Maximum Safety in Surge Protection


SPD/MOV is the Victim of Temporary Overvoltage (TOV)


SPDs not properly designed or incorrectly used and unprotected MOVs may go into thermal runaway, resulting in short circuit, overheating, smoke and potentially fire hazard due to:


  • End of life
  • Sustained abnormal overvoltage / Temporary Overvoltage (TOV)
  • Surge with unexpected energy


MOV or SPD are protectors of Transient Overvoltage (or surge) but victims of Temporary Overvoltage.



Temporary Overvoltage VS Transient Overvoltage

Temporary Overvoltage (TOV)

 Transient Overvoltage

Caused by LV/HV-system faults  lightning or switching overvoltage
Duration Long

millisecond to a few minutes

or hours


Microseconds (lightning)  or

millisecond (switching)

MOV status Thermal runaway  Self-recovery

TOV is more destructive to SPD as its duration is much longer

Temporary Overvoltage is Common

TOV is a very common problem in power quality (ProSurge Thailand)
By Sun Electric and Supply Co.,Ltd.
31-33 ซ.พิพัฒนา1 ถ.สุขุมวิท ต.ศรีราชา อ.ศรีราชา จ.ชลบุรี 20110
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