What you don't know about grounding can hurt you

Proper grounding is the first line of defense against the $1 billion spent annually on damage around the globe due to lightning and 60% of system outages due to lightning on the East Coast alone. Power surge protection equipment also depends on good grounding to defend against power surges and spikes as well as diverting lightning discharges of up to 400,000 amps to ground. Many US industrial grounding systems are in poor repair and the limitations of traditional grounding system testing are hindering efforts to resolve the problem.

Fortunately, there are technologies being designed to keep up with technical advances in the manufacturing and process control industries. Improved ground system testing methods, such as Smart Ground Testing, are now offered by consulting firms such as LEC, which has over 30 years of engineering experience originating in NASA and the US space programs. Any facility experiencing equipment, process, or production anomalies could benefit from a grounding evaluation to determine if it is a possible source of the problem. In fact, any facility without a recent grounding evaluation could benefit, especially those involved in manufacturing, process control, or with sensitive electronic equipment or data centers.

Industrial Grounding Systems Deteriorating
In many cases, the grounding rods in US industrial plants have exceeded their usable lifespan of 30 years because they haven't been properly tested or maintained since installation decades earlier (some pre-date WWII). Out of sight unless dug up, the grounding rods and connectors of these buried grounding grids typically suffer corrosion and undetected electrical discontinuities - causing dangerous faults, processing errors or shutdowns. The problem is especially pronounced in the low resistivity soils near coasts and waterways, which accelerate corrosion.

"Existing grounding capacity is often compromised when contractors dig up or sever grounding wires when burying pipe or telecom cables," adds Lanzoni. "Plant changes and expansions just aggravate the problem when grounding isn't tested and upgraded to meet facility or equipment demands."

These grounding problems often continue for years, causing electrical problems, equipment failure, and even risking personnel electrocution from ground faults that are not safely conducted into the earth through the grounding system.

Until recently, even when facility managers tried to resolve grounding problems, the drawbacks of traditional ground system testing have stood in the way.

The Limitations of Traditional Ground System Testing
Clamp-on ground resistance testers, although convenient, should be limited to testing power distribution poles and residential grounds. Their primary weakness is that their accuracy suffers -- to the point of displaying nothing or a meaningless number -- if resistance is low or a ground loop is present. The grounding electrode being tested must also be parallel with a large number of other electrodes, which is not always practical.

Three-point Fall-of-Potential (FOP) ground resistance testing, which has been used for over 80 years without much advancement, also has significant limitations. Using the FOP test, the grounding system being tested must be disconnected from the equipment being grounded, de-energized, and isolated - but this can be impossible to do in an operating industrial facility where output and processes must be maintained. Because FOP testing doesn't detect grounding discontinuities, the actual grounding rods and connectors to be examined must be physically dug up. Given how expensive and time-consuming this is, checking for grounding discontinuities simply isn't done on a routine basis.

Another drawback of FOP ground testing is that the recommended distance between the grounding grid and current test probe can be excessive - more than five times the diagonal distance of the grounding grid. In a large industrial plant, such as a refinery, this can require extending the current probe several miles onto neighboring property or roadways, an impractical or perhaps impossible task.

The FOP test, which has difficulty measuring low resistance grounds, also has no assurance of accuracy.

"Because of the distance between test probes, weak injected signal strength, and background noise, the FOP test has a poor signal to noise ratio," explains Dr. Sakis Meliopoulos, an IEEE Fellow and Field Award Winner, and professor of electrical engineering at Georgia Tech in Atlanta. "Accuracy suffers when trying to measure low voltage on long leads between test probes, with interference from potentially stronger sources - such as stray current or electromagnetic interference/EMI from nearby power circuits."

Safer, More Effective Plant Production with Smart Ground Testing
Unsatisfied with the limitations of FOP and clamp-on ground test methods for industrial use, Dr. Meliopoulos developed a new type of ground multimeter with sponsorship from the Electric Power Research Institute (EPRI). Output from the Smart Ground Multimeter feeds into EPRI-approved advanced software.

