Feasibility analysis of reduced-scale air breakdown tests in high voltage laboratories combined with the use of scaled test cages

Breakdown and corona extra- and ultra-high voltage tests are expensive, time-consuming and require large and extremely costly high-voltage halls, of which there are very few worldwide. Some of these limiting requirements may be minimized by using test cages and by applying reduced-scale tests. In this work the feasibility of performing breakdown reduced-scale tests combined with the use of test cages is analyzed. For this purpose a three-dimensional finite elements based methodology is introduced to determine the geometric dimensions of the test cage in order to adjust the test voltage according to the allowable output voltage of a conventional high-voltage laboratory. To validate the findings of this work, breakdown tests of a full-scale 500 kVRMS substation connector and a 1:3 reduced-scale model using test cages are conducted in a high-voltage laboratory, which maximum allowable output voltage is of 125 kVRMS. Results from this work show that by using appropriately designed test cages and scaled versions of the test samples the results may be scaled with high accuracy.