PD characteristics in PTFE insulated tubular busbar models measured with HFCT and acoustic sensor

Thanks to its large carrying capacity, excellent insulation property and high mechanical strength, PTFE insulated tubular busbar has been used in a broad range of applications in power station that covers the voltage level from 0.4 kV to 220 kV in China. PTFE has been found to be exposed to a great risk of partial discharge (PD) erosion which is generated due to the presence of defect within the insulation. Such a partial discharge activity is rather harmful as it may accelerate the deterioration of PTFE and introduce dielectric breakdown even when the busbar is put into operation for a very short period of time. From the viewpoint of safety, it is necessary to gain a good understanding of partial discharge activity in PTFE insulated tubular busbar. In this paper, tubular busbar models which were established by taping PTFE film on aluminum tubular conductor were employed as test samples. Three kinds of insulation defects were made within the PTFE insulation. By applying AC voltage between the inner conductor and the grounding shield, partial discharge activity was triggered. High frequency current transformer and acoustic sensor were used to capture the discharge signal. Obtained results showed that the signals measured by HFCT exhibited remarkable phase-resolved partial discharge (PRPD) features in response to the each defect type. The PD magnitude was changed as a function of temperature and voltage applied.