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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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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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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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Active Harmonic Filter With PFC Install at Recycling Plant

A recent catastrophic failure of a 200kVAr Power Factor Correction unit on the main incoming supply at Large Recycling Centre has raised concerns that the quality of the supply may in some way be compromised, resulting in this failure.

 

In order to determine the quality of the power on this site, including the levels of harmonics, general voltage levels and voltage stability, a week-long power analysis was commissioned on the main incoming supply, highlighting the fact that, due to the failure of the power factor correction on this supply, the load was operating power factor is slightly below the minimum target power factor of 0.95. In addition, it was found that the site loading is uncomfortably close to exceeding the limits of main supply.

 

Whilst the reinstatement of the power factor correction would restore the load operating power factor, the high level of load current harmonics means that even with harmonic detuning reactors fitted to the power factor correction, excessive 5th harmonic current absorption within the power factor correction capacitors could still result, possibly resulting in further failures in the future.

 

In addition to potentially reducing the longevity of the power factor correction capacitors, the high level of load current harmonics is producing elevated levels of voltage harmonics and is placing significant stress upon the supply transformer.

 

The results of the PQA also showed Voltage 5th, 33rd, 39th, 45th and 49th harmonic voltages and the voltage THD exceeded the G5/5 design limit. The 5th harmonic voltage dominates the voltage harmonic voltage distortion, which is to be expected given the proliferation of 6-pulse inverter drives within the load.

 

In order to prevent future power factor correction capacitor failures and to minimise the effects of the load harmonic currents, we have recommended that a 450Amp rated active harmonic filter be installed that can perform the combined harmonic filtration and power factor correction requirements in one device.

 

The APQF was designed and built in our workshop, fully tested, and then shipped to site where it was lifted up to the 1st floor of a container switchroom where we have already removed the failed PFC equipment ready for connection of the new Filter.

 

New C.T circuits were installed and the 630A MCCB previously used for the PFC was utilized for reconnection of the Active Filter. Once connected, a full commissioning was carried out and the unit showed a reduced Voltage distortion down from 3.9%VTHD to 1.5%VTHD and a reduced Current Distortion down from 9.2% iTHD to 5.2%iTHD

 

 

 

 

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Active Harmonic Filter Installation – Cardiff

We recently carried out the second phase of our Active harmonic filter installations at a large insulation manufacturer in Cardiff.

 

This supply now consists of 3 x 180amp P300-180/690V units connected in a Master/Slave/Slave configuration all controlled via the New Comsys HMI 4 display.

The harmonic distortion on this supply was around 8.5% THDV and 30% THDI. When the filters were connected and in operation, we saw a drop of over half to 3.5% THDV and 14% THDU.

 

Built by our workshop team into a custom enclosure with added forced air ventilation and remote monitoring, then installed and commissioned by two of our engineers over 3 days with no disruption to the site operation.

Find out more about our Active Harmonic Filters here or contact us today.

 

 

 

Above: Site loadings Before Active Filter is off

 

 

Above: Site loadings Before Active Filter is on

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PFC & AHF Commissioning Ireland

During a recent trip to Ireland, we carried out the commissioning of 6 Active Harmonic filters and 3 new Power Factor Correction units at a large horticultural manufacturing site.

All the equipment had been shipped to the site and installed by the on-site engineering team ready for the energising of a production line. Our engineers spent 3 days on-site reviewing the installation and getting the active harmonic filter set up with the correct parameters and then tested under load conditions. Each Active Harmonic Filter was 300A and set up on two different supplies in a master/slave/slave configuration.

 

While on-site we also commissioned 3 new 360kVAr Power Factor Correction units, each with its own detuning reactor, customed to the site’s load requirements.

 

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Active Harmonic Filter Replacement

We are contacted by an insurance business that occupies a large commercial building in central Ipswich regarding the failure of an Active Harmonic Filter on one of the LV supplies.

We already carry out the annual Power Factor maintenance on site and were familiar with the site’s electrical installation. Following a week-long Power Quality Analysis we were able to provide a quotation to supply and install 2 new 100A 4-wire Active Harmonic Filters to be wall-mounted in the same location as the failed unit. These 2 new filters were designed to go on one LV supply with the filters working in a Master/Slave configuration.

 

Due to the additional AHF being connected a new 4 core cable was also run to a spare switch on the LV panel and the original C.T circuit was reutilized.

 

All works were completed during normal working hours without the need for a shutdown.

 

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Active Harmonic Filter Installation

Harmonic levels at a large grain storage and drying factory had, over the past few years, crept slowly up in distortion eventually leading to some major equipment failures. This increase was also having a detrimental effect on the Power Factor Equipment already installed on site. Though this was detuned PFC equipment, which is designed to prevent the capacitors from increasing the harmonics when the capacitors come into circuit, it too was struggling with the high levels of distortion on the site load.

Following a week-long Power Quality Analysis, it was concluded that the best way to reduce these harmonics would be with a 125A Active Harmonic Filter on each supply in place of the existing PFC Equipment installed in a Master/Slave configuration. The new AHF would also be able to correct the Power Factor with its built-in capacitor banks.

The new AHF Units would utilise the existing power cables feeding the PFC Equipment, and a new multi-core C.T cable would be run along with new Current Transformers on the main LV tales for the filter to see the site’s loads and correct accordingly.

Once the new filters were installed a full commissioning was carried out on by our engineers along with a connection of a remote monitoring device as standard to provide remote access to the Active Harmonic Filter from any desktop PC.

