Grounding devices in areas with high earth resistivity

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 1 General Rules

Grounding and protective measures for electrical safety. Grounding devices in areas with high earth resistivity

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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1.7.105. Grounding devices of electrical installations with voltages above 1 kV with an effectively grounded neutral in areas with high earth resistivity, including permafrost areas, are recommended to be performed in compliance with the requirements for touch voltage (1.7.91).

In rocky structures, it is allowed to lay horizontal ground electrodes at a shallower depth than required by 1.7.91 - 1.7.93, but not less than 0,15 m. In addition, it is allowed not to carry out the vertical ground electrodes required by 1.7.90 at the entrances and at the entrances.

1.7.106. When constructing artificial ground electrodes in areas with high earth resistivity, the following measures are recommended:

1) the installation of vertical ground electrodes of increased length, if the resistivity of the earth decreases with depth, and there are no natural recessed ground conductors (for example, wells with metal casing pipes);

2) the installation of remote ground electrode systems, if there are places with a lower earth resistivity near (up to 2 km) from the electrical installation;

3) laying in trenches around horizontal ground electrodes in rocky structures of wet clay soil, followed by tamping and backfilling with crushed stone to the top of the trench;

4) the use of artificial soil treatment in order to reduce its resistivity, if other methods cannot be applied or do not give the desired effect.

1.7.107. In areas of permafrost, in addition to the recommendations given in 1.7.106, one should:

1) place ground electrodes in non-freezing water bodies and thawed zones;

2) use well casing pipes;

3) in addition to deep earthing, use extended earthing at a depth of about 0,5 m, designed to work in the summer when the surface layer of the earth thaws;

4) create artificial thawed zones.

1.7.108. In electrical installations with voltages above 1 kV, as well as up to 1 kV with an isolated neutral for earth with a resistivity of more than 500 Ohm m, if the measures provided for in 1.7.105 - 1.7.107 do not allow obtaining earth electrodes acceptable for economic reasons, it is allowed to increase the required this chapter, the values of the resistance of grounding devices by 0,002ρ times, where ρ is the equivalent resistivity of the earth, Ohm m. In this case, the increase in the resistance of grounding devices required by this chapter should not be more than tenfold.

See other articles Section Rules for the installation of electrical installations (PUE).

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