Experimental research of disconnector under large power frequency current

Research experiment has been carried out to SPD disconnector for its performance under power frequency large current (the low temperature soldering machine is the disconnecting mode for the SPD), and it is found: 1) When the current reaches 50A, varistor chip will be short-circuited prior to the activation of disconnector, and when the current reaches 300A, 100% probability of occurrence; 2) Once the varistor chip is short-circuited first, the success rate for disconnector to disconnect is greatly reduced; 3) For short circuit of varistor chip, flashing is an important cause of greatly reduced success rate; 4) When the current reaches 300A, varistor chip can withstand 28ms averagely before being short-circuited; 5) Within the above-mentioned withstand period of time, the opening time, closing time and on-time of varistor chip under different currents maintain high consistency, remaining relatively stable in the power frequency half-wave the one just before varistor chip short-circuited. Finally, if the low temperature solder mechanical separation method is applied to the protected circuit which has the greater prospective short-circuit current, the technical problems of varistor short-circuited need to be solved, thus, the technical thought that enhancing the safety of SPD under power frequency overvoltage by adopting overvoltage detection and control contact on-off is put forward.