Bulgaria's gas transmission system operator Bulgartransgaz said it has increased the gas years in Phase 2 of the economic test of the open season procedure for booking incremental capacity from the border with Turkey to the border with Serbia. With a view to improving the parameters and the probability of a positive economic test, the number of the gas years offered for booking have been increased from 15 to 20 and the booking price has been adjusted in line with the longer booking period, Bulgartransgaz said in a notice posted on its website on Monday. The conditions for a successful Phase 1 of the economic test were not fulfilled, although binding offers for participation were submitted by three candidates, Bulgartransgaz said. It did not name the bidders.