HV disconnectors orientation towards OHL or power supply.

[qqitek]

Hi Fellows,

I have question regarding 132kV vertical break disconnecting switch.
Is there any rule (IEC, ANSI, NEC, BS whatever) determining orientation of disconnector in relation to the incoming supply?
That means - jaw end shall be connected towards the incoming supply, while travelling blades side shall be connected to downstream circuit, or opposite?

Let look on typical disconnector at OHL bay.
After opening - jaw end shall be connected to overhead line, keeping the blades on the cut off side, or opposite orientation?

In case of double break or centerbreak DS it doesn't matter, but vertical DS?

Thanks for any guidance.
qqitek.

 

[magoo2]

It shouldn't matter. At 132 kV, it is possible that the source and load ends could be reversed at times.

 

[davidbeach]

Vertical break switches should be installed such that the moving part moves down to open the switch.

 

[jghrist]

The NEC requires knife switches 600 V or less to be connected so that the blade is de-energized when open, unless there can be a backfeed.

I know of no code that requires this for HV switches, but if there no reason to do otherwise, I would do it at any voltage. In most cases, at 132 kV, there are other reasons, but here is an example:

Underhung hookstick disconnect connecting a power transformer (serving load) to a source bus. You can put the disconnect either way, but I would orient it so that the blade hinge is on the transformer side.

 

[DTR2011]

"The NEC requires knife switches 600 V or less to be connected so that the blade is de-energized when open, unless there can be a backfeed."


I wish more switchgear designers would ignore this when making connections to an FT type test switch!!

 

[qqitek]

Thanks Folks,

I've noticed in one of the book from ANSI world, that hinged side is always connected to the nearest circuit breaker side, while jaw end to the OHL side.
However in IEC world I couldn't found any guidance.

magoo2 - probably you are right

davidbeach - i would disagree.
Have a look on

http://www.coelme-egic.com/-Vertical-Break-

regards
qqitek

 

[davidbeach]

OK, maybe my mental picture was of something else. No, that type of switch obviously has to hinge upward. I was thinking of the switch where the open gap is vertical. I certainly agree with the hinged side being toward the thing being disconnected.

 

[bacon4life]

David, These are what I pictured from your comment. The circuit breaker is right below this tower so the hinge side is closest to the the breaker. At the top of the tower is breaker bypass switch, which happens to have the hinge facing the bus and the jaw facing the 230/115 transformer.

http://files.engineering.com/getfile.aspx?folder=670a553d-6fd4-4501-b04c-e7ba4bb0b0b2&file=tower.jpg

 

[davidbeach]

Yeah, something like that. Except we don't have breaker bypass switches to my knowledge.