Electricity + Control August 2017

ELECTRICAL PROTECTION + SAFETY

abbreviations

IT – Information Technology PFC – Power Factor Correction UPS – Uninterrupted Power Supply

Is a UPS Alone Sufficient for Your Power Requirement? Kevin Norris, Jasco Power

Experience and the results of many site surveys have shown that UPSs are not completely effective on their own, and need to be supported by additional power conditioning equipment.

Take Note!

There are many factors that influence the type of UPS required. UPSs are not completely effective on their own. Lightning protection devices are necessary on UPS installations to protect the load and the UPS from failure during lightning activity.

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W hile load shedding has currently been suspended, the reality is that while you are connected to the utility supply, you are still susceptible to the vagaries of an unstable power system in South Africa. In addition, to pos- sible power outages, you are also exposed to volt- age variations, sags, surges, spikes and harmonic problems. Power assurance and power quality solutions are necessary to protect sensitive equip- ment from these problems. An Uninterrupted Power Supply (UPS) is es- sential to provide a failover system between utility power and secondary systems such as a gener- ator. They are also useful for providing sufficient time to safely shut down equipment in the case where secondary power is not available. However, choosing the right UPS technology to suit your ap- plication can be challenging. The right solution for you Determining what power solution is needed is a science that requires careful consideration of sever- al factors. Things such as the proposed installation environment, the dynamics of the load, and wheth- er the customer is looking for continuity of supply only or complete power conditioning. The outcome of this often not asked question will determine the technology required and therefore the final cost of the solution. If not properly planned, power condi- tioning solutions can be less than effective and end up costing businesses more than necessary. It is vital that businesses, particularly those for which quality of supply is critical, plan their solu- tions properly. Before purchasing one or more UPS, or any other power protection equipment, it can be highly beneficial to conduct a power qual-

ity survey. This will enable organisations to gain a sound understanding of the precise challenges of their power environment which, in turn, makes it possible for a tailored solution to be designed to achieve the desired results. Quality of Supply Quality of supply problems can generally be cate- gorised as follows: • Surges: These are sustained over voltage con- ditions, usually as the result of fault conditions on the electrical network. Faulty neutral con- nections and incorrectly tapped distribution transformers can also result in a sustained over voltage condition, resulting in damage to sensitive electronic equipment • Sags: These are generally as the result of poor or ageing electrical distribution networks and too large a load being switched in and out of a weak network, resulting in a sustained under voltage condition. Equipment such as electric motors and refrigeration compressors are very sensitive to these kinds of conditions and a continuation of this condition can lead to overheating and perma- nent failure of the motors. IT based equipment tends to switch on and off under these conditions leading to a disruption in the IT process through- out the environment in which they are being used • Spikes: These are very common during light- ning season and are short duration high voltage conditions. They can also result from network switching and power factor correction compen- sation. Depending on the frequency of these spikes, they can result in data corruption of process plants and IT networks and permanent damage to sensitive electronic equipment

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12 Electricity + Control

AUGUST 2017