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Reading: Managing power problems Contents Introduction 2 Types of power problems 2 Blackout ..................................................................................... 2 Brownout .................................................................................... 3 Power surge ............................................................................... 3 Protection from power problems 4 Surge arrestors........................................................................... 4 Uninterruptable power supplies .................................................. 5 Emergency generators ............................................................... 8 Procedures Reading: Managing power problems © NSW DET 2008 8 1 Introduction All of the live systems you may be required to manage as an Information Technology (IT) worker need electrical power to function. More specifically, these systems will have power requirements with varying degrees of tolerances. Before looking at power problems in detail it is important to have a basic understanding of terminology used to describe electrical power needs: Power. Expressed in watts, power is a measure of how much energy is consumed over time. The higher the wattage, the more electrical energy is consumed for the same amount of time. Typically you will come across this term when working with computer system power supplies. Voltage. Expressed in volts, voltage is a measure of the electric potential difference. It can be thought of as the ‘electrical pressure’ forcing electrons to flow through an electrical circuit. The higher the voltage the greater the electric potential difference and the greater the ‘electrical pressure’. Current. Expressed in amps (ampere), current is a measure of the flow of electric charge. It can be thought of as the amount of electrons that flow past a given point over time. Types of power problems Live systems will suffer errors and faults if power problems are not managed effectively. The three main power problems you will need to overcome are: blackouts brownouts power surges. Blackout A blackout is a complete loss of power. The result is the immediate turning off of all unprotected electrical devices. Blackouts may occur for a wide range of reasons including damaged power lines, loss of power generation, short circuits and overloaded electrical systems. No matter what the cause of the blackout the effect is the same. 2 Reading: Managing power problems © NSW DET 2008 Blackouts may last for several minutes, hours or, in extreme cases, several days. More commonly a blackout will only be momentary ie milliseconds to seconds. These very short dropouts in power supply may go unnoticed by many live systems depending on how long they last and the power needs of the device. Devices with high-tolerance power needs suffer the most from these momentary dropouts. Most IT hardware will not suffer any damage due to a blackout. Once power is restored the hardware will usually function normally. The damage usually comes in the form of lost data or corrupted software. For a client computer, a blackout may result in the loss of a few hours of work on several documents. In client and server computers a blackout may also cause corruption of the operating system or software applications. This will require some form of repair, restoration or reinstallation, all resulting in lost productivity. For other devices, such as switches, modems, routers etc, a blackout will usually cause no damage or data loss. However, in some circumstances, such as upgrading firmware or saving setting changes, these devices can become highly susceptible to data loss if power fails. Brownout A brownout is a reduction in power supply to below the minimum requirements of the power generation system. In Australia a standard power point supplies 240 volts at up to 10 amps. A reduction in voltage of 8—10% usually constitutes a brownout. Brownouts are often caused by an overloading of the local power supply, such as on very hot days when a large number of air conditioners are in use. Brownout may only last a short period of time or may last several hours and may be unstable. The voltage may cyclically drop, causing electronic equipment to intermittently function. Brownouts can cause strange behaviour in electronic equipment. Computers may appear to be on but not functioning; monitors going into standby mode. Brownouts also have the potential to cause damage due to incorrect voltage supply and in some cases overheating where devices draw more current to compensate for the reduced voltage. Power surge A power surge or power spike is the opposite of a brownout. In a power surge the voltage rises above the maximum voltage of the power generation system. Power surges are usually short-lived but the voltage increase can be extremely high. Reading: Managing power problems © NSW DET 2008 3 Power surges are typically caused by lightning strikes, sudden decreases in power draw or faults in the power generation system. Power surges are the most likely power problem to cause damage to electronic hardware. The dramatic increase in voltage and current causes a rapid increase in temperature which often results in ‘blown’ or degraded electronic components within a device. It is important to note that power surges can often enter a device from sources other than a device’s incoming power supply. Network and communications cabling is another common entry point for a power surge. Power surges are often caused by lightning strikes Protection from power problems All of the abovementioned power problems can be effectively managed to protect live systems. Through the implementation of protection equipment and procedures, power problems may cause some downtime but only in extreme cases should these problems cause damage to equipment or result in data loss. There are three main forms of protective equipment. They are: surge arrestors uninterruptable power supplies (UPSs) emergency generators. Surge arrestors A basic surge arrestor can be purchased in a double adapter or power board. Although cheap, a surge arrestor can protect expensive equipment such as digital projectors, large flat-panel monitors or televisions, printers, photocopiers, network devices such as switches, 4 Reading: Managing power problems © NSW DET 2008 routers and modems. Many of these devices may not warrant implementing a costly UPS but still require protection from power surges which can be very damaging. Surge arrestors try to redirect or block the excess energy from the power surge. In many cases the attached equipment will continue to function normally. In cases of extreme overvoltage the surge arrestor may sacrifice itself to protect the attached equipment. If you suspect there has been a significant power surge you may have to inspect all surge arrestors for damage and replace those that show any sign of malfunction or physical damage (usually due to excess heat). Simple double adapter surge arrestor You should select a surge arrestor based on several features: Response time. All surge arrestors have a delay between when the power surge occurs and when they can block or dissipate the excess energy. The shorter the response times, the better the protection. Clamping voltage. Tthis is the voltage at which the surge protection features activate. The lower the clamping voltage, the better the protection. Energy absorption. This is usually expressed as the maximum number of joules the surge arrestor can absorb before failing. The higher the number, the better the protection. Uninterruptable power supplies As the name