Power Quality and Harmonics.

Everyday concerns that affect building operations

More electronic equipment in the workplace raises the likelihood of potential interactions with the electric distribution system and requires a more sophisticated approach to preventing these interactions.

Common power quality concerns, including voltage sags, swells, and surges, have led to the increased use of additional facility equipment, such as uninterruptible sources and battery-supported systems, to increase electrical reliability. In addition, signal interactions in sensitive equipment can be difficult to trace. Energy managers can engage in a number of practices that will improve overall power quality in a facility and reduce the interactions due to harmonic currents in the load devices.

Facility Power Disturbances

Facility design requires the consideration of a variety of load source interactions. The power quality consensus standards of the Institute of Electrical and Electronic Engineers (IEEE 1100-1999) can provide a basis for understanding these load-source interactions. The four areas of load-source interactions are:

* Electrical wiring and grounding of a facility

* Surge (transient) protection system

* Harmonics proliferation demands

* Electrical power reliability

The electrical wiring and grounding of a facility includes the digital signal system and how it operates in the conventional wiring plan found in most facilities, as outlined by the National Electrical Code (NEC). The code provides for the safety of personnel and equipment, and specifically says that the equipment may not operate well (NEC 90-1.B); the NEC has no consensus for how to enhance operating integrity. The task is to find ways of turning electrical noise away from sensitive electronic devices and into the areas of the facility where the noise does no harm.

The surge protection system includes power supplies, signal drivers, and receivers, which must be protected from high-speed surges traveling on the wiring. The IEEE C.62 standard describes a surge as a very fast occurrence of voltage to the system, which could come from a lightning strike, the operation of a lightning arrester, a utility switching operation, or even from energy moving in the earth.

Since most of the printed circuits and chips used in modem electronic equipment cannot withstand more than eight to ten volts, lightning arresters and surge protection systems are needed. Many times, the main electrical service entrance is protected, but telephone, data, paging systems, fire detection, and other digital data systems must also be protected.

Electronic loads also produce harmonics. Harmonics are different electrical sine wave frequencies that power supplies require of the …