Unlike the FOP and clamp-on methods, the Smart Ground Testing equipment has been designed to operate on energized substations and industrial grounds, minimizing downtime and protecting production capacity. This can be done even when real estate is limited or the surrounding area saturated with roads or buildings because the leads between test probes are relatively short - just twice the length of the grounding system, instead of the FOP method's five to ten times the distance.

For greater accuracy in discovering the root cause of industrial grounding problems and for safer, improved plant production, Smart Ground Testing combines several testing functions not available in previous FOP and clamp-on methods. Because of the increased test accuracy, grounding grid continuity can be verified and diagnosed without the expensive, time-consuming digging up of grounding rods and connectors that other approaches may require.

"Not only does the software reduce interference by compensating for stray current, background noise and EMI, but also it is capable of injecting a signal that is many hundreds of times greater than other equipment," explains Dr. Meliopoulos. "Together, this dramatically improves the signal to noise ratio for more accurate grounding measurement."

While FOP ground tests typically employ a test signal with a frequency indicating transient response at less than 420 Hertz, Smart Ground Testing, for instance, raises this up to 2,500 Hertz. And where low impedance locations require higher currents for confident results, the best FOP ground tests do so with just 0.05 amps, compared to Smart Ground Testing's up to 100 amps (a 2,000-fold difference).

"To give facility managers the statistical validity they need to verify or upgrade grounding status, Smart Ground Testing also generates thousands of test data points, compared to FOP's typical hundred or less," adds Lanzoni.

To generate these added data points, each of Smart Ground Testing's six voltage probes makes 10 computer-controlled current injections in contrast to an FOP probe's single current injection - a 60:1 difference.

"The added data and higher signal-to-noise ratio of Smart Ground Testing provide quantified confidence test levels that FOP and clamp-on tests have never been able to make," says Lanzoni. "The result is unprecedented ground test accuracy and analysis. This allows facility managers to either verify their plant meets safe grounding specs or take corrective action to protect plant safety and production."

The Future: Preserving Production, Preventing Peril
Facility managers who have stayed on top of important technology developments to keep up production over the years, won't want to let aging grounding or inadequate ground testing blindside them now. Simply put, the eventual data/equipment loss, process errors or stopped production attributable to worsening grounding problems is preventable if appropriate action is taken.

"Now is the time to look into advanced technology like Smart Ground Testing if your plant's grounding has never been accurately tested; has sensitive equipment or an aging grounding system; experiences process errors; is located in a lightning prone area; or you want to remove a potentially serious source of production problems before disaster strikes," says Lanzoni.

You wouldn't think of using 12-year old Windows 3.11 with your current software so why would you trust your sensitive process control equipment to technology that was developed 80 years ago? Thousands of successful companies worldwide - including Fortune 1000 clients like Mobil, Bechtel, Motorola, Federal Express, General Electric, NASA, and the FBI - trust LEC's expertise in advanced grounding technology to protect their sensitive computer, communication, and process control equipment.

"My engineering colleagues working in western Africa told me how great the LEC equipment was, but the real proof for me was when we finally got it installed," said R. F. Heinschel, Telecommunications Supervisor for Chevron in Papua New Guinea. "We have not sustained any telecommunications equipment damage for those sites that have the LEC equipment installed. The equipment has proved its value far beyond its initial cost."

Using proven scientific and engineering methods and principles for analyzing system reliability, LEC consults on problems related to grounding, surge suppression, and comprehensive lightning protection. The company's Dissipation Array Systems (DAS®) that include grounding and surge suppression equipment are installed in over 55 countries.

For more info about Smart Ground Testing Program services and evaluations, or about LEC's consulting services, write to them at 6687 Arapahoe Road, Boulder, Colorado 80303; call 303-447-2828; fax 303-447-8122; email [email protected]; or visit their website at www.lightningeliminators.com.