Ensuring power quality across the spectrum

The new Engineering Recommendation G5/5 has extended the values for planning and compatibility levels to the 100th order (5kHz), broadening the reach of emissions testing. Here John Mitchell, Global Sales, and Marketing Director of CP Automation, discusses the harmonics gap and how operators can overcome it.

Traditionally, harmonics in the UK were regulated through the EN50160 power quality standard and the Engineering Recommendation G5/4. They were previously regarded as falling between the 50Hz to 2.5kHz range, or between the 1st and 50th order. However, G5/5 has taken the limit up to 5kHZ, or the 100th harmonic.

What does this mean? Most power quality engineers are using measuring devices incapable of seeing above the 50th order. 

While EN50160 is a good benchmark, it was never designed to focus on the end user’s own asset protection. It was designed to ensure the end user does not impact the power network and impact others at the common point of coupling (PCC). Harmonic limits should be thought of as speed limits, with sites keeping under them to reduce risk.

A hidden cost in mitigation

Every sector is impacted, including the UK’s water industry and its various sites that use high-power drives and motors. Often, active front end drives are provided as the solution to keep the harmonics down. While they do a good job at that, the extra 2-3% in losses compared to a standard variable speed drive (VSD) requires more climate control in the control room. This potentially equates to 6kW’s of additional heating on a typical Duty, Assist, Standby on a 90kW application.

Operators also need to consider solving the harmonic issue locally at source or at the common point. Many factors should be considered as there is no one-size-fits-all solution. The nature of the loads and how dynamic they are will also play a role, along with budget and space constraints.

The recent change in regulation means operators and end users should assess the likelihood of harmonic distortion and other noise impacting their equipment. It could also offer answers to unsolved power quality issues.

Uncovering the gap

Harmonics and electromagnetic interference (EMI) are disruptive, triggering equipment failures across the frequency spectrum. Fire alarms can go off at random, components can overheat, and power supply units (PSU) often fail.

One area that is now being addressed in Europe and partly by G5/5 is the area between harmonics and EMC, called supra-harmonics. These are graded in two areas of noise, 2-9kHz and 9-150kHz. This is an area most power quality devices cannot read, and sites can be mistakenly given a clean bill of health by power quality engineers. Often, they unknowingly cannot measure this noise because the equipment they are using only works to the old standards of 2.5kHz (50th order). That’s why at CP Automation Ltd we increased our scope of supply by incorporating devices of fixed and portable meters to help customers measure supra-harmonics. Furthermore, we offer a range of supra-harmonic filters to mitigate these issues.

The increasingly wide scope of harmonics poses an emissions testing challenge for many industrial facilities because many devices operate on entirely different frequency ranges. What’s more, this is before we think about the various pre-existing residential and industrial regulations that must be met.

How can we close the gap?

The harmonics and EMI gap is challenging, but removing blind spots in emissions testing capabilities is a great way of overcoming it. This means knowing where each device sits on the frequency spectrum and identifying an appropriate system to mitigate noise.

Operators can install filters to prevent the distortion of nonlinear loads at the source, whether this is a VSD or another device. Active filters monitor and inject currents to help mitigate harmonics, and or passive filters to filter drives in VSD systems.

Working with an experienced power quality specialist with knowledge of the entire frequency spectrum and who can recommend solutions for every point is also suggested. With Engineering Recommendation G5/5 now in force, businesses should also work with engineers proficient in power quality beyond the 50th order and use equipment that can measure beyond this level.

CP Automation offers a dedicated measure, analyse, report, and solve (MARS) service. This involves its specialists capturing, reviewing, and analysing harmonics data before feeding it back to customers in the form of a detailed report. Its team can also provide solutions to solve these issues.

Noise will always be a risk for industrial sites, but closing the gap in emissions testing and getting the right support can help mitigate noise across the spectrum.