TWO PHASE SWITCHBOARD WITH GENERAL DR AND DPS.
So in the TN-C grounding scheme, where the neutral and the protection have the same conductor (PEN) it cannot be used with the DR, because as we saw the DR will not be able to work with this type of grounding.
In chapter 5 of NBR 5410, in item 5.1.2.2.4.2, TN scheme, letter f, it clearly states that DR cannot be used with the TN-C grounding system.
“f) it is not admitted, in the TN-C variant of the TN scheme, that the function of automatic disconnection aiming at protection against electric shocks is attributed to the DR devices”.
GRADES
1 To make the use of the DR device possible, the TN-C scheme must be converted, immediately upstream of the device installation point, into a TN-C-S scheme. That is: the PEN conductor must be dismembered into two separate conductors for the neutral and PE functions, this separation being made on the source side of the DR device, then passing the neutral conductor internally and the PE conductor externally to the device.
2 It is also admitted that, in the separation between neutral and PE referred to in note 1, the conductor responsible for the PE function is not connected to the PEN, on the source side of the DR device, but to any grounding electrode whose resistance is compatible with the actuation current of the device. In this case, however, the circuit thus protected must then be considered as conforming to the TT scheme, applying the provisions of item 5.1.2.2.4.3 of NBR 5410.
Electrical grounding is one of the ways we have to safely interfere with electricity, it is important to note that it is not only intended to protect us, through protective devices, but also to ensure the proper functioning of the electrical installation.
When we refer to electrical grounding, it means that we are placing the installation and the electrical and electronic equipment at the same potential, so that the potential difference between the earth and the equipment is zero.
The grounding system basically has three functions, one of which is to provide protection in case of rain with strong lightning strikes, as the grounding will protect the user of the equipment that is in use, so that an alternative path is created for the passage of the electric current towards earth.
One more way that electrical grounding can act is on the housings of any machine or electrical equipment, as it is common in these cases to accumulate electrostatic charges in the masses, and there is a need for them to be diverted towards the earth. It is important to point out that in these cases, with a good execution of the grounding system, it guarantees the safety of the physical integrity of the people, because it avoids electric shocks by indirect contact with the metallic parts that are exposed conducting electricity.
Last but not least, a good grounding system contributes to the proper functioning of protection devices, such as fuses, circuit breakers, residual current switch (IDR) and surge protection devices (DPS), which will act at the right times , minimizing the chances of more serious accidents.
According to NBR 5410, item 6.4.3.1.3, the protective conductor section can be determined through table 58. Table 58 — Minimum protective conductor section
Therefore, the section of the Earth conductor used in the circuit will be determined by the dimensioned phase conductor section. When the application of table 58 leads to non-standard sections, conductors with the nearest standardized section must be chosen.
The earth electrode materials and the dimensions of these materials must be selected so as to resist corrosion and have adequate mechanical strength. From the point of view of these requirements, table 51 indicates the materials and minimum dimensions commonly used.
Table 51 — Materials commonly used in grounding electrodes – Minimum dimensions from the point of view of corrosion and mechanical resistance, when the electrodes are directly buried
In the TN scheme, the source neutral is directly grounded, and the masses are connected to this point through protective conductors.
TWO PHASE SWITCHBOARD WITH GENERAL DR AND DPS.
So in the TN-C grounding scheme, where the neutral and the protection have the same conductor (PEN) it cannot be used with the DR, because as we saw the DR will not be able to work with this type of grounding.
In chapter 5 of NBR 5410, in item 5.1.2.2.4.2, TN scheme, letter f, it clearly states that DR cannot be used with the TN-C grounding system.
“f) it is not admitted, in the TN-C variant of the TN scheme, that the function of automatic disconnection aiming at protection against electric shocks is attributed to the DR devices”.
GRADES
1 To make the use of the DR device possible, the TN-C scheme must be converted, immediately upstream of the device installation point, into a TN-C-S scheme. That is: the PEN conductor must be dismembered into two separate conductors for the neutral and PE functions, this separation being made on the source side of the DR device, then passing the neutral conductor internally and the PE conductor externally to the device.
2 It is also admitted that, in the separation between neutral and PE referred to in note 1, the conductor responsible for the PE function is not connected to the PEN, on the source side of the DR device, but to any grounding electrode whose resistance is compatible with the actuation current of the device. In this case, however, the circuit thus protected must then be considered as conforming to the TT scheme, applying the provisions of item 5.1.2.2.4.3 of NBR 5410.
Electrical grounding is one of the ways we have to safely interfere with electricity, it is important to note that it is not only intended to protect us, through protective devices, but also to ensure the proper functioning of the electrical installation.
When we refer to electrical grounding, it means that we are placing the installation and the electrical and electronic equipment at the same potential, so that the potential difference between the earth and the equipment is zero.
The grounding system basically has three functions, one of which is to provide protection in case of rain with strong lightning strikes, as the grounding will protect the user of the equipment that is in use, so that an alternative path is created for the passage of the electric current towards earth.
One more way that electrical grounding can act is on the housings of any machine or electrical equipment, as it is common in these cases to accumulate electrostatic charges in the masses, and there is a need for them to be diverted towards the earth. It is important to point out that in these cases, with a good execution of the grounding system, it guarantees the safety of the physical integrity of the people, because it avoids electric shocks by indirect contact with the metallic parts that are exposed conducting electricity.
Last but not least, a good grounding system contributes to the proper functioning of protection devices, such as fuses, circuit breakers, residual current switch (IDR) and surge protection devices (DPS), which will act at the right times , minimizing the chances of more serious accidents.
According to NBR 5410, item 6.4.3.1.3, the protective conductor section can be determined through table 58. Table 58 — Minimum protective conductor section
Therefore, the section of the Earth conductor used in the circuit will be determined by the dimensioned phase conductor section. When the application of table 58 leads to non-standard sections, conductors with the nearest standardized section must be chosen.
The earth electrode materials and the dimensions of these materials must be selected so as to resist corrosion and have adequate mechanical strength. From the point of view of these requirements, table 51 indicates the materials and minimum dimensions commonly used.
Table 51 — Materials commonly used in grounding electrodes – Minimum dimensions from the point of view of corrosion and mechanical resistance, when the electrodes are directly buried
In the TN scheme, the source neutral is directly grounded, and the masses are connected to this point through protective conductors.
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