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.

As most electrical engineers know, working with switchgear carries with it potential hazards. Improvements in design and better working practices, however, have contrived to make it much safer than it used to be.

If it were an animal, switchgear would be a champion racehorse; highly-strung, unpredictable – and with a powerful bite. But as every champion jockey will tell you: it’s all in the training. If you know what you’re doing and have thorough and appropriate training, you should be able to handle switchgear, no problem. If you are a novice, however, take every precaution and wear all the safety gear you can.

An accident associated with switchgear has been arc flash. These can occur when a large electrical current passes through ionised air and can be triggered when a circuit-breaker fails or when insulation has been seriously compromised. Although rare, these accidents have had serious consequences in the past. When an arc flash occurs, the temperature surrounding it can rise to around 20,000 degrees centigrade, which vaporises conductors leading to an explosion and the release of globules of molten metal. Anyone nearby could be in danger of serious injury or death.

Arc flash can also cause fire, the production of dangerous gasses and the leakage of burning oil in older designs such as oil insulated switchgear.

The good news is that modern designs of switchgear have moulded insulation, which allows good control over electric fields thereby reducing the susceptibility of the insulation to break down. It significantly reduces the chances of arc-related faults. It won’t entirely negate such incidents, or the chances there of, so it is important still to observe appropriate safety information and practices.

Not quite so hazardous but potentially more disruptive is the problem of partial discharge in insulation, which is a common cause of unreliability in MV switchgear. Here, small currents in the form of sparks can leak through the insulation at points where it has deteriorated. In hazardous environments, this could cause ignition of flammable materials but at best it could lead to breakdown of equipment and expensive repair. Needless to say, the best remedy for this is regular testing and inspection of switchgear, including all cabling and connectors.

When you choose Riello UPS for switchgear supply, you can be sure of our expertise. We always design switchgear into the system from the start and our name appears on the panel so you can rest assured we make sure that the quality of our work is consistent with the rest of your UPS and standby power installation.

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.