* Macro factors, volumes cut PLN 1 bln off operating profit
* Q2 refining margins fell 34 percent to $4.6/bbl
* Refined 11 percent less oil y-y
(Adds analyst quote, details, background)
WARSAW, July 28 (Reuters) - Poland's top refiner, PKN Orlen , expects macroeconomic factors and lower volumes to chop about 1 billion zlotys ($342 million) from its year-on-year operating profit in the second quarter, it said on Tuesday.
The state-controlled refiner, which posted two consecutive quarters of deep net losses, had an operating profit of 1.65 billion in the second quarter of last year.
In a trading statement, PKN said refining margins dropped in the second quarter by 34 percent to $4.6 per barrel and it refined over a tenth less oil than year ago.
PKN had said it would turn to a net profit in the second quarter as oil prices rose throughout the quarter and the strengthening zloty cut its financial costs.
However, much of the boost came from one-off gains from the revaluation of the oil it holds as required reserves.
PKN shares edged up 0.3 percent early in the session. They have risen 8 percent this year versus a 15 percent rise of Warsaw's main index WIG20.
(Reporting by Adrian Krajewsk; editing by Simon Jessop)