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Do you have a back-up power supply?

Do you have a back-up power supply?

Feature articles |
By Julien Happich



Research published in January 2014 suggests that we can expect blackouts and brownouts to become more common as our infrastructure struggles to cope with increased demand and inadequate investment. For example, after two fallen trees caused all of Italy to blackout in 2003, it proved that the power generation systems in place were fragile and unreliable.

With network failure due to inadequacy a growing concern, the importance of having sufficient and resilient backup in place is clear. The primary aim for choosing a back-up power system is preventing a complete power outage; therefore, preventing a loss of business and earnings. In some sectors, such as Telecommunications, Mass Transportation, Oil & Gas, Power & Utilities, Data Centers and Healthcare, the implications to public safety and data security mean that having a power back-up solution in place is no longer a choice, but a necessity.

While keeping businesses and public services running at all costs is of course essential, there is another key consideration which is sometimes overlooked when choosing a sustainable back-up power supply – efficiency. As well as providing peace of mind, it is important that your business continuity plan does not place an undue level of financial strain on your business. Some power inverters lose large amounts of energy during the conversion process, amounting to money spent on basically nothing. You should therefore take care to select a system which provides both the safety and security that you require, as well as keeping your operational costs to a minimum.

 

Businesses rely on and sometimes take for granted the ability to keep going, and if you work in one of the critical public sectors, you will be keenly aware of the importance of power and the potential implications of an outage. In today’s modern era where the vast majority of processes have been computerized (records are stored on databases and even local convenience store points of sale are electronic), a sudden power cut can mean considerable loss of earnings, which spells disaster to a business owner.

One of the most challenging areas for implementing power supply systems is in Oil & Gas exploration due to tough environmental conditions and high operating costs. For example, a team in charge of replacing the UPS system on Sonangol’s offshore oil platform in Angola had to mount power supplies on an offshore oil platform in the midst harsh, tropical weather conditions.

 

The platform – powered by an uninterruptible power supply designed to ensure complete reliability of power for all essential systems – had a few problems. The main issue was that if one of the units needed repair or replacement, heavy lifting gear was required, the system had to be taken offline, and expert technicians had to be brought in by helicopter or boat. Sonangol opted to install two modular 40kVA UPS systems with Twin Sine technology, to replace the outdated system. The new UPS would run with a NiCad battery bank, occupy considerably less space and offer substantial maintenance advantages. Able to be completely housed in four cabinets, the new architecture offered several key benefits for Sonangol, including hot-swappable capacity, compact size, capability to run from NiCad battery packs, compliance with Oil & Gas industry standards, and guaranteed maintenance and support from the manufacturer for a minimum of 10 years.

Fig. 1: The two inverter cabinets each contain 16 TSI BRAVO EPC 110Vdc/230Vac Inverters, in EPC mode. Each inverter module has an output of 2.5kVa, making 40kVa in total.

The key component in every effective backup power system is either the power converters (battery charger AC/DC, inverter DC/AC and DC/DC converter) or the batteries. They work in the background, monitoring power levels, detecting commercial power grid abnormalities and, in many cases, correcting them immediately. It is this system which will kick in when a power failure is detected, running off high powered batteries to maintain your power, and allow you enough time to deploy your emergency power source. Although it may only be active for anywhere between a few minutes to several hours, it is vital in ensuring that your critical applications do not lose power and your business activities do not cease. No loss of power means no loss of revenue.


Inverters have been around for a long time, but modern inverters are generally a vast improvement on their predecessors. One example of how a modern inverter should perform is illustrated below. This system uses Twin Sine technology to ensure that there is no loss of power. In the event of a system overload, the system can deliver up to 150% of the nominal power for 15 seconds, then for the next 105 seconds the output power will slowly decrease (to approximately 115%) before 150% of the nominal power is available again. In addition to this, as long as the system is within the correct temperature range (up to approximately 50°C), it will deliver 110% of the nominal power permanently. This is the case whether the system is drawing power from an AC or DC source.

Fig. 2: Overload power capacity as a function of time.

Implementing an inverter or a UPS system which will provide you with that all important back-up (should the worst happen) is not always cheap. Many providers will want to sell you a complete solution, with capacity which will never be a necessity for you or your business as well as a costly maintenance contract tying you in for many years. This is another example of the importance of researching your requirements. There is no ‘one size fits all’ when it comes to back up for critical applications and it is essential to be fully aware of what you need at this point in time, because – provided you have selected the right system – there will be the opportunity to add to it as your business grows.

Although this may sound obvious, it’s surprising how many businesses don’t consider this when setting out their business continuity plan. Modern inverter units should be modular and able to accommodate as many units in parallel as possible. This is important not just for ease of expansion, but also when it comes to installation and maintenance. The ability to isolate individual modules and ‘hot-swap’ them without turning off the main power supply enables your business to function as normal without a drop in power.

But what about the possibility of your back-up power failing? Traditional AC back-up systems are fitted with a static bypass switch which can become a bottleneck, causing a single point of failure in the installation. In the event of a failure, critical AC load could cease, in most cases resulting in service outage. However, some more modern inverters – like the ones discussed in this article – are now using a technology referred to as Twin Sine Innovation (TSI).

Fig. 3: TSI technology packs three energy converters into one module.

TSI is based on a single module containing three converters, which allows for a precise containment of any failures, resulting in a completely redundant system.  In short, this means that – even in the unlucky event that one converter fails – you will not experience a loss of power. The system will simply isolate the faulty component and allow the others to continue supplying the output power.

Of course, every business is different, and it is simply not possible to give a definitive answer on the best method of back-up power for every business. But with a little know how and armed with as much knowledge as possible about your business and the challenges you face, it is possible to select a back-up power supply for your critical applications which will help to protect not only your revenue, but also your balance sheet, for many years to come.

 

About the author:

Olivier Bomboir is VP of Business Development & Product Management at CE+T Power – www.cet-power.com

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