Research On Electric Field Distribution And Dielectric Response Of HV Bushing

With the rapid development and the expansion of power system, the continuous improvement of equipment capacity, the ageing high voltage bushing of transformer will suffer greater thermal stress and loading, the key factor of stability of power grid is the safe and reliable high voltage bushing, with the frequent accidents of high voltage bushing, there is a big threat to production and operation of the power grid. It is become important and urgent to do something in insulation status of nondestructive testing in a time. Due to the special structure of the high voltage bushing and the particularity of operation, it is difficult to detect insulation condition without the dielectric loss test and partial discharge detection. thus there is a great significance to do research on the electric field distribution and the nondestructive testing of high voltage bushing. It is useful to maintain the safe operation of power grid and the improvement equipment manufacturing.The insulation detection methods of high voltage bushing is introduced, some the diagnosis parameters and the attention of AC/DC test are introduced, The off-line insulation diagnosis of high voltage bushing under power frequency are mainly about measuring capacitance C and dielectric loss tan delta. The capacitance C is a sensitive quantity for the detection of partial breakdowns between foils, but the aging degree of high voltage bushing is impossible to be judged. Some the typical fault of high voltage bushing is introduced, it’s important to make sure the tap of bushing is ground.The bushing subject to a large a.c voltage superimposed on a d.c. bias voltage is a complex insulation system. the Electric field distribution of HVDC bushing is analysis by using ANSYS. the Electric field distribution versus time under polarity reversal and the time to the steady-state and the maximum Electric field of different insulating materials and the electric field distribution along sheds of bushing at different moments are also got. Calculation results show that a polarity reversal operated before a steady DC stage is reached results in a lower electric stress. The maximum electric field distribution along sheds of bushing appear in boundary of different Dielectric. the research results provide scientific basis for bushing designing and Polarity reversal testing.The time domain dielectric response characteristics of HV bushing is Analysis at different temperature. The time domain dielectric response function of HV bushing is calculated by using measurement the data of casing in the IEEE model. Finally measurement data using is analyzed by using the CDM (charge difference method) method and the consequence is compared with the conventional measurement calculation. PDC test duration of3000/3000s seems to be optimal from this analysis, without loosing much accuracy. it is of great help to improve the efficiency of field test.