Uninterrupted Power Supply (UPS)
The world has become totally electronic and digital. Every device from the personal computer on your desk to the lift which carries you up to the office each day depends on electric circuitry which in turn relies on electrical power.
Power Problems
The power supply in the majority of countries in the western world is fairly stable and power outages are fortunately a rare occurrence. However, there are variations in power supply and quality which can affect the operation of sensitive electronic equipment. It has been estimated, for example, that some 60% of all computer problems can be traced back to electrical supply problems. Within an office building there are many things which occur to affect the power supply such as lifts can momentarily drain the power load so that the current reaching your equipment is lower than it should be. Moreover adverse weather conditions such as storms, lightening and snow falls can also impact upon the power supply.
Choosing the right power protection solution can be a confusing business. There are a number of different types of UPS each offering different levels of protection. Moreover, one has to consider how the UPSs are to be monitored and controlled with the correct software and what level of support and advice can be expected from your supplier. The aim of this article is to provide a brief guide through the power protection maze to enable you to select the best solution for your organisation.
Power problems fall into nine basic categories as follows.
Power Failure
Power failure is defined as a zero voltage condition that lasts for more than two cycles. It may be caused by the tripping of a circuit breaker, power distribution failure or utility power failure. This condition can lead to data damage, data loss, file corruption and hardware damage.
Power Sags
Power sags involve voltages 80 to 85 percent below normal for a short period of time. Possible causes are heavy equipment being turned on, large electric motors being started, and the switching of power mains (internal or utility). A power sag can have effects similar to those of a power surge such as memory loss, data errors, flickering lights and equipment shutoff.
Power Surge
A power surge takes place when the voltage is 110% above normal. The most common cause is heavy electrical equipment being turned off. Under this condition computer systems may experience memory loss, data errors, flickering lights and equipment shutoff.
Undervoltage
Undervoltage is a steady lower voltage state. An example of undervoltage happens during peak electrical demands in the summer, when utilities can't always meet the requirements and must lower the voltage to limit maximum power. When this happens. computer systems can experience data corruption, data loss and premature hardware failure.
Overvoltage
Overvoltage occurs when there is a sudden, rapid voltage peak of up to 6,000 volts. These spikes are usually the result of nearby lightning strikes, but there can be other causes as well. The effects on vulnerable electronic systems can include loss of data and burned circuit boards.
Switching Transients
Switching transients take place when there is a rapid voltage peak of up to 20,000 volts with a duration of 10 microseconds to 100 microseconds. They are commonly caused by arcing faults and static discharge. In addition, major power system switching disturbances initiated by the utilities to correct line problems may happen several times a day. Effects can include memory loss, data error, data loss and component stress.
Line Noise
Electrical line noise is defined as Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) and causes undesirable effects in the circuits of computer systems. Sources of the problem include electric motors, relays, motor control devices, broadcast transmissions, microwave radiation, and distance electrical storms. RFI, EMI and other frequency problems can cause data error, data loss, storage loss, keyboard lockup and system lockup.
Frequency Variations
A frequency variation involves a change in frequency from the normally stable utility frequency of 50 Hz or 60 Hz, depending on the geographic location. This may be caused by erratic operation of emergency generators or unstable frequency power sources. For sensitive electronic equipment, the result can be data corruption, hard drive crash, keyboard lockup and program failure.
Harmonic Distortion
Harmonics are distortions of the normal line waveform and are generally transmitted into the line by nonlinear loads. Switch mode power supplies, variable speed motors and drives, copiers and fax machines are examples of non-liner loads. Harmonics can cause communication errors, overheating and possible hardware damage.
So how can you protect electronic equipment from these power problems. The answer is to use a UPS or Uninterruptible Power System. At its most basic level the UPS will provide power to your equipment in the event of a total power failure giving you time to save data and shut down files. At a more sophisticated level the UPS actually conditions and filters the electrical supply so that the power reaching your equipment is 'pure'.
UPS units vary in size from small desk top systems which can protect a single PC to very large UPS which can provide power to a entire building. Almost every type of organisation has a power protection requirement from companies with computer networks to hospitals, airports, oil rigs. In fact, anywhere where continuous power is necessary.
