Air Circuit breakers

[benji]

just out of curiosity how long are the singles from the transformer to switchboard

 

[hadleigh sparks]

No disrespect, but i don't think your competent to be mucking around with a switchboard of this size going by your above proposals!! You need to maintain the switchboards fault current ratings bracing, so you would know flexible and bracing is a contradiction. You also don't cut into a switchboard and start altering or cutting into bus bars unless you know exactly what your doing of..

The 1200A ACB may also have connections to protective relays, have you checked?? That ACB IS the over current protection between the transformer and the bus bars !! As Tony has already told you ACBs of this size have a wide setting arrangement in many cases down to 60% or less. I'm also guessing that you also have little idea how to set or reset the parameters of the protection curves on an ACB

There is no need to replace this breaker anyway, as it's there to protect the bus bars and possibly the transformer, not the outgoing cable/loads, they will be protected by the distribution MCCBs or switch fuses...

Let me put it another way, an electrician shouldn't be making these sorts of dicissions on a sub-station supplied main switchboard, that is the work of a qualified Engineer...

Mark my words here, get something like this wrong, and you'll know all about it, ...but fast!!

Thanks very much Engineer 54 , i appreciate your comments and take your advice on board. However their is one point you are missing . their currently is no ACB or any protective device installed between the bus bars and the sub station only a 2000 amp main switch. other than the switch it is a direct connection between the bars and and the loop main from the substation.

With regards to the final design im happy to hand this over to an engineer to specify it correctly , but I wanted to give him or her some idea of my proposals before I did this by gauging peoples opinion on here.
but thanks again

 

[hadleigh sparks]

Tony as above thier currently is no ACB installed

 

[hadleigh sparks]

maximum 3 metres

 

[Engineer54]

Where do these 3m of tails connect to in the substation, directly to the Transformer or to a LV DNO Switchboard??
I can't believe there is absolutly no protection provided between the TX LV terminals and your unprotected main switch!!! Loops as you call it, are normally only seen at the MV/HV side of transformers, by means of RMU's (Ring Main Units)....

My advice, is to get a Qualified Electrical Engineer involved in your planned project now, tell him your requirements, and let him make the dicissions on how to go about achieving them in a cost effective way... Or, Panel manufacturers can also be given the task of providing your needs. Who will send an Electrical Engineer to assess what you have, and what you need and propose a design to meet them, based on/around their panel systems... You could ask 2 or three such manufacturers to quote on your project.

 

[benji]

3mtr not long could there be enough protection on hv side

 

[Engineer54]

The MV side of the TX protection, is normally sensed from the LV side, via protection relays!! Which is why i asked if there was an DNO LV switchboard in the substation. 3m doesn't seem long enough to connect directly onto the TX LV connection bushings/bars. Could also be the location of the protection CT's, (if any) on those LV bushings. Weird set-up all round if what the OP is saying is correct...lol!!

 

[benji]

only reason i asked about length of lv cables was because we did something similar lv was 12mtr with no protection ,but we were installing a c/o panel and installing new 630mm singles 22mtr run we had to install new acb cubicle near tx

 

[SW1970]

Where do these 3m of tails connect to in the substation, directly to the Transformer or to a LV DNO Switchboard??
I can't believe there is absolutly no protection provided between the TX LV terminals and your unprotected main switch!!! Loops as you call it, are normally only seen at the MV/HV side of transformers, by means of RMU's (Ring Main Units)....

My advice, is to get a Qualified Electrical Engineer involved in your planned project now, tell him your requirements, and let him make the dicissions on how to go about achieving them in a cost effective way... Or, Panel manufacturers can also be given the task of providing your needs. Who will send an Electrical Engineer to assess what you have, and what you need and propose a design to meet them, based on/around their panel systems... You could ask 2 or three such manufacturers to quote on your project.

And ask the Engineer to do a discrimination study on the whole set up by the looks of things...