer manufacturing capability means we can specify exactly what’s needed.
5. Voltage Regulation & Switchgear Integration
Where voltage sags or swells are a concern, automatic voltage regulators (AVRs) or conditioners can stabilise the supply. We frequently integrate these components within new LV Switchgear assemblies, giving clients a complete, turnkey power quality solution.
Real-World Impact Across Industries
Power quality problems don’t discriminate; they affect every sector differently.
In data centres, harmonics can reduce UPS efficiency and shorten battery life. Therefore, the implementation of active filters and balanced loading ensures clean power to every rack, safeguarding uptime.
In hospitals, diagnostic and imaging equipment relies on ultra-stable voltage. Our projects in healthcare environments often combine detuned PFC with voltage stabilisation to maintain compliance and patient safety.
And in manufacturing, with hundreds of variable speed drives running simultaneously, harmonic currents can cause production interruptions and expensive downtime. This is where corrective filtering and rebalanced distribution have helped clients restore stability and improve productivity.
Proven Results in Practice
One example of our work can be seen in the Supply Upgrade from 2×800 kVA to 2×1600 kVA case study.
For this manufacturing client, our team delivered a complete high-voltage and low-voltage upgrade, integrating modern switchgear and harmonic mitigation within a single solution. The result was improved reliability, reduced transformer loading, and a significant drop in measured THD levels.
This project, along with others featured in our case study portfolio, demonstrates how addressing harmonics can transform both performance and efficiency across an entire electrical network.
Implementation and Ongoing Support
Once the design is approved, our engineers handle every stage, from manufacturing and factory testing to on-site installation and commissioning. Because we build our own panels and switchgear, we maintain full control over quality and lead times.
After installation, we verify performance using the same high-precision instruments from the survey stage, confirming that THD and voltage stability meet specifications.
For long-term peace of mind, Johnson & Phillips provides nationwide maintenance and support through our 24/7 service network. Periodic re-testing and thermal imaging ensure your system continues performing efficiently for years to come.
Why Work With Johnson & Phillips?
Established in 1870, we’ve been delivering electrical engineering excellence for more than 150 years. Our expertise spans switchgear, transformers, power quality, and generator hire, giving us the in-house capability to design, manufacture, and service complete power systems.
Whether you operate a single manufacturing plant or a nationwide network of facilities, we offer consistent standards, rapid response, and proven results. Our goal is simple: to make your power reliable, efficient, and future-ready.
Conclusion
Harmonics and power quality issues often go unnoticed until they cause costly downtime. Yet with the right analysis and corrective measures, they’re entirely preventable.
By investing in a tailored power quality solution, you not only protect your equipment but also enhance efficiency, reduce energy costs, and improve overall system health.
If you suspect harmonics might be affecting your site, book a power quality survey today or contact our engineering team for expert advice.
At Johnson & Phillips, we believe reliable power isn’t just about keeping the lights on; it’s about keeping your business moving.