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Most often, the appeals relate to the standards of < strong>grounding. Our comment:
Metal cable systems can be used as a protective PE conductor and a grounding conductor, on condition, what ensures the continuity of the electrical circuit and their location eliminates the possibility of mechanical, chemical and electrochemical damage.
According to the PUE, grounding and zeroing with bolted connections (GOST10434-82) without flexible conductors, it is possible to perform on trays in standard design, in indoor and outdoor installations without aggressive media (placement categories UHL4, UHL3, UHL2 are limited).
Reliable electrical connection for sheet trays of the LP, LN series, LPE and LNE, which meets the requirements of GOST 10434-82 for the second class, is provided with B8 screws or bolts BT8 and a special nut with a GS8 flange, preventing unscrewing. For ladder trays, it is necessary to use BT8*20 bolts, washers SSH8, grover washers SSHG8, which prevents unscrewing and nuts G8. The route based on sheet and ladder trays must be grounded at least in two places on different sides of the highway lines, and also additionally at the end of each of their branches.
For wire trays, it is necessary to use UCS kits equipped with a GS8 nut that prevents unscrewing and perform grounding trays every 20 meters.
According to GOST R 52868-2007, the total resistance of the connections of the sections cable systems should not exceed 50 mOhm. Tests for various series cable systems have shown their compliance with this requirement – the total resistance of the connections does not exceed the following values:
1.5 mOhm for LP and LN
1,7 mOhm for LPE and LNE
2.3 mOhm for PL
1.8 mOhm for LL
Connection of sections of cable systems that are subject to frequent dismantling or installed on movable structures or on structures exposed to concussions and vibrations, should additionally include flexible copper conductors that guarantee a more reliable electrical connection in the process operation.
The metal cable tray must be grounded in accordance with the requirements of the PUE, because if the cable insulation is violated or the wires in the tray, the latter may be energized and lead to to electric shock.
Tray covers and other quick-release mounting elements do not require grounding. According to paragraph 1.7.77 of the PUE (Grounding and protective measures of electrical safety): "It is not necessary to intentionally connect the source in the TN system to the neutral and ground in IT and TT systems: removable or opening parts of metal frames of switchgear chambers, cabinets, fences, etc., if no electrical equipment is installed on the removable, opening parts."