Multi Busbar Reliability Considerations 1

[Mbrooke]

An educational lesson from the 136th Protection Sub-Committee Meeting where a kite string resulted in the loss of five 400kv transmission lines, two compensation reactors, and three interconnecting auto transformers where at most only 4 elements would have cleared.


I think this is worth bringing into the engineering and design arena as a serious discussion in that all to often busbars end up being so physically close to each other such that an event on one results in others being effected- the most notable resulting in the 2003 Denmark Sweden Blackout.

Starting on page 9. Other cases of total voltage level clearing also documented.

http://www.wrpc.gov.in/pcm/136_PCM_Minutes.pdf

Regarding the Denmark Sweden blackout, a pentograph disconnect on bus A failed drawing an arc which evolved into a two phase fault involving closely adjacent bus B clearing the entire station interrupting a vital flow path which ultimately resulted in 5 million customer losing power.

http://docplayer.net/50237981-The-2003-blackout-in-sweden-and-denmark-olof-samuelsson.html

With this said please leave space between bars, at least that of the width of a whole set, or the maximum distance which a protracted fault can reach before having the ability to evolve into another zone of protection. In addition to taking work space into consideration, where a grounded bus can be serviced without violating work distances between equipment/persons and energized parts.

 

[sushilksk]

I doubt flashover across horizontal spacing of buses (for first case), it is generally too large. It may be at the point where conductors from Bus-A (after disconnector) are under-crossing Bus-B. Clerances are less in vertical plane.

 

[Mbrooke]

That is possible now that you say that, but I would imagine if the kite string had any metal in it, it might create an arc.


Good point regarding the vertical plane, that is another design issue that I see.

 

[sushilksk]

Synthetic kite thread being used these days is slightly conductive.

From google search:

 

[Mbrooke]

I suspected such... I've seen to many videos on the net where loose balloons or strings trigger a heck of a light show.

 

[davidbeach]

Another reason to prefer BAAH layouts.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Mbrooke]

Being honest BAAH is by far the most ideal design for an electrical substation, over-all when space, reliability, dependability, serviceability and extreme contingencies are taken into account. One can lose both buses yet still have continuity through the center breaker- highly advantageous when looping critical flow gate lines in and out of a station.

 

[cranky108]

Forget kite string, we do look at what happens if one of the shield wires drops. BAAH can be a good arrangement for that.

We have seen more outages from metalized balloons than kites.
That's why the car dealers here use simulated balloons, on fiberglass rods.
Also seen some from fireworks, man with a parachute.