Active Harmonic Filter Installation – Alloa, Scotland

Initial Site Condition

The existing Power Factor Correction (PFC) system at the site was rated at 300 kVAr, configured in three stepped stages. On inspection, the following conditions were recorded:

  • Step 1: Operating at ~55% capacity, with 2 x 200 A fuses blown.
  • Step 2: Operating at ~30% capacity, with 3 x 200 A fuses blown.
  • Step 3: Operating at ~10% capacity and still functional.

With only 90 kVAr of reactive compensation available, system monitoring showed that the Total Harmonic Distortion Voltage (THDV) increased from 3.0% to 4.5%, indicating a significant interaction between the compromised PFC and site harmonics.

Key Observations

  • The existing PFC unit was found to be at end-of-life and required a complete rebuild.
  • Given the requirement for detuned reactors, there was insufficient space within the existing LV mains panel, meaning a new freestanding detuned PFC system would be required for future replacement.
  • Excessive ambient temperatures in the switchroom were identified as a contributing factor. To ensure long-term equipment reliability, it was recommended that air conditioning be installed either for the switchroom environment or directly integrated into any new enclosure.

Power Quality Analysis

A detailed Power Quality Analysis (PQA) was carried out to determine the most effective long-term solution. The analysis confirmed that conventional PFC alone would be insufficient due to the high harmonic content of the site’s electrical load. Instead, the use of an Active Harmonic Filter (AHF) was recommended, either as a standalone solution or in combination with detuned PFC, depending on future reactive power demand.

Proposed & Implemented Solution

Based on the findings, a Comsys P300 Active Harmonic Filter (AHF) was specified, supplied, and installed. The selected model was a 300 A, 480 V P300-300/480 Power Quality Filter, offering advanced harmonic and reactive compensation features.

Application Features

  • Dynamic VAR compensation for improved power factor control.
  • Harmonic elimination, reducing distortion levels across a wide range of orders.
  • Flicker compensation, ensuring stability during fluctuating loads.
  • Load balancing across phases for improved efficiency.
  • Resonance elimination, mitigating potential issues with detuned circuits.

Control Features

  • Customisable harmonic compensation profiles tailored to site requirements.
  • Scalable architecture, allowing multiple P300 units to be paralleled if site load increases.
  • Insensitive to network variations, ensuring stable operation under fluctuating conditions.
  • Idle/standby mode during periods of low load for energy savings.
  • Overload-proof design – cannot be stressed beyond rated limits.
  • Ultra-fast response time (<1 ms) for real-time harmonic correction.
  • ADF Dashboard WUI (Web User Interface) for monitoring and configuration.
  • Multi-SIM enabled GSM gateway for remote diagnostics and reporting.
  • Floating grid frequency support, providing resilience to non-standard network conditions.

Physical Features

  • Standard IP43-rated enclosure (IEC 60529), with higher ratings available if required.
  • Integral door-interlocked load break switch for safety during maintenance.
  • Type 1 and 2 Surge Protective Devices (SPDs) included for transient protection.
  • Correctly rated CT set (xxxx/5) supplied and installed if required.
  • High short-circuit withstand capacity, ensuring resilience in fault conditions.
  • Compact and modular design for simplified installation within the existing switchroom environment.

Outcome

The installation of the Comsys P300 Active Harmonic Filter has significantly improved the site’s electrical performance. Harmonic levels have been reduced to within compliance limits, power factor correction has been dynamically stabilised, and the risk of future equipment failures due to excessive heat or harmonic stress has been mitigated.

This solution provides the site with a scalable, future-proof platform, ensuring stable operation and protecting critical infrastructure from the adverse effects of harmonics, imbalance, and poor power quality.

 

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PFC Replacement – Gym, Newcastle upon Tyne

Initial Findings

During a maintenance visit, the site’s existing power factor correction (PFC) equipment was found to be in a failed state. The following issues were identified:

  • 4 x 125 A DIN fuses had blown, leaving the system unprotected.
  • All 50 kVAr capacitor stages had failed, rendering the PFC system completely inoperative.
  • Given the age and condition of the equipment, an end-of-life replacement of all major components was strongly recommended.

For safety, the defective PFC unit was isolated and left offline, awaiting replacement works.

Replacement Works

A new modular PFC system was designed and installed as a like-for-like replacement for the original ABB equipment. The new trays were engineered to fit directly into the existing framework, allowing:

  • Reuse of existing power leads
  • Retention of original tray fixing points
  • Minimised installation downtime and site disruption

The replacement system incorporates several modern upgrades:

  • Soft-switching contactors – providing smoother capacitor engagement and reduced electrical stress.
  • 480 V rated capacitors – ensuring higher durability and better tolerance to supply variations.
  • Lovato DCRL5 fully digital controller – replacing the outdated relay with an advanced unit offering improved monitoring, automatic step adjustment, and greater accuracy in reactive power management.

Performance Outcome

Following installation, the PFC system successfully restored site efficiency. The gym’s power factor improved from 0.81 inductive to unity (1.00), eliminating excess reactive power demand and significantly reducing the risk of utility penalty charges.

