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Underground power line

An underground power line is an insulated electrical cable system buried beneath the ground surface to transmit or distribute electric power from generation sources to end users, in contrast to overhead lines elevated on poles or towers. These systems employ specialized conductors, often with cross-linked polyethylene insulation and protective jackets, to withstand soil pressures, moisture, and thermal stresses while minimizing electromagnetic interference.^[1] Originating in the late 19th century with direct current networks pioneered by Thomas Edison in urban settings to eliminate street-level hazards and visual obstruction, underground lines faced technical hurdles with alternating current adoption due to insulation and heat dissipation challenges.^[2]^[3] Today, they constitute a minority of global power infrastructure—typically under 10% in most networks—primarily in city centers, high-density developments, and storm-vulnerable regions, driven by empirical reductions in weather-induced outages.^[4]^[5] Key defining characteristics include enhanced resilience to wind, ice, and falling trees, yielding outage duration reductions of up to 14% per 10% increase in underground mileage according to grid analyses, alongside aesthetic and rights-of-way advantages.^[4]^[6] However, vulnerabilities to flooding, seismic activity, and third-party excavation damage persist, often prolonging fault detection and repairs compared to visible overhead systems.^[5]^[7] Installation costs range from 5 to 10 times higher than overhead equivalents—e.g., $2 million versus $390,000 per mile for 138 kV lines—escalating further with terrain and voltage demands, which tempers widespread adoption despite post-disaster advocacy.^[8]^[9] This cost-reliability trade-off underscores causal trade-offs in grid design, where undergrounding excels in localized high-impact scenarios but proves inefficient for expansive, low-density transmission absent targeted justification.^[6]^[10]

Historical Development

Origins in Urban Distribution

The proliferation of overhead electric wires in rapidly urbanizing centers during the late 19th century created significant practical challenges, including visual clutter, heightened fire risks from sagging or damaged lines, and frequent accidents involving pedestrians, vehicles, and structures amid dense populations. Empirical evidence from early electrification efforts demonstrated that overhead systems were prone to outages from wind, ice, and contact failures, exacerbating disruptions in commercial districts where reliability was paramount. These issues prompted initial shifts to underground distribution, prioritizing safety and order over the lower installation costs of poles and wires, with burial expenses offset by reduced maintenance and urban interference over time.^[2] Thomas Edison's Pearl Street Station in New York City, activated on September 4, 1882, marked an early milestone by employing underground conduits to deliver direct current to customers in lower Manhattan's financial area, insulating wires within iron pipes to navigate crowded streets without aerial entanglement. This conduit system, drawing from Edison's prior experiments with jute-wrapped cables, addressed the infeasibility of overhead proliferation alongside telegraph and telephone lines, serving as a model for controlled urban power delivery.^[11]^[12] In Los Angeles, the Los Angeles Edison Electric Company implemented the city's inaugural underground distribution network in 1897, spurred by a municipal ordinance mandating burial to clear downtown streets of overhead utility tangles that impeded growth and posed hazards. This followed the company's formation and reflected broader responses to urban density, where fire-prone wooden poles and entangled wires had already demonstrated unreliability in populated zones.^[13]^[14] European cities pursued analogous developments, with London featuring paper-insulated mains cables from central power stations around 1890 to minimize street-level risks and preserve cityscapes, as engineered by figures like Sebastian Ziani de Ferranti for alternating current systems. These efforts, evident in installations tied to early stations like Holborn Viaduct (1882), emphasized aesthetic integration and hazard reduction over expansive overhead grids, aligning with observations of aerial lines' vulnerability in congested thoroughfares.^[15]^[16]

Key Technological Milestones

In 1925, the first pressurized paper-insulated cables were developed, utilizing oil under pressure to impregnate paper insulation, which significantly improved dielectric strength and minimized voids that caused failures in high-voltage underground transmission.^[17] Polyvinyl chloride (PVC) insulation emerged in the 1930s through initial trials in Germany, providing greater flexibility, chemical resistance, and cost-effectiveness over rubber or varnished cloth, enabling broader adoption in low- to medium-voltage distribution cables.^[18]^[19] Polyethylene (PE) insulation was introduced for power cables in 1942, offering low dielectric loss, high moisture resistance, and mechanical flexibility that reduced installation stresses and enhanced long-term reliability in underground environments.^[20]^[21] Cross-linked polyethylene (XLPE) insulation was invented by General Electric in 1963, achieving thermoset properties through chemical cross-linking that boosted thermal endurance to 90°C continuous operation and reduced thermal expansion, allowing higher current ratings and scalability for medium- and high-voltage underground systems without fluid impregnation.^[22] These material innovations underpinned post-1950 suburban expansions, as evidenced by Fort Collins, Colorado's 1968 ordinance requiring underground utilities in new developments—fully implemented citywide by 2006—based on engineering analyses quantifying 80-90% fewer weather-induced outages compared to overhead lines.^[23]^[24]

Design and Construction

Materials and Insulation Types

Underground power cables typically employ copper or aluminum as conductor materials, selected based on conductivity, weight, and cost trade-offs. Copper offers superior electrical conductivity—approximately 1.64 times that of aluminum—and greater resistance to corrosion, though it is heavier and more expensive. Aluminum, with about 61% of copper's conductivity but only 30% of its weight, is frequently used in medium-voltage distribution cables to reduce material costs and overall system mass, particularly in long runs.^[25]^[26] Insulation layers are critical to prevent dielectric breakdown and accommodate operating voltages. Cross-linked polyethylene (XLPE) is the predominant modern insulation for medium- and high-voltage cables, rated from 1 kV to 35 kV or higher, with properties including high-temperature tolerance (up to 90–125°C continuously) and low dielectric losses that minimize heat generation during transmission. XLPE's extruded application demands precise manufacturing to eliminate voids or contaminants, which can otherwise promote partial discharges and accelerate aging. Industry data indicate failure rates for well-maintained XLPE systems ranging from 0.5 failures per 100 km annually in Danish networks to 0.7–2 failures per 100 miles as reported by the Electric Power Research Institute (EPRI).^[27]^[28]^[29]^[30] Older high-voltage transmission cables often utilize oil-filled paper insulation, such as paper-insulated lead-covered (PILC) or high-pressure fluid-filled (HPFF) designs, where kraft paper is impregnated with dielectric oil for insulation and cooling, encased in lead, aluminum, or steel pipes. These systems, common since the 1930s, provide robust performance under high loads but require pressurized oil to suppress voids and ionization.^[1]^[31]^[32] For compact urban or high-capacity applications, gas-insulated transmission lines (GIL) employ sulfur hexafluoride (SF6) or nitrogen gas as the dielectric medium around aluminum conductors, enabling higher voltages in reduced cross-sections without oil or solid insulation. GIL systems offer low electrical losses and are suitable for direct burial or tunneling, though SF6's environmental persistence has prompted exploration of alternatives.^[33]^[31] Sheathing provides mechanical protection and serves as a moisture barrier, typically using extruded lead, corrugated aluminum, or copper over the insulation, often combined with polymeric jackets like PVC or polyethylene for corrosion resistance against soil acids, alkalies, and groundwater. Metallic sheaths prevent radial water ingress, while semi-conductive layers ensure uniform electric fields.^[34]^[35]

