How to Identify TN-C vs TT Electrical Network in a 1950s House Before Upgrading to TN-CS

Question

How can I recognize what network I have connected to in an old house from the 1950s?
What is the practical difference between TN-C and TT
You can somehow recognize it by how it is connected in the sockets, for example?
How can I find out about this?
I want to switch to TN-CS but I have to be sure I have TN-C.

greetings

kamel_w · Answer

Should help

Łukasz-O · Answer

Buddy, only a phone call to the energy company. In theory you can, but in practice you can't check it yourself.

EAndrzej · Answer

Łukasz-O wrote: Not only a phone call to the energy company, not only - you can check, you can - you just need to know electrical engineering, practice and understand the construction of network systems .

Wirnick · Answer

Hello. It is difficult to know the type of network after the connections in the sockets, especially TT. The TT network is a system of one network receiver (Recipients) - a network without a network. The transformer switchboard is a connection. The earthing point is common to the grid and the installation. Electric shock protection system - earthing. Area protected by earthing - e.g. a circle with a radius equal to the measuring distance using the earthing technical method and the soil resistance is lower than 30? (or direct measurement of the earth loop resistance). To find out if the network is TT, check if there is a transformer on the property and contact the Recipient or Electricity.

michcio · Answer

Jump under the transformer and look at the switchboard.

Łukasz-O · Answer

I am very pleased, Dear Andrzej, that you have so much knowledge and practical skills. Could you tell me the secret of how to check it at home, by unscrewing the socket or switchboard? I suspect a colleague majekkk would also like to know. I assume there is no access to the hopper.

EAndrzej · Answer

No home way. You can bake a cake at home . I wrote that knowledge in the field of electrical engineering is practice and understanding of the construction of network systems, and this, unfortunately, is in at least a dozen electrical engineering textbooks, not to mention practice. Therefore, I recommend studying or studying independently and then practicing. The Internet that is so fashionable nowadays will not do everything.

Madrik · Answer

Assuming that we are all lazy shoemakers in UP learning, with science bookworm, can you tell us how to find out the network layout by turning the socket on? It does not have to be the home method - just write how you recognize the network layout in this case ...

We are all eager to learn about this elementary knowledge.

Wirnick · Answer

Col. EAndrzej is right - science and practice make perfect.
There are Lx, N, PE, CC, E conductors in the installation and depending on the facility and receivers, they are used - regardless of the supply network. We do not recognize the network by the installation cables.
I will write brazenly - you have to look at the net.
TT, TN, TNS, IT networks are point-oriented (they exist within the transformer). TN-C is a wide area network.
The protection of each network (..., MV, LV) is earthing.
In the LV network, installations and installation receivers are within the influence of the above earthing system.
In a TN-C network, each grounding of the PEN conductor is a network grounding (a copy of the transformer's star point grounding), but the protection is zeroing (up to the 90s of the last century, now replaced by peanas).

Anonymous · Answer

Almost on every well-preserved transformer station (maintenance, etc.) there is a plate with information about the power of the transformer, the name of the station (usually a town or street) and information about this network system.
In the case of an overhead transformer, it is enough to have a good look at how the connections are made and what insulators are used on the secondary side.
In new stations, cabinets are not hung on poles, so the matter is easier. The rest are network circuit diagrams.

stomat · Answer

Could you briefly describe the differences in connections on a pole transformer station between the TT and TNC systems? Because according to my knowledge so far, there is NO DIFFERENCE at the trafo station.

Łukasz-O · Answer

Buddy: Mieczysław82, Wirnick and EAndrzej
After all, I wrote:

Quote:
I assume there is no access to the hopper.

No access to trafa = unknown station location, no card, no connection view and god knows what else ...

So far, none of the above have answered my and Madrik's questions.

I still believe that the best and safest method is to call the dispatcher at ZE. You have an answer within two minutes.

michcio · Answer

You cannot rely on checking if there are bridges in the sockets! You might as well have made your own bridges despite the TT.

harlejowiec · Answer

It's best to call and ask, you should also have it written in the contract.

