T501 is the most common antioxidant widely used in transformer oils. Its addition can significantly slow the oxidation rate of the oil

thereby the service life of oil would be prolonged. However

adding excessive antioxidants will affect the electrical performance of the oil

so it is important to accurately determine the content of T501. This article mainly studies the influence of electrolyte type on the T501 test by response surface method(RSM) and square wave voltammetry(SWV)

on the premise of using a three-electrode system and the electrode material has been determined. Then

the most suitable test conditions are chosen. The results show that

the best diameter of the working electrode is 6 mm

the best electrolyte is KOH with a concentration of 0.18 mol/L

and the best organic solvent is ethanol with a water content of 1%. Under this condition

the T501 mass fraction in the transformer oil has a good linear relationship with the peak current Ip

and the standard addition recovery rate is 96.60%～102.20%. The optimized electrolyte solution was used to detect the T501 content in the operating transformer oil

and the measurement results were consistent with those acquired by GB/T 7602.2 liquid chromatography.