Resin Encapsulated bus

[PowerfulStuff]

Hi,
Our project department is installing resin encapsulated bus for a 4MVA/433V transformer secondary connection through to the switchboard.. This is suggested to be able to fit it into the space available (i.e. rather than using cables). We have had many failures previously with 'standard' compact bus due to condensation getting into joints near the transition from tropical heat/humidity to airconditioned switchroom. It's a foregone conclusion that it will be installed but as I would hate to replace it in two years, am looking for design pointers for them. So far I have-
* Joints to be located far from any outdoors to switchroom transitions.

* Bus to be mounted with copper horizontal so that any stress cracking from faults is not on top of the bus where water may pool.

* Any outdoor joints to have additional weather protection installed.

Anyone out there with experience with this type of bus, or thoughts for installation tips?

Thanks,
Martin

 

[alehman]

I've seen several failures of outdoor compact busway. One was used as a service entrance from a transformer into a building. It produced quite a fireworks display I'm told, for 30 minutes until the utility manually turned off the primary. The fault apparently started at the flange on the transformer terminal chamber and propagated all the way to the building wall (which fortunately was masonry).

Avoid compact low voltage busway for outdoor installations, particularly if it will every be unloaded. Even busway manufacturers will tell you that. I would much prefer cable in conduit for this type of installation. If you must use busway, use standard type with spaced conductors rather than compact 'sandwich' type.

 

[PowerfulStuff]

Thanks Alehman. We have two substations where there have been faults with the sandwich type busbar. They have a 'beautiful' conical spray pattern of molten metal on the concrete block walls. Fortunately both transformers have good upstream protection so the fault was only long enough to vaporise the faulty section.

Unfortunately the project people have painted themselves into a corner and this is their only way out. The end users/maintainers don't have the option of saying no, I can only try and minimise the risk (and keep enough spare cable of course).

In this case the manufacturer is well known and they specify it as an outdoor IP68 design. It is slightly different to normal sandwich busway. It appears to be copper bars totally encapsulated with resin. I assume that there is glass fibre in the resin for reinforcing. All joins are made by clamping the bus together through one clamp and then pouring resin into formwork.

Thanks,
Martin

 

[alehman]

http://www.etacomgroup.com/En/Product_1.htm

Interesting product. I'm not familiar with it, but it seems to have a long history according to the literature. Total encasulation might help the moisture infiltration problems of other types of busway. Not sure how I feel about encapsulated joints. Traditionally busway has been constructed with the joint bolts accessible for re-torquing, etc. I wonder how the field joints are encapsulated.