Random Section of GOST 12.1.030-81
2. ELECTRICAL INSTALLATIONS OPERATING AT A VOLTAGE OF 110 to 750 kV
2.1 Electrical installation operating at 110 to 750 kV shall have protective grounding.
2.2. The neutral wire should be made in accordance with the standards for the touch voltage or the standards for their grounding resistance.
Grounding made in accordance with the standards for resistance shall have a resistance no more than 0.5 W throughout the year. With an grounding resistance r exceeding 500 W·m, it is allowed to increase the resistance of the grounding connection according to r.
2.3 The grounding connection voltage when the ground-fault current is drawn from it to the earth shall not exceed 10 kV.
A voltage higher than 10 kV is allowed on the grounding connections from which the potentials cannot be transferred beyond the building or the electrical installations enclosure.
If the grounding connection voltage exceeds 5 kV, measures shall be taken to protect the outgoing communication and remote control cables.
2.4. To equalize the potential in the area occupied by the electrical equipment, longitudinal and transverse grounding elements shall be installed and connected by welding between each other and to the vertical elements of the grounding system.