Application bulletin: using DV Power GGT and RMO-EH instruments to verify the grounding system inside and beneath a data center
Every new data center gets a fall of potential test at commissioning. It is written into the spec, it follows IEEE Std. 81, and it answers one question: how well does the whole facility connect to earth? That number matters. But it tells you nothing about whether the grid buried under the building is actually intact, or whether the bonds tying racks, cable tray, busway, and structural steel to that grid are still tight and low-resistance.
For 20 years, ProgUSA has supplied electrical test and measurement equipment to utilities, NETA firms, and industrial sites. We see the same gap over and over. A site passes its earth impedance test and everyone signs off, while the connections that actually protect the equipment were never measured. That is the test DV Power's grounding instruments were built for, and it matters more as data center loads climb.
Earth impedance and grid integrity are two different tests
A fall of potential test measures the resistance from the whole grounding system to remote earth. It is a single value for the site. It cannot see a broken exothermic weld, a corroded ground rod, a loose bond on a piece of switchgear, or a riser that came disconnected during construction. Those faults hide inside the grid, and a low earth impedance reading will not flag any of them. Fall of potential testing also runs into real field problems on a live site: stray currents, background noise, and buried metal that skews the reading.
Grid integrity testing looks at the connections themselves. You inject a known current between two points and measure the voltage drop to find the real resistance of that path. Do it across the grid and you find the weak welds, the high-resistance joints, and the bonds that never got made. In a data center, where a ground potential difference of a fraction of a volt can disrupt sensitive electronics, those are the faults that matter.
High current injected across a buried grid: the GGT (left) and the RMO-EH (right) measuring the voltage drop to find the true resistance of each path.
Where DV Power fits
The DV Power Ground Grid Integrity Tester, the GGT series, is the core of this work and a solution unique to DV Power. It injects up to 300 A DC to check the continuity of buried ground conductors, connectors, ground rods, and bonding connections. That high current is the point: it proves a connection will actually carry fault current, not just pass a low-current continuity check that a marginal joint can sneak through. Its Both Sides Grounded feature lets you measure connections that stay grounded at both ends, so you are testing the grid in its real condition instead of taking it apart to do it. The unit runs wireless from a remote module to keep the operator clear during high-current injection, and it carries an IP 67 rating for field work in mud and weather.
DV Power GGT300 Ground Grid Integrity Tester.
The DV Power RMO-EH handheld micro-ohmmeter is the companion for walking the site. Battery-powered and under one kilogram, it puts out a regulated test current up to 10 A DC with test leads on a cable reel up to 200 meters, using a Kelvin four-point measurement that cancels the resistance of those long leads. It is built to check the continuity of bonds and conductors across a campus, even where there is no power to run a larger set, while overcoming the background noise and stray currents that throw off other methods. It holds pass/fail limits and stores every time-stamped reading for the report the owner keeps.
The RMO-EH in the field, verifying earthing system continuity at a substation.
Between the two, a technician can verify a data center grounding system end to end: the GGT for high-current integrity of the buried grid, the RMO-EH for portable, long-lead continuity of bonds and conductors across the campus, even where there is no power to run a larger set.
Why this matters now
Data center construction is running hot, timelines are compressed, and grounding is one of the first systems buried and one of the last things anyone checks. A grid integrity survey at commissioning, and again during expansions, catches the connection faults that a fall-of-potential test is not designed to find. It produces a record the owner can keep, and it does not carry the isolation and distance headaches of a proper fall-of-potential test.
Equipment, education, and service is how ProgUSA works. We supply the DV Power instruments, we help your team learn to run the test and read the results, and we back it after the sale.
Call to action
If you commission, expand, or maintain data centers, ask us for a DV Power grid integrity walkthrough. We will show you what the GGT and RMO-EH instruments find that a commissioning fall of potential test does not, and we will help you build it into your grounding scope. Contact ProgUSA at progusa.net.