By hvhipot 
Another ideal application of the clamp ground resistance tester test method is to test ground electrodes in lightning protection tests. The lightning protection effect of any building depends only on the quality of its grounding.
Electrodes are usually placed in every corner of the building, and additional electrodes should be placed between larger buildings. The commonly used conductor is a copper tape with a width of no more than 50 mm.
In many cases, this is difficult because the electrode is buried in a small pit.
In addition, many lightning protection tapes are equipped with movable chain links to allow two-wire continuity testing. These movable links are usually called “pot handles”, which are time-consuming to disassemble, but provide an ideal location for using a clamp-on ground resistance tester.
The clamp-on ground resistance tester will measure the entire circuit, including all connections and tape bonding, the same as the two-wire test.
Many lightning protection systems on factory buildings, especially in European countries, use lightning arresters that are regularly installed on the roof.
This method further reduces the series resistance of the parallel ground path, which means that the measured value is even closer to the true ground resistance of the electrode under test.
Keep in mind that there may be other connections to the lightning protection system. The user must remember to clamp the tape under all connections. Otherwise, the ground electrode will be tested in parallel with other ground paths. May be connected to external metal products (such as metal balconies and handrails).
These must also be above the clamped position of the clamp tester. Also remember the importance of visual inspection. Due to the price of copper, grounding tape can be cut and stolen.
Depending on the location of the cutting tape and how the system is connected, the instrument may return good but false readings.
5. Phone base
The ground electrode of the phone base can be tested using the clamp method. The cable sheaths are all connected to the ground bar, and the ground bar is connected to the ground electrode.
The clamp can be placed around the cable connecting the ground rod to the electrode for testing. If it is difficult to access, you can install a temporary extension cable to facilitate installation on the clamp ground resistance tester.
6. Pad transformer
The ground electrode of the transformer mounted on the pad can be verified using the clamp method. However, sometimes there are many connections to the same electrode, so the user may have to clamp the electrode itself under the connection.
If all these connections are connected to the larger buried pad, the measurement will become a continuity measurement because the test loop will not include the ground path.
7. Pole-mounted transformer
Remember the golden rule of clamp testing, “There must be a loop resistance to measure”! In some cases, the loop does not exist on the pole at all, at least where you want the loop to not exist.
Both sets of electrodes are not connected to the overhead grounding cable. One is connected to the metal casing of the transformer, and the other is connected to the star point of the LV secondary winding.
The danger here is that the circuit under test may be located between the two sets of electrodes, and part of the circuit is the resistance of the wooden pole, resulting in high measured values. This may mislead users into thinking that there is actually no problem.
In contrast, in the figure below, there is a connection with the local distribution and its local ground system. This means that we now have a ground loop to be measured and can be measured.
However, keep in mind that the resistance measurement performed is a combination of two series grounded.
A measurement of 40 Ω does not mean that every electrode system is of cHV Hipot Electric Co., Ltd.se less than 25 Ω, one may be 10 Ω and the other may be 30 Ω. For example, if the measured value is 10Ω, then we are fine.