The safe transmission distance of POE power supply is 100 meters, and it is recommended to use Cat 5e copper network cable. It is possible to transmit DC power with a standard Ethernet cable for a long distance, so why is the transmission distance limited to 100 meters?
The fact is that the maximum transmission distance of a PoE switch mainly depends on the data transmission distance. When the transmission distance exceeds 100 meters, data delay and packet loss may occur. Therefore, the transmission distance should not exceed 100 meters in the actual construction process.

However, there are already some PoE switches that have a transmission distance of up to 250 meters, which is sufficient for 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 farther.

The 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 be no less than 12.95W. According to the 802.3af typical current value of 350ma, the resistance of the 100-meter network cable must be It is (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 only reason for the problem of POE power supply network cable requirements is that many network cables on the market are non-standard network cables and are not produced in strict accordance with the requirements of standard network cables. The non-standard network cable materials on the market mainly include copper-clad steel, copper-clad aluminum, copper-clad iron, etc. These cables have large resistance values and are not suitable for POE power supply. POE power supply must use a network cable made of oxygen-free copper, that is, a standard network cable. PoE power supply technology has high requirements for wires. It is recommended that in monitoring projects, you should never save costs on wires. The gains outweigh the losses.