To solve the problem of distribution network fault line selection caused by too few frequency components and no high amplitude low frequency components in the characteristic frequency band of transient zero sequence current, an improved ensemble empirical mode decomposition (MEEMD) method is proposed. Firstly, the influence of distributed generation on line zero sequence current was considered; then, the zero sequence current after fault was decomposed into multiple frequency signals according to frequency by meemd, and the eigenmode function was obtained and the highest frequency component is extracted; finally, the line selection result was obtained by analyzing the signal waveform of the highest frequency. The basic signal was not needed in this process, so the characteristics of the obtained signal were closer to the original signal. The process of fault line selection based on meemd was described in detail, and the influence of multi scene distribution network considering distributed generation on fault line selection is discussed. The simulation results show that the method can effectively improve the accuracy of fault line selection.

Sulfur was removed from diesel oil by using the ultrasonic oxidation process to reduce the sulfur content in diesel fuel. The effect of different oxidation temperature, oxidation time, oxidant dosage and catalyst dosage on diesel desulfurization were studied by experiments. Experimental results showed that using the formic acid mixture with sulfuric acid as catalyst, catalyst amount 2% (the volume ratio of formic acid and sulfuric acid in the catalyst was 3∶2), oxidant amount 9%, reaction temperature 70 ℃, reaction time 60 min, removing the sulfur in heavy oil catalytic cracking diesel oil by using ultrasonic oxidation, then through DMF extraction and oxidation, the diesel oil desulfurization rate could reach 83%， And cetane value was increasing, thus the quality of diesel oil was refined.