UPS Technologies
There are three types of UPS technology — off-line, line-interactive, on-line. Off-line, sometimes called standby, is designed to protect a single PC or workstation. It is normally the most inexpensive UPS and only offers back up in the event of a total power cut and does not incorporate any significant power conditioning facility. It is called off-line because the UPS circuit only comes on stream when there is a power outage. Such units use a mechanical switch to transfer over to battery power when the voltage drops below a certain level. This causes a delay of two to three milliseconds but generally most computers are able to ride this out. An inverter inside the UPS changes the DC power from the battery into AC which can be used by the computer's power supply.
Line-interactive
Line-interactive is a hybrid technology which offers better protection than off-line but at a lower cost than full on-line. It offers protection in the event of an outage but also line conditioning which smoothes out peaks and troughs in the power supply. For example, if the voltage drops below a predetermined level the UPS will "boost" it back to normal. This type of design works by operating the inverter in reverse during times when the input AC power is normal to charge the battery. If the power fails a transfer switch is triggered and the battery power flows to the UPS output to power the equipment. Line-interactive UPS is best used where power conditioning is not crucial to effective operation of the equipment.
On-line
On-line is widely recognised as the best type of UPS where mission-critical applications are being protected. Although more expensive than the other two technologies such systems ensure there is never a break in the power supply. It does this by what is called a double-conversion technique which continuously converts the AC mains to DC runs the input via the battery and then through an inverter to transform it into AC for the equipment load. The ideal situation is to have electricity as a pure sinewave (see Fig 1). When raw power comes in from the mains it will inevitably be corrupted and have irregularities. What an on-line system does is clean and filter the power so that pure sinewave electrical power is being output to the equipment. With online systems switchover should be almost instantaneous and the effect of spikes and surges in supply can be completely eliminated.
In terms of the nine types of power problem outlined earlier the different types of UPS solution will protect your equipment from the following problems:
Offline/Standby | Power Failure |
Power Sag | |
Power Surge | |
Line interactive | Undervoltage |
Overvoltage | |
Online | Switching Transient |
Line Noise | |
Frequency variation | |
Harmonic Distortion |
Monitoring software
For mission-critical applications on-line technology is the best power protection solution available. However, it can be further enhanced with the addition of UPS monitoring software. There are various levels of sophistication of monitoring software. An IT manager will want to know immediately of any potential power problems which could affect the operation of his network. Power management software can carry out a number of functions including:
• Detailed monitoring of the utility power supply to detect spikes, brownouts, sags and other variations.
• Controlled shutdowns of critical equipment including selection of specific load segments of the network which need to be kept running longer. Users are normally told via a broadcast message on screen that they have X minutes to shut down their applications and save data.
• Maintenance checks of UPS equipment including status of batteries and readiness of the equipment to take over in the event of a power break.
• Recording a log of events so that a pattern of power problems can be established.
• Automatically alerting those responsible for the network by pager or e-mail that there is a power problem.
• Controlled shutdowns of critical equipment including selection of specific load segments of the network which need to be kept running longer. Users are normally told via a broadcast message on screen that they have X minutes to shut down their applications and save data.
• Maintenance checks of UPS equipment including status of batteries and readiness of the equipment to take over in the event of a power break.
• Recording a log of events so that a pattern of power problems can be established.
• Automatically alerting those responsible for the network by pager or e-mail that there is a power problem.
Some of the more sophisticated power management software suites also allow remote monitoring of the UPS from anywhere on the network to analyse the performance of the UPS and carry out preventative work. This is done either through serial port communications, SNMP (Simple Network Management Protocol) software or increasingly via the Web. This means the IT manager in London can control and monitor UPSs on the network wherever they are in the world. Whatever technology is employed the crucial fact is that the UPS should be regarded as an integral part of the network. The majority of businesses, no matter what size, rely on a computer network of some sort. When a power failure occurs many businesses without adequate protection are paralysed because not only do they cease to function but valuable data may have been lost and cannot be recovered.
