on video TN-S, TT or TNC-S Which is the Best Grounding?

 TN-S, TT or TNC-S Which is the Best Grounding?

TT or TN? What is the best grounding scheme? Want to know the answer? So connect!

This is perhaps the subject that causes the most controversy and discussions among electricians. Some prefer the TN scheme where neutral and ground are interconnected in the BEP. Others prefer TT where this connection does not exist.

Those who condemn the TN have the neutral break as justification, claiming that if it happens, carcasses can be energized.

We already made a video about neutral breakout here on the channel (card in the video). In this video we show that carcasses can actually be energized in the TN, but we show that in the TT the neutral break causes us to have a potential difference between neutral and earth, which is also a serious problem. But, as we mentioned in the video, the neutral break depends on a number of factors such as, where did the neutral break? What loads were on at the time of the break? What is the type of food?

In addition, the neutral break is an anomaly that must be corrected as soon as possible, as it puts the entire installation and the equipment connected to it at risk. So we cannot keep analyzing the efficiency of grounding schemes just for this reason.

Leaving aside the issue of breaking neutral, let's move on to the less technical part, where many people choose TT over TN just because they like one more than the other or because they repeat a phrase they learned from someone else.

But after all, what is the best grounding scheme for a residence?

It certainly is TN and I'll explain why. But first, if you like this video, share and leave your like. Take the opportunity to check if you are subscribed to the channel and turn on notifications so you don't miss any news. Don't forget to also follow us on social media, Facebook and Instagram.

In the TT scheme I have two ground electrodes, one for the power supply and one for the building. If we consider the utility's ground rod or rods as the power electrode, often the proximity of these rods to the building electrode ends up causing me to have separate, but not independent, grounding electrodes.

In Professor Ademaro Cotrim's book Electrical Installations we have the following definition already described by us in a video here on the channel (card in the video): “Only electrodes “sufficiently” apart can be considered independent. In general, in practice, a distance five times the dimensions of the largest earthing system is considered sufficient to guarantee independence.”

Note that if my building electrode has only one rod and my utility standard also, I would have to have a distance of 5 times the length of a rod for them to be independent. Taking 2.4m long rods as an example, the distance between them should be 12 meters for them to be independent. This is practically impossible to achieve in a residence. Imagine if I have more than one rod or even if I use foundation hardware? The distance would be even greater.

In addition to the problem of the distance between electrodes, we have the obligation to use the IDR in all circuits in the TT, because the fault current is low, since it depends on the value of the grounding resistance. This condition is often overlooked by electricians. We already showed how dangerous this is in another video on the channel (card in the video).

Another point is related to the DPS. If I have a TT ground, the SPD connection scheme must be NBR5410 3, the one where I connect SPD between phase and neutral and the other between neutral and ground. If this scheme is not followed, the risks are great. And to make the list of obligations worse, the neutral DPS in the TT scheme is not equal to the phase DPS. Once again I'll leave some cards in the video so you can see our videos on the subject in detail.

 TN-S, TT or TNC-S Which is the Best Grounding?

TT or TN? What is the best grounding scheme? Want to know the answer? So connect!

This is perhaps the subject that causes the most controversy and discussions among electricians. Some prefer the TN scheme where neutral and ground are interconnected in the BEP. Others prefer TT where this connection does not exist.

Those who condemn the TN have the neutral break as justification, claiming that if it happens, carcasses can be energized.

We already made a video about neutral breakout here on the channel (card in the video). In this video we show that carcasses can actually be energized in the TN, but we show that in the TT the neutral break causes us to have a potential difference between neutral and earth, which is also a serious problem. But, as we mentioned in the video, the neutral break depends on a number of factors such as, where did the neutral break? What loads were on at the time of the break? What is the type of food?

In addition, the neutral break is an anomaly that must be corrected as soon as possible, as it puts the entire installation and the equipment connected to it at risk. So we cannot keep analyzing the efficiency of grounding schemes just for this reason.

Leaving aside the issue of breaking neutral, let's move on to the less technical part, where many people choose TT over TN just because they like one more than the other or because they repeat a phrase they learned from someone else.

But after all, what is the best grounding scheme for a residence?

It certainly is TN and I'll explain why. But first, if you like this video, share and leave your like. Take the opportunity to check if you are subscribed to the channel and turn on notifications so you don't miss any news. Don't forget to also follow us on social media, Facebook and Instagram.

In the TT scheme I have two ground electrodes, one for the power supply and one for the building. If we consider the utility's ground rod or rods as the power electrode, often the proximity of these rods to the building electrode ends up causing me to have separate, but not independent, grounding electrodes.

In Professor Ademaro Cotrim's book Electrical Installations we have the following definition already described by us in a video here on the channel (card in the video): “Only electrodes “sufficiently” apart can be considered independent. In general, in practice, a distance five times the dimensions of the largest earthing system is considered sufficient to guarantee independence.”

Note that if my building electrode has only one rod and my utility standard also, I would have to have a distance of 5 times the length of a rod for them to be independent. Taking 2.4m long rods as an example, the distance between them should be 12 meters for them to be independent. This is practically impossible to achieve in a residence. Imagine if I have more than one rod or even if I use foundation hardware? The distance would be even greater.

In addition to the problem of the distance between electrodes, we have the obligation to use the IDR in all circuits in the TT, because the fault current is low, since it depends on the value of the grounding resistance. This condition is often overlooked by electricians. We already showed how dangerous this is in another video on the channel (card in the video).

Another point is related to the DPS. If I have a TT ground, the SPD connection scheme must be NBR5410 3, the one where I connect SPD between phase and neutral and the other between neutral and ground. If this scheme is not followed, the risks are great. And to make the list of obligations worse, the neutral DPS in the TT scheme is not equal to the phase DPS. Once again I'll leave some cards in the video so you can see our videos on the subject in detail.