Maintaining uptime in Preston water treatment plant

Together, these can wreak havoc with plant equipment and the mains power supply. When GA Pet Food Partners, a dry pet food manufacturer, began designing a new treatment plant at its Preston site, it knew that it needed to design harmonic mitigation into the plans to prevent unplanned outages from occurring. During the design process, it approached power quality specialist CP Automation to find a solution.

Beginning its journey in 1972 as a mixed arable and livestock farm, GA Pet Food Partners is a private label family-owned and family-run business specialising in the production and delivery of pet foods. The company is headquartered in Preston, alongside an additional Preston facility and two sites in Chorley, Lancashire.

As part of the company’s expansion, GA was developing a new water treatment plant and an odour abatement plant with biobeds, to address any environmental impact the expansion may incur. Following treatment, GA would then sell these products onto its consumers. During the site design process, GA knew that the site would contain many drives, and that this could introduce risks associated with harmonics and adverse noise unless properly addressed. 

The trouble with harmonics

Harmonic frequencies are multiples of the fundamental frequencies and usually cause distortion in the voltage and current waveforms. Any drive, power supply or other load causes a nonlinear current draw, which generates harmonics at various frequencies. For example, single phase switches, such as those found in computers, predominantly generate third order harmonics, while AC drives generate fifth and seventh order harmonics.

Third order harmonics are undesirable for GA’s operations, because they cause a sharp spike in the zero-sequence current, and therefore increase the current in the neutral conductor. Meanwhile, fifth and seventh order harmonics will go straight to the transformer and can cause derating, as well as premature insulation when present in excessive amounts.

The need was also legislative. The latest Engineering Recommendation G5/5 raised the limit on the measurement of voltage harmonics, total harmonic distortion (THD) and sub-groups from the 50th harmonic (2.5kHz) to the 100th (5kHz). Given that the new water treatment site would include at least 40 motors — one of GA’s sites also had over 300 drives — it was clear that harmonic mitigation would need to be designed into any future facility. At this point, the pet food manufacturer turned to power quality specialist CP Automation for support.

Designing for mitigation

To support GA’s engineering team with the design, CP Automation supplied five P300 active harmonic filters from Swedish cleantech company Comsys.  Some were used for the design of the new site, while other filters were retrofitted to replace legacy units.

“The active harmonic filters are a specialist type of inverter that measure the harmonic load on the mains and generate the exact inverse to cancel out any noise,” explained Jayne Whittaker, Engineering Director at GA Pet Food Partners. “In doing so, the Comsys filters can correct power factor, which is vital as power factor capacitors are highly vulnerable to harmonics and the insulation failure they cause.

“As we’ve continued to expand and add more to kit to our sites, this growth has compounded power quality issues,” continued Whittaker. “I first realised these challenges 24 years ago, but only in recent years has mitigation technology caught up so that we can now resolve them constructively and cost effectively. Previously, we would have to overrate equipment to account for harmonics, but this had cost and efficiency implications.”

By supplying the active dynamic filtering (ADF) units, CP Automation could help GA achieve Engineering Recommendation G5/5 compliance while reducing the premature failure rate of equipment, nuisance tripping and other issues.

Clean, reliable electricity

The new ADF P300 units are designed for all size loads and are functioning as intended — eliminating harmonics and reactive displacement at GA’s site. Unlike other mitigation technologies, the Comsys units can correct both harmonics and power factor, which not only improves resilience against noise but also reduces the current drawn from the mains, meaning less power is consumed.

“One of the unique selling points of the P300 is its compact build and that it can deliver significant value with a minimal footprint,” added John Mitchell, Global Sales, and Marketing Director at CP Automation. “This was especially important for GA, who was looking for ways to expand sustainably and in a way that would futureproof its sites from adverse load behaviour.

“On one site, we managed to save the space of four large panels by retrofitting two in their place, achieving a 50 per cent reduction in footprint,” continued Mitchell. “The P300 units are an investment in GA’s future growth, freeing-up floorspace for additional equipment while protecting its sites from harmful power quality issues. We really enjoyed being a part of this project.”