A calculation model for breakdown time delay and jitter of gas switches under hundred-nanosecond pulses and its application in a self-triggered pre-ionized switch

Abstract

In this paper, a calculation model for the breakdown time delay and jitter of gas switches under hundred-nanosecond pulses is proposed and applied in a self-triggered pre-ionized switch. The effects of injection time of pre-ionization, pulse rise time, and the pre-ionization jitter are discussed and verified through experiments. It indicates that the pre-ionization should be injected when the electric field is high enough in the gap, injection after 80% peak-time can ensure its effectiveness. Then the statistical time delay jitter will be determined by the pre-ionization jitter, which is an intrinsic restriction of the self-triggered switch. However, when the changing rate of the pulsed electric field exceeds a certain value, the breakdown time delay jitter can be partly offset in the formative stage because the formative time delay has an exponential relationship with the electric field. Therefore, lower time jitter can be obtained under pulses with a shorter pulse rise time. In general, the results of the calculation model agree with the experimental results, and the experimental parameters which lead to a low jitter can also be used as a reference.

A low-jitter self-triggered spark-discharge pre-ionization switch: primary research on its breakdown characteristics and working mechanisms

“…Because initial electrons are supposed to be generated through photoemission [12] with low efficiency of no more than 1/100 [16], and FWHM of the UV-illumination generated by trigger gap discharge is generally less than 15 ns [12], the triggering time, which is determined by the voltage division ratio between the main gap and trigger gap, must be adjusted carefully. Figure 1(b) indicates that the effectiveness of UV-illumination varies dramatically as the ratio changes [17,18]. The time jitter increases as the ratio decreases (earlier triggering time), and the switch might fail to break down at the front edge, which seriously threatens the insulation.…”

“…The time jitter increases as the ratio decreases (earlier triggering time), and the switch might fail to break down at the front edge, which seriously threatens the insulation. Besides, larger time jitter of the trigger gap under a larger voltage division ratio might also restrict the time jitter [18]. It needs a large number of trials to determine an optimized ratio.…”

Comparative study of pulsed breakdown processes and mechanisms in self-triggered four-electrode pre-ionized switches

“…On the one hand, trigger electrodes are protected from the erosion caused by the main gap discharge current [23]. On the other hand, charged particles in the trigger gap arcing channel cannot drift out [21]. The UV radiation generated by the trigger gap discharge is believed to be the dominant source of initial electrons under this configuration, so the switch is called a UV-illuminated switch, briefly denoted as SW1 [24].…”

“…Though it is known that in nitrogen the switch jitter is mainly determined by the time coordination of trigger gap and main gap discharges [19], and the energy of ultraviolet (UV) photons generated by the triggering spark discharge is 3.1-3.9 eV [20], the generation mechanisms of initial electrons and the breakdown processes of two sub main gaps are still unclear. We have analyzed the pre-ionization mechanisms of selftriggered four-electrode switches under two typical configurations with different electric field distributions [21,22] and speculated that the photoemission at the cathode is the main source of initial electrons, but direct evidence is still missing. Therefore, in this work, the breakdown processes of the main gaps in the two self-triggered four-electrode switches [21,22] are studied through an intensified charge coupled device (ICCD) camera, and the pre-ionization mechanisms are further analyzed.…”

“…We have analyzed the pre-ionization mechanisms of selftriggered four-electrode switches under two typical configurations with different electric field distributions [21,22] and speculated that the photoemission at the cathode is the main source of initial electrons, but direct evidence is still missing. Therefore, in this work, the breakdown processes of the main gaps in the two self-triggered four-electrode switches [21,22] are studied through an intensified charge coupled device (ICCD) camera, and the pre-ionization mechanisms are further analyzed.…”