Installation and Burial Methods

Underground power lines are installed using trenching techniques tailored to voltage levels, site conditions, and accessibility needs, with open-cut trenching commonly applied for distribution lines (1-35 kV) in open areas due to its lower equipment costs and faster execution, while horizontal directional drilling (HDD) is preferred for transmission lines (69 kV and above) or urban settings to minimize surface disruption.^[36]^[37] Open-cut involves excavating a continuous trench, typically 12-24 inches wide and 3-6 feet deep to shield cables from mechanical damage and vehicular loads while allowing access for repairs, whereas HDD bores a pilot path underground before pulling cables through, reducing excavation volume but requiring specialized rigs.^[38]^[39] Direct burial places insulated cables in the trench without additional encasement for simpler, cost-effective installations in stable soils, while conduits—often rigid PVC or HDPE—provide pathways for pulling cables, easing future replacements and offering extra protection against soil shifts or accidental digs.^[40]^[38] Backfill materials, such as sand or fluidized thermal backfill (a mix of sand, cement, and fly ash), are layered around cables to achieve compaction, prevent settling that could stress insulation over time, and enhance heat dissipation by filling voids without sharp aggregates that might damage sheaths.^[41]^[42] HDD typically raises upfront costs by 20-50% compared to open-cut due to equipment and steering needs, though it lowers long-term expenses from reduced restoration in constrained areas.^[43]^[44] Soil conditions critically influence trench design and method selection, as rocky or cohesive soils favor HDD to avoid excessive excavation forces that could deform cables, while loose, sandy soils demand wider trenches or stabilized backfill to mitigate differential settling and maintain cable alignment for longevity.^[45]^[46] High thermal resistivity in dry or compacted soils can exacerbate heat buildup, necessitating deeper burials or engineered backfills to sustain ampacity without derating, as poor conduction prolongs fault risks from thermal runaway.^[47]^[48] Fault detection in buried lines poses challenges absent in overhead systems, where visual patrols suffice; underground faults require time-domain reflectometry (TDR), which sends pulses along the cable and analyzes reflections from impedance changes to pinpoint locations within meters, often combined with surge generators for high-resistance faults.^[49]^[50] TDR's accuracy depends on cable length and soil-induced signal attenuation, making pre-installation profiling essential for effective post-burial diagnostics compared to overhead's straightforward line-of-sight inspections.^[51]^[52]

Comparison to Overhead Lines

Cost and Economic Factors

The installation of underground power lines incurs substantially higher upfront costs compared to overhead lines, primarily due to extensive trenching, specialized insulated cables, and protective conduits required for burial. For transmission lines, underground construction costs range from 3 to 10 times that of overhead equivalents, with urban installations reaching $0.54 million to $12 million per mile.^[4] In distribution systems, new overhead lines average $634,000 to $760,000 per mile, while converting existing overhead to underground costs $3.4 million to $6.1 million per mile for Pacific Gas & Electric (PG&E) in California.^[53] These differentials arise from labor-intensive excavation, which can vary by terrain, soil conditions, and urban density, often necessitating directional drilling or open-cut methods.^[4] Maintenance and repair expenses for underground lines are elevated owing to the need for excavation and fault location, which prolong downtime and increase costs per incident. Repairing underground faults can cost over $20,000 per mile, compared to $3,000 to $5,000 per mile for overhead lines.^[54] Additionally, underground lines exhibit shorter service lives of 20 to 40 years versus 30 to 50 years for overhead, necessitating more frequent replacements and amplifying long-term capital expenditures.^[4] Lifecycle analyses indicate that total ownership costs for underground distribution systems remain 3 to 4 times higher than overhead, as elevated initial and periodic investments outweigh reduced outage-related expenses in most scenarios.^[54] In regions like California, post-2018 wildfire mandates have driven large-scale undergrounding programs, with PG&E reporting costs of approximately $3.1 million per mile as of 2025, down from $4 million earlier in the decade due to efficiencies.^[55] These efforts, encompassing thousands of miles in high-risk areas, contribute to billions in total expenditures recovered through ratepayer surcharges, as approved by the California Public Utilities Commission.^[53] Economic evaluations emphasize that while undergrounding elevates system costs, return-on-investment calculations must account for site-specific factors like population density and hazard exposure to assess viability against alternatives such as overhead hardening.^[4]

Reliability, Maintenance, and Durability

Underground power lines demonstrate superior resilience to transient environmental stressors such as high winds, ice loading, and vegetation contact, which account for a substantial portion of overhead line outages; empirical data indicate underground systems experience roughly 50% fewer outage events overall compared to overhead equivalents, primarily due to physical enclosure preventing exposure to these factors.^[56]^[4] However, this protection comes at the cost of increased vulnerability to localized faults from flooding, which can infiltrate terminations and accelerate corrosion, and third-party damage from excavation or digging activities, often comprising a leading cause of underground failures where mechanical stress severs or punctures insulation without atmospheric indicators.^[57]^[58] Fault propagation in buried systems tends to be more insidious than in overhead lines, as dielectric breakdowns or partial discharges remain concealed, potentially escalating to cascading outages across segments before detection, whereas overhead vulnerabilities like conductor sway or insulator flashover are visually identifiable and amenable to immediate sectionalizing. Maintenance of underground lines is inherently more labor-intensive, precluding non-invasive techniques such as infrared thermography or visual patrols routinely applied to overhead infrastructure; instead, operators rely on time-domain reflectometry, partial discharge monitoring, or direct excavation for fault localization, which introduces delays and risks further soil disruption.^[59] Repair timelines for underground faults typically extend 3 to 10 times beyond those for overhead, with average outage durations 58% longer due to trenching, cable splicing under controlled conditions, and restoration testing, amplifying customer impact metrics like SAIDI (System Average Interruption Duration Index).^[56]^[60] Empirical utility studies, including those from regions with elevated weather variability, reveal net reliability improvements—measured by reduced major event days and lower cumulative outage minutes—only in high-incidence zones for storms or gales, where the baseline frequency of overhead disruptions exceeds the protracted underground recovery periods; in milder climates, the trade-off often erodes overall system performance.^[61]^[62] Durability of properly installed underground cables, especially those using cross-linked polyethylene (XLPE) insulation, is engineered for 40 to 60 years of service under rated loads and ambient soil conditions, with failure rates minimized through moisture barriers and rated thermal withstand.^[63]^[64] Overloading, however, induces thermal runaway in XLPE, where exothermic partial discharges degrade the polymer matrix via treeing mechanisms, curtailing lifespan to as low as 7 to 30 years at elevated temperatures exceeding 95°C, as validated by accelerated aging tests correlating Arrhenius kinetics to insulation permittivity breakdown.^[65]^[66] Long-term integrity hinges on initial burial depth, backfill quality, and periodic dielectric assessments to preempt water ingress or sheath faults, which, if unaddressed, propagate via electrochemical corrosion rather than the mechanical wear dominant in exposed overhead conductors.^[67]

