* Strike expands to include grid operator
* Statnett says will not able to repair grid if problems
* Power supplier to Kollsnes also affected
* Government has made no move to intervene
By Nerijus Adomaitis
OSLO, May 14 (Reuters) - Norwegian power and grid company workers have joined a growing strike, creating a risk of nationwide disruptions to electricity supply, grid operator Statnett said on Tuesday, including to Norway's power and gas exports abroad.
The EL&IT Forbundet union first called a strike on April 29 of 80 members who seek to sign a collective agreement with IT infrastructure company Atea. On May 7, it expanded the action to 3,000 members at regional power companies that are customers of Atea.
As of Tuesday, another 466 members joined the strike, including workers at Statnett, which manages high-voltage transmission lines and power cables going abroad. The state-owned grid operator said it could no longer vouch for security of power supplies and warned of potential blackouts.
"Those of our people who are supposed to repair power lines and substations are on strike as of today. We consider the situation very serious," Oeivind Rue, Statnett's executive vice president, said.
"If something happens on the grid, it would remain unrepaired as long as the strike goes on," Rue said.
The government, which can step in to stop the strike if it threatens human lives, vital infrastructure or national interests, has so far not made a move to intervene.
Among the companies affected by the strike is Bergen-based BKK, the power supplier to Norway's leading gas processing plant Kollsnes, which exports gas to Britain and continental Europe.
Gas processing plants need a stable power supply, and even a small dip in power could halt gas compressors abruptly.
Statoil, which is the technical service provider at Kollsnes, could not immediately be reached for comment. Gassco, the plant's operator, said in an email it was following the situation closely.
Power suppliers affected by the strike put out notices on their websites advising customers to be ready with fresh batteries for flashlights and with cables to charge mobile phones from cars in case the lights go off.