Modelling and experimental verification of barrier effect on breakdown voltage of transformer oil using Box-Behnken Design

Barriers play an important role in enhancing the dielectric strength of the transformer insulating oil since they block the contaminated particle movement and prevent space charge formations that incept the oil breakdown. The effect of barrier factors (gap space (d), the barrier location relative to the high voltage electrode (a/d) %, and the barrier diameter (D)) was demonstrated concerning the insulation performance of the transformer oil for a hemisphere-hemisphere gap under AC voltage. The breakdown voltage (V-BD) prediction due to the barrier effect was developed to cut the experiments cost. The Box-Behnken Design (BBD) mathematical model was developed with only 15 experiment runs that were enough to build the relationship between (d, (a/d) %, and D) and V-BD. The optimal values of d, (a/d) %, and D that achieved the highest value of V-BD was provided. The optimal values of (d), (a/d) %, and (D) were 3 cm, 25% and 10 cm respectively that gave the highest value of the V-BD 106.87 kV. In this study, The BBD mathematical model was used and compared with a central composite face (CCF) model. The results indicated that the mathematical model using BBD gave minimum prediction errors compared with CCF model. (C) 2019 Elsevier Ltd. All rights reserved.