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Basic concepts of lightning protection countermeasures


Shared grounding

Shared grounding   A proper protective device is attached to each equipment interface, and the ground is shared. If there is a lightning arrester for each interface, or the arrester elements have separate grounds, there is a danger that an electropotential difference will be generated between the grounds, and that the equipment may be damaged.

Bypass method (earth-free method)

Bypass method (earth-free method)   A proper protective device (operating at a lower withstand voltage than that between the interfaces) is attached to each equipment interface so that lightning is diverted by the protective devices and does not pass through the internal circuitry of the equipment. Since no grounds are needed, this method is effective for use in ordinary houses, where it would be difficult to lay grounds.

Insulation method

Insulation method   A lightning-proof transformer is used to electrically isolate the power supply system. Lightning is prevented from passing through the internal circuitry of the equipment. In the protection of communications systems, protective devices and communications insulation transformers are installed, and optical fiber used.

Isolation resistance

Isolation resistance   When the grounds cannot be shared, an incoming lightning surge will create an electropotential difference among the grounds and damage the equipment. To avoid this, an earth balancer or similar can be connected among the grounds so that an equal electropotential is generated in the event of a lightning surge.

Lightning protection


Lightning rod (air termination section) angle of protection

The relationship between impulse and DC spark-over voltage

Withstand voltage of communications equipment

●Basic concepts of lightning protection countermeasures

Installation locations of protective devices

Comparison of lightning-proof transformers and power supply protective devices

Equipment withstand voltage damage

Methods of wiring protective devices


How lightning enters

The effect of lightning

Lightning protection related standards

Lightning damage and the human body

Arrester follow current

Operating principles of protective devices (when compared to water…)

Methods of protecting telecommunications equipment

Electropotential (voltage)