SOFIA (Bulgaria), August 1 (SeeNews) – Bulgaria's Electricity System Operator (ESO), a fully owned subsidiary of state-run Bulgarian Energy Holding (BEH), said its preliminary after-tax loss widened to 39.4 million levs ($27.1 million/20 million euro) in the first half of 2014, from 8.5 million levs a year earlier, a financial report indicated.