Theory of the secondary electron avalanche at electrically stressed insulator-vacuum interfaces

Abstract

Several aspects of the secondary emission avalanche along an insulator surface (which is believed to play a role in insulator flashover) are addressed theoretically. The saturation condition for the two extremes of supply-limited and space-charge-limited current are obtained in analytic form, and comparison with the computer simulation of Anderson is made. Also, the effect of a strong magnetic field parallel to the insulator surface and perpendicular to the electric field is analyzed, taking account of the distribution of emission angles. It is found that the critical magnetic field for inhibition of flashover is reduced by a factor of about 2 when the distribution of angles is included in the calculation.

Enhanced flashover strength in polyethylene nanodielectrics by secondary electron emission modification

“…Based on the SEEA model, 5,6 the SEE characteristics of low energy incident electrons, play important roles in SEEA charging, particularly in E 1 . In order to obtain the SEE characteristics of low energy incident electrons in LDPE/Al 2 O 3 nanocomposites, the experimental data were fitted through changing δ m and E p m based on equation (18).…”

“…Many works have been extensively studied the surface flashover phenomena and its related mechanisms. [1][2][3][4][5][6] Typical surface flashover mechanisms, such as secondary electron emission avalanche (SEEA) [7][8][9] and electron triggered polarized relaxation (ETPR), 1,10 have been proposed to clarify the physics of surface flashover. SEEA indicates an electron cascade along the surfaces of the material.…”

Understanding and Improving High Voltage Vacuum Insulators for Microsecond Pulses

“…To our knowledge no one has reported on this mechanism for breakdown. The mechanism of electron avalanche leading to surface flashover from the CTJ is a classically known phenomenon [3], [23] but the notion of a similar mechanism of electron avalanche leading to surface flashover from the ATJ is very new. It is not intuitively obvious why the electrons initiated at the ATJ would not just get absorbed in the neighboring anode and would instead avalanche on the surface of insulator making it to the cathode.…”

“…Cathode initiated surface flashover is thought to be initiated by electrons field emitted from the cathode which strike nearby regions of the insulator with enough energy to eject more electrons, resulting in a net positive surface charge which presumable becomes large enough to draw secondary electrons back to the surface, creating an avalanche of electrons that propagates towards the anode [3]. The prevailing theory explains that by increasing the angle of the insulator, there is a reduced likelihood of an electron emitted from the cathode surface striking the insulator and causing secondary electron emission.…”

Displacement current and surface flashover

“…This deflection is usually assumed to be a result of positive charging of the insulator surface. 2,5 Displacement current may play a similar role in altering the electron trajectories when the rate of change of voltage is sufficiently high, allowing flashover initiation in the absence of a pre-existing surface charge. For a solid cylindrical insulator between parallel plate electrodes, the displacement current during the leading edge of an applied voltage pulse will generate a magnetic field parallel to the insulator surface, which will cause electrons emitted from the surface or the triple junction to be deflected towards the surface (Fig.…”