Aesthetic and Spatial Considerations

Underground power lines remove the visual presence of poles, towers, and conductors from the landscape, thereby enhancing skyline aesthetics and minimizing clutter in urban and suburban environments.^[68]^[5] This elimination supports denser developments by preserving unobstructed views and vertical space, which overhead infrastructure occupies through required clearances and structures.^[4] Proximity to overhead lines has been empirically linked to reduced property values, with one study estimating a 3.9% decrease (£6,657) in housing prices within 1,500 meters, primarily due to aesthetic disamenities; undergrounding thus avoids such depreciations, potentially yielding comparable uplifts in affected areas.^[69] Another analysis of high-voltage lines found vacant lots nearby selling for 44.9% less, underscoring the value preservation from burial in visually sensitive zones.^[70] A Maryland utility assessment further noted a 2.5% rise in property assessments post-undergrounding, attributing it to improved appeal.^[71] Spatially, underground lines enable more efficient use of surface rights-of-way in constrained urban settings, as they eliminate the need for pole footprints and lateral conductor spans that demand ongoing clearances.^[7] However, installation and maintenance require subsurface easements for trenching and access, often necessitating broader corridors than the linear paths of overhead lines in rural or exurban areas, where property fragmentation can arise from utility access demands.^[72]^[73] Compared to overhead systems, underground configurations present fewer avian collision risks, as buried conductors eliminate the hazard of mid-air impacts with wires that annually affect bird populations.^[74] Electromagnetic field (EMF) concerns are also mitigated at ground level, with soil shielding electric fields almost entirely and magnetic fields attenuating more rapidly than the elevated, persistent exposures under overhead lines.^[75]^[76]

Environmental and Safety Aspects

Impacts During Construction

Trenching for underground power lines disturbs topsoil through excavation, resulting in soil mixing, compaction, erosion, and rutting, which collectively degrade soil structure and productivity in the affected corridor.^[77] These localized effects extend to nearby habitats, where vegetation removal and soil disruption temporarily reduce biodiversity and wildlife access along the linear path.^[78] Empirical assessments of transmission construction indicate that such soil alterations primarily impact agricultural or forested lands, with restoration measures aimed at reseeding and stabilizing slopes to limit long-term degradation.^[77] Open-cut trenching elevates risks of soil erosion and increased surface water runoff, particularly on sloped or unstable terrains, as exposed earth lacks vegetative cover during active installation.^[79] However, the overall permanent surface footprint remains narrower than that of overhead lines, which necessitate wide cleared rights-of-way for towers and access, thereby minimizing enduring spatial habitat fragmentation once backfilled and revegetated.^[78] Horizontal directional drilling serves as a key mitigation technique, enabling subsurface installation with minimal surface disruption by creating pilot bores and pulling cables through without continuous open trenches.^[80] This method reduces topsoil disturbance and erosion in environmentally sensitive zones, though its application is constrained in rocky terrains where hard formations heighten drilling difficulties, tool wear, and potential borehole instability, often necessitating fallback to traditional trenching.^[81]

Long-Term Operational Effects

Underground power lines substantially reduce the risk of wildfire ignition compared to overhead lines, as the latter can spark fires through conductor contact with vegetation, arcing during high winds, or equipment failure, accounting for approximately 3% of all U.S. wildfires but a higher proportion of large, destructive ones.^[82] In California, power lines have ignited six of the 20 most destructive wildfires since 2015, often under dry, windy conditions that exacerbate spark propagation.^[83] This operational advantage persists over decades, minimizing ignition sources in fire-prone regions and thereby lowering long-term ecological damage from repeated burns, such as soil erosion and habitat loss. However, the lifecycle burdens of underground systems offset some benefits, particularly regarding non-biodegradable materials like cross-linked polyethylene insulation and copper conductors, which demand intensive mining, manufacturing, and eventual recycling processes with high energy and emissions footprints.^[84] Life-cycle assessments indicate underground distribution lines exhibit greater overall environmental impacts than overhead equivalents due to elevated material inputs and disposal challenges, though they offer longer service life (40-50 years versus 20-25 years for overhead).^[85] In low-fire-risk areas, the preventive gains against outages or ignitions may not justify these persistent resource demands, as operational emissions from periodic maintenance and replacements can exceed avoided fire-related costs when ignition probabilities remain low.^[86] Electromagnetic field (EMF) exposure from operating underground lines is generally lower for the public than from overhead lines, with soil and cable sheathing attenuating electric fields almost completely while magnetic fields, though potentially comparable or stronger immediately above cables, diminish rapidly with distance and pose no established long-term health risks.^[75] Epidemiological studies, including those on childhood leukemia near power infrastructure, show weak or inconsistent associations with low-frequency EMF, with major reviews finding no causal link to cancer or other diseases.^[87] In coastal installations, however, flooding introduces corrosion risks from saltwater intrusion, accelerating sheath degradation and potential leaks of insulating fluids, which could necessitate more frequent interventions and elevate localized soil contamination if not mitigated by robust designs like enhanced cathodic protection.^[88]^[89]

Regulatory Frameworks

Global and National Standards

The International Electrotechnical Commission (IEC) standard 60840 establishes test methods and requirements for power cables with extruded insulation and their accessories, applicable to fixed installations at rated voltages above 30 kV (U_m = 36 kV) up to 150 kV (U_m = 170 kV), with a focus on ensuring insulation integrity through electrical, mechanical, and environmental performance evaluations derived from empirical failure analyses. This standard mandates prequalification and type tests, including lightning impulse withstand and partial discharge measurements, to verify long-term reliability under operational stresses observed in field data.^[90] In the United States, the National Electrical Code (NEC), specifically Article 310, governs conductors for general wiring, including ampacity ratings for underground installations where derating factors—such as those in Table 310.15(B)(2)(a) for direct burial or duct banks—account for reduced heat dissipation in soil, based on thermal resistivity measurements from historical installations exceeding 90°C conductor limits. Burial depths are further specified in NEC Article 300.5, requiring minimum cover of 24 inches for cables under 600 V and up to 36 inches for higher voltages to mitigate mechanical damage risks substantiated by excavation incident data.^[91] These standards trace their development to documented failures in oil-impregnated paper-insulated cables prevalent before the 1960s, which suffered from moisture ingress and dielectric breakdown, prompting the shift to cross-linked polyethylene (XLPE) insulation by the late 1960s for its superior thermal and electrical stability confirmed in accelerated aging tests.^[92] XLPE mandates post-1970s incorporated causal insights from postmortem analyses of paper cable degradation, emphasizing void-free extrusion processes to prevent treeing phenomena.^[93] Causal reliability in modern standards prioritizes verifiable diagnostics like partial discharge (PD) testing, calibrated per IEC 60270, which quantifies micro-void activity in insulation via pulse magnitude in picocoulombs, enabling early detection of defects that empirical studies link to 70-80% of premature cable failures in high-voltage systems.^[94] Such testing protocols, integrated into IEC 60840 and IEEE 400 series, rely on field and lab data rather than unproven assumptions, ensuring standards evolve with quantified failure modes like water treeing in XLPE under load cycling.^[95]

