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.
Effects of insulator profile on the critical condition of AC arc propagation on ice-covered insulators
The critical conditions of AC arc propagation on the surface of ice accumulated on 2 types of industrial station post insulators are investigated. The effects of the air gap length as well as the insulator length and diameter on the critical arc maintenance conditions were determined and analyzed. The obtained results are essential to complete the mathematical flashover model, developed in our previous work, for its further application to long ice-covered insulators.
FORTE observations of lightning radio‐frequency signatures: Capabilities and basic results
The FORTE satellite, launched on August 29, 1997, carries both radio‐frequency‐receiver and optical (imaging and photometric) payloads for the study of lightning. The radio‐frequency (RF) data for the first 7 months of operation are described, both to illustrate the satellite's capabilities and to explain the basic statistical findings so far. FORTE's multichannel RF trigger system represents a significant advance in space‐based monitoring of lightning emissions. We are able to observe even rather weak and diffuse RF emissions from lightning and are no longer limited to the brightest known events, “transionospheric pulse pairs,” or TIPPs. We do see TIPPs, and we show that the FORTE observations of TIPPs are consistent only with the second pulse's being due to a ground reflection. We find that TIPPs are basically bimodal in character, one type having a steep roll‐off of power from 38 to 130 MHz and the other being essentially flat‐spectrum in that range. The steep‐spectrum TIPPs cluster together in the manner of most RF emissions from lightning, while the flat‐spectrum events tend to maintain a wider spacing (>0.1 s) between recurrent emissions.