At a global level, computer and telecommunications technologies have developed so quickly over the last decade that it is a challenge just to keep up, let alone appreciate how they are, and can, be used for our own benefit and growth. It is only a question of time before most (if not all) facets of our lives are ‘controlled’ and managed electronically. Against this background, and bearing in mind that all electronic computer equipment is electrically driven, the need for continuous, clean, and stable electricity supply from the service provider is more than a priority. In fact, it is an absolute necessity, and an issue on which the user cannot afford to compromise.
The global and African scenarios
Without a reliable electrical supply, new age computer, and telecom infrastructures are guaranteed to fail, causing mayhem and catastrophic disruption to lives, businesses and important daily activities. Revenues and personal safety are also bound to be negatively affected.
Looking on the dark side, statistics and future predictions for Africa indicate that national electricity supply grids across the continent are deteriorating as a result of governments inability to keep up with population growth - and increased user demand. As a result, along with decreasing availability of the electrical supply, its stability is regressing. What does this mean for Africa?
It is a well-documented fact that, for African countries to be able to compete on an equal footing with those in the rest of the world, they will need to move from Third-World to First-World production methods. However, with this trend will come exponential growth in the use of electronic equipment and increasing dependency on computer and telecom infrastructures - which are highly susceptible to power irregularities.
Health care and education are just two of the many vital infrastructures which require a 'clean' supply of electrical energy. Effective delivery of health care particularly important on our continent, which is fighting a growing HIV/AIDS epidemic - is directly linked to and highly dependent on technological infrastructures, which are in turn dependent on a reliable supply of electricity. Similarly, education depends increasingly on communications capabilities, which are electrically powered. Thus it is clear that, without stability in the technological and telecom infrastructures that are so essential to economic growth and sustainability, the dreamed of 'African Renaissance' will remain out of reach.
Specific effects
The effect of an unstable electricity supply on electrically-powered equipment is never positive, but hi-tech equipment is particularly susceptible to power supply irregularities. This includes such equipment as computers, telephone exchanges, banking and point-of-sale terminals, television/radio transmitters, security systems, etc. Outcomes can range from an error or a momentary systems collapse, to long term component degradation or most devastating of all - permanent operational damage.
Power problems and irregularities, ranging from total power failures to frequent fluctuations and lightning induced surges, are an increasing threat to our technological infrastructures. The question is how can the individual, commerce and industry protect themselves?
In the short term, there is little that individuals can do about the quality of their electrical supply. However, they can and should ensure the power stability and protection of their operation's mission-critical systems and infrastructures.
Solutions
Solutions are available and are very affordable. Diesel or petrol generator sets, which offer the conversion of mechanical energy (from a diesel-driven internal combustion motor) to an electrical energy (alternator), will provide long back-up and standby electrical supply: for as long as there is a supply of diesel/petrol, that is. This solution, however, is most appropriate to medium to large power/load requirements; and it does not provide for high quality power (pure sinewave!). Diesel/petrol generator sets are best suited to back up large buildings, hospitals, factories, and farms. These are the situations in which they are normally used. They cannot be used in an office environment and do not deliver power of acceptable 'quality' to drive sensitive electronic/hi-tech equipment. On the other hand, uninterruptible power supply (UPS) systems are designed to do just that: supply the most stable, clean, high quality power.
The static on-line, dual conversion UPS will ensure that your load is fed from the best quality, stable power, regardless of how from unstable and/or 'dirty' the utility supply is! It also has a built-in battery for back up purposes. Batteries normally offer back up of only a few minutes. However, using a larger battery bank can increase the back-up period.
Since batteries are relatively expensive, and the UPS system requires a number of them, it is more economical to use the UPS as your source of good, stable electrical supply, and your generator set as the source of long back-up times (autonomy).
UPS systems have been in existence for more than 30 years and have evolved considerably over that time. Nowadays they range from very small to very large. The large and very large systems cater for large buildings, factories, airports, seaports, government, and municipal offices, banks, etc. In such contexts, UPS systems are often used in conjunction with generator sets. The very small (in power capacity and sometimes in physical size), 'line interactive' UPS systems are designed to protect and back up home and SOHO PC, PABX, printer, modem, fax, copier, etc. Medium-sized systems are intended primarily for such systems as small to medium computer networks, point of sale, TV, studios, radio stations, automatic teller machines, store checkouts lanes, and security systems.
