The reasons for equipment damage and increased bit error rate are often hidden in the grounding method and shielding layer treatment. This article does not discuss the specific working conditions of construction, but only extracts three principles that are repeatedly effective in the reliability design of communication and network equipment: single point reference, low impedance short path, and avoiding ground circulation.

Let's first distinguish the roles of the three types of lands

The protective ground is responsible for safety and leads fault current to the earth; the working ground provides a unified reference potential for the power supply and cabinet; the signal reference ground determines the return path of high-speed signals. The three types of ground can be common or separated, depending on the system structure and standard requirements. The key is that any type of ground should not be used as a jumper. If the role of the ground is clearly stated in the design stage, the shielding layer will not be casually placed on the bridge or metal components and left on site.

The shielding layer connection method determines the anti-interference effect

If the shielding layer is suspended, it means there is no shielding. If the connection is wrong, interference will be introduced. Low-frequency and DC signal loops are generally grounded at one end to avoid potential differences at both ends driving circulating currents; high-frequency and long cable scenarios are closer to grounding at both ends, but they must be matched with shorter ground leads and good equipotentiality. The general principle is that the shorter the path and the lower the impedance, the better, and the ground wire does not loop around or subject the shield to mechanical strain. When it is difficult to balance copper cables, equipment with photoelectric isolation can be used to completely separate the grounds at both ends, for example2-way bidirectional RS485 data optical terminal;For ideas on how to deal with high potential difference environments, please refer toOptical isolation renovation of a 220kV substation communication network.

Troubleshooting clues for ground circulation and potential difference

  • The performance of equipment of the same model varies significantly at different points, and faults are concentrated on cross-cabinet and cross-floor links;
  • The abnormality is alleviated after disconnecting the ground connection on one side of the end device, indicating the existence of circulating current driven by potential difference;
  • The processing sequence is usually to make equipotential connections first, then compress the length of the cross-cabinet copper cables, and replace the long-distance parts with optical fibers or isolation conversion.

There is no need to rely on complicated instruments for acceptance inspection. A record sheet can cover most of the risks: the location and conductor specifications of each grounding point, the treatment method at both ends of the shielding layer, the list of cross-cabinet copper cables and the replacement plan. EB-LINK can assist in checking these fields during the project communication stage, call 0755-83179002.