Why do we connect neutral and ground at the transformer?

Question

Why do we connect neutral to ground at the transformer, why can't we just connect that neutral to the ground at our house?

It depends on your local regulations, and we don't know your location. In some locations the neutral is earthed at the house. Please edit your location so we can answer that. — Justme, Jul 02 '20 at 10:55
Does this answer your question? [How does a neutral wire add any protection from near-by lightning strike](https://electronics.stackexchange.com/questions/367295/how-does-a-neutral-wire-add-any-protection-from-near-by-lightning-strike) — Dave Tweed, Jul 02 '20 at 11:27
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score 4 · Answer 1 · answered Jul 02 '20 at 11:27

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A grounded neutral ensures that line-to-ground voltage is the lower phase voltage (240V~ in India). Without a grounded neutral, in the event of an earth fault on one of the lines, the line-to-earth voltage would be the higher line voltage (415V~ in India).

A grounded neutral enables safety tripping during a line-to-earth fault. In the event of failure of the tripping mechanism during a line-to-earth fault, a grounded neutral would ensure that a person coming in contact with either of the other lines would be exposed to phase voltage only and not line voltage.

The electrical utility supplier alone can guarantee effectiveness of the safety mechanisms by grounding the neutral at the distribution transformer.

Grounding the neutral would not be in the consumer's scope unless mandated by local regulations. (In India, consumers are not permitted to ground the neutral).

answered Jul 02 '20 at 11:27

vu2nan

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Do the meters in India contain a RCD? – Ian Ringrose Jul 02 '20 at 22:07
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Hi Ian, Regulations mandate provision of a RCD on the distribution board. The meters do not contain one. – vu2nan Jul 03 '20 at 04:12
Who owns and maintains the distribution board? – Ian Ringrose Jul 03 '20 at 08:23
The consumer, Ian. – vu2nan Jul 03 '20 at 08:27
Thanks, some parts of the third world has a nice system when the meter contains the RCD etc and the consumer plugs in their wiring to the meter, hence making it much safer. (It is to even much such a system check for a broken N.) – Ian Ringrose Jul 03 '20 at 08:30
Anytime, and yes, that's a real safe system, Ian. – vu2nan Jul 03 '20 at 08:52

score 4 · Answer 2 · answered Jul 02 '20 at 11:30

Basically, because the national electric code says it must be done like that.

India mainly uses the TN-S electrical system, which does connect the PE and N at the transformer. PE is also connected to earth ground potential with an electrode at the transformer. All the return currents flow in the Neutral, and in normal use, there will be no current in the PE, so it equalizes the potential between transformer and house.

And since PE is provided to house, there is no need for local ground electrode.

Why do we connect neutral and ground at the transformer?

2 Answers2