Ground Wire, Cable for Lightning Protection—To Copper or Not to Copper

 

Lead art provided by CommScope BiMetals.

Stephen Oaks, Pacific Management Partners Ltd.

Copper wire and cable have been used in the U.S. for many decades as the standard grounding conductor in substations, transmission, generation and distribution systems. Copper wire offers high fusing current (see section on fusing current vs. ampacity) to discharge lightning and fault currents into the ground. It might be time to re-evaluate this method for best practices.

 

Copper Theft

 

Copper prices have doubled in the past year. It has become an easy target for thieves to take from utility properties. Electrical Safety Foundation International’s 2008 survey (partially funded by NRECA) projected that 95 percent of U.S. utilities have experienced copper theft. This survey said there were more than $60 million and 456,000 outage minutes attributed to copper theft. The costs go higher when one considers the 52 injuries and 35 deaths resulting from copper theft. Will copper theft go away? It’s unlikely while copper prices remain high. During the past decade, copper has risen from less than $1 per pound to more than $4 per pound. With copper near its all-time high and inflation suspected to keep copper prices high well into the future, copper will remain attractive to thieves.

What part of our grid is most likely to be hit by a thief? Gut feeling suggests that only highly populated, low-income neighborhoods would have pole grounds cut from them. Not so, found one large Midwestern investor-owned utility. This large utility found more than 2,400 pole grounds missing in a recent review throughout urban and rural areas.

What can be done to reduce or eliminate copper theft? Many utilities have addressed this concern, having been victims of copper theft. Here are some actions they have taken:

  • They’ve added plastic or wood coving over pole grounds to conceal or make it difficult to cut the wire in the first eight to 10 feet above ground. This is costly and does not take the value of the copper away from thieves’ reach. Some thieves have climbed poles and cut them near the tops and bottoms and pulled the wire through the coving.
  • They’ve spray painted the copper wire coming down the pole a gray metallic color to disguise the copper. This might trick inexperienced thieves but not someone who knows where the wire is located vs. its color. Some thieves work at night and can’t see the color. A question about the paint weathering exists, too.
  • They’ve added video surveillance cameras to substation yards to observe thieves entering and beginning to steal the copper. This is costly and doesn’t ensure thieves’ capture, and it doesn’t stop a person from cutting the video camera lines before attempting to enter.
  • They’ve covered substation pigtails above grade copper cables with conduit up to the bolts at the transformers. This only deters unaware thieves. Thieves who know what they are looking for, cable coming out of ground, know the conduit is where the copper is located.
  • They’ve covered the wire or cable with tin plating. This is meant to wires and cables look like they aren’t copper, however, the value is still in the system wiring. Such a plated wire costs more and might have some latent galvanic corrosion potential that has not been tested yet.
  • Most likely to cure theft, some have switched to copper clad steel (CCS). This material has been available for many decades. The manufacturing of CCS has improved since its early usage, such that it has been used in coaxial cable for cable and satellite TV for a couple of decades.

 

 

Copper Clad Steel Wire, Cable

 

This type of wire and cable is lower-cost than copper and provides little to no scrap value. Some thieves notice the difficulty in cutting it immediately and move on. Others take it to scrap dealers who wisely put magnets to it and tell the trader to move on. Still, some scrap dealers buy the CCS the first time, then find that smelters will not pay for it, so it’s the last time they’ll buy it from thieves.

So why hasn’t everyone moved to CCS instead of solid copper? There are some misunderstandings about the capabilities of CCS vs. solid copper. Here are the issues with replacing copper grounds with CCS:

  • Fusing current. This is not the same as solid copper. This sometimes leads to sizing up one or two sizes with CCS. One example is that 4/0 copper is predominantly used in substation grounds. 4/0 solid copper has a fusing current of 42kA at 30 cycles. Many, if not most, distribution substations, however, have fault currents well below 40kA. So use of a 7, #6, 40 percent CCS (over 30kA fusing current) cable might adequately provide grounding for worst-case ground faults within a substation. Similarly, distribution pole grounds might not need to size up with CCS if the ground fault currents are less than the CCS fusing currents.
  • Connectivity. You can use the same connectors as for copper. Exothermic welds are secure with CCS (see lead art, magnified photo). This figure demonstrates the copper along the CCS wire remains in tack while surrounded by the fusing material, making a highly conductive, not penetrable weld joint. The use of compression connectors works well also, with no special attention necessary.
  • Corrosion. This one is probably the most misunderstood CCS concern. Most of the ground rods installed in the U.S have been CCS ground rods. It was learned in a 1970 U.S. Naval Labs study that the CCS ground rods perform well. The CCS wire or cable laid into ground or strung along a pole is less likely to be abused than the rods and more likely to outlast the CCS rods.

 

Will we stop all copper theft? Probably not in the near future, but the problem likely will get worse if we don’t change our grounding systems. As we take the copper value out of the system and replace it with CCS, we are going to at least send copper thieves looking elsewhere for sellable scrap copper. Let’s save copper usage for where it is really needed.

Stephen Oaks is with Pacific Management Partners Ltd. For a year and a half he has contacted 110 U.S. utilities to discuss their copper grounding and theft issues. Reach him at steve@pacificmanagementpartners.com.

 

Fusing Current vs. Current Carrying Capacity (Ampacity)

 

One important, often confusing point on fusing current is it refers to the current that deforms the wire to a point it is incapable of handling a similar current. This is different from ampacity. Fusing current is the measure for short duration high peak currents like lightning of fault currents, where ampacity is the constant current handled by a wire, typically for power conduction. For fault currents, one should concern himself or herself with the fusing current, not the ampacity.

 

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