The upgraded PFC not only restores compliance but also delivers:

  • Improved energy efficiency
  • Reduced strain on electrical distribution equipment
  • Extended lifespan of connected plant and machinery
  • A more stable and resilient electrical supply for the site’s daily operations

 

 

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Fire Station – Voltage Optimisation Replacement (Stoke-on-Trent Area)

A routine maintenance visit identified multiple issues with the existing voltage optimisation (VO) equipment installed at the fire station. The site operates without a standby generator; however, UPS backup is available for essential services, offering limited resilience in the event of extended supply interruptions. Current supply protection was provided via a load breaker (L/B), although for optimal compliance and reliability this should ideally be upgraded to either a fused switch (F/SW) or an MCCB.

Condition of Existing VO Unit

On inspection, the VO system was found to be non-operational. Key issues observed included:

  • The VO remained in inhibit mode, with the key switch failing to restore operation in auto.
  • Contactor banks were not engaging; both C1 and C2 contactors were open, and associated MCBs were found switched off.
  • Phase sequence was confirmed as L1 – L3 – L2, which can contribute to operational anomalies.
  • Residual voltage readings indicated 13 V N–E and 13 V L1–E, traced back as feedback from the fire alarm panel.
  • Solar PV generation was present on site, which can further complicate VO operation and system stability.

Given these conditions, the VO system was left safely in bypass mode as found. Persistent supply-side issues, particularly a voltage rise observed on L2, led to the recommendation for complete replacement of the unit.

Replacement Works

The failed VO system was removed and replaced with a new VM 400 3/5/7/9 Voltage Optimisation unit. The new unit was installed reusing the original terminations and bypass switching system to minimize installation downtime and site disruption.

In line with modern standards, the outdated auto/inhibit control system was fully decommissioned and removed. This ensures greater reliability and reduces unnecessary complexity, while the new VO provides stable, efficient, and fully automated regulation of incoming supply voltage.

Outcome

The installation of the VM 400 VO unit restores effective voltage regulation at the fire station, ensuring equipment protection, extended asset lifespan, and improved energy efficiency. The removal of legacy control circuitry reduces potential points of failure, leaving the site with a simplified, robust, and future-proofed solution.

 

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PFC Upgrade at Community College, Crawley

During a planned maintenance visit to the college’s LV distribution system, engineers discovered a complete failure of the existing power factor correction (PFC) equipment. All six 25 kVAr capacitor units had failed, and four 100 A DIN fuses were found to have blown. This failure left the site operating with no functional PFC, increasing the risk of higher reactive power charges and potential strain on the electrical infrastructure.

A detailed site load test was carried out to establish the actual reactive power requirements under normal operating conditions. The results confirmed that a total of 100 kVAr correction capacity would be more than sufficient to consistently maintain a site power factor above 0.96, comfortably within recommended efficiency standards.

To modernize and simplify the installation, the three failed ABB 25/25 kVAr modules were decommissioned and removed. These were replaced with a single 100 kVAr SBA tray, configured with four independently switched 25 kVAr soft-switching steps. This modular setup ensures greater flexibility, smoother operation, and reduced electrical stress compared to the original equipment.

In addition, the outdated reactive control relay was upgraded to a fully digital Lovato DCRL5 controller. This modern unit provides advanced monitoring, automatic step regulation, and improved accuracy in managing reactive power demand.

The upgrade not only restores reliable PFC capability but also improves system efficiency, reduces electrical losses, and minimizes the likelihood of future reactive energy penalties.

 

     

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Installation of 2 Revcon 200A Active harmonic filters in central London

We were contacted to investigate the increasing harmonic distortion at a large office building in the centre of London, following sites ongoing modernisation plan. After carrying out a week-long Power Quality Analysis, we noticed that while a lot of distortion was coming directly from the grid, site use of Variable speed drives and ongoing LED lighting upgrades were now causing this distortion to exceed the G5/5 design limits.

From this report, we recommend that the existing power factor correction equipment be decommissioned and disconnected. Following this, all of the power factor and harmonic correction requirements of Tx1 & Tx2 main LV supplies could then be provided by a 200Amp Active Power Quality Filter (APQF) connected to each supply and located in the space currently occupied by the power factor correction units. The existing PFC supply MCCB’s and connection cables can then be reused to supply the proposed APQF systems.

 

Installation was carried out over 3 days, including a full commissioning.

 

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100A Harmonic Filter Install at Magistrates Court

During a planned upgrade of this site’s main LV Panel, it was recommended that some Filtering equipment be installed to help reduce the site background Harmonics.

We were then approached to find a solution, and upon review of all the site’s load details as well as the planned upgrade works, we recommend installing a wall-mounted 100A, 4-wire Active Power Quality Filter.

As the new LV panel was still being built, additional specifications were added to allow for an easier connection of the AHF, including a full set of dedicated Filter CTs with shorting links as well as a suitably rated MCCB.

