The electrical industrial steeplechase

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  Posted by: electime      13th November 2019

To celebrate 30 years in business, REO UK has put together a new book, R30 – The past, present and future of power. A key theme throughout the book is power quality, what it means, what affects it and how it impacts electronics in almost every sphere. Here, Steve Hughes, managing director of industrial power quality expert REO UK, provides an appetiser for the book by contemplating some of the potential difficulties looming on the electrical horizon.

Sign up to download your free copy of R30 – The past, present and future of power here:http://bit.ly/PowerQualityBook

From electricity meters to washing machines and even doorbells, it seems everything these days is interconnected. The benefits of this are quite clear to see, bringing boons to efficiency, convenience and security. However, there are certain issues that need addressing, namely harmonic distortion and electromagnetic interference (EMI).

One arena where this problem is laid bare is medicine. This sector maintains close step with electronic progress, keeping up with the latest technological developments in treatment and diagnosis with a view to providing the best medical service possible.

This has brought technology into hospitals in a way not many would have seen coming. For a variety of reasons, including hygiene, safety and convenience, many devices that were traditionally wired have been supplanted by wireless alternatives.

If you’ve ever passed under power lines while listening to a radio, then you have first-hand experience of EMI. But in hospitals the scale is far larger. For example, standard 400 kilovolt (kV) power lines exhibit magnetic fields on the order of micro-tesla (µT). In comparison, hospital magnetic resonance imagers (MRIs) work with magnetic fields of 1.5 tesla — a factor of a thousand stronger.

It’s not just people with pacemakers or metal splints who must worry about MRIs. Such strong magnetic fields interfere with passing wireless communications and induce currents in wiring and electronics from a remarkable distance away, even through walls, floors and ceilings.

While MRIs are a considerable example, EMI can creep in from many sources. Unshielded power lines, mobile phones and even magnetic smartphone cases are just a few objects that can cause issues. Disrupted communications and aberrant currents can have predictable and unfortunate consequences when they effect sensitive medical equipment, potentially putting lives at risk.

Windy weather, stormy power

While consideration of EMI on the local grid is vital, the source of the power is equally so, now more than ever. Worldwide trends are clearly leaning towards renewable generation over carboniferous fuels, but renewables can cause headaches for power quality engineers if left unaccounted for.

With photovoltaics, power is generated as direct current, which is incompatible with the mains alternating current. Therefore, the solar DC must be switched into smooth, sinusoidal AC by electronic components.

This is where harmonic currents rear their head. During the DC–AC switch, any inconsistencies or flaws in the electronics cause the signal to vary slightly from the ideal sinusoid. These harmonic distortions then go on to interfere with one another, adding up into dramatic voltage sags and spikes.

With wind power, while the electricity is originally generated as AC, it’s unlikely to be at the same frequency as the grid. For that reason, wind power is first converted to DC and then back to grid-frequency AC where it is input to the mains, therefore it falls to the same traps as DC solar.

The power failure that struck the UK in August 2019 is an object example of the sensitivity of the grid to frequency distortion. Uncorrelated fuelled and renewable generation failures, in combination with a harmonic-inducing lightning strike, caused a frequency sag of just 0.01 per cent from the nominal 50 hertz, leading to nationwide emergency load-shedding and blackouts.

While harmonics can wreak havoc on the grid at large, they have more subtle and pervasive effects at a smaller scale.

An obvious consequence of intermittent voltage spikes is tripping breakers and popping fuses, but harmonics also stress every component they inflict. This might be as simple as overheating resistors or inductors, or could be as complex as corrupting intricate devices that depend on smooth and consistent current, such as integrated circuits or flash memory.

If renewables continue fording ahead the way they are, with decentralised schemes popping up everywhere, this problem is only going to become more insistent and the impact will continue to grow in severity. It’s for this reason that electrical engineers must ensure that effective power quality filters are integrated into grids to attenuate unwanted frequencies and mitigate the problems of harmonics.

As we explore in our ebook, these are but a handful of the issues affecting the modern electrical infrastructure and electronic devices. As the world becomes increasingly tech-driven, engineers must be equipped with the knowledge and tools to combat these issues before they cause wider problems.

Find out more about power quality, harmonic distortion and the changing nature of electrical engineering in REO UK’s ebook, R30 – The past, present and future of power, free to download here:  http://bit.ly/PowerQualityBook