Grounding and protective measures for electrical safety. Earthing switches

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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. Earthing switches

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

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1.7.109. As natural grounding can be used:

1) metal and reinforced concrete structures of buildings and structures in contact with the ground, including reinforced concrete foundations of buildings and structures with protective waterproofing coatings in non-aggressive, slightly aggressive and medium-aggressive environments;

2) metal water pipes laid in the ground;

3) casing pipes of boreholes;

4) metal sheet piles of hydraulic structures, conduits, embedded parts of gates, etc.;

5) rail tracks of mainline non-electrified railways and access roads in the presence of a deliberate arrangement of jumpers between the rails;

6) other metal structures and structures located in the ground;

7) metal sheaths of armored cables laid in the ground. Cable sheaths can serve as the only grounding conductors when the number of cables is at least two. Aluminum cable sheaths are not allowed to be used as grounding conductors.

1.7.110. It is not allowed to use pipelines of flammable liquids, flammable or explosive gases and mixtures and sewerage and central heating pipelines as ground electrodes. These restrictions do not exclude the need to connect such pipelines to a grounding device in order to equalize potentials in accordance with 1.7.82.

Reinforced concrete structures of buildings and structures with prestressed reinforcement should not be used as grounding conductors, however, this restriction does not apply to overhead lines and support structures of outdoor switchgear.

The possibility of using natural grounding conductors according to the condition of the density of the currents flowing through them, the need for welding reinforcing bars of reinforced concrete foundations and structures, welding anchor bolts of steel columns to reinforcing bars of reinforced concrete foundations, as well as the possibility of using foundations in highly aggressive environments should be determined by calculation.

1.7.111. Artificial ground electrodes can be made of black or galvanized steel or copper.

Artificial ground electrodes should not be colored.

The material and smallest dimensions of the ground electrodes must correspond to those given in Table. 1.7.4.

1.7.112. The cross section of horizontal grounding conductors for electrical installations with voltages above 1 kV should be selected according to the condition of thermal resistance at an allowable heating temperature of 400 ºС (short-term heating corresponding to the time of protection and switch off).

If there is a risk of corrosion of the grounding devices, one of the following measures should be taken:

to increase the cross-sections of grounding conductors and grounding conductors, taking into account their estimated service life;
use earthing switches and earthing conductors with galvanized coating or copper.

In this case, one should take into account the possible increase in the resistance of grounding devices due to corrosion.

The trenches for horizontal grounding conductors must be filled with homogeneous soil that does not contain crushed stone and construction debris.

Earthing conductors should not be located (used) in places where the earth dries out under the influence of heat from pipelines, etc.

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

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