Changing power line inspection periods to five years created an unacceptable fire risk that led to a bushfire, the Victorian Supreme Court has heard.

Barrister Tim Tobin SC told the court, sitting in the regional town of Horsham, that utility company Powercor breached its duty to operate safely.

A class action being led by Victorian farmer Laurie Thomas stems from a grass fire that burned nearly 2500 hectares and destroyed 13 homes and other buildings.

The fire started west of Horsham on February 7 2009, and Mr Tobin alleges the cause was a live power wire falling from a pole and igniting the grass.

The statement of claim says the pole was installed when the line was constructed in 1964. The line was secured to the top of the pole by an insulator and screws holding this came loose.

The plaintiffs allege Powercor had not replaced the pole cap fasteners nor inspected the pole-top since July 2004.

But Powercor counsel David Curtain QC says the company’s maintenance systems were based on expert advice and not cost-cutting. He says the transmission of electricity always carries risks and the risk of starting a fire could not be reduced to zero.

Mr Thomas is claiming damages of more than $300,000 for loss of fences, buildings, crops, farm machinery and 40 lambs.

The case before Justice Terence Forrest is expected to run for six weeks.