The latest research results presented in this paper deals with performance of synthetic air gaseous insulation near the limiting homogeneity. In previous published research [1] numerous tests have been performed to describe the dielectric behavior of strong inhomogeneous arrangements at various gas pressures. Besides that it was of interest if the obtained trends are valid even at higher values of gas pressure, therefore, further investigations were made and results obtained for observed pressures and distances at different level of field homogeneity together with streamer criterion based calculation results are published here. The research had two main targets, breakdown behavior at AC test voltage and breakdown behavior at lightning impulse test voltage. The breakdown behavior at lightning impulse stress shows a certain polarity effect. In opposition to the behavior of SF6 the lowest breakdown values occur at positive polarity of the applied test voltage. The gas pressure was in the range from 0.1 to 0.3 MPa and the electrode distance was in the range from 1 to 9 cm. Used electrode testing configuaration was "tip - bowl". Variously selected test parameters provide different field inhomogeneity (field type).
