Running power 4000 feet

Status
Not open for further replies.
mbrooke said:
:?

Isnt PME just that: multiply earthed neutral? MGN stands for multi grounded neutral, or what the Australians call "MEN", multiple earthed neutral.
Click to expand...

Sorry, only just spotted your post

The DNO’s refer to it as CNE, PME is a term wrongly used by electricians and to save confusing them the DNO will put a PME label on the service head even if it’s TN-C-S. Does that make it clearer?

I’ve confused myself.
 
Tony S said:
Sorry, only just spotted your post

The DNO’s refer to it as CNE, PME is a term wrongly used by electricians and to save confusing them the DNO will put a PME label on the service head even if it’s TN-C-S. Does that make it clearer?

I’ve confused myself.
Click to expand...

Clear as mud :lol::p Not your fault though. Terms trip me up.
 
Tony S said:
They are used on a ring that has two feeds. The ring has an open point so if a section of cable fails it can be switched out and the ring re-jigged to maintain supplies.

There’s actually six switches in the MV unit. The LV side is a MG SAFIF unit, one of the safest types I’ve worked on.

Layout_zps6b3ba164.jpg
Click to expand...

This forum doesn't have a thanks button, so I will give thanks here :thumbsup::)

IS the switch manual or automatic btw?
 
mbrooke said:
This forum doesn't have a thanks button, so I will give thanks here :thumbsup::)

IS the switch manual or automatic btw?
Click to expand...

Tines are a changin.

For densely populated areas telemetry is being installed to suitable RMU’s (Ring Main Units). Suitable units are vacuum or SF6 interrupters. Not striker fused units, someone has to go and change the fuse.
The remote systems use electronic directional earth fault and O/C+E/L relays.

From the feedback to the control room it’s an engineer’s decision whether to remotely operate section switches or go and have a look first.

The unit in the photographs is on a private network. It is a Yorkshire Switchgear “TYKE” fitted with a striker fuse interrupter for the transformer. The earth fault directional relays tell you which direction a fault has travelled but don’t initiate any switching sequence.
 
Only the transformer or feeder switch is fault making, fault breaking. The ring switches are fault making, load breaking.

They are now fitted with anti-reflex mechanisms. If you want to stay alive you learn how to operate them.
 
Tony S said:
The final design I’m putting forward to the developer.

1/3 the DNO/PoCo cost.

900V-25KVA-1_zpsocmvojxr.jpg
Click to expand...

Tony that is beautifully done! :D :cool::thumbsup::)

If I may ask, can a type D MCB be implemented instead to prevent tripping on inrush?

Also, what are those triacs for on the far right? :?
 
mbrooke said:
Tony that is beautifully done! :D :cool::thumbsup::)

If I may ask, can a type D MCB be implemented instead to prevent tripping on inrush?

Also, what are those triacs for on the far right? :?
Click to expand...


I don’t want MCB’s in a distribution circuit. Do PoCo’s use them to protect small transformers?
Fuses can’t be readily reset by the consumer. Unlike a supply from a PoCo this is a private system but like a PoCo whoever works on it has to be authorised/licensed, IE competent for this class of work.

As I said before, this falls under BS7430, outside the scope of BS7671.

MCB’s will be used for the final circuits which is why I’ve had to be careful getting a MPFC that will guarantee disconnection times will be met.

Triacs?
They’re VTS diodes and MOV’s, (SPD).
They clamp any over voltage caused by system and switching transients to protect computers and other electronic devices. I’m not expecting problems with transients but for the sake of £25 I’m having them fitted.

I could specify SPD’s be fitted at the consumer’s LV intake but the internal design is not in my remit.
 
Last edited:
Tony S said:
I don’t want MCB’s in a distribution circuit. Do PoCo’s use them to protect small transformers?
Fuses can’t be readily reset by the consumer. Unlike a supply from a PoCo this is a private system but like a PoCo whoever works on it has to be authorised/licensed, IE competent for this class of work.

As I said before, this falls under BS7430, outside the scope of BS7671.

MCB’s will be used for the final circuits which is why I’ve had to be careful getting a MPFC that will guarantee disconnection times will be met.

Triacs?
They’re VTS diodes and MOV’s, (SPD).
They clamp any over voltage caused by system and switching transients to protect computers and other electronic devices. I’m not expecting problems with transients but for the sake of £25 I’m having them fitted.

I could specify SPD’s be fitted at the consumer’s LV intake but the internal design is not in my remit.
Click to expand...

Ahhh, ok that make sense. SPD are a good idea.

My regaerd to the MCB is on the 400 volt primary side. Cant you use fuses capable of handling the transformer inrush?
 
mbrooke said:
Ahhh, ok that make sense. SPD are a good idea.

My regaerd to the MCB is on the 400 volt primary side. Cant you use fuses capable of handling the transformer inrush?
Click to expand...


Last time I checked M80A BS88’s were fuses rated for inrush.

The drawing is a general arrangement for the client, not a detailed working drawing for the contractor. I’m not doing the work, I’ve been retired four years.
 
Tony S said:
Last time I checked M80A BS88’s were fuses rated for inrush.

The drawing is a general arrangement for the client, not a detailed working drawing for the contractor. I’m not doing the work, I’ve been retired four years.
Click to expand...

Then what are the 0.47 ohm resistors for?
 
The transformers will cost £1000+ each, I’m not risking burning one out to save £6 for the resistors.

The fuses, contactor and timer are standard stores stock for where the supply is fed from, they will just get booked out on one of the plant maintenance budgets.
Standard maintenance practice, charge spares to someone else’s budget.
 
Tony S said:
The transformers will cost £1000+ each, I’m not risking burning one out to save £6 for the resistors.

The fuses, contactor and timer are standard stores stock for where the supply is fed from, they will just get booked out on one of the plant maintenance budgets.
Standard maintenance practice, charge spares to someone else’s budget.
Click to expand...

Ahhh, there is the DIN system at work :D Here in the US inrush limiting circuits are unheard of that I know.
 
Just got the prices in:
Cable £7,250. ($11,150)
Transformers £3,500. ($5,400)
MV/LV protection and metering £500. ($790)

Total £11,250 ($17,300) plus my cut.


Less than ½ the price of the supply company going OH.
 
Status
Not open for further replies.
Top