Regional Implementation Examples

In Europe, underground power lines are extensively used in dense urban environments to address spatial limitations and aesthetic concerns, with national policies often aligning with EU guidance on infrastructure integration. For instance, Germany's Network Infrastructure Line Construction Act (NABEG) mandates undergrounding 110 kV lines when the cost ratio to overhead equivalents does not exceed 2.75, facilitating higher underground penetration rates—reaching about 40% for distribution networks by the 1990s and continuing to expand in cities.^[96] This approach has reduced weather-related outages in urban settings, though construction costs remain 5-10 times higher than overhead alternatives, with operational data indicating fault rates for underground lines at least 50% lower than overhead per 100 miles annually.^[97] Japan prioritizes seismic-resistant underground designs, particularly following the 2011 Tohoku earthquake, which toppled 42 transmission towers and disrupted power supply across affected regions. Post-event enhancements include specialized cable anchoring and fault-tolerant layouts, yielding underground systems with 20-50% fewer seismic-induced failures compared to reinforced overhead lines, as evidenced by comparative resilience metrics from high-voltage networks.^[98] However, these implementations incur elevated expenses—up to 10-15 times overhead costs for equivalent high-voltage segments—driving selective deployment in urban and coastal zones rather than nationwide rural grids, where hybrid reinforcements predominate.^[99] In the United States, regional disparities are pronounced, with California's aggressive mandates post-2017 and 2018 wildfires prompting utilities like PG&E to underground over 1,000 miles of distribution lines by October 2025, at an average cost of $3.1 million per mile (down from $4 million initially due to process optimizations).^[100] This has achieved up to 98% reduction in wildfire ignition risk from covered lines, alongside lower outage durations from wind and fire events, though total program costs exceed billions, largely recovered via customer rates.^[101] In contrast, rural states impose minimal undergrounding requirements, favoring overhead lines for their lower upfront costs (under $0.5 million per mile) despite higher vulnerability to storms, resulting in outage rates 2-5 times those of urban undergrounded equivalents without comparable mandates.^[102]

Practical Applications and Case Studies

Urban and Suburban Deployments

In the United States, many suburban developments constructed after 1950 incorporated underground power lines as a standard feature to improve visual aesthetics and eliminate overhead poles, aligning with post-war emphasis on orderly, scenic residential landscapes. This approach reduced minor outages caused by wind, falling branches, or vehicle collisions, though full adoption varied by locality and developer preferences.^[103] San Diego's undergrounding program, initiated in 1970 to prioritize aesthetics in suburban neighborhoods, has converted significant portions of overhead lines but faces scalability limits, with approximately 1,000 miles remaining as of 2025 due to funding constraints and phased implementation across districts. Recent completions, such as in Bay Park in April 2025, highlight incremental progress in reducing outage-prone infrastructure, yet the city's efforts stand at about one-third overall completion.^[104]^[105]^[106] Urban retrofitting presents greater challenges than suburban new builds, with costs for converting existing overhead grids often reaching 10 times those of installing new overhead lines, driven by excavation disruptions, traffic coordination, and integration with aging infrastructure in dense areas. In Las Vegas, new subdivisions have increasingly adopted underground lines for reliability, with projects achieving 75% completion of targeted lines by August 2023 and full integration in select developments by that year, though broader urban scalability is hindered by similar economic barriers.^[107]^[108]^[109] These deployments underscore limits in scaling underground systems across populated regions, where high retrofitting expenses—estimated at $2 million per mile for urban transmission versus $390,000 for overhead—constrain comprehensive adoption beyond targeted suburban expansions or wildfire-prone zones.^[8]

High-Risk and Specialized Uses

In wildfire-prone regions like California, utilities such as Pacific Gas & Electric (PG&E) have accelerated undergrounding of distribution lines since the early 2020s as part of mandated wildfire mitigation under the state's Wildfire Safety Division. By October 2025, PG&E had energized over 1,000 miles of underground powerlines in high fire-risk areas across 27 counties, targeting circuits responsible for about 18% of historical ignitions and aiming for an overall 98% reduction in spark-related wildfire starts compared to overhead equivalents.^[55]^[101] Empirical data from PG&E's Community Wildfire Safety Program indicate that underground sections experienced zero weather-related ignitions in monitored high-risk zones during the 2020-2024 fire seasons, demonstrating clear return on investment in ignition prevention amid events like the 2020 August Complex Fire, which was exacerbated by overhead lines. However, these installations remain vulnerable to flooding, where water ingress can corrode insulation and cause faults, potentially complicating resilience in areas with concurrent wet-season risks.^[110]^[111] In hurricane-vulnerable coastal states like Florida, underground power lines have shown substantial empirical benefits in reducing storm-induced outages, with Florida Power & Light (FPL) reporting that underground segments under its Storm Secure Underground Program performed over six times better in outage rates during major events compared to overhead lines. Duke Energy Florida's analysis of post-2017 hurricanes, including Irma, found underground lines incurred a much smaller number of outages—estimated at up to 86% fewer storm-related interruptions—despite longer average restoration times due to excavation needs.^[112]^[113] This resilience edge was evident in Hurricane Ian (2022), where underground infrastructure in hardened zones restored power days faster than overhead areas, yielding a positive ROI through avoided outage costs exceeding $1 billion annually statewide from reduced tree-contact failures. Nonetheless, post-flooding repair delays can extend from hours to weeks, as saturated soil hinders access and increases corrosion risks, underscoring tradeoffs in flood-prone subtropics.^[114]^[115] Following Hurricane Maria in September 2017, which devastated Puerto Rico's predominantly overhead grid and left over 95% of customers without power for months, federal and local recovery efforts have emphasized resilient redesign, including selective undergrounding for critical distribution in flood- and wind-exposed zones. The U.S. Department of Energy's grid modernization initiatives post-Maria incorporated underground hardening to mitigate repeat failures, with pilot projects demonstrating faster outage recovery in undergrounded urban circuits during subsequent storms like Fiona (2022).^[116]^[117] However, implementation has lagged due to terrain challenges, with underground lines proving susceptible to saltwater flooding that accelerates insulation degradation and elevates fault rates by up to 20% in saline environments.^[118] For seismic hazards, Japan employs specialized high-voltage direct current (HVDC) underground cables in select long-distance links, such as the Hokkaido-Honshu DC Seikan Tunnel system, to enhance inter-regional stability amid earthquake risks. Operational since the 2010s, these buried HVDC lines have maintained transmission integrity during events like the 2018 Hokkaido Eastern Iburi earthquake, where overhead grids failed broadly but underground segments avoided seismic shear disruptions through flexible polymer insulation and deep burial.^[119] Toshiba and Hitachi data from the Hida-Shinano HVDC link (commissioned 2021) confirm minimal downtime in simulated seismic tests, with fault rates under 1% versus 5-10% for overhead AC lines, supporting ROI via sustained power flow to isolated areas. Yet, post-quake flooding or soil liquefaction can delay repairs significantly, as accessing buried HVDC requires extensive trenching, contrasting with overhead lines' quicker visual inspections.^[120]^[121]^[122]

