A Quebec man who targeted Hydro-Quebec power lines in an aerial attack that left tens of thousands without power in December 2014 was sentenced Monday to seven years in prison.

Normand Dube, a local entrepreneur, was found guilty in September of using his small plane in what the Crown described as an unprecedented strike on institutions and ordinary Quebecers.

Dube, described in local media as a "pilot to the stars" for his past life transporting Quebec entertainers, was impassive as Quebec court Judge Paul Chevalier handed down his sentence Monday on three counts of mischief.

Although Dube, 56, has no previous criminal record, his responsibility for the crimes was complete, Chevalier noted.

"The modus operandi of his crime shows that he carefully prepared it and did not act impulsively," the judge said. "The motive held by the court -- vengeance -- underlines his moral culpability."

The Crown had sought the maximum 10-year sentence for the attack on two power lines northwest of Montreal, described by prosecutors as the jugular and spinal column of the Hydro-Quebec network.

The way the crime was committed and the extent of the damages made it a first in Canada, with neither the Crown nor the defence able to find legal precedents. But Chevalier concluded the Crown's recommendation was excessive.

The exact method used to create a short-circuit in the Dec. 4, 2014 attack cannot be reported under a publication ban imposed in the interest of national security.

Much of the trial took place with the public barred, and the decision finding Dube guilty in September is partially redacted.

The defence had argued for a much shorter sentence -- either three years in prison or less than two years in a provincial jail followed by three years probation.

A lawyer for Dube, Mario Lavigne, said he plans to appeal the verdict and sentence and seek bail for his client. He declined comment on Monday's decision.

The Crown said a hearing on the defence request is expected before the Quebec Court of Appeal on Thursday. Dube was taken into custody after the sentence was rendered.

The pilot, inventor and entrepreneur held a deep grudge against Hydro-Quebec that stemmed from a dispute over work done by the utility on land he owned in Ste-Anne-des-Plaines, north of Montreal.

According to the prosecution, Dube also blamed the utility for his tax problems.

The Crown argued Dube merited an exemplary sentence for an act of sabotage that nearly crippled Hydro-Quebec's power grid.

Some 188,000 people were left without power during two winter days as a result of the attack. Institutions including McGill University's health network were also affected. Some companies had to reduce power consumption, and Hydro-Quebec temporarily cut its exports.

During sentencing, a former Hydro-Quebec executive testified the outage cost the public utility $28.6 million -- a cost assumed by all Quebec taxpayers. Hydro-Quebec is suing Dube in a civil matter to recoup the costs.

Retired Hydro-Quebec executive Pierre Paquet called the attack on two main power lines on Dec. 4 "extremely severe." He said the electricity on the affected lines was transferred to adjacent lines, which was more than they could handle.

The initial attack left about 120,000 clients without power in a wide swath of southwestern Quebec. A second cut of service to about 60,000 clients was necessary to maintain the network's stability as Hydro crews searched for the cause.

The Crown said it was satisfied with the sentence.

"The message to take from this judgment is that we can't attack with impunity in Canada a public service with a motivation like vengeance and paralyze a system like hydroelectricity," Steve Baribeau said.

Chevalier also agreed to the Crown's request to confiscate the plane Dube used in the attack, a single-engine Aerocruiser 450 that he designed.