Union members engaged in a "partial work ban" starting on March 15 where they were not allowed to use various Transgrid systems including their phones, tablets, switchboards, electrical cabinets and circuit breakers.

The Electrical Trades Union has sued Transgrid in the Federal Court, claiming the privatised electricity network company breached employment law by neglecting to pay members for 12 days during the protests.

"The union alleges that energy company Transgrid wrongly stood down its workers without pay while they engaged in protected industrial action in March," said ETU NSW/ACT secretary Allen Hicks.

"ETU members have been taking legally protected industrial action during the campaign to further their wages and conditions but at the same time it appears Transgrid has decided to play dirty, as it tries to rip off workers in more ways than one."

According to court documents, a notice sent by Transgrid to staff regarding the claimed non-payment of wages during the work ban was "defective".

The notice was not delivered to workers personally and the company did not take all reasonable steps to ensure staff received it, the union alleges.

Transgrid then did not pay workers for work they were rostered to perform during the industrial action, the ETU said.

"The Fair Work Act is very clear about when and how people get paid and the union believes Transgrid hasn't complied with it," said Mr Hicks.

As well as compensation plus interest for the allegedly unpaid wages, the union is also seeking pecuniary penalties against the energy company.

Transgrid said with the case before the court, it would be inappropriate to make any specific comments other than to indicate the claim is denied and will be defended.

The matter has yet to come before the Federal Court.

Australian Associated Press