 

Upon completion of the works, the new AHF lowered site’s average voltage distortion down from 6% to 2% across multiple harmonic ranges and corrected the Power Factor from 0.89 inductive to 0.99 inductive.

 

PFC

Original Power Factor Correction Equipment on site.

 

  Active Harmonic Filter

Active Harmonic Filter Active Harmonic Filter

 

Active Filter – Off

 

Active Filter – ON 

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Active Filter Install in Central London

A number of under-voltage trips on the roof plant chillers, including some failures involving physical damage to the chiller plant have occurred at a large commercial site in central London.

 

A previous analysis carried out on the roof plant on Chillers 1 – 5 identified very high levels of voltage harmonic distortion on certain chillers and moderate levels of voltage harmonic distortion on others.

 

From the PQA results, it was clear that the majority of the voltage harmonic distortion is being imported from the UKPN MV network. In the past, the reduction of harmonic voltage distortion imported from the MV network has not been possible but active harmonic filter algorithm technology has advanced to the point where this is now possible, albeit with the trade-off of drawing more harmonic current through the transformer.

 

With this in mind, a quotation was provided to replace panel-built Power Factor Correction with 2 sets of 300amp, 480volt P300-300/480 type Active Harmonic Filtration. 1 set for each affected supply.

 

Prior to the installation, our engineers visited the site and removed all the old equipment and measured up the existing cubicle so that new mounting plates could be produced. These plates would then be fitted with the Comsys filters back in our workshop and fully tested prior to installation on-site.

 

During the install, the new mounting plates were fitted along with all the pre-built filter equipment. Additional forced air ventilation was installed to the cubicle and a multicore C.T cable was run to the LV incomers.

All the works were completed over 3 days by 3 of our engineers including a full commissioning of the new Active Filters.

 

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Panel Built Active Harmonic Filter

High harmonic distortion at Recycling plant.

Due to the proliferation of inverter loading at this site, concerns have been raised as to the amount of harmonic distortion being produced at this site and its potential effect on the other connected load as well as the wider effect on the MV supply to this site.

In order to determine the level of harmonic distortion present at this site as well as monitoring other power quality indices, a two week long power quality analysis was commissioned.

In addition to power quality indices, general power consumption data is presented in the form of active power (kW), reactive power (kVAr), apparent power (kVA) and operating power factor.

 

From the preceding results for this analysis it was clear that the load at this Recycling Centre operates with very high levels of harmonic distortion, high enough to distort the voltage to the point where the levels of voltage harmonic distortion exceed the G5/5 design recommendations

 

Despite the very high levels of harmonics on this supply, it will be possible to operate power factor correction at this site as it incorporates harmonic detuning reactors to prevent overload damage to power factor correction capacitors operating under such conditions.

Due to the very little additional space within the switchroom a stand alone AHF would not be possible, however the space within the distribution board allocated to power factor correction is generous and can be utilised to install harmonic filter modules that could be configured to remove the load harmonic currents and also correct the load operating power factor simultaneously.

 

With all these factors considered, a 300amp, 480volt P300-300/480 type Power Quality Filter System was installed inside of the existing LV panel along with 200kVAr of fully detuned Power Factor Correction.

All works and commissioning was carried out by 2 PFC Engineers over the course of 2 days with no interruption to sites load, with the majority of the equipment being pre-built and tested in our workshop prior to the install.

 

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Active Filter Installation at Food Factory

After carrying out a site survey for large food manufacturing site it was found that the harmonic voltage distortion levels of over 9% THvD which are extremely high and of major concern.

 

The measured voltage distortion exceeds the harmonic compatibility limits specified by BS EN 56160 & IEC 61000-2-2 of ≤8.0%. The fact that the voltage harmonic distortion exceeds these compatibility limits is of real concern as equipment carrying a mark will have been tested with voltage harmonic distortion up to the compatibility limits.  If equipment is exposed to voltage harmonic distortion beyond this limit, its correct operation will no longer be guaranteed by the equipment manufacturer.

 

Furthermore, the level of voltage distortion is such that the site MV connection point is highly likely to exceed ENA EREC G5/5 recommended limits and as such, contradict the network operator’s connection agreement conditions.

 

Transformer Harmonic Derating

 

The presence of harmonics increases the losses in a transformer, for example the iron core losses are proportional to frequency and the eddy current losses are proportional to frequency2.  It is therefore not hard to imagine that the presence of significant levels of harmonics will lead to increased transformer heating and consequently a derating effect.

 

Transformer derating factor is the factor by which you must derate a transformer by, given the specific harmonic content of the load current on each phase at any given time. The effective load current when the transformer derating factor is applied (derived from the load current divided by the coincident derating factor) must be considered when calculating the required transformer rating or when adding additional load to an existing supply as the effective rating or spare capacity can be significantly less than it may appear to be.  If the effective load current of the transformer exceeds the transformer rating, damage may occur to the transformer even though protective devices do not operate.

 

Based on the harmonic current levels observed during our site survey, we estimate a transformer derating factor of 30%, Increasing the effective load on the transformer from 1835kVA to 2385kVA.

 

Recommendations

  1. In the first instance, detailed load and power quality analysis is to be carried out on all transformer main LV supplies.
  2. Carry out maintenance inspection of all existing PFC systems and carry out remedial works as necessary.
  3. Install harmonic reduction solutions on the Roof Chiller Supply and any other supplies identified as “problematic” following both of the above.

Solution

Following the repairs of the sites existing Power Factor Correction units, we recommended the installation of 2 x 300amp, Active Harmonic Filter Units type ADF P300-300/480 to reduce the harmonic distortion on the supply and ultimately reduce the stresses on the Transformer.

 

     

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