Thoughts on Cable Tray in Substations

[colin321]

I have an Operations Manager who is adiment over the idea on putting "Cable Tray" inside a substation. Says its the best thing since sliced bread and will save big dollars on installation over conduit and cable trench.

I'm just curious if anyone has seen this... I've told him that putting cable tray in a yard would lead to serious clearance issues, not to mention limit access to already hard to get to areas, plus the addition of supporting foundations!

Just looking for some thoughts and documentation to show how this would end up costing more money and or violate electrical safety. Plus just want a gut check, maybe this is a good idea...

Thanks
Colin

 

[dpc]

We've done trenches. Are you talking about running tray outdoors in the yard? At what elevation? Because of the exposed live parts, it's generally better to run the low voltage wiring down a structure and get it out of the way.

"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg

 

[7anoter4]

In the substation basement-if any- the cable trays will be a good idea. In outdoor area if it is extended and very crowded one may state between duct banks and manholes or cable trays through deep and large trench. The problem will be water penetration on both systems and mainly on the last one. I'd prefer cable bank ducts.

 

[Marmite]

In the UK, copper theft from substations is rife. Not just earthing, but any exposed cables are at risk, particularly protection and control cables.
We also have to be careful to design out tripping hazards and climbing aids in open bushing compounds, so personally I would avoid cable tray, except to neatly bring wiring down structures to the point where it goes underground or into a trough.
Regards
Marmite

 

[PEwannabe2]

Colin321, Can you clarify your question? Are you talking inside the control house, or outside in the yard?

 

[colin321]

Thanks for the replies...

I am referencing metallic cable tray that runs from the control house out to the major equipment carrying control and power cable, much like a cable trench system but obvisoly elevated.

Elevation is tricky, if you want to it be where construction workers can pass under it it has to be something like 9' high, which means if you run 161kV Bus, for expamle, over the cable tray that bus is going to have to be higher to meet electrical clearances. Not to mention the trouble of pulling cable.

If you try and run it just above grade then its a tripping hazard and you have to have certian "Bridges" where workers can pass over the cable tray.

I've seen cable tray under elevated Control enclosures to route cable directly to switchgear panels rather than going through a marshling cabinet, however extending that cable tray to the yard seems painful.

Of course there are some options for a fully enclosed Cable Tray system to keep cable out of sight, but for those that know what is there its never out of mind.

Thanks again,

Colin

 

[racobb]

We have used conduit between multiple manholes, but prefer cable trench with removable covers down the center of the structure with short transitions of underground conduit to the equipment. It is then very easy to add cables/conduit if needed in the future. Would not even consider overhead tray in the yard.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin

 

[jghrist]

I think it's a bad idea for the reasons you have mentioned. Also:

Exposure of critical control circuits to damage
Exposure of cable to UV
Increased exposure to electrical interference

It probably will end up costing a lot more also.

 

[apowerengr]

I've seen some utilities with "box" type steel structures run cable tray from the control building right into the yard on the steel structure to all equipment bays - then transition to conduits carrying control conductors to the equipment. It worked fine if your box steel structure leads to the control building wall.

 

[ScottyUK]

As with most things in life it really depends on the type of substation. For an indoor MV substation with cable or bus duct connections tray or ladder rack is not a bad idea, especially if the sub is part of an industrial facility where the majority of servcies tend to be above ground. If it's an unmanned location and you have the problems Marmite describes - are you never tempted to disable the protection completely just to surprise the pikies? - or it's an open terminal sub then trenches will almost certainly be a better solution. For an HV gas-insulated indoor substation then trenches and tray can work well together: the tray is useful if not inevitable on the gear itself, but trenches to carry the cables to the bay controlers makes for an uncluttered sub layout.


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If we learn from our mistakes I'm getting a great education!

 

[BHZZ]

In the most east-asia industrial projects, cable tray is the most porpular solution for cable routing.

not only in cable room under the switchroom, but also for whole outdoor plant .

 

[7anoter4]

If there is a pipe bridge high enough or a coal conveyor bridge you may use it for cable tray support, also.
That has to be above the pipes or under the conveyor bridge. The uppermost tray has to be covered against direct sunshine and if the trays are solid bottom type draining holes have to be provided. Along the tray stack a walkway will be provided in order to facilitate cable pulling and supervising.This method is recommended where no snow or ice is expected in the region.