The following rules are for cable tray grounding rules, which is included NEMA VE2 and also applied in power plants:
* Wire or non-metallic cable trays cannot be used as a grounding conductor.
* Pull the grounding conductor through the cable tray and attach it to the tray with the screw or jaw earthing clamp shown in the figure below. This process must be repeated in each cable tray or section.
* Bare copper grounding conductor should not be used in aluminum cable trays.
* Communication, data, and signal cables must be grounded and the conductivity of the cable routing must be ensured by means of suitable trays fitting/connection parts and at least 10AWG (6mm2) jumpers. If the signal cables and the power cables are to be pulled in the same tray, they must be grounded.
* Tray connection jumpers is connected by a jumper cable lug and bolt by opening a hole 5cm from the tray connection part. The bolt head must be in the tray and should be assembled using a flat washer and locking nut.
* In case of cable layers with more than one cable tray, the tray is grounded in the shape and detail shown in the figure below. Pull the cable grounding conductor into the top tray. The other cable tray layers are connected to this grounding conductor with jumpers every 30 meters. It should be noted that the conductivity continuity and quality of the cable trays on each floor is ensured through the cable layers by means of trays fittings and connection jumpers.
** Linking to Grounding System
If the cable trays are not mounted well onto the properly grounded buildings steel construction, it must be connected to the grounding network (or to a well-grounded building steel construction) in order to prevent short circuit and radio interference by a grounding conductor at every 60 feet (20 meters).
* Result
The cable trays must be grounded in accordance with the rules described above for the purpose of a healthy operation and to prevent the radio interference and fires that may occur during earthing faults. In our country, connecting trays to grounding network at certain intervals is not a sufficient grounding method and a common misapplication.
Although the standards bring some exceptions, it is essential to ensure the continuity of the conductivity on the cable trays by using cable jumpers on the connection parts, angle turns and jump sections of the cable trays. These jumpers shall also ensure that the ceiling itself is a reliable alternative for grounding short circuit even if the appropriate tray grounding conductor is not selected.
