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July 25, 2023

Safe Transmission Distance Of Poe Power Supply? How To Select The Network Cable?

The safe transmission distance of POE power supply is 100 meters, and it is recommended to use Class V all copper network cable.The standard Ethernet cable can be used to transmit DC power for a long distance. Why is the transmission distance limited to 100 meters?


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The fact is that the maximum transmission distance of PoE switch mainly depends on the data transmission distance. When the transmission distance exceeds 100 meters, data delay and packet loss may occur. Therefore, in the actual construction process, the transmission distance should not exceed 100 meters.But now there are some PoE switches whose transmission distance can reach 250 meters to meet the requirements of long-distance power supply. It is also believed that with the development of PoE power supply technology in the near future, the transmission distance will be extended further.


POE IEEE 802.3af standard requires that the output power of the PSE output port is 15.4W or 15.5W, and the received power of the PD device after 100 meters of transmission must not be less than 12.95W. According to the typical current value of 802.3af, which is 350ma, the resistance of the 100 meter network cable must be (15.4-12.95W)/350ma=7 ohms or (15.5-12.95)/350ma=7.29 ohms.


The standard network cable naturally meets this requirement. The IEEE 802.3af poe power supply standard itself is measured by the standard network cable. The reason why POE power supply network cables are required is that many of the network cables on the market are non-standard and not produced in strict accordance with the requirements of standard network cables. The non-standard network cables on the market are mainly made of copper clad steel, copper clad aluminum, copper clad iron, etc. The resistance of these network cables is large, and they are not suitable for POE power supply. POE power supply must use oxygen free copper network cable, namely standard network cable.

PoE power supply technology has high requirements for wire rods. It is recommended that in the monitoring project, the cost of wire rods should not be saved.


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