Lightning electrodes

the diameter is not unusual - what we do not know is how deep it goes - it may well have failed at a threaded joint, as such things are often driven in stages, and deeper then a house electrode, or there is a buried mesh and again it has come detached. 

If the small parish church is supplied by a small parish transformer on a pole in the small parish churchyard be aware that a test using a loop tester includes the DNO electrodes, which on a single pole pig may be comparable resistance  or even higher than those of the LPS. 

Foundation electrodes are very good for TT and small surges. They can have the weakness of the concrete cracking if the worst happens in terms of LPS.

In this case, 200 odd ohms has ‘broken’ as the unwritten label as i is a figure suggest something has come off under ground leaving just a short rod.

Lightning voltages and the megavolt/metre rule do not scale for lightning - rather the discharge has more in common with a chain of unevenly charged capacitors breaking down, where only one in the chain has to be stressed enough to fail, and then overstressing the next weakest.

Clouds are 5-10km up and at a megavolt per metre, you may think gigavolts are involved, but not really, more like about 20- 50MV and a lot of jumps of a few tens of metres at a time, as short regions of space are stressed and then break down, until a continuous discharge is formed.  This more modest voltage is part of the physics justification of the rolling balls model where the decision of what is within side-strike distance is modelled as being within a sphere of radius proportional to strike voltage.

It is complex.

Mike.

the diameter is not unusual - what we do not know is how deep it goes - it may well have failed at a threaded joint, as such things are often driven in stages, and deeper then a house electrode, or there is a buried mesh and again it has come detached. 

If the small parish church is supplied by a small parish transformer on a pole in the small parish churchyard be aware that a test using a loop tester includes the DNO electrodes, which on a single pole pig may be comparable resistance  or even higher than those of the LPS. 

Foundation electrodes are very good for TT and small surges. They can have the weakness of the concrete cracking if the worst happens in terms of LPS.

In this case, 200 odd ohms has ‘broken’ as the unwritten label as i is a figure suggest something has come off under ground leaving just a short rod.

Lightning voltages and the megavolt/metre rule do not scale for lightning - rather the discharge has more in common with a chain of unevenly charged capacitors breaking down, where only one in the chain has to be stressed enough to fail, and then overstressing the next weakest.

Clouds are 5-10km up and at a megavolt per metre, you may think gigavolts are involved, but not really, more like about 20- 50MV and a lot of jumps of a few tens of metres at a time, as short regions of space are stressed and then break down, until a continuous discharge is formed.  This more modest voltage is part of the physics justification of the rolling balls model where the decision of what is within side-strike distance is modelled as being within a sphere of radius proportional to strike voltage.

It is complex.

Mike.