Negative DC corona patterns for different wire particle geometries in air insulation

This work deals with an investigation of negative corona discharge generated from standing wire particles in air insulation. Eight samples from different particle lengths and diameters were studied to understand the effect of particle geometries on discharge characteristics. The particle was stood artificially on the ground inside parallel plane electrodes and was energized with a positive HVDC generator. Pulse sequence analysis (PSA) technique was used to evaluate the corona discharge patterns and behaviors. Under the same applied voltage, it is concluded that an increase in particle length causes a rising trend on the average discharge current and pulse magnitude, as well as the pulses appear more frequent and fluctuate. Meanwhile, variation of the particle diameter shows that a larger particle size generates fewer pulses and a lower average discharge current. However, the pulse magnitude is higher and appears randomly with larger particle diameter. A simulation model based on Finite Element Method (FEM) was also established to explain the behaviors better. It is found that the pulse repetition rate is related to the electric field distribution and negative ions movement, while the pulse magnitude is related to ionization rate and positive ions velocity.