Why Effective Shielding Matters in Your Cabling System

The physical characteristics of the cabling system play an important role in the performance and reliability of cables. Apart from the physical characteristics, the grounding, bonding, and shielding in a proper way is also essential for the high-performance of the cabling system.

In this article, we will talk about the grounding and bounding system of cables. Let’s start with the basic definition of grounding. Grounding is managed on the electrical side. It is used for generating an electrical connection with the ground. The simple method of grounding is to place the copper pole into the ground which can be connected to the electrical devices. For example, if you have lmr 400 coax, then one end of the cable must be grounded in order to create a connection with the ground.  In order to equalize the ground potential of equipment and reduce static discharge between devices, bonding is created to that grounding system.

How does bonding look?

In this system, the cabinets or racks are connected to a panel, which is then connected to cabling infrastructure.

The racks or cabinets are further connected to an SBB (secondary bonding busbar), which is then connected to the PBB (primary bonding busbar) via a TBB (telecommunications bonding backbone). The PBB is connected to the grounding system of the building through the TBC (telecommunications bonding conductor). This provides shielding to the infrastructure of the cabling system. 

The cabling setup does not require a shield for the jack at the work outlet if the infrastructure is dependent on the ground of the connected equipment.

Why is it Necessary to get Effective Shielding?

A cable can pick any interface which is released in the surrounding environment which can cause electromagnetic interference. This interference can be reduced by using the shielding in cabling systems. Usually, the cabling systems are the areas of high electromagnetic interference so it is good to get the effective shielding. 

The signal interference can be avoided by using effective shielding. It also helps in increasing the practical operating bandwidth levels. There are several factors on which the success of a shielding system depends. Here, we have mentioned some important factors:

• The quality of cable installation and proper handling of cables
• The quality as well as the reliability of shield terminations. (Always remember that the foil connection should make good contact with the connector housing)
• The balance of the twisted pairs
• The impedance value of the ground connection
• The difference of ground potential between local and remote grounds

Different myths related to Effective Shielding

The ground loops can also be protected by using effective shielding. The ground loops usually develop at the places where there are multiple ground connections. The noise may be induced in the cabling if there is a difference in common-mode voltage potential at these ground connections.

Most of the people believe that they can avoid the situation by using an unshielded patch cord at the other end of the shield of the system. They believe that this strategy will break the flow of current from a large ground coupling and will prevent a ground loop. But that is not true as it will not solve the issue. In case, if a common-mode voltage potential difference is larger than 1V at each ground, then the current will travel through that way. Hence, if you will remove shield at one end then it will simply leave it exposed to the next point of danger. Therefore, the problem is still there.

We recommend you to do grounding at both ends of a shield. If you will not do this then the common-mode voltage potential difference may exist and current may be flowing. This will lead to a ground loop. Do not forget that the resistance must always be less than 1 Ohm path to ground.

What the Standards Say about Effective Shielding:

There are some standards which provide a guide related to grounding, bonding and shielding. These standards include IEC 60364-1 and ANSI/TIA-607-C.

TIA standards have the following points:

• The shield of shielded and twisted-pair cables should be properly bonded to the SBB or PBB. Generally, this is done by terminating the cable shield to the connector.
• The connector is bonded to the panel frame of metal. The bonding is done according to the TIA guidelines

The voltage higher than 1 Vrms between the shielded cabling system at the outlet of the equipment and the ground wire of the corresponding electrical outlet which is required to power the equipment is not grounded. That is why it is not recommended.

A Good Cabling System

Good solutions make sure that the wires are always grounded at both ends. This makes the system completely shielded and also helps in preventing the ground loops.

Moreover, a well-balanced system consists of panels which contain a metal connector. These metal connectors are grounded to the rack or cabinet. The cable shield is connected to the jack. This jack is transmitted to the work area outlet by using a shielded patch cord.

It is essential to have a well-balanced cabling system as these systems are not prone to external noise. Therefore, they show good performance and less interference.

In case of a quality twisted-pair cable, the impedance of the two wires in each pair is balanced relative to the ground. Therefore, noise and crosstalk are not unequal. Both the factors are coupled equally on to both pair conductors. Hence, they do not interfere with the differential data signal.  So, the more balanced cable will have greater ability to reject noise from external sources. Furthermore, it also limits the emittance of its own EMI signals.

We hope that this article will help you in understanding grounding, bonding or shielding. You can also seek expert advice before grounding or bonding your cabling system. Keep visiting our website for more information related to cabling systems. If you have any question related to the article, please feel free to ask in the box below: