Bus Bar Sleeves in Switchgears 1

[NickParker]

Do you utilize bus bar sleeves for MV/LV switchgear? What are the advantages and disadvantages of the following options?
1) Epoxy-coated
2) Heat-shrinkable (Polyolefin, PVC)

 

[che12345]

"Do you utilize bus bar sleeves for MV/LV switchgear? What are the advantages and disadvantages of the following options? 1) Epoxy-coated 2) Heat-shrinkable (Polyolefin, PVC)"
I have the following experience for your consideration.
1. In majority of installations, neither MV/LV Busbars are sleeved nor epoxy coated. They do NOT increase current rating but increase cost. For LV, they do offer some usefulness in against rodent or snake running across the bars etc...
2. Epoxy-coating or heat-shrinkable sleeving are used mainly on LV when encountered with where clearance distance unable to comply with the Std.
3. a) Epoxy-coating is done on prefabricated bars dripped/coated with powder epoxy and is cured in oven, carried out in the w/shop.
b)Heat-shrinkable sleeving of various sizes and lengths can be cut and heat shrink on with oxy-torch at site.
Che Kuan Yau (Singapore)

 

[NickParker]

they do NOT increase current rating but increase cost.

I do hear that blank copper busbars do have a much reduced ampacity compared to either painted or insulated busbars.

 

[che12345]

"..I do hear that blank copper busbars do have a much reduced ampacity compared to either painted or insulated busbars".
I have the following opinion for your consideration.
1. Paintings/coating are very thin layers, they do NOT increase the natural cooling surface area.
2. Over the years, dull paint and low emissibility tape/coating had been tried out, hoping to increase the current rating; to lower the cost. The mechanism is the "emission (e-factor)". Dull paint/coating with e-factor approaching say 0.8 as against the new bright BB from the mill with e-factor say 0.3. This great difference in e-factor is only for a short period. The bar starts to oxidate with increase in e-factor to say 0.7 etc... The initial advantage of higher e-factor starts to diminish.
3. Painting/coating in the w/shop add material and lobour cost. Note: usually NOT convenient to be carried out at site after installation or on existing boards.
Che Kuan Yau (Singapore)

 

[cranky108]

I think, and I maybe wrong, but medium voltage switchgear in the US is required to be coated. But that maybe just from where we purchase them. The typical is power coated.
But for low voltage, I don't have much work around that, so I can't say.

 

[JezNZ]

According to IEEE Gold Book - Insulated Bus Bars reduces the likelihood of a bus fault by approximately 90%.

Depending on your reliability requirements and cost of outage impacts, that may or may not be a significant figure.

On a recent project of 100k/hr plant outage we calculated insulating the LV busbars as having a Cost-Benefit return of greater than 4x when accounting for Net Present Value.

 

[edison123]

Any electrical insulator is also a thermal insulator and so the bus will run hotter.

Muthu

http://www.edison.co.in

 

[che12345]

"..Any electrical insulator is also a thermal insulator and so the bus will run hotter".
1. Most insulator are thermal insulator, TRUE.
2. They are usually dull in colour with e-factor say 0.7... The e-factor for BB from the mill say 0.3...In general, the end result is NOT very significant.
3. In LV, insulation is valuable preventing shorting by rodent/snake...This property is NOT applicable to MV !
Che Kuan Yau (Singapore)