Debates on Adoption and Future Directions

Economic and Policy Controversies

The push for widespread undergrounding of power lines, often framed as a resilience measure against climate-driven extreme weather, has ignited debates over government mandates versus utility-led, market-driven decisions informed by localized cost-benefit analyses. In the United States, utility investments in underground lines surged to $11.8 billion in 2023, more than doubling from two decades prior, amid federal incentives like those in the Bipartisan Infrastructure Law for grid hardening.^[123] ^[4] Proponents cite reduced outage durations—such as a 95% improvement in system average interruption duration index (SAIDI) observed by Wisconsin Public Service Corporation post-undergrounding—but critics highlight that these policies frequently overlook the 4-10 times higher construction costs compared to overhead lines, without commensurate reliability gains in low-risk, low-density areas.^[8] ^[56] ^[4] A 2024 U.S. Department of Energy guide emphasizes that undergrounding is economically viable primarily for targeted applications in high-value corridors prone to wildfires, storms, or aesthetics-driven needs, rather than grid-wide deployment, due to elevated upfront costs ($0.16 million to $12 million per mile), shorter asset lifespans (20-40 years versus 30-50 for overhead), and potential rate hikes or taxpayer burdens from subsidized conversions.^[4] Empirical studies, including those by the Edison Electric Institute, reinforce that full undergrounding often fails cost-benefit tests outside such contexts, as repair times can exceed those for overhead systems (e.g., 5-46% higher customer average interruption duration index per Duke Energy data), and underground lines remain vulnerable to flooding or excavation damage.^[124] ^[4] In low-risk regions, the absence of proportional outage reductions—overhead lines already achieve high reliability through maintenance—renders universal mandates inefficient, potentially diverting funds from broader grid upgrades.^[6] Alternatives like overhead hardening, including enhanced tree trimming and vegetation management, offer outage prevention at lower marginal costs per avoided interruption; trees contribute to up to 50% of outages, and proactive trimming has proven more economical than burial in many utility analyses.^[125] ^[6] Policies mandating undergrounding, as seen in post-hurricane Florida legislation allowing cost recovery for conversions, have faced pushback for imposing these expenses on ratepayers without rigorous, site-specific justification, echoing broader critiques that climate-focused incentives prioritize symbolism over causal evidence of net benefits.^[126] ^[127] Such approaches risk uneven reliability outcomes, as undergrounding does not eliminate all hazards and may exacerbate issues like flood susceptibility in coastal or low-lying areas.^[113]

Emerging Technologies and Challenges

Enel Group's innovation challenges in 2023 and 2025 target solutions for faster and simpler undergrounding of overhead power lines and medium-voltage cable installation, aiming to reduce time and costs through optimized processes, potentially incorporating automation like robotics for trenching and laying.^[128]^[129] Advanced nano-composite dielectrics enhance underground cable current capacity by improving insulation properties, while composite core technologies in conductors reduce sag and enable capacity increases at roughly one-third the cost of new lines, with project savings of 10-20% in construction.^[130]^[131]^[132] The underground high-voltage cable market is forecasted to reach $21 billion in 2025, fueled by grid hardening needs, but fault detection lags behind overhead systems due to burial inaccessibility, relying on emerging AI, IoT, and resonance frequency analysis for localization, though traditional methods like ground-penetrating radar remain limited in accuracy and speed.^[133]^[134]^[135] High-voltage underground cables for renewables integration face thermal limits from soil resistivity and mutual heating in dense arrangements, as evidenced in wind farm cases where design inaccuracies cause failures under variable loads, constraining capacity without dynamic rating or spacing adjustments.^[136]^[137] 2024 studies on hybrid overhead-underground lines emphasize their practicality for fault localization, such as tree flash events via improved traveling wave methods, suggesting hybrids optimize costs and reliability over full undergrounding where scalability of pure buried systems remains unproven amid high installation expenses.^[138]^[139]

