Hochspannungstechnik

Dielectric breakdown of epoxy-based composites: relative influence of physical and chemical aging

“…Beyer et al [22] and then Dissado et al [1] suggested that this phenomenon could also be induced by the electric field.…”

Circuit simulation of electrical breakdown in air using Kind's equal-area criterion

“…For convenience of calculations, the concept of the relative area of the volt-time characteristic A s is used. Table 1 [13] shows the values of A s for some electrode configurations. Using expression (1), it is possible to construct a simplified model for calculating the breakdown time of an air gap when an impulse voltage is applied.…”

SF6 high voltage circuit breaker contact systems under lightning impulse and very fast transient voltage stress

“…A microscopic electric field of 1 MV/cm [4] up to 10 MV/cm [9] has to be present in order to enable this process. Such field stress can be reached at the electrode surface even in low inhomogeneous field configurations due to small surface defects or electrode roughness.…”

“…6 A breakdown in the gas gap between two contacts with a homogeneous (or slightly inhomogeneous) electric field distribution can occur (necessary condition) if the critical electric field strength (E/p) crit is exceeded in some places and if the streamer criterion is fulfilled [4]. For typical filling pressures of gas insulated switchgear (p fill = 0.4-0.6 MPa (4-6 bar)), the streamer criterion is fulfilled on very short lengths of a few 100 µm or lower in the frequent case, where electrode roughness determines the breakdown voltage [4,5]. Therefore, a simpler and more practical criterion is often used for SF 6 gas circuit breaker design: the maximal macroscopic field strength E max on an electrode surface.…”