Dealing with Age

Does this sound familiar? A circuit board mysteriously fails on a production line. The maintenance staff troubleshoots the problem, and then, what seems like forever, waits while the computer searches the network to locate the part. Finally, the part is replaced and the production line is reset, but the cause of the board failure may never be known, and the productivity loss is significant and ...

By Rachel C. Fore, P.E., Electrical Engineer, Hayes, Seay, Mattern & Mattern, Roanoke, Va. March 1, 2005

Does this sound familiar? A circuit board mysteriously fails on a production line. The maintenance staff troubleshoots the problem, and then, what seems like forever, waits while the computer searches the network to locate the part. Finally, the part is replaced and the production line is reset, but the cause of the board failure may never be known, and the productivity loss is significant and expensive.

Whatever the process, when electrical equipment or systems malfunction or cannot operate or expand to keep pace with demand, the result is lower productivity. The problem may be a result of:

Limited power and distribution capacity.

Aging or obsolete distribution infrastructure, including the wiring and cabling.

Poor power quality.

Any combination of these factors.

Fortunately, with good planning, maintenance and the diligent attention of electrical engineers and maintenance personnel, not only can older electrical systems operate safely and effectively, but also accommodate growth needs.

Whether one is adding a major piece of equipment, planning a major renovation or designing for a new structure, it’s essential to know the immediate power requirements, as well as those anticipated for future needs.

The first step is a thorough system analysis—including end-use receptacles and wiring—to evaluate the basic service and distribution. There are three main issues: aging and obsolete power systems; aging and obsolete signal systems; and power quality. All of these issues can produce problems that harm productivity levels.

Past Their Prime

Aging or obsolete systems develop faults and weaknesses through years of normal use and modifications—in many cases, improper use and maintenance. In addition to their negative effect on both power capacity and quality, these issues can lead to a variety of failures and safety hazards, often making an otherwise quick or easy fix impossible.

An overloaded circuit can go unnoticed for a long time, sometimes the only indication being hot wiring or the occasional nuisance trip of a circuit breaker. Over time, overheating of wiring causes its insulation to break down. Other factors, such as vibration, exposure to moisture or chemicals, and wide variations in the ambient temperature, can compromise insulation. When insulation deteriorates, it may turn brittle or fray, leaving the live conductors exposed. Not only does this create a shock hazard, but can also cause a short circuit or arc to other conductive elements in the system.

Fires can start from faulty wiring, overheated conductors and overloading of older circuits when the overcurrent device fails, as well as from occasional arcing or overheating from increased resistance at the connections. For example, the aluminum wiring widely used in the late 1960s through the mid 1970s was particularly prone to overheating because of its higher coefficient of expansion. Over time, the accumulated effect of frequent expansion and contraction loosened the aluminum wire connections, thereby increasing the resistance at those connections, causing dangerous heat levels.

Fortunately, the electrical industry has benefited in recent years from higher quality products. Today’s insulation, for example, provide better fire resistance. Another improvement is the use of advanced aluminum alloys in contemporary wiring that have almost eliminated the thermal expansion and contraction problems.

Another frequent complaint about older electrical systems is lack of adequate outlets. Faced with too few outlets to serve proliferating electronic equipment, people often resort to plug strips and extension cords, sometimes “daisy chained” together. This practice can overload both the wiring of the plugstrips and extension cords, and the circuits as well.

While the National Electrical Code (NEC) does dictate the numbers of general-purpose receptacles for new residential construction, the code doesn’t specify the number of receptacles for general use in commercial facilities. The power quality and safety risks in older structures posed by this overload potential call for a thorough and comprehensive system analysis—down to the number and placement of outlets—when planning improvements.

Newly constructed electrical systems use products that are more rugged and better able to survive mechanical stresses and environmental conditions. They perform with greater reliability in rough service applications, resist rodent damage and generally survive other operating conditions more ably.

But while NEC is updated every three years to embrace safety and product advances, many older installations do not even begin to meet current code and safety standards. In too many of these older facilities, jury-rigged modifications to inadequate systems leave facilities vulnerable.

Moreover, these adaptations and misuses of older systems can set up a chain of trips of the circuit breakers. Without a regular testing program to monitor breaker condition, constant tripping and resetting will wear out breakers, eventually leading to possible failures during a fault. Nuisance tripping circuits are sometimes “fixed” by increasing breaker capacity to avoid tripping. This alteration results in breakers not tripping when they should, and can ultimately result in damaged equipment or fire.

Inadequate grounding is another problem in older installations. In some cases, there is no grounding whatsoever, while in others, the system may be grounded through a raceway. The danger with the latter is that while not against code, it’s not the best solution for protecting today’s high-tech equipment. Raceways might not offer sufficient conductivity due to poor connections, paint or poor connection to the ground system itself.

Older systems are also typically at or close to their service capacity—usually about 80% of the overcurrent device rating, since most overcurrent devices are only rated for 80% of their nameplate rating. These systems generally have little, if any, space available for panel board expansion. Furthermore, equipment suppliers usually do not support older panel boards. Manufacturers are now building to new, more stringent NEC requirements, such as the minimum space required above or below the panelboard insert for wire bending. An owner may be forced either to completely replace large equipment or maintain it with reconditioned parts.

