How to Connect Power Transformer Neutral to Earth Through NGR?

I recommend that you not get involved.

Yes. Use 6.6 kV rated cable. Do not use bare earthing strip.

But transformer manufacturer provided bare earthing strip from Transformer neutral bushing to upto Bottom of transformer on epoxy support at regular interval.

Will this right??

At a time of earth fault on one phase a L-N voltage (6.6kV/1.732) will be between the NCT terminal and NGR/Ground and approx. line to line (6.6kV) voltage on other phases, is it?????

Regards,

T.D.

Assuming the transformer manufacturer know what they are doing and obviously you don't. I think you would be best served by leaving the whole matter in their hands.

Who is the manufacturer and in which country it was made. Nowadays European manufacturers have plants in Asia,Africa & South america.

The transformer manufacturer will have recommendations on the basis of best practice, if not national electrical standards. If the user manual that was supplied with the transformer has somehow gone missing, use the telephone to obtain correct advice.

From my own experience, you can use bare conductor to do this connection(i.e. from the NCT to the NGR and to ground.)

The Neutral point is at ZERO POTENTIAL under steady state conditions and consequently current flowing is also ZERO. Hence you can use BARE CONDUCTOR to do the connection and save money.

Regards

I have seen MV cable connecting transformer(34.5/13.8kV) neutral to earthing resistor in Saudi Arabia,for which project consultants were from UK.

but what about ground fault condition....??? 6.6/1.732 voltage will appear between neautral and ground??? isn't it? plz advice

Regards,

T.D.

"Upstream" of the NGR could have substantial voltage w.r.t. ground; thus insulation would make sense.

"Downstream" of the NGR is small voltage to ground, but the cable resistance still means that the end next to the NGR will have some voltage. Ohm's Law can tell you how much. I don't think most Codes require this cable to be insulated, but check locally.

Regarding the downstream cable from NGR. Do you have any international code reference that it can be bare or low voltage, irrespective of transformer L-N voltage.