H. X. Ji, G. M. Ma, C. r. Li, Z. k. Pang and S. s. Zheng, "Influence of voltage waveforms on partial discharge characteristics of protrusion defect in GIS," in IEEE Transactions on Dielectrics and Electrical Insulation, vol. 23, no. 2, pp. 1058-1067, April 2016.
doi: 10.1109/TDEI.2015.005488

The CIGRE WG D1.03 has indicated the breakdown voltage of GIS with protrusion

defect under standard lightning impulse (LI) voltage is significantly smaller than that

under standard switching impulse (SI) or AC voltage, and LI withstand test is more

efficient to find protrusion defect. The question is that whether the partial discharge

(PD) inception voltage of protrusion defect under LI is also lower than that under

standard switching impulse or AC voltage. In order to understand the relations

between voltage waveforms and protrusion defect, three kinds of protrusion with

different curvature radius are designed, namely, 0.025 mm curvature radius, 0.25 mm

curvature radius, and 0.5 mm curvature radius, and the PD characteristics of

protrusion defects are measured under four types of voltage waveforms (standard

lightning impulse, standard switching impulse, oscillating switching impulse (OSI), AC

voltage), and the influence of voltage waveforms on PD characteristics of protrusion is

analyzed. The results indicate that, for protrusion with 0.025 mm curvature radius, the

steeper the impulse voltage front is, the lower PD inception voltage of protrusion defect

is, and PD under LI has higher detection sensitivity to protrusion compared with AC

voltage and SI. While for protrusions with 0.25 mm curvature radius and 0.5 mm

curvature radius, the steeper the impulse voltage front, the higher the PD inception

voltage of protrusion defect is, and PD under LI has lower detection sensitivity of

protrusion with 0.25 mm and 0.5 mm curvature radius compared to AC voltage. As PD

exacerbated, the shape changes occur in the q φ scatter plot , Nφ histogram under

oscillating switching impulse voltage, and q t scatter plot and Nt histogram under

non-oscillating impulse voltage, which can be used as important criterion in assessing

the severity levels of the partial discharge triggered by protrusion under impulse

voltage waveforms.