Ground Testing Ensures Safe Industrial Plants
Trusting an industrial plant's operation to a grounding system installed decades ago -- or testing it with a technology developed 80 years ago -- can cause a loss of data and equipment. Grounding systems often are allowed to go out of spec due to aging, corrosion, facility and soil changes, and infrequent and inadequate grounding test evaluation.
“Failing to properly evaluate and fix grounding problems can not only result in unnecessary lightning and transient damage, but also data and equipment loss, process anomalies, plant shutdown and increased fire and personnel risk,” said Joe Lanzoni, a manager with Boulder, Col.-based Lightning Eliminators & Consultants Inc. (LEC), a firm specializing in electrical grounding, surge suppression and lightning protection. “Particularly susceptible to these disruptions are plants with sensitive process control, computer and communication equipment requiring low grounding impedance from one to ten ohms to work properly.”
In many cases, the grounding rods in U.S. industrial plants have exceeded their usable lifespan of 30 years because they have not been properly tested or maintained since installation decades earlier. 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,” said Lanzoni. “Plant changes and expansions just aggravate the problem when grounding isn't tested and upgraded to meet facility or equipment demands.”
LEC offers Smart Ground Testing, a ground system testing method designed to keep up with technical advances in manufacturing and process control industries. Power-surge-protection equipment depends on good grounding to defend against power surges and spikes, as well as diverting lightning discharges of up to 400,000 A to ground.
Traditional testing methods for grounding systems include clamp-on ground resistance testers and three-point fall-of-potential (FOP) ground resistance testing, which must be disconnected from equipment being grounded. FOP ground testing also can require excessive distance between the grounding grid and current test probe.
“Because of the distance between test probes, weak injected signal strength, and background noise, the FOP test has a poor signal-to-noise ratio,” said 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 from nearby power circuits.”
Meliopoulous developed the Smart Ground multimeter, which is designed to operate on energized substations and industrial grounds, minimizing downtime and protecting production capacity. With this system, the distance between test probes is relatively short. It was developed through the Electric Power Research Institute (EPRI) and feeds into EPRI-approved advanced software.
“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,” said Meliopoulos. “Together, this improves the signal-to-noise ratio for more accurate grounding measurement.”
For more information about the smart ground testing services and LEC, visit www.lightningeliminators.com.