The Impact of Lightning Surge on the Operational Stability of Network Switches

Lightning rods on buildings typically only protect against direct lightning strikes, while the powerful electromagnetic fields and pulse voltages induced by lightning can still threaten the stable operation of network communication equipment. Instantaneous high-voltage lightning surges are often a major cause of instability in network switches. The primary sources of surge voltages in network signal systems include induced lightning strikes, electromagnetic interference (EMI), radio frequency interference, and electrostatic interference. Surges are not solely caused by lightning; they can also occur due to short-circuit faults in power systems or the operation of high-power loads. Given the vast coverage of power grids, a lightning strike hundreds of kilometers away can still generate surges that, after attenuation through substations and other infrastructure, may retain thousands of volts by the time they reach your network equipment. Although such high-voltage surges last only tens to hundreds of microseconds—often insufficient to destroy a network switch—they can cause significant damage to internal components. As this damage accumulates, the stability of the network switch deteriorates.

Therefore, designing high-voltage surge-resistant circuits in network switches is crucial. Beijing Fibridge's industrial network switches incorporate an anti-lightning surge circuit based on varistors, transient voltage suppression (TVS) diodes, and ceramic gas discharge tubes. The entire circuit includes protection for both network ports and power supply circuits. The protective circuit combines TVS diodes, varistors, automotive-grade ceramic gas discharge tubes, and surge suppressors to form a composite circuit, providing comprehensive common-mode and differential-mode protection. This design ensures the instantaneous discharge of high-voltage surges, effectively safeguarding industrial network switches.

In the circuit, varistors are connected in series with ceramic gas discharge tubes to extend service life and ensure safety. The automotive-grade ceramic gas discharge tubes are selected based on the required current-handling capacity. In the power supply section, wire-wound resistors serve for current limiting and voltage division. Multiple high-voltage filtering capacitors (denoted as *C*) connect the power ground to the chassis ground, while decoupling capacitors (denoted as *Y*) are also employed. Resistors (*R*), capacitors (*C*), and diodes (*VD*) form an absorption-clamping circuit for the switching power supply's MOSFET, protecting the chip. This lightning and surge protection circuit has proven highly effective in practical applications.

The lightning protection circuit, based on TVS diodes, varistors, ceramic gas discharge tubes, and automotive-grade surge suppressors, is widely used in Beijing Fibridge's industrial switches. It has demonstrated excellent performance in real-world applications and has successfully passed various domestic and international tests.