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Should you trust your life to a wet or aged conductive wooden pole?
In the above sketch there are three parallel resistances that form current paths to earth.
The total resistance to earth is calculated as follows: the worker on pole plus 2 earthed poles.
1 1 1 1 1 = 77.82 Ohms
R tot = 165** + 1165 + 165 = 0.006 + 0.00086 + 0.006 = 0.01285
1000volts* will facilitate the following current flow to earth.
I = V/R = 1,000/77.82 Ohms = 12.85 Amps.
Possible current flow at earthed poles I =V/R = 1,000/165 = 6 Amps.
Possible current flow through worker on pole: I = V/R = 1,000/1165 = 0.85Amps.
The current safety earthing procedure in Ireland is based on the mistaken belief that a wooden pole is always an insulator therefore dangerous current cannot flow through the worker on the pole.
Electrocution has occurred while climbing a wet wooden pole on a faulted line.
€10,000 awaits anybody who can scientifically prove that dangerous current cannot flow through the worker on the pole and that the worker is protected from death and injury.
Closing Date 4th April 2018. See competition Terms & Conditions
Note: Resistance values for wooden poles may not be included as there is no way of ascertaining the exact resistance of a wooden pole that is wet or has become conductive with age. (Ref. Swedish Study).
*L-E (line to earth) voltage appearing on 20 kV networks may be up to 11.6kV.
165 Ohms** = Measured resistance to earth at pole locations.