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Grounding test

I thought about that, and had planned on checking section to section continuity. But I am guessing if there is a problem it will bad or corroded ground rod. Can you think of a way to check that without a megger?

reply to inova
To get a true picture of resistance to ground you need a megger. You could do a check on the ground leads with a amp clamp and see if there is any stray current running on the ground leads. If so, I would try to eliminate that first.

reply to slipstream1

Or you can eliminate the mechanical connections of the tower completely by using a down conductor that is attached to tower ground field. If you suspect that the connections, on the tower are corroded, this may be a good quick test. If you disassemble be sure to use some sort of non-oxydizing compound to slow down corrosion between parts that would need a excellant electrical connection.

reply to inova

reply to inova
I think that it is best to divide what has been discussed in this thread into two items to be tested. One thing is the resistance from whatever is at the top of the tower, to the bottom of the tower. The other thing to be tested is the resistance between the bottom of the tower and the earth.

When testing the resistance between tower sections there is no need for a megger. A megger is used when testing insulation or anything else that won't conduct well at low voltages. If you test insulation (like the insulation on a motor winding) with a common multimeter, it SHOULD read like an open circuit. If you use a megger on the same insulation it will typically generate about 500V (or whatever you set it at) and the higher voltage will likely get some measurable current to flow. This current flow will typically register as a reading in the Mega-ohm range. If this higher voltage is necessary to get current flow between tower sections, you have some serious issues. The connections between tower sections should not require any significant voltage to get current to flow. A standard multimeter is adequate for the test. If you want to test the connection more accurately, you can use a digital low resistance ohmmeter. They clamp to the two sections to be tested and inject up to 10A and then check to see what voltage is generated as a result of the current. These meters have great resolution at the hopefully low resistance range between the tower sections. It could easily be argued that the meter would not be so practical for towers because they usually have leads 30 feet or less and they are pretty heavy units.

To measure the connection of your tower to earth, ideally you would use a ground resistance tester. It uses one or more probes or you could think of them as test ground rods. If you are getting the corrosion on the tower ground rods like they report happens to copper plumbing, this tester would show that.

If you don't want to get a ground resistance tester, you can do a crude but effective test with a standard multimeter and a couple of ground rods. Drive one of the ground rods maybe three feet out from the tower ground rod(s) and then the other ground rod the same distance further out. Measure the resistance from the tower to the first ground rod and compare that to the resistance between the two test ground rods. The two readings should be in the same ball park. If the reading from the tower to the first ground rod is significantly higher than the reading between the two test ground rods, you have found a problem with the grounding of the tower to earth.

Sorry for the long post. Hope it helps.

I think we found it. With my ohm meter I could get a measurement 1400 ohms from the ground rod to a reference rod. I got 150 ohms from the reference to my probe in the ground only 1 inch deep (same distance apart). We dug up around the ground rod 6" deep or so and I could see no evidence of galvanization at all only corrosion. I had to file the top of the rod off just to make probe contact. It was enough to convince him (and me) his ground rod was a dead duck. He is off to purchase a shiny new one. I realize this is rudimentary testing but it still seemed pretty obvious to me. Thanks Wireless Dav and everybody.

Typical farmer (oops did I say that out loud?), the rod was probably in the ground for 20 or 30 years and it was a salvaged rod when he put it in (his confession). It may have indeed been copper clad but I can't say for sure. I rounded up a shiny new galvanized one and just got home from installing it. The measurements I could make with my ohm meter (to a makeshift reference) went from 1400 ohms to about 8 to 50 ohms, a marked improvement. It did seem to do some hunting in that range as if there was some capacitance involved but none the less much better. It is currently very dry here, that probably has something to do with it also. I installed a ups and when the wind dies down I will climb up and install delib2315 #3. Fingers crossed... It is costly but I am learning things and I like that.

But I am guessing if there is a problem it will bad or corroded ground rod.

It did seem to do some hunting in that range as if there was some capacitance involved but none the less much better

reply to inova
I would avoid galvanized ground rods as they can develop high resistance due to interaction with chemicals in the soil. If copper plated rods are not holding up switch to stainless steel. While a galvanized rod might measure low resistance with a VOM under high current from a strike it may fail to provide a good connection to earth.

Avoid using any type of clamps or crimp type connecting devices on your ground system. Connections should be made with exothermic welds only. If you are only doing a few systems then the Cadweld one shot system is they way to go.

Also where you place your ground rods install a small round 12 inch or so sprinkler housing with a removable lid over the rod. This will provide ready access to both the top of the rod and the weld for easy inspections and testing plus because the housing can be seen from ground level it may help prevent the rod and connection from being damaged by other contractors.

Wayne
--
If you cannot fix it with a buttset and some beanies you ain't a technician.

Would one of these units be good and if so witch one is better to have?
ECOS 2167 MEGGER FRAME GROUND MONITOR RESISTANCE TESTER
AEMC Ground Soil Resistance Tester 3640

reply to inova
Why was there only one rod?? Even the safety ground on a house needs a minimum of two 8' ground rods. If you are only going to put in one ground rod, then why bother at all? Drive in AT LEAST two more, a minimum of 16' apart, and bond with #2 copper wire or larger. Yes, it's a pain in the ass, but it will save your equipment.

I've spent the last 12 years working around tall towers, I've seen the difference between good grounding and poor grounding. My 2000' foot(yes, I said two-thousand feet) tower was struck by lightning twice this morning on my drive in, no damage to anything when I got here. That's the beauty of a good grounding system.

Yes I already pointed that out to the customer and he said he would install them but I am sure it will take some prodding.

2000'! Cool! Can you post a pic? Can I come climb it and check out the view? Better yet, do you have any pics from the top of that puppy?

reply to Stealthwave
AEMC is the best units that you can buy. I believe that we have the 3500 series units.