Faults in 132-KV Transmission Lines

The purpose of the overhead "earth wire" is to shield the transmission lines so it probably is. You would have to check where the strikes take place and see if they match the line sections where the protection is missing.

You can certainly attribute a major part of the trips to missing earth wires. Assuming there is an overhead shield or sky wire, properly located to shield the phase conductors, missing earth wires would render it ineffective. In order to be effective the shield wire must be solidly grounded through low footing resistance. The situation you describe will also cause backflashover and an abnormal number of shielding failures.

We also call this as gaurd wire running between tower to tower and as far as I know, it is for lightning protection only. This need be earthed at frequent intervals to dissipate the energy. Hope i am in line with your point.

Yes, you are right. It is a shield (guard) wire formerly for lightning protection only and it should be grounded at every structure to less then 25 ohms resistance. The reason that I say it was "formerly for lightning protection only" is that there are now overhead shield wires that have a fiber optic core that can be used to transmit data.

BTW, this is a great forum and I'd like to thank everyone for their participation.