Strength investigations on long oil gaps

We deal with the electrical strength properties of oil gaps. The investigations were carried out with uniform electrical fields and electrode distances up to 30 mm. Measurements were performed with alternating current (50 Hz), lightning impulses and switching impulses. Such investigations usually have a relative high dispersion of the measurement values. It will be shown that it is possible to minimize the coefficient of variation to values of about 5 to 6 percent.