Earthing arrangement

[davespark24]

Is anyone able to clarify with me how i can work out what earthing arrangement i have on site.

Supply comes into one of our motor switch rooms from an 11kv to LV transformer located directly outside. I can see 4 big copper bars (3phases and neutral) coming in which will then feed off to the Motor panels. There is an earth bar at the other side of the room which has various large earth cables connected.

There is one earth cable larger than the rest which i assume is the earthing supply cable and then the other slightly smaller ones i have traced which go to some of the bigger motors we have (100kw+).

Speaking to a few of the other guys (not electrical) and they said there are various earth spikes all over the site (may or may not be lightening protection). So would it be possible for our entire plant to be a TT or is it more likely that earth is derived from the neutral point of the hv transformer. Or is there an easy way to work this out

Thanks

 

[UKPN]

Is anyone able to clarify with me how i can work out what earthing arrangement i have on site.

Supply comes into one of our motor switch rooms from an 11kv to LV transformer located directly outside. I can see 4 big copper bars (3phases and neutral) coming in which will then feed off to the Motor panels. There is an earth bar at the other side of the room which has various large earth cables connected.

There is one earth cable larger than the rest which i assume is the earthing supply cable and then the other slightly smaller ones i have traced which go to some of the bigger motors we have (100kw+).

Speaking to a few of the other guys (not electrical) and they said there are various earth spikes all over the site (may or may not be lightening protection). So would it be possible for our entire plant to be a TT or is it more likely that earth is derived from the neutral point of the hv transformer. Or is there an easy way to work this out

Thanks

It is the transformer earth. (at the mains position)

 

[ipf]

sounds like TN-S......…..(five words again)

 

[davesparks]

The most likely is TNS with the neutral to earth link being at or in your intake/main switchgear.

 

[Bobster]

^^ Agree with the above. TNS. There will be a N>E link somewhere.

There will also be rods to reference the transformer star point to ground. (This is not TT).

Unless the star point is linked to the HV earthing system. However this isn't very common.

 

[Megawatt]

Is anyone able to clarify with me how i can work out what earthing arrangement i have on site.

Supply comes into one of our motor switch rooms from an 11kv to LV transformer located directly outside. I can see 4 big copper bars (3phases and neutral) coming in which will then feed off to the Motor panels. There is an earth bar at the other side of the room which has various large earth cables connected.

There is one earth cable larger than the rest which i assume is the earthing supply cable and then the other slightly smaller ones i have traced which go to some of the bigger motors we have (100kw+).

Speaking to a few of the other guys (not electrical) and they said there are various earth spikes all over the site (may or may not be lightening protection). So would it be possible for our entire plant to be a TT or is it more likely that earth is derived from the neutral point of the hv transformer. Or is there an easy way to work this out

Thanks

Dave you mention that you had a neutral bar in the gear what is all the ground cables connected to