That makes perfect sense. For example if an EM relay coordinated with down-stream Microprocessor.
Assume EM Trip in 2 second and Down-stream trip in 1 second. The EM Relay will have turned 50% of the way toward trip upon the down-stream relay opening.
Now on a second shot of the recloser, if...
Dave, I guess what I'm trying to say is if your EM relay uses a delayed reset could that impact coordination with an inst reset down-stream numeric relay? What exactly could be a sputtering fault?
Hello All,
All the relay vendors have "Electromechanical reset" or "instantaneous reset" on their protective function reset curves.
GE Says "use when coordinating with other Electromechanical devices".
SEL says "use when there is an upstream electromechanical device".
My question is, what if...
I think I now finally understand.
Arc refers to fault across air. This can happen if conductor gets too close together, or can happen if say a tree falls onto conductors, tree will melt down and then there will be gaps in tree which will cause rapid ionization of air. And once air is ionized...
Does the conductor melting cause an arc due to molten material causing air to be more easily ionized? I’ve seen a video where a tree fell on a power line and once the tree fried, a huge arc was formed.
All,
I was reading this paper by EPRI.
https://www.epri.com/research/products/000000000001022632
It turns out a few things.
1. Most typical gap values have been calculated using much lower voltage equipment (under 15 kV).
2. Arc pro which limits gap length is not verified for transmission and...
if you don't mind me asking then, if we're saying that there's no problem with the fault arcing phase to phase or phase to ground due to the bird or tree that got in the way.
For example ANSI C2 Table 410
Then why do these standards list the arc gaps so low for a high-voltage system where the...
Lets say this is a aluminum terminal/bushing.
Are you saying that as the current is heating (and potentially melting) say the aluminum, that is affecting the dielectric breakdown therefore you have less kv/mm for the fault to arc?
The reason I was asking is because those arc-flash line to...
Hello All,
I am a young engineer trying to wrap my head around arc flash protection within substations.
Here is a simple hypothetical.
Say you have a 138 kV 3-phase breaker with the following spacing:
Phase-phase = 6 foot
Phase-ground = 7 foot
Now if you got a jumper (let's be theoretical...
