Rewirable fuses and the old wylex boards

[Engineer54]

QUOTE ....This must be the case. The transformer is the DNOs property and is padlocked off and only accessible via the back door. I've never seen it. I don't have the knowledge needed to understand transformer neutral earthing points but the green and yellow single I mention seems to come from the transformer and up to what is used as the MET, bolts on top of each section of the panels connected together with more 50mm (I think) green and yellow single...heading up to the structural steel. This doesn't seem to go near the back of the panel marked PME but I haven't had a look since December.


Still can't see the need for PME in your Switch room, let's face it your right next to the TX, the only earth you need will be from LV earthing arrangement at the TX. the neutral is, or should be earthed at your switchboard! You don't need in any shape or form a PME connection. Who knows what the DNO have done?? Is there any switchboards in the Transformer house?? Perhaps the N-E connection has been moved from your existing switchboard to any new switchboard the DNO have installed.... Even then, your so close to the TX, why would they bother changing your earthing arrangement?? The mind boggles ....lol!!

 

[Knobhead]

It’s EE System 4 gear with MiniForm! Built like a tank.

The N/E link is about 1’ up from the bottom of the panel. You will find plastic covers over the phase connections and the neutral is open. The N/E link is to the right, with this being DNO territory it may be in a sealed unit. Ours weren’t as they were our own gear. BTW it was System 4 gear that the numpties disconnected the earth from!

 

[hillbillie]

I'll take some more photos and post them here. Wifey has my camera and she returns to the UK on Sunday.

 

[Engineer54]

It’s EE System 4 gear with MiniForm! Built like a tank.

The N/E link is about 1’ up from the bottom of the panel. You will find plastic covers over the phase connections and the neutral is open. The N/E link is to the right, with this being DNO territory it may be in a sealed unit. Ours weren’t as they were our own gear. BTW it was System 4 gear that the numpties disconnected the earth from!

One thing i noticed on this TX fed switchboard, there's no sign of any TX etc, protection relays, are they hidden in the EE System 4 equipment Tony?? Also i'm not conversant with the Dorman Smith ACBs or these panels come to that, i take it that the adjustable setting parameters are hidden behind the breaker enclosure door?? Did notice a castel type lock on the main switch though!!

Another thing, if this DNO TX is being used for other purposes/loads now, why is the 1600A ACB/MCCB still in circuit
Also noticed from the snaps all the fuse switches are in the ON position, but none of the instrumentation is showing any values??? lol!!

 

[Knobhead]

O/L I would assume is in the Dorman Smith ACB, but there’s no display. Restricted earth fault is usually a separate unit to trip the 11KV supply. Normally with System 4 just above the incomer in the space forward of the central bus-bars.

To be honest without seeing more of it I don’t know.

It’s unusual to see a Doorman Smith ACB in an EE board. EE had their own brand of ACB’s which were very similar internally to Ellison or OtterMill. Ellison and OtterMill had different isolation mechanism to EE but the “guts” looked the same.

Now I’m going against my faith in EE, but I didn’t like the lock off facilities provided. It didn’t provide a positive locking point. Lock off just stopped access to the racking mechanism. That said it’s no worse than Telemecanique or Merlin Gerin. I don’t like them either!

 

[hillbillie]

Did notice a castel type lock on the main switch though!!

Another thing, if this DNO TX is being used for other purposes/loads now, why is the 1600A ACB/MCCB still in circuit
Also noticed from the snaps all the fuse switches are in the ON position, but none of the instrumentation is showing any values??? lol!!

Yes there is a castel key, as you noticed. There is an 800A MCCB next to the main MCCB for the jenny that used to be there, with a castel lock too. I assume the castel key was removed from the main MCCB and used for the jenny MCCB when switching over.
And yes no amps or volts showing...the ammeters aren't working and the voltmeters were switched off when I took the photo. I'm not sure what the problem is with the ammeters, its not the fuses, they're fine, so why would all of them fail? I'd like to replace them; I rang Dorman Smith and they said they sell ammeters that I could fit that could read the usage on all 3 phases, which would be very useful but a pain to fit. I might end up just replacing the analogue ones (that only read the current from red phase) unless one of you learned gentlemen points me in the direction of a common fault with these ammeters that I could fix?

It’s unusual to see a Doorman Smith ACB in an EE board. EE had their own brand of ACB’s which were very similar internally to Ellison or OtterMill. Ellison and OtterMill had different isolation mechanism to EE but the “guts” looked the same.

The installation dates from 1965, please see the photo with this post. I found the framed installation diagram covered in dust under some boxes of clothes left in the switch room when I first started working there! I'm not sure if you can make out what the installer, Mr J R Fielding wrote/drew but obviously a lot of changes were made. He mentions a 1000A air breaker, whereas now we have a 1600A MCCB manufactured to BS 4752 (1977). He also wrote that there were '4X.75 single core lead cables from transformer' I don't understand '.75', what was that? 75mm? But anyway, there are now 7 cables, not 4...and they are most certainly all much bigger than 75mm!

So I'm guessing that the switchroom has had several improvements, one of which being the Dorman Smith MCCB, probably in the early 1980s.

Much of the other information on the framed chart is still accurate, regarding busbars and distribution boards.

I love this old installation diagram, real old workmanship, neatly drawn out and framed. I have to shamefully admit to using microsoft excel and a printer to create the up to date version of this!

 

[Knobhead]

Transformers were often connected with PILC singles. Only one end earthed, normally the switch gear end would be the earth free end. (Oh god no!!! don’t start that argument)! .75 is the CSA of the conductors in real money (square inches). To be honest .75 would handle a 1000KVA transformer quite happily. OK a bit warm, but paper lead will just sit there and put up with it. The new ones would be double insulated, if they are copper they will most likely to be 2 X 500mm singles or 2 X 600mm aluminium. Both nice to work with.

View attachment 10453

 

[Engineer54]

To be honest Tony, i've never used metal sheathed singles to connect switchboards to TXs only sheathed singles, and many of them, per phase too. But i can understand the the reasoning behind earthing one end only!!

On this project all the LV connections between the TXs and main switchboards will be made via a cast resin bus duct/bar arrangement, where the connections between each section will be cast in situ. Haven't seen this arrangement before so it should be interesting. We are also using the same stuff as one of our means of building rising mains. Only difference being, that the tap off points are again made in situ and a custom breaker unit fitting directly on to the exposed conductor studs.... All a bit down the line yet, but expecting some samples to look at in the near future...

 

[Knobhead]

Would be nice to see some photo’s of the joints. I’ve put bus ducting in but not cast.

 

[hillbillie]

Hillbillie,

Any chance of you taking a few photo's of your main switchboard, the PME labelled panel and if possible the TX itself?? I'd be very interested to see what your working with here.
Thanks in advance... lol!!!

Here's the other photos I promised:

 

[Knobhead]

See what you mean about the label. But I think it’s a mix up of terminology, yes there will multiple earth points but restricted to the N/E point. After this point there will be no further N/E connections so giving a TN-S system.

View attachment 10545

 

[Knobhead]

Just taken the line drawing in to Photoshop to get a better look. It looks like the transformer has been replaced / up rated at some point and the PILC singles replaced. The original ACB must have come out of the ark, Noah would be proud of it. The ACB was made by Statter. This picture will give an idea of their gear, this is from the 1950’s
View attachment 10574