Unzapped

What is 30,000 times faster than a speeding bullet? It's a bolt of lightning that can take down your sensitive telecom equipment with one strike.

Thunderstorms produce a bolt of danger to many kinds of sensitive equipment and electronics, which is why these critical systems require protection. It's important to formulate a strategy for appropriate power protection to meet the specific needs of telecom and wireless applications.

There are many levels of protection, and you should base your technology selection on application, associated costs and available resources. When applications only require protection from hardware-damaging power spikes, surge protection may be all that you need. However, if frequent brownouts are disrupting your operations, or you need to shut down systems in an orderly fashion in the event of a power outage, then you may need the additional protection of an uninterruptible power supply (UPS). For ultra-critical systems that cannot be down for any reason, you will need battery and generator backup.

Surge Suppression

A lightning bolt striking the ground has a powerful magnetic field. This field can produce an enormous transient voltage surge in nearby power lines through magnetic coupling. The lightning bolt need not directly strike a utility line for this to occur. All that is required is for the electrical lines to be within the magnetic field. Transient voltage surges account for approximately 20% of all power problems in the workplace, with 15% of these attributed to lightning strikes.

In general, surge-protection devices (SPD), also referred to as transient voltage surge suppression, provide cost-effective protection against transient voltage surges and noise for all kinds of sensitive electronic equipment. Due to the breadth of protection offered, the IEEE Emerald Book (www.ieee.org) recommends that, a listed and properly rated SPD should be applied to each individual or set of electrical conductions (e.g., power, voice, data) penetrating a structure.

SPD are designed to reduce potentially damaging short-duration transients present on utility power lines, data networks, telephone lines, closed-circuit and cable TV feeds, and any other power or control lines connected to electronic equipment. Another benefit of an SPD is that it can reduce noise energy. This is due to high-frequency noise filters that can detect and clamp down on small surges, minimizing interference with normal utility power. This protective filtration feature is one of the few methods of limiting ringwaves, the associated aftershocks of a rapid reduction or increase in the power load.

It is important to note that the effectiveness of even the most advanced SPD depends on how it is grounded and installed. Before installing any surge or power-protection device, you need to conduct a thorough site audit. The audit should include ground-impedance factors such as the type of soil, the humidity and the grounding methods.

These factors can vary site to site, and if grounding is in any way compromised, much more than signal confusion can occur. Improper grounding can cause actual system malfunction.

Special Needs of Remote Sites

Communications shelters and other remote sites, by their definition, are more vulnerable to lightning strikes than larger, centrally located installations. Often unmanned and sometimes located at the end of a long utility power circuit, remote wireless sites and related equipment shelters pose special power problems. These remote sites typically house critical telecom equipment, and failure in one location could be catastrophic to the entire system. For such applications, you need to consider some method beyond surge protection, including a setup that provides a warning system that alerts you to potential failures or malfunction and allows for an orderly shutdown in these situations.

UPS

If control and management over power protection is necessary, then a UPS may be the solution. This kind of power protection will supply a short period of battery backup while offering some additional layers of protection including voltage regulation and communications capabilities for monitoring and shutdown of systems.

There are different UPS types to choose from, and your choice will depend on a number of criteria: whether you require voltage regulation; how much time you need for an orderly shutdown; whether you need the equipment to keep working even during a blackout; and whether you require either network or remote monitoring and management of power-protection systems.

For continuous systems availability, only a UPS that offers double-conversion technology provides true isolation from problems originating from utility or generator power. In this configuration, power is continuously supplied to the batteries via the rectifier while at the same time, the inverter is providing a constant flow of power to the load. This allows for a seamless transition in the event of a power outage while supplying the load with a continuous source of superior-quality ac voltage. The main benefit of this configuration is that the critical load is electrically isolated from incoming power and, therefore, protected from noise and other frequency fluctuations that often happen during bad weather, particularly with a lightning strike. Second, the UPS' double-conversion design, in combination with other UPS options such as redundancy and dual-bus configurations, creates an incredibly fault-tolerant system. In this configuration, remote sites that house ultra-critical network components can be assured of the highest level of power conditioning and protection for continuous systems availability.

