Overhead Line Down Detection

[saladhawks]

I am working on a project focused on the detection of downed energized primary overhead lines to support wildfire mitigation on exposed feeders.

Looking at the SEL-451 relay with Arc Sense Technology (AST) high-impedance fault detection. What other technologies / grounding should be considered for this application? Web search has been pretty fruitless so far.

 

[davidbeach]

I think GE has something similar. Most of the research has been conducted at Texas A&M.

 

[stevenal]

ABB too. Might also want to see what PES had to say:

http://www.pes-psrc.org/d/d24/D24 High Impedance Fault Detection Technology.doc

 

[cranky108]

I think they work with the same effectivness. But none of them are 100%.

 

[gattie]

I have used a sensitive earth fault relay successfully for
11kV Overhead lines.
GEC have a relay that is fed from a split core balance type C/T fitted to the outgoing feeder circuit breaker cable.
I don't have the model no. to hand but will follow up with details.

 

[davidbeach]

That could work if there aren't any line-neutral loads being served, but would be way too sensitive where there can be significant standing imbalance due to single phase loading.

 

[gattie]

GEC Sensitive Earth Fault Relays:

Electromechanical type: CMU

Solid State type: MCSU

Both relays are used with split core type C/T & method of routing earth conductor & the insulation of cable termination box & any cable armouring is important.

 

[dpc]

This is the final frontier of distribution relaying. Siemens and ABB both have "solutions" as I recall, along with SEL.

I'd chat up your local sales folk and see what they can offer up from the various relay groups. I'm sure they are all working on it in one form or another.



David Castor

http://www.cvoes.com

 

[davidbeach]

gattie, my guess is that you are the only person on this thread that isn't working in North America. What we have here as the typical distribution feeder is a solidly grounded wye source with the feeder neutral grounded at multiple points along the way. The neutrals are all tied together out in the field where ever they run into each other, such as at open switches between feeders. Your use of a sensitive ground fault relay suggests you have a rather different type of circuit to protect.

The current that would "return" to the substation on one feeder neutral can be load from that circuit, load from other circuits, ground fault from that circuit, ground fault from other circuits, or any combination. No attempt is made to do any form of protection based on measurement of neutral current.

The solutions being discussed are all looking for the signature of an arcing fault, particularly an arcing fault with very high fault resistance. One of the characteristics being looked for is the high frequency component of the arc.

 

[gattie]

davidbeach
Could you please post a single line diagram of a typical system used in USA where the problems prevail.
Thanks