Shanghai Chenzhu Instrument CO., LTD.
Shanghai Chenzhu Instrument CO., LTD.

Safeguarding Electrical Systems: The Role and Application of SPD Electrical Devices

May 16 , 2024

SPD electrical device is an indispensable device in the surge protector working principle diagram of lightning protection of electronic equipment. Its role is to run into the power line, the signal transmission line of the instantaneous overvoltage limit in the equipment or system can withstand the voltage range, in order to protect the equipment or system from impact and damage.

Main Function

SPD electrical device is usually a parallel circuit system. When lightning occurs, the metal pipe at the entrance, various building lines to the electromagnetic induction phenomenon, generating a large amount of energy intensity. SPD electrical device will play a role in the current import of each port of the low potential difference with the earth. It is suitable for the requirements of surge protection in the industrial field, with protection modes of relative phase, relative earth, relative center line, center line to earth, and their combinations.

Principle of Operation

  • Switching type: When there is no instantaneous overvoltage, it presents a high impedance, but once it responds to a lightning instantaneous overvoltage, its impedance suddenly changes to a low value, allowing the lightning current to pass through.

  • Voltage-limiting type: High impedance when there is no instantaneous overvoltage, but its impedance decreases with the increase of surge current and voltage, and its current-voltage characteristics are strongly nonlinear.

  • Shunt type: Connected in parallel with the protected equipment, it presents low impedance to the lightning pulse and high impedance to the normal operating frequency.

  • Choke type: Connected in series with the protected equipment, it shows high impedance to lightning impulse and low impedance to normal working frequency.


SPD electrical device is widely used in various electrical systems, including but not limited to industrial, communication, transportation, and other fields. In the industrial field, SPD can ensure the stable operation of production equipment. In the field of communication, SPD protects the communication base station and transmission line from interference and damage. In addition, SPDs also play an important role in transportation, medical, and financial fields.

Future Prospect

With the continuous development of electrical technology, the role of SPD electrical device in the electrical system is becoming more and more important. It can not only protect the equipment from damage, but also improve the stability and reliability of the electrical system. In the future, with the wide application of smart grid, IoT, and other technologies, SPD electrical device will face greater challenges and opportunities. We need to continuously develop new SPD technologies and products to meet the higher requirements of safety, stability and reliability of electrical systems.

In conclusion, SPD electrical device is an important and indispensable part of the electrical system. Understanding its functions and application areas will help us to better understand and use SPD electrical device to provide a strong guarantee for the safe and stable operation of the electrical system.

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