For comparing the influence of different types of impulse currents on DC aging of Zinc oxide (ZnO) varistors

the same type of Zinc oxide varistor samples are used to carry out 2 ms square wave (peak at 2 kA) withstand test and 4/10 μs impulse current (The peak value is 100 kA) test. The experimental results show that under the impulse withstand of 1-3 rounds (3-9 times)

the 2 ms square wave has a definite optimization on the aging characteristics of the ZnO varistor. While

the high current impulse at 4/10 μs keeps the ZnO varistor’s aging characteristics continue to deteriorate. The scanning electron microscope (SEM)

spectrometer

digital source meter are used to study its microstructure and electrical performance parameter changes. The reason is analyzed in combination with the experimental results

the damage degree of the 4/10 μs impulse current to the ZnO varistor is greater than that of the 2 ms square wave impulse current

which is more likely to cause the aging of ZnO varistor. Under the 2 ms square wave withstand for 1-3 rounds (3-9 times)

the aging characteristics of varistors can be improved. The reason is that the thermal effect due to impulse current makes the interstitiated Zinc ion

which is a metastable component of the grain boundary barrier

react in the grain boundary and reduce its concentration

and obtain a more stable grain boundary junction than before the impact

thus improving its aging characteristics.