Commercial Property Blackout Problem Solved with Active Harmonic Filters

How an Active Harmonic Filter Solved Breaker Trips

The random tripping of a main circuit breaker supplying a busy commercial hub recently led to an interesting application for our Sinexcel Ultra Series AHF.  For one property owner, these outages were becoming all too common. The events were causing shutdowns across multiple businesses at once and were occurring during peak business hours.

The property owner had an existing relationship with an electrical consultant as well as an electrical contractor. Power Electronics New Zealand (PENZ) worked together with all parties to propose a solution. The site was experiencing excessive harmonic distortion, current imbalance, and elevated neutral currents. The solution would come in the form of several Sinexcel Ultra Active Harmonic Filters (AHF’s), spread throughout the tenancies.  On-site power quality analysis was used to determine the best placement of the modules to provide maximum effect to the entire electrical system. 

A shared commercial complex hosting a diverse range of tenants, each with its own high-demand equipment:

• A bakery with industrial ovens and refrigeration units.
• A fast-food outlet with high-efficiency cooking appliances.
• A large retail store with extensive LED lighting and HVAC systems.

All these businesses draw power from a shared electrical network, supplied from the same main switchboard. While each piece of equipment is energy efficient in isolation, the combined effect of these loads, many of them non-linear, was creating an increasingly unstable electrical environment at peak loadings.

Non-linear single-phase loads such as LED drivers, refrigeration compressors, and switch-mode power supplies are notorious for producing harmonic distortion. When combined across multiple tenancies, they can introduce electrical imbalances, cause overheating in cables and switchgear, and lead to nuisance tripping of protective devices.

Months of unexplained outages had already led to increased maintenance costs and strained tenant relationships. Detailed power quality analysis was completed throughout various tenancies of the installation.  Load profiling and harmonic spectrum analysis revealed:

• Total Harmonic Distortion (THDi ) exceeding 75% on some phases.
• Phase current imbalance of up to 30%.
• Neutral current reaching 80% of phase current due to triplen harmonics

These readings were well above best-practice thresholds. In practical terms, the distortion and imbalance were pushing the main breaker beyond its thermal limits. Each trip represented the breakers’ protection doing its job, but the underlying cause was eroding the resilience of the entire electrical system. Without intervention, the problem may potentially worsen as tenants upgrade or add more high-efficiency but harmonic-rich equipment.

Replacing the breaker or upsizing switchgear would have been a short-term fix, addressing the symptom without tackling the cause. PENZ recommended the installation of an Active Harmonic Filters at each of the three identified tenants’ switchboards.

Active Harmonic Filters work in real time, continuously measuring electrical waveforms and injecting corrective currents to cancel harmonics and balance loads. The system was tailored to:

1. Mitigate harmonics to cancel any distortion at the source.
2. Dynamically balance phase currents to reduce load asymmetry.
3. Lower neutral current by mitigating triplen harmonics.
4. Improve power factor and load efficiency across all connected equipment.

Current transformers (CTs) were installed on each of the conductors, giving the AHF the precise, continuous feedback it needed to deliver effective compensation. 

Once the AHF was commissioned, the improvements were both immediate and quantifiable:

• THDi reduced to below 10%.
• Phase current imbalance cut to less than 5%.
• Neutral current reduced by over 60%.

Beyond the technical results, the operational impact was significant. Circuit breaker trips ceased, tenant operations stabilised, and maintenance callouts dropped. By operating within safe limits, the electrical infrastructure was no longer being thermally stressed, extending the life of switchgear and cabling.

The site also benefited from improved energy efficiency. With less wasted current circulating in the system, overall electrical losses decreased, a small but meaningful contribution to reduced operating costs.

This application is a clear demonstration that power quality issues can exist even in modern facilities. Energy-efficient equipment doesn’t automatically mean a “clean” electrical supply, especially when multiple non-linear loads are involved.

Without proactive monitoring and mitigation, harmonic distortion and current imbalance can:

• Causes unplanned outages and business disruption.
• Increase wear and tear on the electrical infrastructure.
• Lead to higher maintenance costs and shorter asset lifespans.
• Compromise compliance with power quality standards.

Installing an Active Harmonic Filter is a targeted, long-term solution. With a full response time of <5ms, the AHF Ultra can correct the waveform, restore balance and stability to the network, and deliver benefits that extend far beyond the initial scope for this project.

By targeting the cause rather than the symptoms, PENZ, in conjunction with the electrical consultant and electrical contractor, helped to restore reliability for the property owner's tenants. The installation of Active Harmonic Filters, being strategically placed, eliminated disruptive breaker trips, protected electrical infrastructure, and provided a stable foundation for future tenant upgrades.

For property owners, managers, and consultants, this case shows how investing in power quality pays off in operational continuity, reduced costs, and extended asset life.

If your facility is experiencing unexplained outages, overheating cables, or high neutral currents, talk to the team at Power Electronics New Zealand about a site-specific power quality assessment. Contact us today to get started.