Investigation of the Partial Discharges in the High Voltage Measurement Transformers

It is well known the use of on-line partial discharge (PD) measurements as an indicator of stator winding insulation condition. The scheduled PD measurements could be used as a test to evaluate the quality of the equipment. The test results could help to diagnose the insulation problems, call for corresponding action before failure occurs. High voltage transformers are one of the most important elements in an electric power system. Each one of them is affected by various external factors: overvoltage, partial discharge (PD), overheating, vibrations etc., which are created by the strong electric field, thermal effect, humidity, impurities, factory defects, dissolved water and gas in oil type transformer's insulation. These and other factors caused by the environment, reduces the device's exploitation period. This work reviews different contact and non-contact methods, used to evaluate the condition of transformers, by measuring the level of PDs. The selected method of non-contact measurement of electromagnetic waves radiation was used to evaluate voltage transformers status. The experiment was performed at 110 kV substation. Authors discusses efficiency of the selected method to evaluate the voltage transformers insulation condition.