Abstract
We performed corona investigation of ungrounded conducting framework upon applying impulse voltage. Corona images from the framework were observed using a camera with an image-intensifier. Coronas from the edges of the investigated frameworks were observed at a wave front of applied voltage and they developed with increasing applied voltage. However，in the case of the cubic framework with beams corona onset voltage was higher than that for the simple cubic framework. In addition，the corona extension was also greater，than that for the simple cubic model. The difference on corona extension behavior between two frameworks should be associated with the effect by the space charges near the framework by the corona in earlier stage. Corona behavior and current behavior were depending on the grounding resistance. Especially，in decreasing grounding resistance a wave front duration of current became longer. The corona behavior might be affected by the changing the current form.
