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 between different systems and between different parts of the building.
Systems are grounded improperly when voltage on the ground wire varies at different parts of the building. This may happen as new equipment is added to the system or as other design changes are made. Consequences of improper grounding include noise injected into data circuits by the power system ground or fault currents, and circulating currents in the ground system that can corrupt data or cause equipment failure.
A good grounding system is the foundation for good power quality. If you don't have a good ground system and you add power quality equipment, you may not see any improvements from the equipment you added.
In today's world of computers, special grounding considerations also must be made for data centers and computers. The trend used to be to run separate grounding wires for the sensitive equipment. But, with networked computer systems, the theory no longer proves valid, and codes require that all system grounding wires be tied together.
If facility changes are made, facility staff must go back and look at how systems were grounded originally, and then make any modifications as necessary.
4. Reduce Voltage Fluctuations
While not as common as harmonic currents or improper grounding, voltage fluctuations also can cause serious system damage. A similar effect happens to electrical systems when a motor is started up or a contact is opened. In these cases, the electrical current spikes, causing a voltage change in the distribution system that can affect sensitive equipment.
Protective equipment such as transient volt surge suppressor equipment can be installed to redirect voltage spikes into the grounding system. However, if a building does not have a good grounding system, the transient volt surge suppressor will be ineffective.
Motor spikes also can be controlled by limiting the size of the motor across the line and then using reduced-voltage starting. However, this practice can be expensive.
In some cases, specialty equipment, such as medical X-ray machines, can cause voltage dips. The general practice is to design the systems so that the specialty equipment is isolated from the other building loads.
5. Conduct Routine and Preventive Maintenance
There's an old saying among engineers: If you don't test your systems, nature is going to test them for you. And, when maintenance personnel get busy, it is easy to forget about the electrical system. However, simple care and maintenance can keep your electrical system operating properly and reduce power quality concerns.
Infrared testing: A "heat" picture of system components shows where components are stressed and what parts ultimately will fail. Testing is conducted by testing associations, certain electrical contractors and firms specializing in the process.
Like anything, testing can be overdone, but you probably want to do the main equipment. Ultimately, the building owner has to decide between the cost of testing vs. the cost of unscheduled repairs and downtime for tenants. A good testing technique allows you to schedule repairs because you find the problem early and you're not under a tight schedule to fix it.
In-house Knowledge
Finally, we recommend that maintenance staff participate in some type of basic training about how the electrical system operates and that maintenance manuals be required in the specifications. Many projects are delivered with an operations and maintenance manual written by project team members. On those projects, team members also may go to the site to provide basic training.
Training people who are going to operate the system is as critical as designing the system well.
Power quality is an issue that only is going to be more critical in the coming years. By addressing power quality concerns up front, facilities will not only operate better, but tenants will be happier. Systems need to be evaluated individually for the most appropriate, cost-effective solutions. Money invested in good power quality will earn its return through reduced downtime and improved operations.
Julian Arhire is a Manager with DtiCorp.com - DtiCorp.com carries more than 35,000 HVAC products, including industrial, commercial and residential parts and equipment from Honeywell, Johnson Contols, Robertshaw, Jandy, Grundfos, Armstrong and more.
