Investigation of ground wire's twist-off and its repairing methods

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Supervisor:
Dr. Németh Bálint
Department of Electric Power Engineering

In this paper I am investigating the damages caused by lightning strikes on the ground wire of high voltage power lines. I also analyze the possible live line fixing methods and technologies.

Nowadays live line working is not applied on the high voltage power lines of the Hungarian grid, but it expectedly appears on these voltage levels, too - according to the international trends. Live line maintenance increases the reliability of the system considering economical aspects as well.

On high voltage power lines one of the most frequent damage type is the twisting-off of ground wire’s elementary threads. Repairing this type of damage with live line work will significantly decrease the number of planned maintenances which require switching off the lines.

High voltage power lines are passing above their environment, so they are much more endangered from lightning strikes than the other elements of the power system. Ground wires - among some other functions - protects the line from lightning strikes. If a lightning strikes this wire, its elementary threads often melt, and the phenomena “twisting-off” is appearing.

The increase of the international power transport requires not to switch off power lines to preserve the reliability of the whole system. The solution is to apply live line working technologies during repairing and maintenance on the power lines. The possible working methods cause many technical, economical and physiological questions. In case of applying optical ground wires (OPGW) - which are widely used nowadays - another further problem is that the radius of their bend is very limited, so the weight of the repairer car using to fix the damaged wire is limited as well.

The aim of this paper is to find out a technology to repair the twisted-off elementary threads of ground wires safely, preserving the reliability of the power system.

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