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1897. Underground power lines in Los Angeles' downtown district. To eliminate the growing overhead clutter of power, telegraph, and telephone lines in ...
[15]
Mains cable from power stations in London, around 1890
Ferranti developed paper-insulated cables with conductors arranged in circles around a shared centre. Layers of waxed paper separated the outer earthed ...Missing: Paris 1880s
[16]
[PDF] The History of Electricity Generation | Distribution | Utilisation - IET
Jan12: Holborn Viaduct power station, named the Edison Electric Light. Station, was the world's first coal-fired power station generating electricity for ...<|separator|>
[17]
[PDF] HISTORICAL OVERVIEW OF MEDIUM & HIGH VOLTAGE CABLES ...
1925: The first pressurized paper cables. 1937: Polyethylene (PE) developed ... Laminated Insulation High Pressure. Extruded Insulation. Page 10. History ...Missing: date | Show results with:date
[18]
FAQ: The history of electrical cables
The 1970's heralded XLPE insulations replacing paper insulated cables in medium voltage applications. In the 1980's optical fibres were being introduced in ...
[19]
Development History of PVC Insulated Cable
Because of its good physical, chemical, electrical and flame retardant performance, PVC has been used as cable insulation material since the 1930s and 1940s.
[20]
[PDF] Power Cable Technology - EthERNet
The first pressur- ized paper cables were introduced in 1925. Polyethylene (PE) was invented in 1937, and by 1942, PE cables were introduced in the market.
[21]
History of Underground Power Cables | PDF | Insulator (Electricity)
It outlines the historical evolution of underground power cables, from Thomas Edison's early inventions to the development of cross-linked polyethylene (XLPE) ...
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Fort Collins avoids power outages with underground lines
Nov 13, 2019 · In 1968, the City Council approved an ordinance requiring underground utility lines in all new developments. Research by senior electrical ...
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Light & Power History Timeline || Utilities - City of Fort Collins
City Ordinance passed requiring all new subdivision utility installations to be constructed underground. 1968. The cities of Fort Collins, Longmont, Loveland ...Missing: lines | Show results with:lines
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Can Aluminum Really Beat Copper in Underground Power Cables?
Copper has much better electrical conductivity than aluminum – by a factor of 1.64. But it is over three times heavier and much more expensive.
[26]
Why aren't the main conductors in this underground power cable ...
Dec 22, 2017 · Aluminum has 61 percent of the conductivity of copper, but has only 30 percent of the weight of copper. That means that a bare wire of aluminum ...
[27]
Low Voltage vs. Medium Voltage Cables: Key Differences and ... - Iewc
Voltage Rating: Typically between 600V and 1kV; Conductor Material: Copper or aluminum; Insulation: PVC, XLPE, or rubber for enhanced protection; Shielding: ...Missing: properties | Show results with:properties<|separator|>
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[PDF] XLPE cable technical review
HV underground cables were made of paper lead prior to the introduction of XLPE high voltage (HV) underground cable in the mid-1970s. Due to advantages in ...<|separator|>
[29]
Results from Danish failure statistics for medium voltage XLPE cables
Authors in a study [28] , enumerated the failure rate of XLPE cables experienced in Denmark, which is about 0.5 failure rate on yearly basis per 100km, which is ...
[30]
A review of power cable aging monitoring and diagnostic techniques
As noted by the Electric Power Research Institute (EPRI) 2023, underground cable systems report failure rates ranging between 0.7 and 2 failures per 100 miles ...
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[PDF] Underground Electric Transmission Lines
Introduction. This overview contains information about electric transmission lines which are installed underground, rather than overhead on poles or towers.
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PILC cable - We're still living with it - Electric Energy Online
PILC cables are paper insulated, lead covered cables used in medium voltage underground power distribution systems, introduced in the 1930s.
[33]
Gas Insulated Transmission Lines - Beta Engineering
May 25, 2016 · It is also possible to install gas insulated lines directly underground, without a tunnel. In this case, the land above the GIL is usually ...
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Underground Cables: Know Construction, Classification, Insulation
In order to protect the cable from moisture, acids (or) alkalies, and gases in the soil and atmosphere, a metallic sheath of lead (or) aluminum is provided over ...
[35]
[PDF] Underground Power Cable Considerations: Alternatives to Overhead
A radial moisture barrier (e.g., metallic sheath), if present, may consist of extruded lead, corrugated or foil made of copper or aluminum, or corrugated.
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Horizontal Directional Drill vs Trencher - Westerra Equipment
Apr 29, 2022 · Trenching equipment is less expensive than a horizontal directional drill. If you are working on a jobsite which is relatively open with low to ...
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Choosing the Right Installation Method for Underground Utilities
Sep 2, 2020 · Open-cut methods including trenching, plowing and microtrenching are a more cost-effective and efficient method.
[38]
Understanding the NEC Code for Outdoor Buried Electrical Wiring
Apr 17, 2025 · NEC requires direct bury cables at least 24 inches deep (or 18" in conduit), low-voltage wires at 6 inches, and using listed direct burial ...
[39]
How Deep Must Electrical Conduit Be Buried?
May 2, 2024 · Generally, electrical conduit should be buried 24 inches deep, but may be 18 inches under concrete. Local codes may require deeper burial in ...
[40]
Direct Burial Wire: Where and When to “USE” It
Jan 30, 2023 · Underground Feeder (UF) cable must be buried at least 24 inches underground. Meanwhile, PVC conduit only has to be buried 12 inches underground.
[41]
[PDF] Thermal Backfill for Underground Power Cable Installations
Aug 11, 2014 · FTB is a uniform and efficient heat conducting medium that also provides 100% compaction, structural support, and mechanical protection for the.
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Trench Backfill: Best Methods & Materials, Ultimate Guide
Mar 14, 2025 · Comprehensive guide for applications of trench backfills · Best Materials: – Sand. – Gravel · Compaction Methods: – Layered backfilling. – Hand ...Common Uses of Trench Backfill · Selecting the Best Backfill...
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Boring vs. Trenching for Underground Utilities: Pros, Cons, Costs ...
Mar 14, 2025 · Trenching: $5 – $12 per linear foot; Directional Boring: $10 – $30 per linear foot. It's important to note that these base costs can be affected ...
[44]
Directional Drilling vs. Traditional Trenching: A Cost-Effective ...
Oct 3, 2023 · Directional drilling has reduced surface disruption and restoration costs, but higher equipment costs. Trenching has lower equipment costs but ...Missing: power | Show results with:power
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Undergrounding Powerlines: The New Challenges and Risks
Utilities must navigate numerous technical and physical obstacles, such as varying soil conditions, groundwater, and existing underground infrastructure - such ...
[46]
How to Decide when to Use a Trencher or Horizontal Directional Drill
May 18, 2007 · Open-cut trenching is a fast, economical way to place utilities in undeveloped, rural areas. There is no added cost wrapped up in time and tools ...Missing: comparison | Show results with:comparison
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The Effects of Soil Thermal Conductivity on Energy Transfer
Nov 1, 2021 · Soil thermal conductivity impacts heat transfer from cables, affecting their effectiveness and lifetime. Air in soil increases resistance, ...
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[49]
Prelocation of Cable Faults using Time Domain Reflectometer Method
Apr 6, 2022 · The TDR method is a good way to accurately determine the location of an underground cable fault. For more information on SCOPE cable fault ...
[50]
How to effectively identify and locate power cable faults | Megger
Sep 25, 2024 · Step 1: Initial testing · Step 2: Using a time domain reflectometer (TDR) · Step 3: Dual-channel TDRs · Step 4: When the TDR can't find the fault.
[51]
Cable Fault Location Measuring Methods - HV TECHNOLOGIES
Time Domain Reflectometry (TDR): The TDR method is the most established and widely used measuring method for establishing the total length of a cable and the ...
[52]
[PDF] PRIMARY CABLE FAULT LOCATING - High Voltage Inc
TDR's or Time Domain Reflectometers allow users to see changes in impedance in cables. Examples of impedance are splices, terminations damage etc. Modern ...
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CPUC Undergrounding Programs Description - CA.gov
Undergrounding refers to the conversion of existing overhead electric facilities, which consist of poles, wires and related equipment, to underground ...
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Life-Cycle Cost Analysis: Overhead vs. Underground Systems
Compare life-cycle costs of overhead distribution systems and underground T & D services. TW Powerline helps clients plan smarter, long-term investments.
[55]
Thousands of PG&E Customers Now Protected from Wildfires as ...
Oct 3, 2025 · Since the start of the program, the cost per mile of undergrounding has decreased from $4 million to $3.1 million in 2025. Further reductions ...
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[PDF] Underground vs. Overhead Power Lines
Underground lines have 50% less outage frequency but 58% longer duration, and older underground lines are less reliable than older overhead lines.
