ABB’s specialist power quality service has enabled Paragon Print & Packaging, the UK market leaders in food packaging for the fresh and chilled food sector, to solve potential plant reliability and efficiency issues at three of its key printing facilities in the east of England.
ABB’s Advance power factor correction (PFC) systems have been installed at the Paragon sites in Spalding and Wisbech, while a PQFI active harmonic filter has been installed at Boston.
Spalding – detuned PFC equipment addresses harmonic current issues
The project commenced when CV Electrical, the contractor responsible for maintaining Paragon’s electrical infrastructure, called in ABB to investigate an issue with frequent nuisance tripping of the main incoming supply protective device at the Spalding site. Paragon had already taken an important step in maintaining the site’s power quality by installing a series of capacitor banks to ensure that the power factor on the 415 V network was held at the acceptable industry standard level of 0.95 lag. However, it was found that the harmonic currents present on the network were causing the five capacitor banks (5 x 50 kVAr) to degrade prematurely. Not only was this reducing the operating efficiency of the capacitors, during peak load periods it was causing the main incoming breaker to trip – a major concern for a site where the reliability and availability of the production lines are core to its business.
It was actually Paragon’s investment in the state-of-the-art printing technology required to maintain its position as the UK’s largest manufacturer of self-adhesive food labels that was contributing to the problem. This is because advanced printing equipment utilises variable speed drives (VSDs) that are a notorious source of network harmonics.
ABB’s detailed investigation established that the total harmonic distortion (THD) on the network was above the recommended levels stipulated in Energy Networks Association Engineering Recommendation G5/4-1 – Stage 2 Table 12 ‘Planning levels for harmonic current distortion and connection of non-linear equipment to transmission systems and distribution networks in the UK’. If this issue, together with possible system resonance, was not addressed then the output of the existing capacitors would continue to degrade over a period of time, reducing the power factor and allowing the site’s peak demand to increase, with the possibility of further main incomer tripping occurring.
The recommendation was to remove the existing capacitors completely and replace them with a 250 kVAr Advance automatic capacitor assembly fitted with detuning reactors to mitigate the damaging effects of the harmonics. A year on from the installation, the Spalding site is operating efficiently with no reported tripping incidents.
Boston – harmonic filtration solution
Following the success of the Spalding project, ABB was asked to investigate Paragon’s Boston site. It was found that again the harmonic distortion on the network was outside the G5/4-1 recommendation.
ABB was able to offer the ideal solution in the form of its new generation PQF (power quality filter) family of active filters. They operate by continuously monitoring the current in real time to determine what harmonics are present and then injecting harmonic currents into the network with exactly the opposite phase to the components that are to be filtered. The two harmonics effectively cancel each other out so that the feeding transformer sees a clean sine wave.
A 450 A PQFI unit designed specifically for heavy industrial loads was installed and harmonic distortion assessments carried out following its commissioning confirmed that the harmonics are now limited to well below the G5/4-1 requirement.
Wisbech – PFC solution
At Wisbech, ABB was asked to help improve the site’s power factor (PF). PF is essentially a measure of how effectively electrical power is being used. Ideally it would be 1 (unity), and the closer to this figure it actually is then the more effectively electrical power is being used and vice versa. The investigations found that the PF of 0.845 lag was well below acceptable industry standard levels, which usually call for a PF of 0.95 or better. In fact, a site PF lower than 0.95 can now result in penalty charges being imposed by the local electricity supply company.
To rectify the situation, ABB installed sophisticated power factor correction (PFC) equipment in the form of its Advance 400 automatic capacitor equipment comprising a total bank of 300 kVAr, complete with a detuning reactor to eliminate any issues with network harmonics.
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