An Extended Power Outage

Does your equipment need to keep working for hours at a time even during a total outage? If so, incorporating a generator into your power-protection system may be a cost-effective method of delivering adequate power to telecom systems and equipment.

However, there are some issues to consider: Starting loads on the generator, for example, cause the generator's output-frequency to vary, which may cause a UPS to cycle on to battery operation. Generator instability also can happen when the UPS load is transitioned to the generator. The UPS load transfer causes the generator voltage and frequency to sag, causing the UPS to go back to battery operation, and repetitive battery cycling begins again.

These problems are eliminated by using a UPS that offers double-conversion topology. This technology can accommodate the large swings in power-supply frequency while continuing to provide regulated, stable output frequency without the use of the battery. Moreover, the most advanced UPS designs now come complete with techniques that reduce current distortion and greatly improve the compatibility of the double-conversion UPS with generators.

Monitoring & Control With a UPS

Above and beyond power protection is the need to monitor and control power-protection solutions. With today's communications networks growing in both traffic and service, it isn't uncommon for one system to contain hundreds of unmanned shelters scattered across a broad geographic area. This makes it vital to have the highest level of power availability and reliability. With today's sophisticated UPS, it is possible to monitor a single UPS unit within a shelter remotely or oversee power points throughout a network of remote telecom sites. And the range of managing critical environments in the event of a lightning strike is just as flexible. An operator can see what's happening in real time, choose an alarm-management system and have access to trend and analysis information for future planning and prevention of problems.

A Word on Service

Servicing of power-protection systems is an integral part of the products themselves and should be provided by factory-trained personnel while maximizing singular points of accountability.

In particular, UPS systems require regular maintenance to provide the continuous availability required by telecom and wireless applications. Therefore, you should consider some key aspects when designing and implementing power-protection solutions. First and foremost, regardless of manufacturer reputation or the reliability of the UPS and related equipment, the system should be de-energized for preventive maintenance at least once per year. The good news is that certain UPS configurations permit concurrent maintenance, supporting the load equipment on one source of conditioned power while de-energizing a second power system back to the service point.

When designing and setting up a power-protection system, you also need to take into consideration business and environmental changes, including increasing power densities, as well as the levels of reliability. A key to dealing with these changes is to use modular and scaleable solutions that allow for flexibility and incremental investment. These issues will change over time, along with the inevitable changes that technology will determine. Proper planning with a manufacturer that can design and implement a solution that is tailored to a specific application is key. Arranging this with the manufacturer prior to installation is a preventative measure against future problems.

Bauer is Liebert president Americas (www.liebert.com or call 800-877-9222).

Speak the Language of Reliability

• Reliability. Individual UPS modules, static-transfer switches and other power equipment must be incredibly reliable, as measured by field-documented mean time between failures. In addition, the system elements must be designed and assembled in a way that minimizes complexity and single points of failure.

• Functionality. The UPS must be able to protect the critical load from the full range of power disturbances, and only a true double-conversion UPS can offer this level of protection. Alternative UPS topologies do not protect against all disturbances including power-system short circuits, frequency variations, harmonics and common-mode noise. If your critical facility is truly critical, only a true double-conversion UPS is suitable.

• Maintainability. The system design must permit concurrent maintenance of all power-system components supporting the load with part of the UPS system while other parts are being serviced.

• Fault tolerance. The system must have fault resiliency to cope with a failure of any power-system component without affecting the operation of the critical-load equipment. Furthermore, the power-distribution system must have fault resiliency to survive the inevitable load faults and human error.

Enterprise Hosting Center

The need for reliable power protection of mission-critical equipment can be captured in Infinium ASP's (www.infiniumasp.com) enterprise hosting center, which develops and deploys flexible and reliable enterprise business solutions that are tailored to customer needs. Infinium's challenge was to develop a solution to succeed in the ASP industry, one that is expected to grow from $5 billion in 1999 to $23 billion by 2003. The answer was to put together a 68,000-square-foot facility with world-class power protection for 247 availability. Unlike telco hotels that are converted from other uses, the center was built from the ground up specifically for data-center functionality.

Our base infrastructure servers, network, power and cooling is the best of breed, correctly set up the first time and pro-actively managed on an ongoing basis, said David Andrews, Infinium ASP data center director.