< Back
Print PDF file

The policy decision by the major utility companies to reward clients by providing rebates to firms that help to reduce the utility company's need for capital expenditures met with great success. In addition, various programs to introduce more efficient sources of lighting have essentially relegated high power consuming incandescent lights to decorative use. The widespread use of personal computers with their corresponding peripherals such as scanners, laser printers, and file servers, however, is now negating the savings in electrical usage.

A new wrinkle in electric distribution relates to the nature of computers and other solid state devices. These devices are categorized as "non-linear loads". Very simply, electricity traveling through non-linear loads causes various electric reactions commonly referred to as harmonics. Harmonics generate interference on lines, and on 3 phase, 4 wire systems may overload the neutral wires. In many existing buildings, the neutrals were sized at 25% to 50% of a phase wire since neutrals theoretically carry no current. The neutral wires serving non-linear loads have the potential to carry higher currents than the phase wires. Neutral wire issues must be addressed when implementing occupancies with major PC usage in existing and new buildings.

When addressing the electrical infrastructure a key issue to be aware of is voltage ratings. Since power is a multiple of the current times the voltage and wire size is dependent only on the current capacity, the higher the voltage the smaller the current. For long runs of wire, higher voltages are desirable to reduce cable size and correspondingly cost. For this reason, it is not uncommon to see site distribution voltages at 34,000 and 13,000. Building voltages are generally at 277/480 or 120/208 volts. Voltages may be raised or lowered through the use of transformers.

Typically during the summer months, utility companies have problems meeting the demands of their customers because the total demand exceeds the generating as well as the purchasing capacity of the utility company. During this time the utility company may initiate "brown outs". During a brown out the utility company unilaterally lowers the voltage automatically to reduce power draw from the utility company. However, below certain levels of voltage there is a risk of equipment damage.

Electric utility companies provide periodic maintenance on their switchboards and sub-stations. During this period, loads may be transferred from one sub-station to another in order to maintain service. Highly sensitive office equipment many be affected by this transfer. Uninterruptible power systems, stand-by generation and multi-utility sources are methods to increase the reliability of electric power serving essential and critical loads.

Building electrical systems require maintenance as a result of the stresses developed in copper and aluminum wiring and connections. This usually entails making sure that lugs are tightened to their proper tolerances. In addition, it is recommended that all electric gear be thermographed at lease once a year. The purpose of the thermography is to identify any "hot spots". A hot spot is simply a point of stress where contact is not being properly made between electrical connections causing heat to be generated. If not corrected a potential hazard could exist.

An additional factor in urban areas is the reinforcement of utility service by the utility company in the streets causing an increase in available short circuit current. In some cases the utility company's available short circuit current is greater than the capability of the existing switchboards to withstand a fault; so what was originally adequate, may now present a danger should a fault occur. Because electrical systems rarely give warning before they fail it is essential to be proactive in their monitoring and maintenance.