Breakdown voltage reliability improvement in gas-discharge tube surge protectors employing graphite field emitters

Abstract

Gas-discharge tube (GDT) surge protectors are known for many decades as passive units used in low-voltage telecom networks for protection of electrical components from transient over-voltages (discharging) such as lightning. Unreliability of the mean turn-on DC breakdown voltage and the run-to-run variability has been overcome successfully in the past by adding, for example, a radioactive source inside the tube. Radioisotopes provide a constant low level of free electrons, which trigger the breakdown. In the last decades, any concept using environmentally harmful compounds is not acceptable anymore and new solutions were searched. In our application, a cold field electron emitter source is used as the trigger for the gas discharge but with no activating compound on the two main electrodes. The patent literature describes in details the implementation of the so-called trigger wires (auxiliary electrodes) made of graphite, placed in between the two main electrodes, but no physical explanation has been given yet. We present experimental results, which show that stable cold field electron emission current in the high vacuum range originating from the nano-structured edge of the graphite layer is well correlated to the stable breakdown voltage of the GDT surge protector filled with a mixture of clean gases. V C 2012 American Institute of Physics.

Development of a simple quantitative test for lack of field emission orthodoxy

“…Žumer et al [44] consider that gas breakdown is initiated/stimulated by CFE from the edge of graphite platelets used in the device; obviously, the test result here supports this proposition.…”

“…Test 24 is particularly interesting because it relates to a large-scale electrical engineering device, namely a gas-discharge tube surge protector (used, for example, to protect telecommunication circuits from lightning strikes). Žumer et al [44] consider that gas breakdown is initiated/stimulated by CFE from the edge of graphite platelets used in the device; obviously, the test result here supports this proposition.…”

Experimental Study on The Performance of External Open-Circuit Failure Gas Discharge Tubes under Power-Frequency Follow Currents

“…It normally functions in the first stage of the signal multistage line protection, discharging the lightning transient over-currents and limiting overvoltages. By offering high insulation resistance and very low parasitic capacitance, it shows a superior performance in the lightning protection of high-frequency signal lines [1][2][3][4][5]. But it should also be noted that the response time of switching components may have long response times in the case of low-frequency (slow-front) transient overvoltages [6,7].…”

Reliability improvement of gas discharge tube by suppressing the formation of short-circuit pathways

“…When the protection terminal voltage is lower than its nominal breakdown voltage, the GDT is in a high-impedance state. Under the action of transient overvoltage, the inert gas inside the GDT breaks down to form a plasma channel, which short-circuits the system, thus providing an energy release path to the ground to protect the system [3][4][5][6]. However, engineering operational experience indicates that the insulation performance of a GDT generally declines after cumulative discharges, thus reducing the protection level provided and eventually nullifying the protection altogether.…”