24 Top Considerations for Utilities to Defend Against Storms, Mitigate Wildfires, and Modernize the Grid
In an era marked by increasingly severe natural disasters and escalating wildfire risks, utilities face mounting pressure to enhance the resilience and reliability of their power delivery systems. Utilities should adopt strategies to modernize their transmission and distribution systems. As climate change intensifies the frequency and severity of storms and wildfires, it becomes even more important for utilities to invest in advanced technologies and practices that not only protect infrastructure, but also improve overall grid performance.
This comprehensive guide covers a range of innovative solutions, from upgrading to track-resistant coverings on conductors to employing advanced materials and techniques for enhanced durability and safety. By implementing these top considerations, utilities can protect their systems against natural threats, reduce the risk of fire ignition, and ensure more reliable power delivery among the growing challenges of a changing climate.
DELIVERING POWER...RESPONSIBLY
Here are the top considerations for utilities modernizing the transmission & distribution systems to defend against natural disasters and wildfires.
SHIELD BARE WIRES WITH TRACK-RESISTANT COVERING
Tree wires are self-supporting overhead conductors covered with an extruded track, UV, and abrasion-resistant covering that provides protection against momentary contact between phases. Also known as CAMVTM CAMV™(Covered Aerial MV) cable, it prevents direct shorts and flashovers should tree limbs or other grounded objects contact the conductor. Upgrading bare overhead conductors to CAMVTM CAMV™ products can reduce faults caused by trees and minimize fire ignition in dry areas with dense vegetation.
PROTECT EXPOSED GROUNDS USING COVERING
Protected Ground Wire (PGW), Covered Line Wire, and Covered Riser Wire are specified for applications where protection from momentary contact with wildlife is needed. Bare copper conductors are covered with either an extruded polyethylene (PE) or a crosslinked polyethylene (XLPE) layer to protect the exposed copper. Because the metallic appearance is concealed by a black covering, it also deters vandalism and copper theft.
DELAY CORROSION USING COPPER
Copper is more corrosion-resistant than aluminum and steel, which are often used on overhead lines. A good practice in coastal areas, where weight is not a major concern, is to utilize hard-drawn copper wire as an overhead distribution conductor. Metallic corrosion can occur both above and underground, and there are methods to delay corrosion below grade, which are challenging to inspect. Replacement of corrosive native soil with an engineered backfill is a great option. Improvement of local drainage is also essential as it diverts water around the exposed wires and lowers concentration of the contaminated water.
FIGHT WILDFIRES BY REPLACING BARE WIRES
The most successful wildfire mitigation solution for high fire risk areas is the conversion of overhead lines to below grade systems. There have been more intense wildfires due to climate change that are difficult to prevent. If undergrounding is not possible due to time, budget, or right-of-way, then bare overhead lines can be upgraded with tree wires to minimize arcing in drought regions. The 3-phase bare conductors can potentially collide with one another during windy conditions, which trigger sparks. Replacing bare wires with CAMVTM CAMV™ cable or covered conductors not only lessens the burden of vegetation management but also reduces the fire risk.
UPGRADE CONDUCTORS OR UPSIZE MESSENGERS
To reinforce overhead systems against storms, many conductor types can be specified for bare transmission lines, CAMVTM CAMV™ distribution designs, or 600V service drop cables with a messenger. AAC containing 1350-H19, AAAC made of a 6201 alloy, and ACSR are standard options. Greased ACSR or mischmetal ACSR are frequently deployed to hamper steel corrosion in coastal areas. Additionally, ACSS with a higher thermal rating and C7® conductors with high-temperature & low sag are gaining acceptance for long span lengths located in hurricane-prone regions.
