Grounding issues of communication cables

The main screen and the shield are grounded at both ends, while the separately shielded cabinets are grounded at one end; see 3081 for details

This post was last edited by zhouds on 2023-12-8 09:13: grounding at both the armored enclosure and the main panel； Split-screen single-ended grounding.

The grounding design of communication cables is intended to ensure their stable operation, prevent external interference, and enable safe electrical conduction in the event of a cable failure. When grounding armored communication cables, local codes and the manufacturer’s recommendations should be followed. Here are some general principles: 1. **Grounding of the main shield and branch shields**: - The main shield refers to the layer of shielding that surrounds all pairs or triples, usually made of woven copper tape or copper wire. - Branch shielding (split-screening) refers to the shielding that surrounds each pair or each triplet of wires within a cable. These two are usually grounded separately. Total shielding grounding is intended to protect against common interference to all wires within the cable, while branch shielding grounding protects against individual interference to each pair or trio of wires. 2. **Grounding at one end or both ends**: - Generally, whether the shielding layer is grounded at one end or both ends depends on the requirements of the system and the actual level of interference. However, the most important thing is to avoid creating a ground loop, as this can lead to loop interference. - In some applications, the armor may be grounded at only one end to avoid grounding currents caused by differences in ground potential, thereby reducing loop interference. - However, in environments with high EMI (electromagnetic interference), grounding at both ends may be required to provide better protection. 3. **Grounding method**: - The overall shield is usually grounded at the cable connection point or to the grounding system in the switchroom. - Branch shielding may be grounded at the device end where it is used, to protect the signals at that device end from interference. 4. **Selection of grounding point**: - The cable grounding point is usually chosen near the system’s common grounding point, so that the grounding current can be quickly and effectively conducted into the ground. - The grounding point should be selected at the location where electromagnetic interference is minimal and cable operation is most stable. 5. **Standards and Guidelines**: - Before implementing grounding, relevant **and regional standard specifications, such as IEC, ANSI, etc., as well as the recommendations of cable manufacturers, should be referred to. - The specific requirements of the building’s electrical grounding system and communication infrastructure should also be taken into consideration. Since the grounding strategy depends on various factors such as the type of cable, the nature of the signals, the sources of interference, and the electrical environment, it is necessary to consult a professional electrical engineer when designing a grounding scheme, or to conduct on-site tests in order to determine the best grounding method. .