Most of the reasons for communication interruptions caused by lightning strikes and surges are not the lack of protective devices, but the wrong selection of protection points and the lack of energy coordination between levels. This article summarizes the general design ideas: first find the intrusion path, then do classification and coordination, and finally come to selection and verification.

Determine three types of protection points according to the intrusion path

There are usually three ways for surges to enter equipment: power lines, along outdoor signal lines, and ground potential rise through grounding conductors. The three types of disposal methods are different. The power port relies on a surge protector and isolation transformer. The signal port relies on a combination of gas discharge tube, varistor and TVS. The ground potential rise requires equipotential connection to reduce the potential difference between the two ends to the range that the equipment can withstand. Drawing protection as a path map is more effective than adding devices port by port.

The core of hierarchical protection is energy coordination

The line entry device is responsible for discharging most of the energy and limiting the residual voltage to several thousand volts; the equipment port device is responsible for reducing the residual overvoltage to a level that the chip can withstand. The wire inductance between the two levels itself participates in decoupling. It is generally recommended to keep a cable length of more than 5 m between the entrance device and the port device. If the length is insufficient, decoupling components must be supplemented. When selecting a model, first estimate the flow capacity based on local thunderstorm days and line length, and then check the residual voltage and response time in the data sheet. Do not just look at one indicator.

Optoelectronic Demarcation and Selection Checklist

The optical fiber medium itself does not conduct lightning current. Replacing long-distance copper cables with optical cables is a common method to reduce the risk of intrusion. However, the metal reinforcement core and armor in the optical cable are still conductive paths, and the entrance section must be grounded or insulated. Data links can use photoelectric conversion to shorten the metal section, and the isolated optical transceiver in the outdoor terminal box can also cut off the potential difference between the two places at the same time. Before finalizing the plan, it is recommended to pressCommunication transformation plan for electric power and new energy stations and Security video surveillance fiber optic transmission solutionThe general structure checks four items: protection device parameters and backup fuses, port residual voltage, photoelectric boundary position, and ground conductor cross-section.

The goal of reliability design is not to select the maximum specifications for each stage of devices, but to allow energy to be discharged at the correct level. If you can answer three questions during the review—where the lightning current comes in, at which level it is cut off, and how much the equipment port ultimately withstands—the protective structure is basically formed. EB-LINK can help organize this route table by point category during the planning stage, reducing temporary changes during the construction stage.