CHOOSE XLPE TO BOOST THERMAL STABILITY
When considering dielectric materials for overhead or underground circuits, there are two designs that can impact the long-term performance due to a conductor’s thermal rating. The standard option is a thermoplastic Polyethylene (PE or LLDPE) covering/insulation, while the premium grade is a thermoset or Crosslinked Polyethylene (XLPE). Replacing PE with XLPE raises the cable’s normal operating temperature from 75°C to 90°C, emergency overload from 95°C to 130°C, and short circuit from 150°C to 250°C. A thermoset insulation will not soften or melt easily in comparison to a non-crosslinked material.
SELECT HDPE TO WITHSTAND ABUSIVE USAGE
If a more robust cable is desired, then a High- Density Polyethylene (HDPE) material should be selected instead of the common Linear Low-Density Polyethylene (LLDPE). HDPE’s excellent abrasion resistance protects cables from abusive tree limb contact or other grounded contact and can also minimize damage during shipment, handling, and installation. HDPE’s superior durability compared to LLDPE can protect cables from wildlife attack and mechanical impact from backfill.
UNDERGROUNDING TO PREVENT OUTAGES
With the increasing frequency of natural disasters including hurricanes, tornadoes, wildfires, and winter storms, electric utilities have proactively transitioned overhead lines to underground circuits to boost reliability. Approximately 80% of power outages occur in distribution systems. For example, 15kV distribution conductors made of ACSR can be direct-buried by converting to a 15kV primary aluminum MV cable with a TRXLPE insulation, concentric neutrals, and an overall LLDPE jacket, which has become the preferred method for the upgrading of old lines overhead or underground and installation of new systems.
WATER-BLOCK TO DEFEND AGAINST MOISTURE
Water intrusion is one of the primary causes of cable system failures. Moisture accelerates the dielectric breakdown of insulation and triggers metallic corrosion. Corrosion-resistant designs such as solid conductors over stranded wires and copper tinning over uncoated counterparts have proven to be effective. A strand fill compound to water-block the conductor is frequently specified for underground MV cables. Water-swellable powder can be applied over shielding wires, under the jacket, to absorb and retain moisture, which hinders the water penetration between the layers of jacketing and shielding wires along the installed cable.
SPECIFY EPR OR TRXLP FOR UNIQUE APPLICATIONS
MV cables rated 15-46 kV can be insulated with either EPR or TRXLPE depending on project requirements. EPR is a heavily-filled synthetic rubber formulation exhibiting excellent thermal stability, lower temperature flexibility, increased flexibility at low temperatures, and improved flame retardancy compared to the unfilled TRXLPE. Both designs can achieve the minimum 40-year service life and deliver excellent performance. However, installations in colder climates or locations requiring a UL optional flame rating can benefit from pairing EPR with a different shielding and jacket.
LOWER ELECTRICAL STRESS USING 133% INSULATION
The cable insulation level is dictated by how fast kV the protective equipment can de-energize the circuit in case of a fault. If a fault can be cleared within 60 seconds, then 100% insulation is sufficient. However, if a fault will sustain beyond 1 minute, but less than 1 hour, then 133% design is required. A 25kV 1/0 AWG cable insulated with a 133% wall yields a 15% reduction in electrical stress at the conductor shield and insulation interface compared to one with only 100% insulation. A thicker insulation is recommended for systems prone to electrical surges, and lowering electrical stress by using a heavier insulation can extend cable life.
UNDERGROUNDING TO PREVENT OUTAGES
With the increasing frequency of natural disasters including hurricanes, tornadoes, wildfires, and winter storms, electric utilities have proactively transitioned overhead lines to underground circuits to boost reliability. Approximately 80% of power outages occur in distribution systems. For example, 15kV distribution conductors made of ACSR can be direct-buried by converting to a 15kV primary aluminum MV cable with a TRXLPE insulation, concentric neutrals, and an overall LLDPE jacket, which has become the preferred method for the upgrading of old lines overhead or underground and installation of new systems.
