It was standard procedure to treat any electrical cables as live, Mr Roberts said, and to immediately contact the lines company Vector for assistance in cutting power to scene.
When the lines were still live an hour after Northpower engineers arrived at the scene, Mr Roberts asked them to cut power to the suburb in a bid to speed the process up.
"I made a verbal request [to the Northpower engineer] to kill the power to a larger area as a matter of urgency," he said, saying that he had never heard of anyone from the Fire Service making such a request before but felt he had to because "something needed to be done".
Questioned about his decision by lawyers for Vector, Mr Roberts said he was simply "grasping at straws".
"Anything to get the power off, and get them to try harder," he said.
"I just wanted them to try something different to what they were doing because it just wasn't working."
However, counsel for Northpower, Brian Dickey, said it was not possible to do what he asked
"The request is not meaningful in a technical electrical engineering sense," he said, because the engineers would still have to go through the same procedures and it "wouldn't have sped it up".
"You can't just switch off a suburb and be safe," he said.
Mr Roberts said he now accepted that, but he wasn't aware of how the system worked at the time.
His request came after he had already made it clear to the Northpower engineers on the ground that this "was an urgent/death situation".
This afternoon, Coroner Morag McDowell, lawyers for the various parties, and Glenda Olsen, Mr Tuporo's mother, all took part in a site visit, in which they examined the crash scene and the area's electrical control room.
The inquest continues.