Triggered breakdown time-lags of transformer oil subjected to uniform power frequency fields

In this paper we report some of the results obtained in a study of triggered breakdown in technical grade transformer oil. The gap studied consisted of two brass hemispheres of 12 cm diameter with the gap axis mounted horizontally in an oil tank. One of these electrodes was connected to a 60 Hz high voltage transformer, the other was permanently grounded and contained within it a 1.5 mm diameter tungsten rod set in a 3.2 mm diameter hole to form a trigger gap of approximately 0.85 mm. The tip of the trigger pin was mounted flush with the hemispherical surface. Figure 1 shows a simplified diagram of the trigger circuit. Additional circuitry permitted firing the trigger circuit at any phase position of the 60 Hz voltage applied to the main.