01.07.14 , , , ,
Perm Region, Perm. On site, there is a transformer substation 10 / 0.4 kV, brick building with equipment installed, including transformers. The conductor - 40x4 band - that is placed along the internal perimeter of the walls is called the Main Ground Bus (MGB). The assemblers who were installing the grounding connected the MGB to the grounding loop through a metal box at the entry gate, but not with a separate grounding conductor.
As it turned out, the reason for this was the unwillingness of assemblers to make a hole in a 50-cm wall for laying this conductor. They also mentioned the need to connect the other extraneous conductive parts (metal door) to MGB (PCS).
As it seemed incorrect to the Customer, they asked us for help.
ZANDZ experts confirmed the Customer's concerns referring to the provisions of regulatory documents, e. g. Par. 1.7.144 of EIC, 7th ed. "Series connection of any open conductive parts to a protective conductor is not allowed. The conductive parts are to be connected to the equipotential bonding system with branches".
Therefore, a separate conductor is required to connect the transformer substation MGB and a grounding device, while connection through a metal gate frame is unacceptable.
The same is stated in Par. 5.10.3 OPERATING AND MAINTENANCE RULES FOR RF POWER PLANTS AND POWER GRIDS RD 34.20.501-95: "Every plant part to be grounded must be connected to the grounding electrode system through a separate ground conductor. Series connection of several plant parts with ground conductors is prohibited".
This situation makes it obvious, you can trust in professionals only. You can find such ones on the Experts search page.
Safety has priority!