suggests, a UPS will continue to supply power to a system even if that power is interrupted by a blackout, brownout or power surge. For business-critical systems, such as servers and core network equipment, a UPS is a vital addition to the system design. A UPS is connected between the mains power supply and the protected device. If power fails (blackout) or a brownout occurs, the UPS switches over to built-in batteries to continue to supply power until the mains power supply returns, an alternate power supply can be brought online (eg emergency generator) or the connected device Reading: Managing power problems © NSW DET 2008 5 can be safely shut down. If a power surge occurs, the UPS relies on built-in surge arrestors to protect connected devices. Many UPS devices also offer other power ‘conditioning’ capabilities to improve the quality of power being supplied. There are several UPS features you need to consider when selecting an appropriate UPS: Form factor. UPS’s are available as small stand-alone pedestal units, rack mounted units and dedicated, freestanding UPS systems. Standalone UPS unit Mode of operation. Standby, line interactive and double conversion modes represent increasing complexity and power quality. The mode chosen depends on the needs of the connected devices. For more information have a look at the following websites: - Simple explanation of UPS modes www.elecpowertech.com.au - Detailed explanation of UPS modes - www.mgeups.com (requires Adobe Reader) 6 Number of protected outlets. Small to medium UPS systems allow you to connect power cords from the UPS to the protected devices. There are differences in the number of available power sockets and not every socket may offer battery backup. Some sockets may only offer surge protection. Reading: Managing power problems © NSW DET 2008 Rear view of UPS showing six protected power sockets, two phone sockets and a serial communications port Management ports and software. If the battery in a UPS becomes completely depleted it will turn off connected devices, potentially losing data. To avoid this, most small to medium UPS systems have a serial or USB controller port which can connect to a computer protected by the UPS. Using management software, the UPS is then able to communicate with the computer, initiating a safe shutdown before the UPS battery is depleted. The computer connected to the UPS may also be able to act as a UPS server. When client software is installed on other computers the UPS server can communicate via the network to these client computers and initiate a safe shutdown. This system relies on both the client computers and the interconnecting network hardware to be power protected. VA (volt-ampere). UPS systems are commonly rated with a VA number. This is an indication of the apparent power a UPS is capable of supporting. The higher the VA number, the higher the power load the UPS is capable of supporting. This is an important figure to correctly assess. If calculated incorrectly, when power fails, the UPS may not be able to deliver the required power for the connected devices or may not be able to do so for long enough to ensure a safe shutdown of these devices. The websites of most UPS manufacturers have guides to help you select an appropriate UPS for the devices it will protect. Reading: Managing power problems © NSW DET 2008 7 Emergency generators In highly mission-critical scenarios, such as hospitals, defence, banking systems etc, any downtime of live systems can have catastrophic consequences. In some remote locations and developing countries, mains power supply can be very unreliable. Utilising UPS systems alone will not ensure that computer systems continue to function when prolonged power problems occur. In these scenarios it may be necessary to consider the use of a backup power generation system. This may range from a small, portable, petrol-powered generator to large-scale, shipping-container sized diesel generators. Despite the size the same principles apply. If the mains power supply fails, the emergency power generation system must be brought online before UPS batteries are depleted. A small generator may require a manual pull-start and a transfer of power connections. Large generator systems automatically cut in and are integrated with a site’s power distribution system. Except in simple, small-scale situations, the design and implementation of emergency power generation should be left to qualified electrical engineers and product specialists. Small emergency petrol generator Procedures During times when power is affected by blackouts, brownouts and power surges, live systems become vulnerable to hardware damage and data loss or corruption. The abovementioned protective devices provide some measure of protection against these consequences. The effectiveness of a response to power problems can be significantly improved by implementing some basic procedures. 8 Reading: Managing power problems © NSW DET 2008 The following list provides some ideas that can help minimise the impact of power problems: Find the source of the problem. It is important to rapidly assess the source of the power problem as either internal or external. For example, does the power problem affect only your business or does it also affect neighbouring businesses? Is it within a building or does it affect a larger region? If a single office or building is affected the problem may be caused by a blown fuse or a tripped safety switch from an overloaded circuit or faulty appliance. Localised problems need to be isolated where possible and an electrician called if necessary. Wide area problems require contacting your electricity provider. Know your electricity provider. When power problems arise most computers will go offline and PABX and VoIP phone systems will not function. This will cut you most of your communications. Know who your electricity service provider is and put their emergency/faults contact number into your mobile phone. Have a record of your account number and call the provider so that you can quickly assess the severity and estimated duration of the power problem. Turn everything off. When power problems occur for an extended time it is sensible to turn off all electronic equipment. This is particularly the case during a brownout where devices can attempt to function without adequate power, causing overheating or cycling on and off. Save regularly. In most business settings client computers do not have a UPS attached. To avoid data loss from power problems, staff should be trained to save work regularly. If they are spending hours working on a document they should constantly save their work. Some software can also be configured to force automatic saving at regular intervals. Regularly backup data. Power protection devices and procedures are all part of establishing an adequate disaster recovery plan for your business. Effective backup strategies are an integral part of this plan. You must ensure that key data and systems are regularly backed up so that in the event of a power problem causing data loss or corruption the data can be quickly restored. Don’t forget to include the configuration settings in devices such as routers, switches, phone systems, printers, photocopiers etc. This reading should have provided you with an overview of the power problems you may be faced with when managing IT systems. More importantly, you should have a better understanding of the protective Reading: Managing power problems © NSW DET 2008 9 devices and procedures you can put in place to protect and recover from power problem events. 10 Reading: Managing power problems © NSW DET 2008