Those lines look to carry a higher voltage than 72 kV to me.
More like 132 or 275 kV looking at the strings of disc insulators.
We use 12 for 220 kV in NZ this looks like 16 discs to me ( 275 kV ? )
Very likely that magnetic fields induce eddy currents in the steel tent poles and cause a possible voltage build up.
What are the Grid / POCO poles made off, concrete or steel ?
A possibility is that one Grid / POCO pole is partially live due to a faulty insulator string, either in the steel or via the reinforcing steel.
Might pay to get the Grid / POCO asset owner to check out their poles for leakage and check up with the local regulations re safe working distances for temporary buildings, tents near these lines.
If to close, this is a very dangerous situation.