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Flooding & Underground Cables: Myth or Reality?
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[PDF] Undergrounding: Hidden Lines, Hidden Costs
underground is significant, with undergrounding costing as much as 10 times that of an overhead line.
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Repairing Underground Power Cables Is Nearly Impossible
Sep 21, 2021 · That's a major benefit of pipe-type oil-filled cables: they're surrounded by a gigantic liquid heat sink that can be circulated to keep the ...
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Do the Benefits of Underground Power Lines Outweigh the Costs?
Better public safety; Lower feeder energy losses; The cost of tree maintenance is removed entirely during the life of underground facilities; Reduced route ...<|control11|><|separator|>
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Distribution System Reliability: A Brief Overview of Electrical Grid ...
Apr 28, 2025 · Converting overhead lines to underground lines eliminates these risks, significantly improving reliability. While undergrounding is costly ...
[62]
Impact of Weather Conditions on Reliability Indicators of Low ... - MDPI
Sep 4, 2024 · The main advantages of cable lines are their high reliability, relative independence from weather conditions, and low maintenance costs, while ...
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Strategic Undergrounding from the Perspective of Cable Insulations ...
Oct 4, 2021 · Both EPR/EAM and TRXLPE cables can achieve the maximum service life of 40 years and more. Applications expand from power generation, substations ...
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[PDF] reducing-failure-rate-in-cables.pdf - EA Technology
Failure modes for XLPE cables include insulation deterioration due to natural ageing, water treeing, electric treeing and outer metallic sheath arcing. It is ...
[65]
A study of expected lifetime of XLPE insulation cables working ... - NIH
Experimental findings of this study show an estimated cable lifetime between 7 and 30 years for rated operating temperatures between 95 and 105 °C.<|separator|>
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The Effect of Insulation Characteristics on Thermal Instability ... - MDPI
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[PDF] Medium Voltage Underground Cable White Paper.
Apr 5, 2006 · Damage to cable insulation during or prior to installation may be crucial to a cable's longevity, particularly for medium voltage systems.” 2.3 ...<|separator|>
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Top 5 Reasons to Use Underground Transmission Lines - HDR
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Are friends electric? Valuing the social costs of power lines using ...
We measure the impact of overhead power lines on housing values using a DID approach. · Housing prices 1500m from power lines are 3.9% (£6,657) lower after ...
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How Much Do Power Lines Decrease My Property Value?
Jun 23, 2021 · A 2018 study from the Journal of Real Estate Research found that vacant lots near high-voltage power lines sell for 44.9% less than equivalent lots that aren't ...
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[PDF] Cost Benefits for Overhead vs. Underground Utilities
The lifecycle cost comparison of overhead and underground utility installations/relocations based on similar service capabilities used several variables to ...
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[PDF] PSEG Undergrounding 85x11 v11.indd - Long Island Power Authority
Transmission and distribution power lines can either be overhead or underground. To place overhead electrical lines, you need utility poles in the ground. Once ...
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Overhead vs. Underground Power Lines | San Patricio Electric ...
Cons · More susceptible to bad weather, such as high winds. · More vulnerable to damage from trees and vegetation, which requires right of way trimming.
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[PDF] Reducing Avian Collisions with Power Lines
Overhead versus Underground Power Lines. Electric utilities install power lines either overhead or underground depending upon numerous considerations. Some ...
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Underground cables - EMF-Portal
Similar to overhead power lines electric and magnetic fields are produced by underground cables. Electric fields of underground cables are nearly completely ...
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[PDF] Environmental Impacts of Transmission Lines
Soil mixing, erosion, rutting, and compaction are interrelated impacts commonly associated with transmission construction and can greatly affect future crop ...
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[PDF] Environmental Effects of Underground & Overhead Transmission ...
ROW corridors can enhance plant diversity. Positive effect on some individual species, however… Habitat generalists can thrive. Replacing rare plants.
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[PDF] MODELLING THE CABLE TRENCHING PROCESS ON SAND DUNES
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Horizontal Directional Drilling Explained - GPRS
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Navigating the Challenges of Directional Bore Projects
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How Power Lines Can Spark Devastating Wildfires - Fire Lawsuit
Improperly maintained power lines only account for about 3 percent of wildfires ... One felled tree on a high-voltage power line can instantly spark a fire.
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Report 2021-117 - California State Auditor - - CA.gov
Mar 24, 2022 · ... fire to spread quickly, making it difficult to control. Since 2015 power lines have caused six of the State's 20 most destructive wildfires.
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Life Cycle Assessment of Overhead and Underground Primary ...
Jun 16, 2010 · This paper assesses environmental impacts from overhead and underground medium voltage power distribution systems as they are currently built and managed by ...
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Underground vs. Overhead Power Lines - A Complete Comparison
Dec 3, 2024 · Under-ground power lines last 40 to 50 years, whereas over-head power lines last about 20 to 25 years. Under-ground systems have greater initial ...
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Life-cycle assessment of 11 kV electrical overhead lines and ...
The life-cycle impacts of five different 11 kV electrical power cables (three overhead lines and two underground cables) were analysed.
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Power Lines, Electrical Devices, and Extremely Low Frequency ...
Oct 28, 2022 · Most of these studies have found no increase in the risk of any type of cancer. In fact, the risk of some types of cancer was actually lower in ...
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Sea Level Rise Is Reshaping Our Cities: The Truth About Coastal ...
Electrical substations and power plants in coastal areas are particularly at risk, with saltwater intrusion threatening underground cables and equipment.
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Hidden threat: Global underground infrastructure vulnerable to sea ...
Apr 5, 2024 · As sea levels rise, coastal groundwater is lifted closer to the ground surface while also becoming saltier and more corrosive.Missing: power cables
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[PDF] IEC 60840:2020 - iTeh Standards
This document specifies test methods and requirements for power cable systems, cables alone and accessories alone, for fixed installations and for rated ...
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(2) Burial Depth of Underground Circuits - UpCodes
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History of Underground Power Cables - ResearchGate
Aug 7, 2025 · ... The first underground cables were laid in the latter part of the 19th century [13] . Installing underground cables is a complex and time- ...<|separator|>
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[PDF] LONG-LIFE XLPE INSULATED POWER CABLE - Jicable
When medium voltage (MV) XLPE insulated cables were first installed in the late 1960's, cable manufacturers and electric utilities expected them to perform ...
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Introduction to Partial Discharge (Causes, Effects, and Detection)
IEEE-400 and IEC 60270 PD Tests for partial discharge offline (VLF, etc.) Also known as No-Outage testing, this type of testing requires no de- energizing of ...
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Partial Discharge Testing of Cables | EA Technology Americas
The purpose of partial discharge testing of MV/HV cables is to find the discharge before it leads to flashover and catastrophic failure.
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Going Underground: European Transmission Practices
Oct 1, 2011 · The policy requires utilities to underground any 110kV line if the comparative cost factor to an overhead line is not above 2.75. NABEG does ...Missing: urban | Show results with:urban
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Two-Stage Seismic Resilience Enhancement of Electrical ...
The 2011 Tohoku earthquake damaged 42 transmission towers, 70 transformers, and 14 power plants in Japan [3]. The Christchurch earthquake destroyed 15% of ...Missing: rates | Show results with:rates
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[PDF] Overhead or Underground A Comparison
Within Europe the total amount of underground cable used has risen from 15-20% in. 1960 to 40% in 1994. In Japan at 275 kV there was 11.5 % in. 1980 and in 2001 ...
[100]
PG&E achieves milestone with 1,000 miles of underground powerlines
Oct 7, 2025 · Since the program's inception, the cost of undergrounding has decreased from $4 million per mile to $3.1 million in 2025, with further ...Missing: outage | Show results with:outage
