Improving Grid Resilience Through Cablecure XLG? Injection of Secondary & Service Cables

James Steele, Director of Engineering

July 17, 2024

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Challenge:

Secondary & service cables deliver electric power to homes and businesses and form the last link in the power grid. Relative to the total amount of installed underground cable, these low-voltage secondary and service cables are responsible for a disproportionately large number of service interruptions throughout the world and for aged systems, the rate of failure is getting worse with age.?

Failures are often caused by a loss of ampacity due to corrosion.? The corrosion occurs when moisture encounters the aluminum conductor strands and can be accelerated through stray current and the creation of corrosion cells.? Due to the high specific volume of the corrosion product relative to pristine aluminum, swelling and deformation of the cable is common with breaks in the insulation revealing white aluminum hydroxide powder as shown in Figure 1.?

Figure 1: Low-voltage service cable failure due to corrosion.

Coupled with today’s increased demand for electricity to support the full electrification of the home and at-home EV charging, secondary and service cables are especially vulnerable to the effects of severe weather events including summer heat waves, winter freezes, and increased precipitation.?

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Solution:

Southwire’s Cablecure XLG? injection process adds resilience to aged secondary & service cables by increasing the aluminum conductor strands’ corrosion resistance.? Cablecure XLG? injection purges water from cable and forms a non-flowable gel that reinsulates the conductor and blocks water intrusion (Figure 2).

Cablecure XLG? injection is a two-part formula that is field-mixed prior to injection and undergoes a chemical reaction that transitions the mixture from a fast-flowing fluid into a non-flowable gel in approximately 48 hours.? The injection purges standing water from the conductor, fills cracks in the cable insulation, and prevents the water ingress and water migration along the conductor necessary for corrosion to occur.

Figure 2: Cablecure XLG? injection purges water from the conductor and forms a non-flowable gel that reinsulates the conductor and blocks water intrusion.

Watch the Cablecure XLG? injection process here! https://bit.ly/3Si33V7

Relative to pristine conductor, laboratory study has found Cablecure XLG? injected cables maintain conductor resistance nearly 400 times better than non-injected cables upon exposure to a highly corrosive environment (Figures 3 and 4).? The benefits have also been confirmed through field measurement, where the DC insulation resistance of damaged triplex service cables increased by an average of 3.8 times after Cablecure XLG? injection over pre-injection levels.?

Figure 3: Comparative view of Cablecure XLG? injected conductors (top) and non-injected conductors (bottom) after exposure to an AC-driven corrosion cell.?

Figure 4: ?Quantitative results after exposure to an AC-driven corrosion cell measured in % increase of resistance relative to a pristine conductor.

Benefits:

Cablecure XLG? injection of secondary and service cables offers many advantages over the alternative of cable replacement.? As with other forms of cable rejuvenation, Cablecure XLG? injection can be considered a capitalizable improvement and can often be achieved in half the time and at half the cost of cable replacement.

While cable replacement requires the use of heavy equipment like drills or excavators to operate on residential properties, Cablecure XLG? injection often requires only foot access to the cable terminations located in the meter base, transformer, or pedestal.? In mature neighborhoods, boring pits and trenches can lead to extensive landscaping and hardscaping costs.

Case Study:

A Municipal Utility operating a service territory of 52 square miles and servicing over 15,000 customers was alarmed by growing trends in their reliability metrics and began a search for solutions.? While less frequent than events occurring on their overhead system, this municipal utility identified their underground system as a key driver for duration-based reliability metrics like CAIDI and SAIDI.

Particularly troubling was a population of pre-1990 vintage underground cable installed in a mature neighborhood.? Many of the large acre-size properties had manicured lawns, irrigation systems, swimming pools, and elaborate brick and concrete drives.? The cost and time to repair each cable failure was further increased by the need to restore the property to its as-found state.? Southwire’s Cablecure? technologies were identified as an ideal solution, and the utility began a 2-year grid resilience program.?

·?????? During phase 1 of the program completed in 2023, 45 medium-voltage underground residential distribution (URD) cable segments (24,000 ft) were addressed using Southwire’s innovative Cablecure? 732 injection fluid.?

·?????? During phase 2 of the program completed in 2024, the low-voltage secondary and service cables feeding the homes were addressed using Southwire’s Cablecure XLG? service.? Over the course of 5 weeks, a combined 63 services (7,645 ft of triplex cable) were addressed (Figure 4).? Overall, 75% of the secondary and service cables were injected.? Cables with excess corrosion that prevented flow or splices installed in areas that could not be excavated were scheduled for replacement.? ??Compared to a cable replacement-only approach, the project was completed 4 weeks faster using Cablecure XLG? injection and saved the municipal utility approximately $220,000 (51% savings).?

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Figure 5: Crew injecting secondary and service cables in a residential neighborhood with Cablecure XLG? fluid.

Conclusions:

Southwire’s Cablecure XLG? injection increases the resilience of aged secondary and service cables.? Cablecure XLG? fluid purges water from the cable and forms a physical barrier against water intrusion that protects the conductor from corrosion.? Compared to the alternative of cable replacement, Cablecure XLG? injection is non-invasive and does not require heavy construction equipment on property.? The process is easily integrated into reliability programs as a capitalized expense and often at half the cost and half the time of cable replacement.?

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To learn more about Southwire’s Cable Rejuvenation Service, visit ?https://bit.ly/3y7p8Ps .