The filter was then mounted and installed during normal working hours, along with a full commissioning by our site engineer.

 

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Panel Built Detuning Trays for Fresh Food Factory

Following a review of the load at this large UK food manufacturer, it was found that the standard Power Factor Correction equipment was beginning to elevate low levels of background harmonics above 3% VTHD, causing premature failure of the capacitor banks. Due to space limitations, it was decided to remove all the existing standard PFC components and replace them with our fully detuned 189Hz PN54 Trays.

 

Each tray consists of 1 detuning reactor, a soft switching 415V contactor and a 50kVAr 480V rated capacitor bank. As well as the new tray assemblies, we also upgraded the control relay to the more reliable fully digital Lovato DCRL5 and installed additional forced air ventilation to help keep the reactors cool while under load.

With 2 units being rebuilt the same way, all works were carried out by a single engineer over 2 days without any disruption to the site’s load.

 

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FS300 Power Factor Unit Install at Brick Factory

We were asked to carry out a service of a Power Factor Correction unit at a Brick Factory near Huntingdon, UK, that had no previous service history since its installation in 2011.

During our investigation, we found multiple failures of the internal components including failed capacitor banks, contactors that had welded themselves closed, multiple fuse failures and a high amount of dust and debris inside the cubicle.

Due to the high amount of failures, high levels of dirt and lack of annual servicing we recommend an end-of-life replacement of the PFC panel with a new FS300 Unit.

The new power factor unit would consist of 5 x 50kVAr capacitor stages and 2 x 25kVAr stages allowing for finer correction at lower loads. Incorporating high quality, long-life metallized polypropylene capacitors (480V rated) with over-pressure disconnection devices and discharge resistors fitted.

The unit would also include a built-in 630A load break switch and forced air ventilation.

 

Using the existing power and C.T cables the old unit was stripped down and removed from the site and the new FS300 was placed in the same position as before at the end of the LV panel. When in operation the unit would bring the site’s power factor up from 0.80 indictive to unity with 200kVAr of capacitors in circuit.

 

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PFC Unit upgrade at the supermarket

An end-of-life replacement was required for an old Power Factor Correction unit at a supermarket in central London.

A new wall-mountable FS100 PFC unit was to be installed using the existing power and C.T connections. The unit would incorporate 4  25kVAr capacitor banks, 480V rated with IMO MC32 soft switching contactors, sub fusing and additional forced air ventilation.

 

The unit would be controlled via a local Lovato DCRL 5 digital control relay and also include an integrated 200A load break switch for local isolation.

 

When operating the site power factor would be improved from 0.81 inductive to a unity power factor helping to save money on the monthly electricity bills by removing any reactive charges.

 

This unit was installed in 1 day by 1 engineer during normal working hours without any disruption to the site’s supply.

 

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Revcon Harmonic Filter Install

During the annual Power Factor Correction maintenance at a large Salad Factory in the south of England, it was found that the standard PFC on site was failing.

 

An instantaneous load and check carried out by on service engineer show levitated harmonics on the supply, which we suspected was the cause of the capacitor failures.

A week-long power quality analysis was conducted and the results showed that the VTHD was around 6.5% and elevated higher when the standard PFC capacitor banks were in operation.

 

It was concluded that to help reduce these harmonics, as well as the inductive load on the supply an Active Harmonic Filter would be the best solution.

We designed and built a 350A ADF using 2 x 100A  and 1 x 150A REVCON filter modules which we built into a custom enclosure along with additional forced air ventilation and a built-in HMI display.

The filter was also set to a power factor of 0.98 to help reduce the inductive load using its built-in capacitor banks.

 

Using the existing cable infrastructure and switch we were able to remove the old PFC equipment and install the new ADF without any disruption to the sites supply.

After commissioning the Active filter reduced the sites VTHD from 6.5% > 3.2% and the iTHD from 22.5% > 12.2%, along with a Power Factor of 0.98i.

 

   

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PFC Engineering Update 2025

As we come to the end of our first month of 2025, the workshop team have been hard at work getting units built and equipment into stock ready for another busy year here at PFC Engineering Ltd

 

We currently have 4 of our FSi400 fully detuned 400kVar Power Factor Correction units built, tested and wrapped ready for delivery to a site in Dungannon, Northern Ireland.

 

We have a 150A Comsys Active Harmonic Filter in one of our custom enclosures, built and ready for testing with the new 7’’ HMI 4 touchscreen display and remote access gateway supported by our partner.

 

In the stores, we have 3 more Comsys PPM modules for our continued Active Harmonic Filtration project at Rockwool in Cardiff, Wales. As well as another 3 Comsys PPM modules for a Harmonic Filtration project overseas with Tesla in Los Angeles.

 

And of course not forgetting our Maintenance team who have been travelling all around the UK carrying out Power Factor servicing, as well as a host of repairs and upgrades to a wide range of PFC equipment, Harmonic Filters and other energy-saving products.

 

 

     

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Merry Christmas from PFC Engineering Ltd

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