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Steps To Prevent Power Problems From Becoming Serious
A common belief among facility executives is that designing for good power quality is an expensive process. Unfortunately, through value engineering, power quality planning often is pushed aside because it's not seen as a problem that needs immediate attention.
As the world relies more on data-processing and other digital equipment, facility executives are going to see more problems - such as equipment downtime, systems failure, loss of data or data corruption and, perhaps, tenant loss.
To stop power quality problems from becoming serious, facility executives can follow five steps.
1. Know Your Loads
Regardless of whether you operate an existing building or a new facility, it is essential to understand what types of equipment will be used in the facility and if building equipment is sufficient to handle the loads. Does your tenant have a computer on every desk? Will an uninterrupted power supply (UPS) system or backup generator be installed? Are other sensitive systems, such as medical equipment, a part of the tenant's operations? Even the type of office furniture the tenant uses can have an effect on systems design because each office furniture system has a different way of delivering power.
Understanding the system requirements in turn affects how electrical systems are planned. The most prevalent strategy is to separate the loads. Mechanical systems are located on one line; sensitive equipment, such as computers, is located on another line; and miscellaneous building loads are on a third. Systems designers also need to know, for example, how many cubicles are to be connected, if enough outlets are available to complete the job appropriately, and how equipment is going to be arranged.
Facility executives also may want to limit the types of equipment a tenant can install to prevent disturbances to other tenants' equipment. For example, the owner may require 12-pulse drives if the tenant uses variable frequency drives because they produce lower harmonic distortion than six-pulse drives. Or, if a UPS system is used, the owner may require the tenant to install a filter on the input side.
2. Reduce Harmonics
Harmonic currents are one of the most serious power quality problems facing facility executives. Left unattended, harmonics can cause computer problems because of voltage waveform distortion (called flat topping), as well as reduce equipment life by overheating cables, motors and transformers. Ironically, harmonics often are caused by equipment installed to improve building operation and efficiency, such as electronic lighting ballasts and adjustable speed drives. However, the main cause of harmonics is from the computers themselves, which have switched-load power supplies.
The first line of defense against harmonics is a robust electrical system designed to take the hits. K-rated transformers, oversized neutrals, line reactors and harmonic filters all can make electrical systems stronger to combat or cancel out harmonics. Including this equipment is essential when designing new facilities. The challenge, of course, is in retrofitting existing buildings. Before applying solutions, however, facility executives should first conduct a power quality survey to determine the problem.
A power quality survey involving the measurement of harmonics within a system can help determine the quality of supply voltages, as well as the sources of offending harmonic currents. Depending on the case, the solution may be to attack the problem at each source, which can be costly, or to provide a system-wide solution. But, each case must be reviewed independently.
3. Ground Systems
To ensure optimal performance of the electrical system and its components, as well as sensitive equipment such as computers, and to ensure safety for facility staff, all equipment, outlets and circuits must be connected to the common building grounding system. This limits potential voltage differences be