6. Analysis of the electrical diagram of the electrical installation
6.5. CONNECTION OF PROTECTIVE CONDUCTORS PE. CAPACITY EQUATION
The rules for connecting the protective conductor PE should be explained in detail. The combined zero and working conductor PEN is divided into a zero protective PE and a zero working N conductors in the input device (Figure 6.6).
Fig. 6.6. Execution of the TN-CS grounding system
In the PUE (7th ed., 7.1.36) it is indicated "... The zero working and the zero protective conductors must not be connected to the common terminal". The meaning of this requirement is, in order to ensure the electrical safety of preserving the connection of the protective conductor to the ground in the event of the destruction (burnout) of the contact clamp.
In Fig. 6.7 shows examples of the implementation of this connection in the floor or flats.
Fig. 6.7. Examples of how to connect PE and N conductors to PEN
The implementation of a system of potential equalization is important for ensuring electrical safety in a particular electrical installation.
The rules for the execution of the potential equalization system are defined in the standard IEC 364-4-41 and paras. 7.1.87 and 7.1.88 of the PUE of the 7th ed. These rules provide for the connection of all conductors to be grounded to a common bus (Figure 6.8).
Fig. 6.8. Example of a potential equalization system
Such a solution avoids the flow of various unpredictable circulating currents in the earthing system, which cause the appearance of a potential difference on the individual elements of the electrical installation.
In Fig. 6.9 shows an example of the implementation of a system of equipotential bonding in electrical installations of a residential house.
Fig. 6.9. Example of a system for equalization of electrical potentials in a building
Recently, with the increased availability of modern residential buildings and industrial buildings with various electrical appliances and the continuous development of their electrical installations, the phenomena of accelerated corrosion of pipelines of water supply and heating systems have increasingly begun to occur. In a short time - from six months to two years on the pipes of both underground and air laying, spot fistulas are formed, rapidly increasing in size. The reason for accelerated point (pitting) corrosion of pipes in 98% of cases is the flow of wandering currents along them.
The use of an RCD in combination with a correctly executed potential equalization system makes it possible to limit and even eliminate leakage currents, wandering currents flowing through the conductive elements of the building structure, including through pipelines.
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