Usually a comprehensive survey will turn up “creative” but non-compliant modifications in aging electrical systems, including improperly sized or coordinated—or even missing — overcurrent devices, improper or missing grounding and insufficient workspace for routine maintenance.

In a nutshell, yesterday’s standards quickly become obsolete. This is a fact of life in a technologically advancing environment. For example, older systems often have undersized neutrals in the circuits. Such wiring schemes served their purpose well when they were first installed, but they are not adequate for modern electronic equipment. Today’s more sophisticated electronic devices generate harmonics that circulate on the neutrals, which in some cases, can create power quality problems adversely affecting computers and other sensitive electronic equipment. Another example is the use of ground fault circuit interrupter (GFCI) protection. Although today’s code mandates using GFCI protection in selected locations—and it is good engineering practice to use this protection in other locations—few GFCI outlets are found in older systems.

Dealing with the Aging Process

To get a grasp on an aging system’s condition and needs, a power quality study should follow the guidelines of IEEE 100-1999 “Recommended Practice for Powering and Grounding Electronic Equipment.” This survey has several levels, but general practice includes visual inspection of the distribution system; survey of selected or problem spaces to identify loads, test for excessive voltage drop and test for wiring and grounding problems; monitoring of voltage, current and harmonics at selected distribution system locations over a period of a week or more; and analysis of the distribution and grounding systems to identify specific problems.

Once problems have been identified, many types of power-correcting devices are available for improving power quality and reliability. Typical devices eliminate noise and can stabilize the voltage, frequency and waveform.

TVSS equipment, isolation transformers, voltage regulators and UPS systems are some of the technologies available to correct transient voltages and allow equipment to ride out these disturbances. Voltage regulators and UPS systems can be effective for correcting voltage distortion, sags, swells and over/under voltages, as well as protecting equipment from these power anomalies. Where non-linear loads introduce harmonics into the system, harmonic mitigating transformers—K-rated transformers—and harmonic filters can trap these harmonics and reduce their effects on the system. Installing dedicated neutrals for each circuit is another effective preventive measure.

Where non code-compliant items are found in the system survey, install appropriate corrective measures, where required, to satisfy code requirements, with special emphasis on proper sizing and coordination of overcurrent protection.

Proper maintenance of the power distribution system is essential. End users must initiate and maintain a routine maintenance program on all equipment, following the manufacturers’ recommended guidelines. For example, the wiring and the connections of both current and non-current carrying conductors should be checked routinely, and infrared scans of critical connections can be used to detect overheating before a failure occurs. Proper breaker and emergency equipment operation should also be verified routinely.

It’s also essential to plan for the replacement of system components when they are approaching the end of their normal lifespan. Putting such a program into practice inherently introduces product and electrical code enhancements into the system, making operations safer, more efficient and more reliable. And many owners say working closely with a professional engineer provides a more reliable evaluation of future power and telecommunications needs, resulting in better coordination between needs and available funding.

The Cost of Outages

A 2001 report by the Electric Power Research Institute estimated that outages and other electrical complications cost businesses between $100 and $200 billion annually , with billions more spent on often ineffective preventive measures. While capacity problems can originate with the electric utility, they usually occur within a facility when critical distribution components are overloaded or unbalanced. Thus, it is prudent to conduct a thorough facility survey to identify weak links in a distribution network.

No Longer Up to Speed

As is the case with aging wire, telecommunication cabling is always in need of upgrading. With data transfer rates doubling, on an average, every six months, cabling is aging not because of its chronological years of service, but rather, because capacity is not adequate for newer, more demanding equipment.

Today’s telecommunication cabling systems are designed with improved performance characteristics that allow more data-intensive applications such as multimedia, voice/data, Voice over Internet Protocol (VoIP), videoconferencing and other heavy bandwidth.

Problems in today’s telecommunications networks are usually noticed by users as reduced functional speed, typically due to the cables not delivering data fast enough or insufficient bandwidth. Problems with cable capability persist despite the fact that cabling represents only a small percentage of a business’ IT investment. Also, poor splices and connections can seriously compromise cable system efficiency, whether it’s copper or fiber-optic.

The cabling topology, or configuration, can also be a source of unreliability for these systems. Older systems generally use a series topology because the data being transferred is not considered critical, and because the cost of redundant wiring is prohibitive. Failures in series configured systems propagate downstream, potentially disrupting many users. Contemporary systems typically have a redundant cabling topology to enhance system reliability. The amount of data, the speed at which it is transferred, the distance it has to travel and the reliability of the transfer are vital factors in operating an efficient telecommunication network. While copper cabling was the obvious choice just a few years ago, it is now considered obsolete for many applications because copper cannot meet today’s higher data transfer rates and distance requirements as effectively as fiber-optic cable. Fiber also has an advantage of being able to withstand more rugged environments.