Anyone reading an electrical magazine of late can’t help but notice the rising interest in (and column inches devoted to) the subject of voltage optimisation.

In 1995, the European Union set out to harmonise the single-phase mains supply voltage across countries. Prior to that, variation existed country-to-country from 220, 230 or 240Vac 50Hz. It was down to manufacturers of electrical equipment to optimise their products for each country or region. 230Vac became the nominal standard (prior to which the UK operated at 240Vac). Three-phase mains nominal voltage was harmonised to 400Vac.

A problem arose because many large electricity consumers found that much of the electrical equipment they use to run their businesses now operates inefficiently at the new rating and thus wastes considerable electricity each year.

Voltage optimisation technology providers stepped in to stem the problem by developing technology that sits between mains power and connected loads to provide a steady-state 230Vac or 400Vac supply to ensure optimal load voltage efficiency, whether resistive or inductive/capacitive loads.

My question is: can it be recommended for mission critical applications and is such technology really the best option when UPS themselves are the ultimate voltage optimiser?

Firstly, UPS protect connected loads from breaks in mains supply AND from mains-borne power problems such as sags, surges, brownouts and so on, which a voltage optimisers cannot do as effectively.

Secondly, although most online UPS are installed as 230Vac (single-phase) or 400Vac (three-phase) output, they can be configured manually to provide other voltages such as: 220/230/240Vac or 380/400/415Vac. Loads are automatically supplied by a UPS with the level of voltage and current required to perform at their optimal frequency. UPS also provide battery back up and/or connection to an alternative energy source (such as a generator) to protect loads in the event of a mains failure. Today’s online UPS can also achieve operating efficiency figures of 96% and higher (if operated in certain power modes).

Voltage optimisers carry a lower capital cost compared with UPS but they do not provide the higher levels of power protection required by the critical loads that run today’s always on businesses. In my view, UPS are better at the job of both power protection and voltage optimisation.

The National Grid is buckling under the pressure of increasing demand for electricity – and modernisation is not happening fast enough. In densely populated areas like large towns and cities, it is a real problem exacerbated by the fact that more and more renewable energy sources, such as wind turbines and solar installations are being connected into the grid. These facts are introducing even greater instability into an already precarious system.

The primary purpose of a UPS (uninterruptible power supply) and generator is to provide an immediate source of back up power in the event of a mains failure. A secondary, but increasingly important, purpose for a UPS is to condition the voltage that is delivered to connected loads, but this can only happen if UPS and generator are properly synchronised to work together.

Power Problems

Power problems associated with raw mains energy are defined as any variation in electrical power resulting in a malfunction or equipment failure. Power problems include: sags, surges, brownouts, electrical noise, spikes, transients and harmonics, alongside frequency variations and complete blackouts.

It’s not only problems brought about by external mains power, however, that can cause problems for connected loads. Certain types of power load that are connected internally to the site electricity distribution system – such as motor loads (lifts, mechanical machinery), certain types of lighting (Tungsten) and air-conditioning can cause problems for equipment upstream without the correct filtering and power conditioning.

A generator must be able to accept the load of the UPS and the UPS rectifier and static bypass supplies must be able to operate with (and synchronise to) the output of the generator. There are several elements that enable this to be achieved: correct generator sizing. In UPS installations, generators are typically larger than the installed UPS so that they can deal with the harmonics the UPS generates and any overload conditions that may occur during operation.

For load acceptance to occur, a UPS must be able to synchronise to the voltage waveform supplied by the generator. UPS normally have a wide input voltage window, which will more than accommodate most generator output but the frequency can vary and this potential problem can be simply overcome by widening the UPS operating parameters to accept wider frequency ranges.

There is a whole chapter on generators in The Power Protection Guide – the design, installation and operation of uninterruptible power supplies, which offers more information. Visit the Riello website for details of the power protection products and services we supply.

The importance of power conditioning within a power system cannot be underestimated and it is a little-known but very important feature of a UPS system.

At its source, mains power is ‘unclean’ and generally badly behaved and this can cause all sorts of problems within an internal power distribution system and for any equipment attached to it. It can ultimately lead to costly and disruptive breakdown or system crashes.

