Repeated Impulses’ Influence On Energy Matching Between Gas Discharge Tube And TVS

Residual voltage can be effectively reduced by using Double Signal Surge Protector-GDT (Gas Discharge Tubes) combined with TVS (Transient Voltage Suppressor), thus lessening disturbance and even damage to electronic devices from lightening. But the Impulse Sparkover Voltage of GDT will become unstable after repeated over-voltage impulses, and then leading to unfitness in the Double Signal Surge Protector, as a result, its protective effect will be affected.Based on the consideration that repeated impulses and AC (Alternating Current) aging can impact the Impulse Sparkover Voltage of GDT, we discussed the accumulation and dispersion of GDT’s surface charges. Based on the Charge Accumulation Theory, and with the usage of AC & DC (Direct Current) thermal stability instrument, we simulated the GDT’s AC and impulses ageing environment, and analyzed the resulting data with statistical software. The results showed that after long-time AC influence, the accumulated surface charges on the surface of GDT were quite fewand impulse sparkover voltage remain stable on the whole.Aiming at the GDT surface coarseness’influence on impulse sparkover voltage, and based on the theoretical model SEEA (Secondary Electron Emission Avalanche), different pieces of abrasive paper were used to roughen the overall or partially surface of GDTs. Then with the usage of the finite element simulation software Maxwell-2D, surface electric field intensity distribution were shown under different time impulses on GDTs with different surface coarseness. The results showed:the accumulated surface charges are relatively less if only under numerous impulses, and is not capable to influence the stability of impulse sparkover voltage. However, repeated impulses can roughen the surface of GDT, and in turn affect the accumulation of surface charges. Surface charges can distort the electric field and then change impulse sparkover voltage. The coarser the surface of GDT, the more influence the impulse sparkover voltage bear. When the rough surface is partial, obvious fluctuation of impulse sparkover voltage can be observed.Aiming at the influence of repeated impulses on the cooperation of 2-leveled signal surge protector,10 decoupling resistor with different resistence were chosen for the connection of GDT and TVS in the 2-leveled signal surge protector. Then the open circuit voltage wave (1.2/50μs), the 8/20μs lightning impulse platform and the double wave (1.2/50μs,8/20μs) were used in the impulse experiments. The results showed that when the resistence of decoupling resistor is increased from 2Ω to 4Ω, influences from repeated impulses can be effectively weakened. Moreover, with the implementation of the network analyzer, insertion loss is measured, and within the prescribed transmission bands, the 2-leveled signal surge protector still has preferable transmission characteristic with a 4Ω decoupling resistor.