Who blocks zone 2 / zone 3 reclosing? 3

[Mbrooke]

I seem to get answers in the extremes, either you should block (being a really good idea) or not block (very bad idea). I guess there are pros and cons to both. I want to ask the members here: In practice do you block zone 2 or zone 3 from re-closing? If so, why so?

For me I block zone 3 because this would mean that protection elsewhere has failed to clear a fault, and reclosing would seem to be re-energizing an already consequential problem.

 

[marks1080]

Mbrooke - Yes I agree. the comment was hyperbolic. But the point remains true. I would never recommend running a HV power system without breakers lol

 

[cranky108]

Besides some of us would never want to operate on a single phase. We only operate three phase on breakers.

Besides the fact that fuses can not be scada controllable.

I went through a like thought process years ago trying to figure out how to not have batteries at a small substation. The protection on the X0 bushing to operate a high side device was the difficult part.

Then again, on a small three phase transformer, at times only one phase would blow, and as it had a delta winding, one of the other fuses should have been damaged.
What happened was the service man would replace the one blown fuse, and we would have a random fuse blow at a latter date.

So unless you have a single phase power system, or you don't care about the quality of delivered power to your customers then use a three phase breaker.
Yes there are special cases where this does not apply.

 

[Mbrooke]

@Marks1080: Yahhh, I know. But I figured I might as well give an explanation to students and those who wondered what would happen if such an idea was put to practice. And technically it is on secondary 208 & 480 networks with fault limiters and burning clear.

@Cranky: Were substations in the 50s remote controllable? Just wondering how they did it back then without SCADA.


In regards to the small sub, the trafo fuse should not blow, secondary side protection should take care of that for line faults. They make hydraulic relcosers:

http://www.cooperindustries.com/con...s/three-phase_reclosers/types_6h_and_v6h.html

http://www.cooperindustries.com/con...w_vw_wv_vwvthree-phasehydraulicreclosers.html

Which eliminate the batteries, and 32 step regulators if v reg is needed which again is self powered.

 

[cranky108]

Mbrooke, what makes you think I am that old?

When I started in this industry, some of the substations were maned. And some had an EM version of scada over power line carrier. An interesting study if someone wanted to understand it.

Actually interesting how you can get control/indication and voice, and telemetry over the same carrier.

We still use some hydraulic reclosers, and when they are working, they work well.

 

[Mbrooke]

No on the contrary, you sound young. But I figured you might know a guy or an old substation still around. I am fascinated in how systems did it all without SCADA. I know of many old substations that were all EM and not manned, so even more interesting.

 

[MatthewDB]

SCADA is very old. Systems were in place by the 1920's. They were based around automated telephone equipment. Rotary phone selectors were used to select a specific channel, which could be either a reading or a control. For a meter reading, a voltage, current, PF, etc. would be converted into a variable tone, sent down the line, and converted back to a display on an analog dial. For controls, the far end sent two different tones to indicate breaker open / closed, and an open or close command was sent back via to other frequencies.

My grandfather worked for a large electric rail system that had fully automated rotary converter systems. He took film footage of it before it was taken out in the early 1950s. They had 1,500V rotary converters that would start on low third rail voltage and shutdown on low current with a time delay. They had a SCADA system that would let them asses what was going on at any of their remote substations.

 

[Mbrooke]

Thank you for this- I did not know they used this technique. Or that it was used as far back as the 1920s.

 

[crshears]

I recall that when in training many years ago [think mid-1980's] I was in a transformer station that was remotely controlled via a quite ancient [at least to me] SCADA system; switching was being performed prior to my minder and I being issued an Order-To-Operate, and I could distinctly hear five tones in sequence, and an action would take place promptly as the fifth tone came in.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Mbrooke]

Neat stuff.


In regard to zone 2/3 at higher levels like 500kv, is it more advisable to block? I know at those levels it is very common for 3 phase faults to block reclosing altogether.

 

[marks1080]

Block on timed backup... i wouldnt block reclose on a 500 line for zone 1 or zone 2 instantaneous.