SNE Earthing

[Cerkit]

Can anyone explain why we would ever need to use SNE earthing instead of CNE? Is it because if we lose the neutral then there is still a return path for fault current? In CNE if you lose the neutral you will know as the voltages will deviate. With SNE you could lose your earth and you would not know.

Please can someone advise on the above?

 

[davidbeach]

What are SNE and CNE?

 

[Cerkit]

Separate Neutral Earth (SNE) and Combined Neutral Earth (CNE).

So with SNE you have a neutral and an earth conductor run to the consumer property. With CNE just one combined conductor is used as the return path for the load and fault current.

 

[davidbeach]

CNE is on the utility side of the meter and SNE is everywhere beyond the meter. Probably no options in either case.

 

[waross]

CNE is on the utility side of the meter

Both the primary and secondaries are grounded at each transformer.
This has to a lot to do with lightning protection on the primary.
In the case of one ground being lost, there are backup grounds.
Utility grounds are outside, may be poorly protected and may go for decades without inspection and/or maintenance.

SNE is everywhere beyond the meter. Probably no options in either case.

Words:
Beyond the meter there may be, and often are, several grounds.
You may mean to say, SNEC Single Neutral to Earth Connection.
You may have many interconnected grounds past the meter, but only one CONNECTION to the system neutral.
System ground connecting links are generally well protected from mechanical damage and the environment.
More than one ground CONNECTION to the system neutral may defeat ground fault detection and protection or make it more difficult.
More than one ground CONNECTION to the system neutral is prohibited by codes in North America.
There are few exceptions.
In the unlikely event of the loss of the neutral-ground connection, the utility multiple grounds will provide back-up.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

From

https://electrical-engineering-port...f-earthing-arrangements-tnc-tn-s-tnc-s-and-tt

N says how the (transformer) neutral/Midpoint is grounded and there T means Ground (Terre) while N means Neutral (Neutre) and T means dug into the Earth we live on (Terre, again).

The C and S says how N/PE are treated. The TN-C is the common four-wire system where PE and Neutral are the same (Common). The TN-S is the "modern" way of doing it with Separate N and PE. This is a prerequisite for the use of RCD:s

TT is not very common in Europe, but we are told that such systems exist in the "new world"

IT does not mean Information Technology in this context but says that there is no ground or neutral in the system. Except an impedance ground (can be isolated as well) of the transformer midpoint. Found in France and Norway - and likely in other countries.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[zeusfaber]

There used to quite a lot of TT systems in rural bits of the UK (I was served by some as a child). The Protective Conductor in the house was a high impedance affair connected to an earth electrode through the trip coil of a circuit breaker that isolated the whole installation.

A.