Testing The Lightning Earth - Lightning Protection International Stormaster ESE 15 Installation Manual

4. After installation of the HVSC Plus downconductor:
∆
Remove the waterproofing tape from the lower termination
∆
Disconnect the HVSC Plus downconductor from the lightning earth
∆
Use a digital multimeter or, preferably, a Megger to measure the continuity between the
inner conductor at the top (upper termination) and the shield (outer copper tape conductor)
at the bottom of the cable. The measurement should be a "short circuit" (less than 1 W ,
excluding the resistance of the leads, the exact value depending on the length of HVSC Plus)
∆
Reconnect the HVSC Plus lower termination to the lightning earth and re-seal the termination
using waterproofing tape to ensure that it is waterproof
5. Report any problems arising from the above tests to your local LPI distributor for further advice

Testing the Lightning Earth

The procedure for obtaining the resistance of the lightning earth is described below. The method
that is used is called the "fall-of-potential" (FOP) or "three-point" method. It relies on the use
of a suitable 3-point or 4-point earth tester. As testing is carried out, please record all values
per the table on page 48.
1. Disconnect the bonding cable from the structure to the lightning earth, as shown in Figure 42.
2. A "standard" LPI lightning earth will comprise radials of length 10 m. Assuming a 10 x 10 m
earthing system, the current injection point for the FOP test should be at least 50 m, but
preferably 100 m away from the lightning earth, with no intervening buried conductors.
For a larger earthing system, this distance should be increased. Install a remote current
injection electrode (RCIE) at a suitable location at about the above distance. This
electrode may be a simple driven rod of sufficient depth to get a low resistance. (Note:
if the resistance of this rod is too high, the instrument may be incapable of injecting a
current to make the test).
3. Now install a rod at about 62 % of the distance between the RCIE and the lightning earth. The
depth of this "potential rod" is not important (it can be less than 100 mm). Make a 3-point
resistance measurement and note the value.
4. Shift the potential rod 1 m closer to the lightning earth, measure and note the value.
5. Shift the potential rod 1 m further away from the original test point, measure and note
the value.
6. If the RCIE is sufficiently far away and there are no buried conductors affecting the results,
the three values recorded should all be within 5 % of each other. If this is the case, then
the resistance value measured is a true indication of the resistance of the lightning earth.
46
LIGHTNING PROTECTION INTERNATIONAL PTY LTD www.lpi.com.au