The ZANDZ Technical Center has received a request to calculate the grounding for the balanced TCT type transformer located in an industrial building. It is also known that the soil in the site is sandy loam with the resistivity of 100 Ohm/m.
According to item 1.7.101. of the EIC, the resistance of the grounding arrangement to which neutral wires of generators or transformers of single-phase current source terminals are attached, in any season of the year, should be not more than 2, 4, or 8 Ohm, respectively, with the linear voltage 660, 380, and 220 V of a three-phase current source. In this option, the linear voltage is 380 V; therefore, the resistance of the grounding arrangement should not be more than 4 Ohm.
Solution:
The grounding arrangement consists of three vertical electrodes (copper-plated threaded rods D14; 1.5 m ZZ-001-065 - 2 pcs per 1 electrode), which are interconnected by a copper-plated bar 30 x 4 GL-11074 laid in a trench at least 0.5 m deep from the ground surface and attached to the "ground" terminal of the transformer using a copper-plated bar 30 x 4 GL-11075.
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