Ground testing maintenance schedules

16 January 2014

We are in the dead of winter, but what better time to look forward to the spring – especially just coming out of Polar Vortex 2014!!  So when is the best time to perform ground resistance testing? The most prevalent time to perform a ground resistance test is upon installation.  Unfortunately, this is often the last time as well.  This should not be the case!

Once installed, a ground rod or grid should not be taken for granted….It is not a static element of the electrical system.  It needs to be managed and maintained.

Meeting installation specifications is only the first step in what should be an ongoing maintenance program that takes into account the year round variations that affect the ground electrode’s performance when a fault current brings it into service.

If a maintenance schedule was not initiated at the time of installation, now is as good a time to start.  Once there is a schedule, establish a testing routine that can be quickly and easily implemented.  Note, getting the right procedure for the specific conditions at a particular site may require a little trial and error at the start. Hence, our suggestion of ground testing in the spring – especially in the northern climates.  Like a hibernating animal, the ground is awakening from a stressful period and may need some nurturing, in this case in the form of maintenance.

In the North, winter is probably the worst season for ground effectiveness because ground conductivity (the ability of the soil to readily dissipate a fault current being carried to earth by the electrical system’s protective circuits) is seriously impeded by freezing. Current in the soil is carried by dissolved ions (salts) in soil moisture, similar to the action of a battery.  And like a battery, freezing solidifies and immobilizes this function.

By starting a maintenance plan in the spring, things should run a little more smoothly - work out the particulars of the local site, establish the correct distances and directions, select the most effective method, and be prepared to handle the rigors of the more difficult seasons. In spring, thawing will have saturated the soil, so that the ground electrode should be sitting in optimal conditions.  However, it may not have emerged from winter unscathed.  Freezing and thawing can exert pressures that disrupt and damage a grounding system just like they break up highway surfaces.

Since you can’t see the ground electrode, testing is the only way to know if there’s been deterioration.  With the soil relatively moist and soft, it should be comparatively easy to run multiple tests in order to establish and refine the best routine for your particular situation. Furthermore, it will be relatively easy to make necessary adjustments by driving additional rods, digging up broken connectors, and the like.  Remember, in spring, you don’t want to just barely meet specifications!  If you’re reading 5 Ohm against a 5 Ohm spec, that doesn’t leave much to compensate for the rise in soil resistivity that commonly occurs in the worst seasons.  How much “compensation” is needed?  There’s no way to tell from a single test, but the approach of summer can provide an opportunity.

In summer, drying of the soil tends to increase resistivity, making a ground electrode less effective.  If you’ve established what appears to be a good ground in the spring, summer can give some indication of how susceptible it is to seasonal variations, while you still have time to do something about it.  The soil is still readily workable, so if measurements skyrocket, adjustments can be made to bring the system back into spec, and you’ll probably be ready for winter.

Fall rains should bring measurements back comfortably under the maximum allowable resistance, while an early frost may give an indication of what lies ahead, while it’s still comparatively easy to dig – preparing you for winter, which is likely to be the worst season for grounding.

Having had time to work out the best method and procedure for your situation, a winter test can be performed quickly and easily, without a lot of trial and error.  With any luck, spring and summer maintenance will have gotten the ground safely within spec, so that you won’t be faced with the alternatives of digging up cement-like soil or praying that the electrical system doesn’t experience a fault before the ground thaws! Spring is the optimal time to start, especially in the North, and after that, a regular test schedule can fall into place.

With spring just around the corner, now is the perfect time to begin preparing a test schedule for all four seasons.