Performance of Surge Protection Device (SPD)

Normally, people pay a lot of attention on the performance of a surge protection device (SPD) like its surge capacity. Surge capacity is indeed very important. There are too many surge protection devices (SPDs) on the market can not meet the surge capacity it proclaimed. Here is a picture and video of a SPD that exploded at surge current test (Imax 40kA):

low quality surge protection device exploded

Safety of Surge Protection Device (SPD)

Yet few attention is paid on the safety of a surge protection device. However, bad designed SPD can be extremely dangerous and is one of the major causes for fire hazard. Below is some burnt SPD pictures:

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.

MOV Burnt Under Temporary Overvoltage (TOV)

MOV Burnt Under Temporary Overvoltage (TOV)

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

Surge Protection Device Safety Solution – TPAE Technology

Prosurge has developed TPAE (Thermally Protected Arc Extinguishing) technology to solve the safety problem of SPD and we’ve got this technology patented in USA, Germany, Korea and China.

Patent in USA

Patent in Germany

Patent in Korea

Patent in China

Based on TPAE technology, we have developed our key SPD component – SMTMOV and PTMOV.


TPMOV - Thermally Protected MOV


You can see how our product stay safe in a sustained overvoltage situtation while our competitor’s product burnt.

At 415Vac temporary overvoltage, our SMTMOV with TAPE technology cuts itself off this abnormal condition and stays safe

At 415Vac temporary overvoltage, SPD component without TPAE technology burnt badly.

In below test, the two SPDs are tested under TOV(transient overvoltage). See how the result differs for SPD with TPAE protection and  SPD without TPAE protection:

With Prosurge patented TPAE technology, the SPD is fail-safe and self-protected.

Without arc extinguished device, the SPD causes smoke and fire, which will be dangerous to the circuit.

Maximum Safety in Surge Protection

Thermally Protected MOV

AC DIN-rail Surge Protection Device

DC DIN-rail Surge Protection Device

UL 1449 Panel Surge Protection Device