MODELING AC ARC RE-IGNITION CONDITIONS ON ICE -COVERED INSULATORS USING ARTIFICIAL NEURAL NETWORKS
The propagation of local arcs are necessary for a flashover to occur on an ice-covered insulator. It was supposed that the local AC arc extended when it satisfied the arc re-ignition conditions. In this paper an attempt has been made to model Va = f ( I , L , x ) for estimating the arc re-ignition conditions as function of leakage current and insulator length using multi-layer feed-forward neural network with back propagation technique. Once trained with experimental results taken from the CIGELE model , the proposed ANN model is then capable of predicting arc maintenance voltage , under any given set of leakage current and insulator length. With the use of the optimized ANN parameters , a prediction accuracy with a %MAE of 2.85% was achieved.
Propagation of ac and dc arcs on ice surfaces
Using a high-speed camera, the fundamental behavior of arcs on ice surfaces, including propagation velocity and root radii were studied under both ac and dc voltages. It was found that the arc may propagate randomly inside or outside of the ice with a relatively low velocity before the critical length is reached, and then at a much higher velocity. Moreover, the relationship between the radius of the arc root and leakage current was determined. The results obtained allowed us to improve our previous model dealing with insulators. There is a good concordance between the critical flashover voltage of ice-covered insulators calculated from the model and laboratory results.
A Study of Corona Discharges at Water Drops Over the Freezing Temperature Range
Foul weather corona have been observed to behave differently at temperatures above and below the freezing point1.2. Generally speaking, the discharge activities are much more intensive at temperatures above than below the freezing point. Such behaviour of the discharge is so far associated with the differences in the physical properties of water in its liquid and solid phases. No detailed study has, however, been made to correlate the discharges characteristics with the macroscopic changes in the water drop over the freezing temperatures range. In the present study, the development of corona discharge at a watet drop in a cylindrical field was investigated during its transition from the liquid to solid phase. This was done by correlating the discharge current with variations of the water drop temperature. The results obtained show that the noise generation and energy losses are related to both the corona discharges in the surrounding air and to the continuously changing conditions at the water drop during its transition into ice (and vice versa).