UPS Planning
Installing a UPS on the network requires careful thought and planning. Many network managers feel that it is enough to protect the main server. However, they often neglect the routers, bridges and hubs which carry data traffic. Likewise there may be certain users processing data locally on their PC who require the added security of an individual UPS.
Ideally UPS should be considered when an IT installation is being planned or a building is first being constructed. Power protection specialists can advise on what equipment is needed to protect the load and any special considerations which need to be taken into account. For example, networks running a Unix operating system need to be shutdown in a specific order otherwise it could take IT staff days to reboot the system and recover files once power is restored.
In organisations which need to guarantee continuity in the event of prolonged power outages, such as hospitals or financial institutions, the autonomy time of a UPS (typically 10 minutes to two hours) is not enough. In such cases a back up generator is required. However, even here a UPS is essential as there is always a time lag before the generator reaches sufficient output to produce the required current and a switchover to emergency power can be implemented.
Companies like Powerware have many years experience of recommending and installing power protection solutions which are easy to use and manage yet effective in ensuring business continuity and maximise uptime.
Powerware Corporation:
Powerware is a part of Invensys Power Systems, a global provider of premier power systems, integrating a full line of uninterruptible power systems (UPS), telecom power systems, software, turnkey integration and 24/7 maintenance services. Customer applications include critical network and communications facilities requiring maximum availability such as IT networks, data centres, fixed line and wireless telephony and other critical applications. Powerware products are used in networking, PC, financial, medical, industrial, voice and data communications, military and aerospace applications — wherever continuous power is essential to daily operations.
Invensys Power Systems, headquartered in Raleigh, North Carolina, USA, is a US$2.6 billion leader in total power solutions for the IT, telecom and industrial markets. The parent company Invensys plc, headquartered in London, is a US$12 billion global leader in intelligent automation, controls, power systems and drive systems. Invensys Power Systems leads the world in power control and energy storage products for IT, telecommunications and industrial applications. Comprised of five product groups — Energy Systems, Energy Storage, Power Conversion, Distributed Solutions and Teccor — Invensys Power Systems provides customers with a single source for critical elements of their power systems.
GemNet
GemNet is the authorized distributor for Powerware Corporation (formerly Exide Electronics), and offers a large range of specialized power related products and services. The company has local offices in Pakistan (GemNet Private Limited) and Jebel Ali, Dubai, U.A.E. (GemNet Gulf). GemNet offers Powerware's entire range of products including technical and after sales support.
GemNet's target markets are the emerging markets, and it's activities are currently focused in South Asia, and the Middle East. Since inception, it has been GemNet's goal to be a leading supplier of it's power protection product range in the markets in which it is present. To this end, GemNet has been focused on getting a detailed understanding of these markets, building relationships, and setting up the required infrastructure to support such an operation.
GemNet's Services:
Service and Support:
• Qualified team of engineers provide quality installation and after sales service.
• Service contracts that provide for loaner equipment if repair time is to be more than 24 hours.
• Custom tailored service plans to fit the clients needs, including plans that cover the client's existing UPS equipment.
• Services also include: Needs Analysis, Comparative Product Analysis, Cost Justification, Consulting, End-User Training, Maintenance and After Sales Support.
• Service contracts that provide for loaner equipment if repair time is to be more than 24 hours.
• Custom tailored service plans to fit the clients needs, including plans that cover the client's existing UPS equipment.
• Services also include: Needs Analysis, Comparative Product Analysis, Cost Justification, Consulting, End-User Training, Maintenance and After Sales Support.
Power Consulting:
Hardware Audits: Audit of existing UPS, Recommendation of a Power Solution.
Quality Analysis: Analysis of the quality of power feeding your systems, Improvements in the powertrain system.
Solutions Consulting: Inspection of your complete facility, Identification of the solution, Correction of the Problem.
Quality Analysis: Analysis of the quality of power feeding your systems, Improvements in the powertrain system.
Solutions Consulting: Inspection of your complete facility, Identification of the solution, Correction of the Problem.
CIRCUIT DIAGRAMS OF UPS:
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