Power Problems

Alongside total blackouts and power failures, power problems manifest in several different ways:

• sags – short duration voltage reductions in mains power supply, which can cause computer equipment to malfunction and lead to data loss.
• Brownouts – longer duration reduction in mains power supply voltage, which can also result in equipment failure.
• Surges – these are short duration voltage increases, which can lead to system crashes from activated automatic cut-out protection within the equipment. Surges can also cause wear and tear and general equipment degradation over time.
• Spikes and transients – are fast-moving, high energy bursts (in excess of 6kVA in some instances). They last only a few milliseconds but can cause widespread and costly damage to equipment and motherboards.
• Electrical Noise – electrical noise exists in all electrical systems and if not filtered out can disrupt the operation of circuits and equipment and cause damage.
• Harmonics – harmonic pollution is a problem associated with proliferation of SMPS (Switch Mode Power Supplies) being connected to electrical distribution networks. Harmonics can cause distortion of the mains power supply voltage, overheating of building wiring circuits and nuisance tripping of breakers.

Power conditioners within a UPS system are designed to attenuate spikes, transients and electrical noise. But in environments where these problems are most severe, such as in industrial settings, for example, other types of power conditioner and/or filter may also be employed. Constant Voltage Transformers (CVTs) can be used to stabilise voltage over a wide input voltage window. This is a type of Ferro resonant design.

Other types of protection include AVS (automatic voltage stabilisers), which can protect from sags, brownouts and surges. TVSS (transient voltage surge suppressors) can be employed to guard against transient voltages and high-energy spikes. Some also have filters that protect from spikes, transients and electrical noise. Standard filters and filter strips may be employed in some installations to protect against spikes, transients and electrical noise but rather than attenuating performance, they ‘clamp’ peak voltages to predefined, acceptable levels.

A power quality review, prior to embarking on a power protection project, upgrade or change to your power protection plans, is recommended as it will reveal essential information pertinent to the design and configuration of your new system. For more information, visit our website.

Did you know the UK’s National Grid (and I should imagine most other energy utilities the world over) employs a team of people who do nothing other than demand forecasting?

Electricity is one of those things we take for granted. You come into the office, switch on the lights, computer, kettle and – hey presto – it all works! Simple! So why a whole team to manage and forecast demand? Well, too much electricity entering the Grid can cause problems like overloads, circuit-breaker tripping and even blackouts. Too little and the frequency of supply falls, causing sags and brownouts. It’s great that we can sleep at night knowing there is someone out there taking care of all this so that we don’t have to! Or do we?!

With demand for energy so high and supply increasingly challenged, isn’t it time, particularly as business people, we started to adopt a more proactive stance towards energy consumption?

Measuring true electricity usage, particularly by businesses, is not straightforward but nor is it rocket science. There is a science to it, which, with a bit of professional guidance is within the grasp of most business professionals. But imagine what you could do armed with that information? Firstly, you’d have greater ability to consolidate you energy bills with your supplier and get a cheaper rate perhaps. With a better idea of peaks and troughs in consumption you could even consider money saving initiatives like ‘Peak Lopping’, which is a way of reducing energy bills and securing supply during peak times. It is the practice by which the user has a contractual agreement with their energy supplier to switch from mains to back-up generator during peak periods. In return for this ‘interruptible’ supply, the user gets a significant reduction in their energy bill. A by-product is that the power continuity plan, UPS and back-up supplies are being utilised and tested under load conditions. And if you have an accurate graph of energy consumption, you will have an accurate idea of power protection requirements in terms of sizing your generator and back-up UPS.

At the moment, most companies are happy to leave this in the hands of their utility supplier to ‘guess at’ and manage but how do you know that their ‘assumptions’ or readings about how much energy you use are accurate and that they have your best interests at heart? The time will come I believe - and in the not too distant future – when demand forecasting and energy consumption management will be mandatory practice for big business. But you might as well start now so that when it does happen, you’re ahead of the game.

For more information about demand forecasting and measuring energy consumption read The Power Protection Guide.