UPDATE 2-Polish heatwave cuts power supply to industry

* Heat may hit 39 degrees this week, no rain or wind

* Not enough water to cool coal power plants

* Copper, steel, chemicals sectors suffer

* Grid operator intervenes to purchase power abroad (Adds details, grid operator market intervention)

By Wiktor Szary and Marcin Goettig

WARSAW, Aug 10 (Reuters) - A heatwave has forced Poland to sharply cut electricity supply to industry for the first time in over a decade, pushing some companies to limit production.

Prime Minister Ewa Kopacz called the situation “very serious” as weather forecasts for the coming days showed high temperatures will persist. She added that currently she saw no risk of limiting energy consumption for households.

Europe’s second largest copper miner, Poland’s KGHM , warned it might have to curb output. The local unit of the world’s largest steel maker ArcelorMittal halted some of its operations.

The heatwave and lack of rain cut the amount of water needed to cool coal-fired power plants, from which Poland generates about 90 percent of its electricity. The country has virtually no solar energy generating capacity.

Temperatures in Poland topped 30 degrees Celsius last week and may reach 39 degrees this week, according to Poland’s meteorology institute.

The national grid operator Polskie Sieci Elektroenergetyczne (PSE) introduced the sharpest possible limit on energy consumption for large energy consumers - in excess of 300kW.

“This is an extreme phenomenon,” PSE’s head Henryk Majszczak said. “We are recording high air temperatures and a lack of wind, which could be used by wind farms.”

PSE said the limits on energy consumption will be in place from 0800 GMT to 2000 GMT on Monday. Last week, PSE said that if continued, the heatwave may put its operations at risk.

The operator said it had expected consumption in the coming days at 22,000-22,200 MW, one of the highest ever recorded in the summer peak.

At the same time potential power generation stood at about 25,100 with actual production shortages at over 4,000 MW.

The operator said it limited the export of electricity and had been buying power from neighbouring grids.

Deputy Prime Minister Janusz Piechocinski said he has asked the government to extend limits on energy consumption for large consumers until Aug. 30.

The Polish unit of ArcelorMittal said on Monday it was getting the minimum amount of power it required.

“The most important issue now is to maintain the production of our primary operations, including blast furnaces and steel shops, as bringing them to a halt would result in their irreversible damage,” said ArcelorMittal’s spokeswoman Sylwia Winiarek.

Poland’s largest chemical group Azoty said the limits to power use may force one of its units, Grupa Azoty Kedzierzyn, to cut production by about 10 percent, but this should not put annual production targets at risk. (Additional reporting by Adrian Krajewski and Wojciech Zurawski, editing by William Hardy)