SP Manweb was granted permission to run 10.5 miles of overhead cables between two wind farms in Clocaenog Forest to a substation near St Asaph last year.
But local action group Pylon the Pressure won the right to a judicial review.
It claims the double wooden poles would be a blight on the countryside.
Part of the cables would pass near the 16th Century Berain Farm, Llannefydd, which was home to Catrin o Ferain, the granddaughter of Henry VII and a prominent member of the Tudor gentry in Wales.
At Monday's hearing in Llangefni, Peter Dickson, the barrister representing the appellant, argued that the cables should be placed underground near the farm.
He said the option was not considered by SP Manweb and that the Secretary of State, Greg Clark, should not have granted permission.
Counsels on behalf of SP Manweb will present their submissions later on.
The judge has said he will reserve judgment.

Sarries' Australian lock Skelton slapped the GB Olympic Sevens Rio silver medallist in the face late in the 22-22 European Champions Cup draw.
BBC pundit Brian Moore was among those to accuse Davies, 26, of over-reacting.
"It's not good is it? If one of our players did that I'd be devastated," said McCall.
"But I don't think they would. It's terrible, but you don't need me to tell you that."
Moore wrote: "Scarlets should have won but, had they done so, it would have been spoiled by another example of simulation (cheating by exaggeration) from Davies."
Scarlets head coach Pivac defended Davies' behaviour - and questioned how clean former England hooker Moore was as a player.
"I've spoken to our medical staff, and they tell me he [Davies] is getting acupuncture on his neck," Pivac said.
"The facts speak for themselves: 140kg, swinging arm, hit him on the chin. We've confirmed that.
"Unless you've been hit by 140kg or been struck on the jaw, you really should keep your comments to yourself.
"James tells me it [falling over] was more shock from being struck. He fell to the ground and he got straight back up.
"If I was the Saracens coach I'd be sanctioning my player for throwing a punch which is against the rules of the game."
Asked about Moore's criticism, Pivac added: "I don't condone taking a dive, that's why I don't watch football.
"Brian Moore? Well, he was squeaky clean as a player wasn't he?"
A High Court hearing has begun into plans to erect a 17km line of pylons along the Denbighshire and Conwy border.
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Saracens boss Mark McCall has criticised Scarlets' James Davies after Will Skelton was sin-binned during the meeting of the side last weekend.