Breakdown measurements

Tayek JA, Herber D, Chlebowski RT. 1987. Effect of hydrazine sulphate on whole-body protein breakdown measured by " C-lysine metabolism in lung cancer patients. The Lancet 241-244. 

Samples used for dielectric breakdown measurements were not metallized. These films were placed between a copper plate and a 6.4 mm steel ball as electrodes.The voltage source was a Bertan Model 205A-10R Power supply driven by a ramp generator at 200 V/s. 

Dielectric Breakdown Measurements. The dielectric breakdown strength was measured on the freely standing BCB-2 films as described above. The breakdown strength was 2.5 x 10 v/cm for 22 mm thick films. This value is -50% of the breakdown strength measured for 1.5 mm polyimide films on Si (8). However, the breakdown strength does not vary proportionally to the film thickness. The breakdown strength was also measured for 1.7 mm BCB-2 films deposited on a Si substrate. The value obtained from this measurement was 4.0 x 106 v/cm. The latter value was much closer to breakdown strengths observed in polyimide films of comparable thickness. 

Dielectric breakdown measures the abihty of rigid insulating materials to resist breakdown parallel to the laminations (or in the plane of the material) when subjected to extremely high voltages at standard AC power frequencies of 50 to 60 Hz (see Fig. 8.18). As with electric... 

Figure 28 Coaxial setup for breakdown measurements. (Redrawn from Proud, J.M., 1976 Annu. Rep. Conf. Electr. Insul. Diel. Phenom., NAS, Washington, D.C., 1976.)...

Figure 30 Coaxial setup for breakdown measurements. (Redrawn from Fuhr, ]., Schmidt, W.F., and Sato, S., /. Appl Phys., 59, 3694, 1986.)...

In experiments with voltage pulses, the impedance matching of cable and test cell is of great importance in order to avoid voltage reflections (Arii et al, 1979). A test cell used for time lag to breakdown measurements and a typical oscilloscopic trace obtained are shown in Figure 46. 

Figure 46 Time lag to breakdown measurement test cell and oscilloscopic trace. (Redrawn from Arii, K., Kitani, L, and Kawamura, M., /. Phys. D Appl Phys, 12, 787,1979.)...

Haidara and Denat (1991) investigated the onset of partial discharge pulses in a test cell with 50 D impedance consisting of a fine tip as cathode and a plane metal disk as anode. By comparing the threshold voltage in the vapor and in the liquid they were able to estimate values for a in the liquid phase as a function of applied field. Their data and for comparison the ionization rates reported for silicon are included in Figure 1. A crude estimation of a in liquid n-hexane obtained from time lag to breakdown measurements with thin liquid layers by Arii et al. (1979) is also included. 

The electric breakdown of a dielectric liquid under high electric stress is a complex phenomenon where many elementary processes contribute to the change of the electrical current through the test gap from values of pico- to nano-amperes to values of kilo-amperes on a time scale of nanoseconds. Electronic processes are always involved in the initiation of the electric breakdown of nonpolar dielectric liquids. Unambiguous experimental evidence is scarce in the literature since a multitude of other effects obscures the electronic contribution of the breakdown process. In addition, many breakdown tests were performed on industrial-grade liquids, such as transformer oil etc., which are not pure liquids but rather mixtures of several components. More unambiguous information on electronic processes can be obtained from breakdown measurements with impulse voltages of nanosecond to microsecond duration. Complementary are studies of the laser-induced breakdown. 

It was pointed out that measurements of laser-induced breakdown suffer from the same artifacts as DC-breakdown measurements. Impurities of low ionization energy, submicroscopic particles (dust or ice), and microscopic gas bubbles may serve as centers for the initiation of the breakdown process and mask the development of a pure avalanche breakdown (Brueck and Kildal, 1981). Subsequent investigations on the optical breakdown of liquid helium (Abrikosova and Anshukov, 1973 ... 

Fig, 9.7. Electrode arrangements for (a) dielectric strength (field perpendicular) and (b) dielectric breakdown measurements (field parallel). 

For a description of dielectric breakdown measurements and interpretation, although for soft elastomers, we refer to the work by Carpi et al. (2015). 

McLeod, A.R., 1987, Water breakdown measurements of stainless steel and aluminum alloys for long charging times, 1987 Pulsed Power Conference. 

There has been much speculation as to whether current increase in conduction or breakdown measurements can be attributed to... 

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