Engineering problem, please help!

[Silly Sausage]

What is the purpose of having an isolated driven ground field seperate from any other grounds in a high voltage seperately derived neutral high impedance grounded system?



I think I know the answer but need confirmation.

 

[Guest55]

youre kidding right ?

most of the knowledgable guys on here are on their 4th beer by now.

 

[Silly Sausage]

I was hoping Mr Tony could help me out...

 

[Guest55]

why not ask your cow ?
shes stood in an isolated field.

 

[Knobhead]

Look in the confrence room, any answers yet? I had to read it 2 or 3 times. I think he's on about the spacing required for the seperat earth nests for say a 33/11KV transformer fitted with a NGR (neutral earth resistor) and a LV earthed neutral from the star point of a local transformer. You can sepperate them with distance, or as we used to do, solidly bond them. It's to stop voltage gradients between the two nests.

PS Run in to coolyaar yet? Great ideas about running a neutral!

 

[Marvo]

I'm not sure about the HV application you're talking about but on an LV network it would help ensure sustaining service in the event of a fault for critical applications. Damage limitation in the event of a ground fault or repeating ground fault might be another reason and limiting transients although this is all at the expense of it usually taking longer to identify the fault location.

Can you outline the specific distribution network you have?

 

[Silly Sausage]

why not ask your cow ?
hes stood in an isolated field.

She won't speak to me anymore after being electrocuted from having 4 feet on the floor.

 

[Knobhead]

She's learnt about voltage gradients then :angelsad2:
Seen an entire heard of sheep killed through it.

- - - Updated - - -

The meat is still OK though.

 

[Silly Sausage]

She's learnt about voltage gradients then :angelsad2:
Seen an entire heard of sheep killed through it.

- - - Updated - - -

The meat is still OK though.

Well, it would be pre tenderised I suppose.
Anyway, don't talk about sheep to me, I had a herd of them following me up a path on Whernside once...those sheep eyes!

 

[Knobhead]

Pervert!

Clear you're in box. coolyaar's in action

 

[Silly Sausage]

Foock that.
That's high level bull sh!te, I'll leave that place to you, haha.
You love it really!

 

[Knobhead]

I love it. You make me sound like Frank Drebben, up to his eyeballs in sewage.

 

[Silly Sausage]

Who the rudeword is Frank Drebben?
Can't be arsed goooling

Sewage wise, I must admit, I get enormous satisfaction from clearing a blocked drain.
(clears the mind hahahha )

 

[Engineer54]

What is the purpose of having an isolated driven ground field seperate from any other grounds in a high voltage seperately derived neutral high impedance grounded system?



I think I know the answer but need confirmation.

The NGR limits the neutral current that can flow. The isolated grounding field ensures the integrity of the system. Never seen or heard of linking such an arrangement to an LV ground field. I'll have to have a think about that one!! ...lol!!

 

[Knobhead]

The NGR limits the neutral current that can flow. The isolated grounding field ensures the integrity of the system. Never seen or heard of linking such an arrangement to an LV ground field. I'll have to have a think about that one!! ...lol!!

I'm not going back digging them up! They've been like that for the last 40 years. The tapes from the NER were connected to the MET along with everything else. Obviously the star point to the NER link was separate. Nice set up too, the link was a knife switch operated through linkage from the ground.
The 11KV and 3.3KV set ups were the same.

 

[Geordie Spark]

why not ask your cow ?
shes stood in an isolated field.

I was told she is outstanding in her field.

 

[Engineer54]

I'm not going back digging them up! They've been like that for the last 40 years. The tapes from the NER were connected to the MET along with everything else. Obviously the star point to the NER link was separate. Nice set up too, the link was a knife switch operated through linkage from the ground.
The 11KV and 3.3KV set ups were the same.

I'm just looking at the drawings of our Main MV/LV Substation Building for the general Hospital. Which incorporates 3 X 16OOKVA TX and a 3MVA standby MV generator (c/w it's NGR) Drawing showing a common earth mat for the 3 TX, with connections to a 3 way split removable link earth bus bar located in the MV Switch room. A small but separate mat for the MV generator that is supplied via a separate link earth bar. Mat connected to one side and the NGR on the other... The LV side of things are earthed via the 2 large earth fields one at each end of the site, via a 240mm from each earth field... These connect to the buildings main LV wall mounted multi split main earth bar.

So not even the normal MV earthing fields have any link or connection to the MV generators NGR...