Justin Hollins was working replacing step bolts on the pylon at Treforest Industrial Estate in Pontypridd, when he received an electric shock of 33,000 volts.
The 50-year-old sustained burns to 40% of his body, including to his arms and legs, and also lost part of his right buttock.
Hollins, who had six operations in the space of his first 10 days in hospital, told of how he required 24 hour care for months after the accident on December 3 2020.
He said: “This was a very difficult time, with relentless operations and endless, painful changing of dressings.
“Every day was a huge battle.
“I stopped needing to attend hospital appointments in August 2022 but will remain a burns patient for the rest of my life.
“At the time of my accident I was in peak physical condition, which I was told by the hospital is probably the reason I survived.
“I have been stripped of the opportunity to provide for my family doing the job I loved.
“Although I appreciate that I have been lucky to survive, I have to live with the physical and mental effects of the accident for life. I also have to live with the uncertainty of the long term damage 33 thousands volts have done to my internal organs.”
Cardiff Crown Court heard that Hollins, who also suffered nerve damage that affects mobility, was wearing a climbing harness and left hanging on the pylon for some time before being rescued by his colleagues.
An HSE investigation found that maintenance subcontractor 4 Power Ltd of Cheshire, failed to properly plan and assess the risk. Had this been done, it would have identified that the arms of pylon were too short to do the work safely, while maintaining the specified safety distances as per industry standard.
National Grid Electricity Distribution (South Wales) Plc who are based in Bristol failed to ensure that the electricity was off in order to do this work safely on the pylon.
4 Power Ltd pleaded guilty to safety breaches and were fined £80,000 and ordered to pay costs of £14,123.
National Grid Electricity Distribution (South Wales) also pleaded guilty and were fined £3.2m and ordered to pay costs of £20,460.
Speaking after the hearing HSE Inspector Rhys Hughes said: “The injuries sustained by Mr Hollins have been truly life-changing. He is lucky to be alive.
“Those in control of work have a responsibility to devise safe methods of working and to provide the necessary information and instruction to workers.
“What is so frustrating in incidents like these is if a safe system of work had been in place before the incident, his injuries would have been prevented.”