Research On Heat Dissipation Characteristics Of Voltage Limiting Surge Protector Module

Since the ZnO varistor has the characteristics of non-linearity,fast response,no freewheeling,large current capacity,limited overvoltage and strong energy absorption,the voltage limiting SPD with ZnO varistor as the core is widely used in electric power.Surge protection for systems and information systems.In recent years,there are more and more incidents of short-circuit and ignition of voltage-limiting surge protectors caused by the thermal effect of ZnO varistor.In order to ensure the safe operation of the power distribution system,it is necessary to study the heat dissipation characteristics of SPD.In this paper,the SPD of the 60kA/100 kA class with 8/20?s waveform is taken as an example to study the heat dissipation performance of the SPD module through the combination of heat transfer theory calculation analysis,thermal characteristic test and software simulation.The main conclusions are as follows:(1)The heat transfer process of the SPD module was analyzed by heat transfer theory calculation combined with the power frequency thermal characteristics test.It was found that in the heat transfer process of the SPD module,heat conduction and heat convection play a leading role,which is one order higher than the heat transferred by the heat radiation;The heat transferred by heat conduction is about 3-4 times that of heat convection,which is approximately inversely proportional to the distance between the resistor and the casing.Further comparison experiments were carried out with SPD modules with different pitches.The results show that the smaller the spacing,the faster the SPD module dissipates heat.(2)Single-pulse and multi-pulse impact tests were carried out on different SPDs of two sets of internal parallel structure(two-piece encapsulation),three-piece parallel(single-piece encapsulation),three-piece parallel(two-piece encapsulation),and found that 3 Group SPD can withstand 100 kA single-pulse shock well,and the number of withstands is about 2:1:3.However,under 100 kA multi-pulse impact,only three parallel(double-packaged)SPDs can withstand multiple times.The ability to impact.The temperature of the ZnO varistor of the SPD module at the last impact damage was measured.It was found that the maximum temperature reached 110 °C under multiple pulses and only 52 °C under single pulse,indicating the aging damage of the SPD module under single/multiple pulses.The mechanism is different,and the theory of heat aging is dominant under multi-pulse impact.(3)The ANSYS finite element software was used to simulate the bare ZnO varistor and SPD module with the pitch setting of 0-5mm.Under the same heat generation condition,the larger the distance between the ZnO varistor and the outer casing,the higher the temperature rise of ZnO and the spacing.The temperature rise at 5 mm is 85% higher than the 1 mm pitch and 171% higher than the 0 mm pitch.The SPD module can improve the heat dissipation performance by reducing the distance between the resistor and the casing during the design.Combined with the simulation results of the bare ZnO varistor,the effect is best when the pitch is set at 0-1mm,and the smaller the pitch,the flame retardancy to the outer casing.The higher the requirement.The simulation results were compared with the thermal characteristics test results.It was found that the two were basically consistent,and the correctness of the simulation results was verified.