Detecting underground cable theft 2

[HowyD]

Hi!

We've been experiencing a lot of cable theft in past years. i would like find out what possible method i could deploy with numerical relays with SCADA system to overcome this challenge.

 

[86ed]

Are these loose cable reels in a substation or actual energized cable (voltage? application?) and/or grounding cables?

We're going to need a lot more information than what you have provided.

 

[davidbeach]

You may be able to learn of it sooner, but you probably can't stop it.

 

[cranky108]

Energized cables seem to be less likely to diappear. Or that's what we found.

If you make it difficult to steal, or less valuable, the thefts seems to go down.

 

[Overvoltage]

Not always. There have been cases where criminals have cut down the pole with a chainsaw to drop the transformer (and drop) to the ground on rural farmsteads. This blows the fuse cutout (thus de-energizing the transformer). They then dump the oil out and take the copper from the transformer and wires.

You have to make it difficult and less valuable, but you also need to have salvage yards stop "taking a blind eye" to people bringing in questionable scrap metal.

 

[ScottyUK]

Wouldn't it be terrible if the protection scheme failed to operate? Tragic in fact.


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If we learn from our mistakes I'm getting a great education!

 

[HowyD]

86ed

This are energized 11kV cables coming from a Substation supplying customers. Most of these cables are in trenches, so what this criminals do, dig them out.... then cut them or burn the cable first when they know that the distributor tripped then cut it, or just pull it out using a truck.

I though of ideas, of maybe using numerical relays that got functions such as negative sequence and negative to positive sequence ratio. But i had issues achieving it using negative sequence functionality since its the same as having earth fault.

 

[jghrist]

This are energized 11kV cables coming from a Substation supplying customers. Most of these cables are in trenches, so what this criminals do, dig them out.... then cut them or burn the cable first when they know that the distributor tripped then cut it, or just pull it out using a truck.

You need to educate your criminals. It is safer to steal bare ground wire and it has a higher scrap value because you don't have to remove the insulation.

 

[86ed]

These thieves sound pretty ballsy…..f.y.i some cities are beefing up scrap metal laws to prevent this sort of thing from happening.

It sounds like the only solution to this problem is your field crew’s response time to an outage--try to catch them in the act.. Maybe, look into a fault location scheme to assist in reducing response time/ fault location.

--or you can add a reclosing scheme with, let’s say a 60 min time delay, and reclose as they’re cutting into the cable.

By the way…bare ground cables can have some serious circulating currents. I’ve seem pictures of dead hobos that snuck into distribution substations and got zapped while cutting into these cables with pliers.

 

[potteryshard]

There are inexpensive plastic-based 200 micron fiberoptic cables which if buried above the cables proper could serve as a dig-in warning. Because the unjacketed versions (indoor) are fairly frangible, this would provide a half hour or so of advance warning of the actual electrical event, and might allow either catching them in the act or preventing the act.

 

[DRWeig]

I was going to suggest some smallish land mines, but I think potteryshard's idea is super.

Good on ya,

Goober Dave

 

[cranky108]

So what exactly are they digging up? Copper or Aluminum?

We haven't had people digging up underground power, but we have had people digging up underground street light circuits.

We started placing junction boxes underground, and only bringingup the pig tails. So they would only get a few feet at the most.

 

[HowyD]

cranky108

After digging when they find is aluminium, they leave it the way it is. so mostly they want copper.

 

[veritas]

HowyD

Are we talking single phase or threephase? If threephase, you may wish to consider an undercurrent alarm. If sections of a phase is removed nps functionality may help. This is, however, heavily dependant on the load current. Higher load current, the higher the nps current when a phase is removed. I have not done the analysis for when two phases are removed but have seen it presented in various textbooks.

Regards.