Experts of the Company have mastered a new chromatographic testing procedure for ionol, an antioxidizing additive. Defining the concentration of ionol is extremely important, as its lower concentrations result in intensive oxidation of transformer oil, which negatively affects the condition of equipment isolation. Physical and chemical methods of testing, which allow effective assessment of the condition of oil-filled equipment, are now quite widespread. The Saratov branch began using the chromatographic method for diagnostics of transformers and oil-filled lead-ins in the 1980s. Over time, the technique was constantly improved, becoming more effective. One of the most informative ways to test the condition of electric equipment and detect any possible defects lies in analyzing gases dissolved in oil. Defining and analyzing presence and concentration of hydrogen, methane, acetylene, ethylene, ethane, carbon oxide and carbon dioxide in transformer oil of electric equipment, may help detect various defects, including heat buildup, arc processes, spark and partial discharges and isolation ageing. The received data allow to decide whether the equipment can still be used or should be repaired. An important advantage of this method lies in that the equipment can be tested while in operation. In turn, the timely diagnostics allows to optimize planning and implementation of repair programs and, in the end, decrease expenses for equipment operation. In 2009 the staff of the Saratov branch of IDGC of Volga, JSC carried out more than two thousand chromatographic tests of oil-filled equipment with the voltage ranging from 35 to 220 kV. The diagnostics revealed defects in 6 transformers and 6 leak-proof oil-filled lead-ins, which were repaired. Experts of IDGC of Volga, JSC continue working on improving the effectiveness of chromatographic analysis. The Company plans to introduce devices using the principle of photoacoustic spectroscopy in order to receive more precise and verifiable data.