Another solution is voltage stabilisers, which ensure stability but don't offer any back up. As these systems offer no protection against power fluctuations/irregularities other than voltage instability, they should ideally be used in an environment where power is readily available but unstable. The solutions discussed above refer to the AC electrical supply.
UPS systems have for a while been considered an integral part of any electronics equipment installation, especially computers. Their main function is to ensure the quality and continuity of electricity power hence regulating the power to one's critical load, while providing protection against supply irregularities, surges, lighting. Back-up during blackouts (power failures) is yet another important function. In general, the benefits thereof are quite commonly known, which is why this article emphasis is on exploring the different solutions available together with the relevant implications.
Rotary UPS and standby generator sets
In many situations, the application requires extended back-up times to maintain operation during prolonged power failures. Where long autonomies are required, standby generator sets probably provide the most economical solution, yet their power quality and stability is often of an unacceptable standard to sensitive electronic equipment, and the user must connect a UPS between his generator and his load. UPS systems offer extended back-up times but at relatively high premium, as batteries are expensive.
'Generator', and other standby power generation sets in combination with a UPS form an integral part of the 'total power protection and back-up installation'.
Rotary UPSs have excellent 'static' and 'dynamic' behaviour, crest factors almost three times their closest 'static' competitors, and enhanced reliability. For reasons of economy, 'rotary' systems are usually sold into applications requiring above 100 kVA.
What about DC?
DC should never be ignored. However, AC is how electrical energy is normally generated and distributed, and one should consider the AC supply first. Another angle to approach the problem of unstable power in areas where the availability of power is reasonable, but the stability and quality are poor (most urban areas) is to use a line voltage stabiliser. In rural areas the use of solar panels, which converts sun energy to DC electrical energy is viable. DC can then be inverted to AC, using a 'DC to AC inverter'.
Standby (off-line) UPS or true on-line double conversion?
This is a major debate among UPS suppliers and customers. Both topologies have their market niche, but when comparing the two the following distinctions must be made:
The true on-line, dual conversion UPS is by far the best solution, providing the best power quality, protection and conditioning. It normally offers input to output galvanic isolation, as well as stable, clean and disturbance free electricity to the critical load. This does, inevitably make the true on-line, double conversion UPS the more costly solution.
Off-line and line-interactive ('glorified' off-line) designs may cost less, but the level of protection they offer is correspondingly poorer. It is generally accepted that this topology gives less protection against frequency variations, voltage sags, surges, as well as voltage spikes. The choice between the two is largely a matter of application and budget. It should be noted, however, that off-line or line interactive systems should not be used for 'mission critical' equipment, or in an environment where any power interruptions, distortions, harmonics and/or waveform quality deviations are not acceptable and will not be 'tolerated' by your protected equipment.
Although Gamatronics offers a reliable line interactive product range for the so-called small office/home office (SOHO) and the small-to-medium enterprise (SME) markets, the company promotes the true on-line, dual conversion system as the best, uncompromising UPS solution.
The 'Intelligence' of modern UPSs
Firstly, internal checks constantly monitor the UPS's 'vital signs' to ensure high reliability and performance. Secondly, the UPS communicates to an external (remote) management point. Thus, the user has access to realtime operating parameters such as voltage, current, temperature, frequency, load, crest factor, power factor, etc. Remote management and control is achieved by means of direct serial connection, together with driver software which is proprietary to the system manufacturer. Auto shutdown capabilities of the operating system are also supported. Network SNMP connectivity is yet another function available.
In this way, the user can be notified of problems relating to the UPS's normal and proper operation, and can cater for the operating system's unattended orderly auto-shutdown. SNMP communications are achieved using an SNMP adapter, where a full graphic user interface is supported.
This makes the UPS as easy to control and manage as any other device on the network, minimising network downtime as the demand for overall network reliability increases. The UPS then becomes a 'true network protector'.
About the author:
Shahar Cohen is the Managing Director of Gamatronics, a company that has its headquarters in Jerusalem, Israel and branches in 36 countries across the world. Gamatronics designs, manufactures, supplies, and supports a full spectrum of solutions, including: UPS systems, voltage stabilisers, battery chargers, telecom rectifiers systems, frequency converters, telecom inverters and converter equipment, as well as mil spec systems.
For further information contact Shahar Cohen, (011) 807 4148, [email protected]
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