The pressure-sensitive resistance overheat protection technology has the following:  
(1) Hot melt fuse technology. The technique is to mount the low melting point metal with wax protection to the pressure sensitive resistance by a certain process, and when the pressure sensitive power leakage current is too large, the temperature is raised to a certain extent, the low melting point metal is blown, thereby using the pressure sensitive resistance from Remove in the circuit, effectively prevents the pressure sensitive resistance from raising the fire. However, there is a reliability problem in hot melt fuses, and only about 5 years of reliable life in the enhanced thermal cycle. In a thermal cycle, the hot melt fuse requires regular replacement to maintain normal operation.  
(2) Use the spring to pull the low melting point solder technology. This technology is currently the technology used by the vulnerability-based SPD, which increases a low-melting point solder welding point at the pin of the pressure sensitive resistance, and then uses a spring to pull this welding point, in When the pressure-sensitive electrometric leakage current is too large, when the temperature is raised to a certain extent, the soldering point is fed, and the solder joint is rapidly separated under the tension of the spring, thereby resection of the pressure sensitive resistance from the circuit, and the alarm contact is issued. Alarm signal. Since the low melting point metal flows and produces a crack in the stress point, the solder of low-melting solder joints in the spring tension will also flow and produce cracks, so the biggest problem with such devices is to be solder, resulting in unhabited devices. open.  
(3) Temperature fuse technology. The technique is arranged together with the pressure sensitive resistance and the temperature fuse, and the heat conduction will use the heat conduction to conduct the heat transfer temperature fuse generated on the pressure sensitive resistance. When the temperature is raised to the temperature fuse, the temperature fuse blows, The pressure sensitive resistance is removed from the circuit. In addition to the problem of the same life and reliability, the temperature fuse is used to overheat the pressure-sensitive resistance to heat the pressure sensitive resistance: the heat transfer path is long, the response speed is too slow, and the heat is through a certain heat transfer medium (filler material), The temperature fuse housing, the internal filling material of the temperature fuse, and then transmitted to the melt of temperature insurance, thereby determining the response speed of the temperature fuse.  
(4) Isolation technology. This technique is mounted in a closed cassette, isolated with other circuits, preventing the spread of pressure sensitive electric resistance smoke and flame. In the case of various backup protection, the isolation technology is not a simple and effective way, but it is necessary to take a large equipment space, but also prevent smoke and flame from opening from the casual leads. come out.  
(5) Potting technology. In order to prevent the pressure sensitive resistance to smoke, fire and explosion, some vendors use this technology to block the pressure resistance resistor, but because the pressure sensitive resistors are scaled inside, there will be racing, resulting in the failure of the sealing material, and produces Carbon, carbon production will cause the arc to be maintained, so it is often caused by short circuit and smoked black, and even causes the entire equipment room to be severely smoked.  
Experiments show that after the pressure sensitive electrical resistant sleeve heat shrinkable, since the heat dissipation of the pressure sensitive resistance is affected, the maximum dissipation power is lowered, which affects the power-frequency voltage tolerant resistance of the varistor, from another angle, The heat dissipation is also accelerated to accelerate the aging of the pressure sensitive resistance, affecting the life of the pressure sensitive resistance.