Wirnick · Answer

From 100 to 200 meters from the station, the difference is - earthed 1 of 4 wires (excluding lighting wire). Then it is TN-C.

Łukasz-O · Answer

I do not know how it is in other ZE, but in my area you call the ambulance and give the street and house number, yes, giving the station's number will not hurt.

A colleague Akrzy74 found a second, in principle, even better method (the cost of a phone call goes away), namely a peek at the connection conditions - of course, if they have been preserved, because it can be different.

On the other hand, looking at the bridges in the sockets as my colleague Michcio noticed is not a reliable method.

Quote:
From 100 to 200 meters from the station, the difference is - earthed 1 of 4 wires (excluding lighting wire). Then it is TN-C.

That's how it should be, Buddy Wirnick, just don't be surprised sometimes

Anonymous · Answer

IT layout: How to Identify TN-C vs TT Electrical Network in a 1950s House Before Upgrading to TN-CS

TN-C system: How to Identify TN-C vs TT Electrical Network in a 1950s House Before Upgrading to TN-CS

TN-CS system: How to Identify TN-C vs TT Electrical Network in a 1950s House Before Upgrading to TN-CS

TN-S:

Number 5:

TT system

For low voltage networks up to 1kV, the following systems are distinguished:

* TN the neutral point of the voltage source (transformer or generator) is earthed, while the connection between PE and earth of accessible conductive parts that are not normally live (e.g. metal housings of receivers) is made through the supply network:
o TN-S with a separate PE protective conductor. This conductor is for device protection only, it must not be included in any current circuit, a separate neutral conductor N is used for this.
o TN-C with the common protective-neutral PEN
o TN-CS in the part closer to the transformer with a common PEN conductor, separated in the further part of the network
* TT - the neutral point of the transformer is earthed (the neutral conductor connected to the transformer's working earth electrode), while the PE points of the receivers and the available conductive parts (e.g. metal enclosures of devices) are earthed independently of the power grid, most often directly at the installation site, with protective earthing separately for each receiver. There are individual, group and team earthing systems.
IT - isolated transformer neutral point (connected by a jump fuse with earth), PE points connected to protective earth separately for each receiver

Designations in the diagrams:

* L1, L2, L3 - line - phase conductors,
* N - neutral - neutral wire,
* PE - protection earth - protective earth.

Naming rules

For the basic division, a pair of letters is used:

* the first letter indicates the connection of the neutral point of the power source (generator or transformer) to the ground:
:arrow:

T - the neutral point has a direct connection with the earth
:arrow:

I - the neutral point is isolated from the earth potential

* the second letter indicates the method of connecting electricity receivers to the ground:
:arrow:

T - direct connection to the ground of each device separately
:arrow:

N - connection to the earth via the mains

Symbols in the nomenclature of systems:

:arrow:

T - terra - ground
:arrow:

N - neutrum - neutral,
:arrow:

I - isolate - isolated,
:arrow:

C - common - common,
:arrow:

S - separate - separable,

Wirnick · Answer

It applies to the IT, TT scheme and installation in the TN-C / TT system. In the remaining PE - the protective conductor. I will explain later (drought, decay).

Akrzy74 · Answer

Col. Michcio and Łukasz-O - Sure, you can't rely on the bridges in the sockets. If someone does not distinguish between network systems, he is certainly not an electrician and I believe that there are 3 methods of network recognition for him: Mieczysław82- wrote Łukasz-O wrote Akrzy74 wrote

Wirnick · Answer

Explanation to my previous post - pean is a praise literary work praising, for example, Connection of a protective pin with ... (transformer star point).
The protective connection in the installation is defined by the names of the network systems.
In installations powered from TN and derivative networks, connections:
- the pin (or the housing of the electric receiver) with the N (neutral) conductor is TN or TN-C (formerly zeroing)
- the pin (or the housing of the electric receiver) with the N (common) point is TNS or TN-CS.
Common is the common point (reference point).
- TN-C / TT islands.
The island reminds me of the use of a differential current relay, where the bridge to it is Protect Emergency and the surface of Protect Earth, and the neutral wire is separable. An island can exist without a bridge.

