Power quality paramount in digital age

Power quality paramount in digital age

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The days of rooms full of rows of filing cabinets are rapidly disappearing into distant memory. These days we don't have to stand for hours each week painstakingly shuffling paper into alphabetical and date order, we simply drag and drop electronic files into a hard drive. However, as Google discovered recently, this isn’t as fool proof as it seems.
By eeNews Europe

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When lightning struck the local power grid supplying one of Google’s data centres in Belgium – four times – several of the discs stored there were completely wiped. Data centres have to ensure there is additional protection to defend against power disruptions such as surges or shortages.
However, it just goes to show that even when these measures are in place, as they were at the Google data centre, they can’t protect your electronic systems from everything.

However, it’s not just data centres that need to take power quality into consideration. These days you’d be hard pressed to find a business that does not rely on electronic systems and electronic data and, while you may think you’ve got everything covered, if you’re not thinking about power quality you could be leaving your business vulnerable.

It’s easy to picture how disruptions to, or caused by, power can cost your manufacturing, automation or industrial business time and money. A power surge or shortage can cause expensive downtime, damage to parts being manufactured, or damage to equipment. But power quality is also a threat to the business side of business; it’s not just large scale operations that rely on consistent power anymore.

Banks, accountancy firms, telecommunications, retail outlets, designers and pretty much any business you can think of now operate based on electronic systems and rely on electronic equipment, devices and data.

Power surges

A power surge occurs when a system receives more electricity than it should for more than three nanoseconds. While there are several reasons this would happen, lightning strikes are the most common cause.

At the extreme end of the spectrum, a power surge can wipe data from hard drives, as it did at Google’s data centre. However, there are more subtle problems a power surge can cause. For instance, frequent power surges can reduce the physical life span of your hard drive.

Upon power loss the read/write head of the drive will jump back to its starting position. This abrupt motion can lead to the formation of minute imperfections that accumulate over time until they cause a head crash, where the drive head scrapes the disc surface and destroys the hard drive.

Harmonics

Compact power supplies in electronic devices and controlled motors are possible thanks to switch-mode power supplies (SMPS) in both personal usage and variable speed drives (VSDs) in commercial and industrial settings. This is achieved by manipulating the mains power supply using components in rectifier and chopper circuits in a process of high frequency switching or pulse width modulation (PWM).

Although PWM achieves very low power losses, the process introduces harmonic currents into the power supply. Harmonics are essentially multiples of the fundamental 50Hz frequency and are responsible for numerous problems, particularly in industrial environments.

Harmonics can lead to increased energy consumption and noticeable component damage. In addition, the electromagnetic interference (EMI) that is generated as a result of harmonics, can begin to affect telecommunication equipment and metering apparatus. High levels of harmonics also contribute to voltage distortion.

Voltage distortion

Internal SMPSs that draw a nonlinear current waveform can cause voltage distortion. While linear loads produce a sine wave current, an SMPS draws current pulses at one portion of the applied voltage waveform, which increases with every device added to the system.

The nonlinear current and impedance of circuit conductors and the power source creates a visible voltage drop, the greater the loading demands of a system, the greater the voltage drop. A little distortion isn’t going to grind your business to a halt, but where the distortion is in high enough levels, there is the risk of decreased efficiency of the power system.

In addition, localised power distortion such as voltage ripples can be reintroduced into the mains supply. This is can be especially problematic in industrial settings where SCADA and DCS systems are in use over wide geographic areas.


Sharing responsibility

The quality of electricity provided by any power grid operator in Europe has to be in compliance with the parameters laid out in the EN 50160. However, users of this power can have a negative effect on the quality of power in the grid for other users.

Issues like current harmonics, voltage harmonics, flicker and surges collectively create harmonic pollution. Polluting loads leaking into the grid have an adverse affect on network components and can distort the network’s voltage, creating a vicious cycle of poor power quality between businesses and the grid. Businesses of all shapes and sizes are aware of the responsibility of power suppliers to provide quality power, but it’s important to be aware of how their own operations have an effect on the supply.

High levels of power quality emissions from customers make it difficult for network operators to maintain high voltage quality at points of common coupling (PCC) – the point in the electrical system where multiple customers or multiple electrical loads may be connected.

It’s also recommended practice under IEEE-519 regulations as a joint approach between utilities and customers to limit the impact of non-linear loads by reducing harmonics. It’s an ongoing challenge for OEMs and network providers to guarantee acceptable levels of total harmonic distortion (THD) in the face of high emissions, requiring investment and expert knowledge to achieve.

The same type of damage of caused by harmonics to components in a manufacturing plant are simply magnified when they enter the mains supply, impeding the smooth operation of components and systems on a large scale.

Harmonic pollution is a growing problem and it is a problem for polluted sites, power grids and other customers being supplied energy by the utility providers across the network. Many polluters are not even aware they are causing a problem. The Engineering Recommendation G5/5-1, from the Energy Networks Association, outlines acceptable levels of harmonics. Where these levels are not, or cannot be met, consumers have an obligation to communicate with the utility provider before connection to come to an arrangement or they can face penalties.

In order to minimize problems on both ends and ensure smooth, consistent power quality there needs to be a shared responsibility between both sides and a united approach.

By working with an expert, such as REO UK, to put power quality measures in place you can mitigate the effects of these core threats to your business and play your part in supporting the local power grid in your area.

It’s in times of crises like these when a solid disaster recovery and business continuity planning procedure comes into its own. The rise of cloud computing has made it even more essential that traditionally centralised data and resources are now backed-up to and accessible from multiple, geographically disparate locations. In doing so, businesses can ensure that, no matter what happens, they can keep their customers up and running.

Given the unpredictable nature of lightning it’s always advisable to also take a leaf out of Google’s book and back everything up somewhere safe. After all, like a fire in a room full of paper, you can’t ever fully control nature and stop it from wreaking havoc on the power grid and your business.

About the author:

Steve Hughes is the Managing Director of REO (UK) Ltd – www.reo.co.uk

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