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Undergrounding Case Study: Pacific Gas & Electric (PG&E)
Pacific Gas and Electric (PG&E) suggesting that underground powerlines reduce wildfire risk by 98% compared to overhead powerlines in a given location.
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Cost and reliability comparisons of underground and overhead ...
Aug 10, 2025 · Our research indicates that undergrounding reduces O&M cost and enhances reliability by reducing power outage durations.
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Underground Wiring in New Residential Areas
and benefits and challenges — of providing underground power and telephone lines in new ...
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Overview/History | City of San Diego Official Website
Although the City has been undergrounding lines since 1970, approximately 1,000 miles of overhead utility lines remain to be undergrounded.
[105]
Burying power lines: Progress made and a long way to go - KPBS
Apr 25, 2025 · In the last two months another two San Diego neighborhoods finished having their power lines put underground. The city's about a third of ...
[106]
Bay Park Community Celebrates Completion of Undergrounding ...
Apr 23, 2025 · A community celebration in Bay Park today marked the removal of more than three miles of overhead power lines in the neighborhood.
[107]
Editorial: Underground power lines are too costly - CT Insider
Sep 30, 2025 · ... underground power lines than it is to gravity-defying automobiles. It still costs up to 10 times as much to build or move a power line ...
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2023 Industry Update: Buried Utilities - Champion Fiberglass
Oct 26, 2023 · As of August 2023, they have completed 75% of the total lines and expect to finish by 2030. In southwest Las Vegas a new housing subdivision ...
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Underground utilities, more reliable and lasting, still slow to take root ...
May 17, 2023 · Placing utilities underground creates a more efficient and reliable distribution system, reducing the likelihood of outages brought on by weather damage.
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System Hardening & Undergrounding | PG&E
October 2025: Thousands of PG&E Customers Now Protected from Wildfires as 1,000 Miles of Powerlines are Energized and Underground. May 2025: PG&E Proposal ...
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Isn't it better to just bury power lines? That may depend on where ...
Sep 14, 2017 · Burying power cables, or “undergrounding,” makes lines impervious to damage from wind and ice, and harder for would-be attackers to target.
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[PDF] Undergrounding to Reduce Florida Power System Vulnerability to ...
Jun 9, 2024 · 14 While their average restoration times were greater, underground lines experienced a much smaller number of outages.15 In 2018, Duke Energy.
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Should power lines go underground? - UF Research
Sep 13, 2017 · Putting power lines underground will make electricity service more resilient to wind damage but also make flooding a bigger concern.
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Reliability | Storm Secure Underground Program - FPL
The Storm Secure Underground Program (SSUP) replaces overhead power lines with underground lines to avoid tree contact, reducing restoration costs and outage ...
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Power outages and social vulnerability in the U.S. Gulf Coast - Nature
Jun 26, 2025 · For underground power lines, hurricanes and storm surges can lead to flooding and power outages. Before hazards strike, utilities often work ...
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Puerto Rico Grid Recovery and Modernization | Department of Energy
In September 2017, Hurricanes Irma and Maria caused most of the transmission and distribution system in Puerto Rico to collapse, leading to one of the ...<|separator|>
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[PDF] Energy Resilience Solutions for the Puerto Rico Grid
The eye of Hurricane. Maria careened just south of the United. States Virgin Island of. St. Croix in the early hours of September 20,. 2017, and landed in.
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Aug 9, 2022 · Puerto Rico utilities are shoring up their defenses using a PNNL-devised planning tool, the Electrical Grid Resilience and Assessment System (EGRASS).
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Connecting Regions for Stable Supply of Electric Power
The New Hokkaido-Honshu DC Seikan Tunnel project was initiated to construct an underground power transmission line in the Seikan Tunnel.
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New East-West HVDC Commissioned, Interconnecting Nagano and ...
Apr 1, 2021 · This high-voltage direct current (HVDC) *1 system is the first HVDC system in Japan that interconnects the east-west grids operating in 50Hz and 60Hz, *2 ...
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Key Technologies Used in Hida-Shinano HVDC Link - Hitachihyoron
It is the first such project in Japan in which a high voltage direct current link connects via overhead lines between grids operating at different frequencies ...
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Why Japan Uses Overhead Power Lines Instead of Underground?
Overhead lines are easier, quicker, and cheaper to inspect and repair after earthquakes compared to underground cables, which can be difficult to access if the ...
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Grid infrastructure investments drive increase in utility spending over ...
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[PDF] A study on the costs and benefits of undergrounding overhead ...
When compared to overhead power systems, underground power systems tend to have fewer power outages, but the duration of these outages tends to be much longer.
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Trees and power lines don't always mix - Entergy
Jul 10, 2024 · Trees can be a contributing factor to as many as 50% of power outages. Problems can occur suddenly, such as when a branch breaks during a wind or ice storm.
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Gov. DeSantis signs bill approving underground power lines
Jun 29, 2019 · Ron DeSantis on Thursday signed a bill that could lead to more underground power lines in hurricane-vulnerable Florida and vetoed two measures ...Missing: controversies | Show results with:controversies
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[PDF] Underground vs. Overhead Executive Summary
In general, the costs of undergrounding far outweigh its benefits. In a research conducted by the Virginia commission, the benefits.
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Faster and simpler installation of underground cables in Medium ...
Challenges Faster and simpler installation of underground cables in Medium Voltage (MV) lines ... enel.com banner v11. Cookie Preferences.Missing: robotics | Show results with:robotics
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Faster and simpler undergrounding of overhead power lines
Jun 3, 2025 · Join the challenge to reduce time and cost in undergrounding power lines with innovative solutions contributing to Enel's grid reliability.Missing: projects | Show results with:projects
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Enhancement of the underground cable current capacity by using ...
Jun 21, 2024 · This article proposes the use of nano-composite dielectrics to increase the current capacities of underground power cables. Nano-fillers are ...
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[PDF] Advanced Conductor Scan Report - Department of Energy
Dec 19, 2023 · Advanced conductor technologies make it possible to increase transmission capacity for roughly one-third of the cost of building new lines and ...
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The Economics of Advanced Conductors
For new construction, TS Conductor enables longer spans with fewer, shorter structures, reducing total project costs by 10-20%. By focusing investment on the ...<|separator|>
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Underground High Voltage Cable Market Size, Report 2034
The underground high voltage cable market was estimated at USD 20.9 billion in 2024. The market is expected to grow from 21 billion in 2025 to USD 58.8 billion ...
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[PDF] Challenges and solutions of Artificial Intelligence-based fault ...
The underground cable installations, maintenance, and fault detection are difficult and high cost compared to overhead lines. However, underground cables are ...<|separator|>
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Deep learning-based fault detection and location in underground ...
Sep 6, 2024 · This study introduces a pioneering approach that integrates long short-term memory networks with conventional power signal analysis techniques ...
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Insulated Cable Failures in Wind Farms: The Role of Soil Thermal ...
Aug 11, 2025 · Cable failures were due to underestimation of soil thermal resistivity, inadequate spacing, and lack of clear soil compaction guidelines, ...
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Investigation on improving the asset utilization ratio of underground ...
Apr 1, 2025 · The prevalent dense cable arrangement can lead to serious overheating problems due to the mutual thermal effects between cables, ...
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Research on Tree Flash Fault Localization of Hybrid Overhead ...
Abstract. The occurrence of tree flash faults in hybrid overhead–underground lines presents a significant challenge to the smooth operation of power systems.
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(PDF) Research on Tree Flash Fault Localization of Hybrid ...
The occurrence of tree flash faults in hybrid overhead–underground lines presents a significant challenge to the smooth operation of power systems.