Vandalized tower repaired while still energized

By Conor Golden,
News Editor for A.M. Costa Rica

The Costa Rican electricity institute had to apply the method of external reinforcement to one of its transmission towers in Siquirres following damage caused by the theft of around 50 pieces to the frame.

The Instituto Costarricense de Electricidad said that the pieces stolen were part of the straight body of the tower that left the entire structure severely weakened and subject to potential toppling.

The move to create the exoskeleton that was mounted on the structure was extremely risky.

The entire crew worked on the damaged tower without suspending the energy transfer. In other words, the tower was still on and powering electricity through the circuits during the full duration of time it took to repair.

According to the institute, the tower was built and fully integrated into the power grid back in 2003 as part of the Trapiche-Moín line.

The tower has two circuits transferring energy through it with each circuit containing about 230 kilovolts of electricity.

If a worker or person were electrocuted on this tower, the voltage would be enough to not only kill that person but also severely burn them as well.

Such accidents are usually work-related and occur when a worker’s piece of equipment such as a crane or ladder bumps up against a cable while touching the ground.

Electricity will stray from a power line only if it has a direct path to the ground. This is why birds can often sit on the electrically charged lines that have no protective insulation covering it.

Air around a power line is not the best conductor but huge transmission lines can still have a radius of up to a foot or more within their electrical field.

This means that if there is something nearby planted on the ground or that touches the ground, then a person within that radius can still be electrocuted even if they don’t physically make contact with the thing.

It should be noted, however, that these towers usually maintain insulators on the structure so the frame holding up the lines is not electrified.

The exoskeleton model has been in use by the institute since last year as a base prototype.

A workshop in Freehold de Siquirres was created as the site to manufacture and build all the framework, the institute said. The model began to be installed back in April and the assembly for the exoskeleton on this tower took less than two weeks, electricity officials said.

“The Salud Ocupacional maintained permanent supervision at the site,” Miguel Sibaja, the designer and inspector for the project, said.

To date, there are no international reports of similar work of intervention due to vandalizing infrastructure of energized lines, Sibaja said.

The technique is expected to be used in future mechanical interventions by the Instituto Costarricense de Electricidad on structures with energized lines.

*Editor’s Note: The author would like to thank Kevin Golden, a retired electrician formerly with the Ohio Building Authority, for his consultation in the article.

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