Users Need to Learn More about Power Management

A recent survey of Control Engineering readers about power management indicates most respondents underestimate the extent and cost of poor quality power in their plants. Of the survey respondents, 67% place the source of problems on their utility, although industry experts say two-thirds of all power problems actually originate from within a plant.

12/01/1998


KEY WORDS

 

  • Process control & instrumentation

  • Power management systems

  • Power quality

A recent survey of Control Engineering readers about power management indicates most respondents underestimate the extent and cost of poor quality power in their plants. Of the survey respondents, 67% place the source of problems on their utility, although industry experts say two-thirds of all power problems actually originate from within a plant.

The survey was underwritten by Square D Co. (Palatine, Ill.), a leading supplier of industrial power management systems, and executed by Bull's Eye Marketing Inc. (Fond du Lac, Wis.), an independent research firm. Nearly 38% of respondents are involved in equipment design, systems/process design, or manufacturing engineering; while 43% have plant engineering, plant management, or general management responsibilities.

Power quality is an umbrella term for various power issues, such as harmonics and power factor, that can impact a manufacturing facility. Specific power quality problems include voltage sags and swells, fluctuations, transients, waveform distortions, phase imbalances, power frequency variations, and wiring/grounding problems. Quality of power has significant impact on a plant's power costs, its power distribution systems, and its downtime. That impact also extends to manufacturing yields and product defects.

Power quality misconceptions

Survey findings reveal misconceptions about power quality problems and its causes. "Nuisance tripping"—a symptom of an underlying power quality problem—was viewed by more than 60% of respondents as the cause of power disturbances. Most power management experts, on the other hand, say improper grounding and wiring and harmonics are the chief culprits behind poor power quality. Another 20% were unsure what was causing the power problems (see bar chart above).

A significant finding is the belief among a majority of respondents that power quality has "little or only moderate effect" on their manufacturing processes—in particular, product yields and product defects. However, respondents believe poor power quality does have "moderate to great effect" on equipment maintenance and production costs. The real impact on manufacturing results is probably much higher than reported, based on misconceptions about causes of power quality problems.

Toward PM systems, deregulation

Numerous methods are used to mitigate power quality problems. Uninterruptible power supplies (UPSs) and transient voltage surge suppressors (TVSs) are most common, according to survey responses (second chart, previous page). These corrective methods, however, merely prevent equipment damage and do not correct the problem at its source.

About 30% of respondents said they are using either power monitoring or power management (PM) systems. Importantly, another 56% are exploring the use of these kinds of systems. Main reasons cited were energy management, including cost center billing, utility bill negotiations, or as a way to identify power quality problems (bar chart above).

Many manufacturers have designed their PM systems with open protocols for easy communications. Yet, most plants still tend to keep power monitoring separate from their plant control systems. While 69% of respondents are involved in selecting power management systems, an overwhelming majority of respondents (84%) indicated they're not yet integrating their PM with plant control systems.

Survey respondents are very concerned about electric utility deregulation. Almost half believe quality and reliability of power will decrease with deregulation, in exchange for lower costs. As a result, use of outside consultants and sophisticated power management systems is predicted to increase. The table below summarizes other factors concerning deregulation.

True cost of poor power

Power costs consist of three main components— electrical energy costs, power delivery costs (capital equipment, depreciation, and maintenance), and total downtime costs. Power quality impacts all of these costs in one way or another.

Power delivery costs represent a huge investment. Most plants budget for upgrades, replacements, and modifications to this investment each year. Some of the budget devoted to these recurring expenses would be better spent on upgrading power quality systems, thereby avoiding accelerated wear and failure of components by avoiding harmonics, poor voltage regulation, and related unbalances.

Poor power quality is also costly in lost productivity. Equipment failures and unexplained shutdowns are just part of the problem. Like an iceberg, many power quality costs are hidden below the surface and not easily accounted. What is the true cost of downtime in a facility in terms of total opportunity costs? Factor in costs for overtime, scrap, lost sales, etc. and this figure can be very high. Poor power quality can further affect costs of power. High harmonics can lead to a lower power factor and higher utility rates.

Treating power as a raw material to be managed—not just another expense—is the solution to effective power management. Power can be monitored and managed to improve yields, reduce costs, and improve quality. To do that, users need to understand the causes and have the measurement and management tools in place to make informed decisions.

Square D is part of Groupe Schneider, a global leader in electrical distribution, industrial automation and control. Its Power Management Organization in La Vergne, Tenn., (formed in 1989) offers a full range of hardware and software solutions for power monitoring, lighting control, power factor correction, and a variety of power system analyses and engineering services.

For more information about Square D Co., visit www.controleng.com/info .

Impact of Utility Deregulation

Factors

% Respondents Indicating Increase

% Respondents Indicating Decrease

Source: Control Engineering citing Square D survey

Quality of power

8.8%

46.5%

Reliability of power

15.8%

46.5%

Cost of power

35.1%

42.1%

Use of outside consultants

43.0%

10.5%

Engineering services and support

23.7%

37.7%

More sophisticated power management systems

44.7%

4.4%