krzyshan · Answer

Hello, and I have such a suggestion - in order to distinguish the TNC from TT system in a home installation, just check in the socket or in the main board if there is a transition between the PE and N conductors, with the TT system it should not be because they are two separate wires not connected together , while in the case of a TNC system, there should be a transition between the PE and N conductors because it is one conductor separated at some point by N and PE. The condition is that the network is correctly made and not, as is often the case, that PE is connected to N in the TT network system.

Łukasz-O · Answer

This is my friend's theory and theoretically you are right and in practice it can be different ... How can you be sure that the neighbor from the bottom in the TT system will not make a flower because he read on the electrode about zeroing? Oh, one more thing, the TNC does not have an N and PE conductor - so by the way :D Friend Akrzy74 in one post, he collected three practical methods from the whole thread, that should be enough for electricians.

krzyshan · Answer

Mr. Lukaszu-O, you are right that in the TNC system there is no PE and N here, on my part, a small understatement but I meant the grid system after the PEN division into PE and N, of course, this is the TNC-S system in this case.
When it comes to the neighbor, of course, you can never be sure that someone in the network has not mixed up, and by the way, more than half of the installation is to be reworked from scratch because it is not known who put their hands there and often a PE wire is used as N.

Wirnick · Answer

Mr. Łukasz-O is partially right. PEN - protective-neutral conductor is: - earthed on both sides and several times between the ends, - reinforced at communication crossings (e.g. roads, bridges), - withstands the short-circuit current of the network, - cross-section increased by the network development factor, - the cross-section must not be less than 10mm? - Cu. The conductors connecting to the PEN conductor and not meeting its characteristics may be N, PE or CC conductors (one-sided grounded). I might be surprised it might be otherwise, but that's a different topic.

Łukasz-O · Answer

What about this gentleman :D My friend Wirnick you are right but not entirely. Let us analyze it calmly. The PEN conductor cannot have a cross-section below 10mm - right? Now my question is what is the name of a cable that performs the same function but with a smaller cross-section, e.g. for 230V sockets. Wirnick is right, the minimum PEN cross-section is 10mm and what's next with that. Following my colleague's reasoning, when does PEN turn into N and when in PE if we are dealing with the same conductor 40 years ago. Let's discuss this considering all the pros and cons. I hope for a meaningful conversation without reprimands and gibs.

Wirnick · Answer

Protection includes, among other things, effective disconnection of the supply voltage.
The PEN is to ensure that the voltage in the transformer station is disconnected.
N, PE is to ensure disconnection in the receiver's connector.
The conductor cross-sections are limited by fuses and a set of technical measures (eg RDC).

Łukasz-O · Answer

And sometimes my colleague does not mean the TN-CS system when talking about N and PE in the junction.

Wirnick · Answer

I also do not know the name of the bridge between the Common point and the N strip and the PE strip in the fuse box, but it should be 10 mm?.
In the old 40-year-old installations there was a "0" (zero) wire and the zeroing was unambiguous.

Łukasz-O · Answer

Just remember that these installations did not disappear with the introduction of the new regulation and will not disappear for a long time. I suspect that even in 40 years, some of them will still be spinning. Just like aluminum in a large plate. Please note that the old installations do not meet the requirements of the new regulations, but after all, the PEN (the heavier one) still fulfills its original role, even though theoretically it cannot. Whether we like it or not, it is. In my opinion, these changes caused a lot of confusion, first of all, there was no transition period - because it is better to demand it right away and have the problem solved. Secondly, strange creations began to appear, such as 6-wire risers / lines and divagations or 3f PEN, N and PE or maybe 3F N PEN or 3f PEN and PE.

How to Identify TN-C vs TT Electrical Network in a 1950s House Before Upgrading to TN-CS

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