WITHSTAND SHORT CIRCUIT USING MORE NEUTRALS
The outer insulation shielding for many primary MV cables contain “one-third” neutrals relative to phase conductor size when used for a 3-phase supply, or "full-size" neutrals for a single-phase system. With modern rapid- switching equipment at substations, available short circuit current and duration are reduced compared to decades ago. Using a reduced possibly neutral rating ranging from 1/4, 1/6, to 1/12 saves material cost upfront but can pose significant risk due to an insufficient short circuit capacity.
REDUCE DIAMETER VIA COMPACT STRANDS & FLAT STRAPS
PILC (Paper-Insulated Lead Cable) replacements typically require retrofitting new cables into an existing old conduit system with smaller size conduits than currently used. In order to reduce overall cable diameter and maximize flexibility utilities are using a full compact copper conductor
insulated with the flexible EPR/EAM system shielded with flat strap neutrals with a ruggedized HDPE or PP jacket that have proven to be successful. A triplexed design with reduced insulation and/or jacket thickness helps to further lower the overall diameter to fit into a small conduit. HDPE or PP jackets also feature an improved oil resistance compared to LLDPE, which is critical if the cable will be subjected to oil residue leaked from old PILC cable.
USE LSZH TO BOLSTER SAFETY
Heavy-duty network cables rated 600V, 1kV, or 2kV are often installed in vaults or manholes located below congested downtown streets and are operated to meet peak power demand. They are designed to withstand high temperatures, moisture ingress, and chemical exposure and are flame-retardant and inherently abrasion- resistant. Insulation material options include leaded or lead-free EPR/ EAM, Chlorinated Polyethylene (CPE), and Low Smoke Zero Halogen (LSZH). LSZH is ideal for use in establishments where reduced smoke and low acid emissions are desired for public health and safety.
INCORPORATE SHIELDING TO DEFEND EMF
For substations containing a variety of extra high-voltage equipment, significant sources of electromagnetic interference (EMI) are present. Shielded control and power cables are specified in transmission substations to mitigate EMI. The EMI shielding efficiency depends on electrical conductivity, cable coverage, and shielding thickness. Doubling the number of helically applied copper tape shield with a greater thickness and a higher percentage of overlap will improve shielding effectiveness compared to a thinner and single-wrapped tape shield.
ADD CONDUIT TO IMPROVE SAFETY
Many methods can be deployed to install cables underground, including the use of PVC pipes
or HDPE conduit, installation of concrete duct banks, or direct burying cables in earth. While direct burial is cheaper upfront, cables are susceptible to backfill damage and accidental dig-ins. Using conduit creates a durable barrier both electrically and physically to protect cables from mechanical forces and avoid electrocution. Pulling cable in conduit improves safety compared to direct burial as the protective plastic pipe can prolong cable life and lower replacement costs and frequencies.
ADOPT CIC TO SAVE TIME & LABOR
Adopting an all-in-one Cable-in-Conduit (CIC) system not only saves labor and shortens installation time, but also can help prevent field injuries and is a proven solution to mitigate wildfires. Medium voltage and 600V cables can be preassembled in HDPE conduit at the factory. The long continuous CIC length provided on a standard reel can be installed with fewer or no joints which are labor-intensive to build. CIC can be deployed via Horizontal Directional Drilling (HDD), plowing, or trenching. HDD minimizes the construction impact with less interruptions to residential areas or busy commercial districts.
OPTIMIZE SAG & TENSION VIA SAG10® SOFTWARE
Southwire's SAG10® software is recognized as the industry's benchmark for overhead conductors’ sag-tension modeling based on the Alcoa Graphic method. It combines 70 years of conductor data, customer feedback, and field expertise into one powerful tool. Over 500 utilities and consultants rely on Southwire’s & SAG10® software to design overhead systems.
ASSESS GRID RESILIENCY DIGITALLY
Southwire offers Digital Grid Resiliency Assessments identifying areas for improvement by leveraging your outage and GIS data. This program locates problematic circuits at the device level and prioritizes maintenance actions. It also provides recommendations with expected benefits and cost justifications. Assets are scored by an overall equipment ranking based on health and network criticality.
RUN VOLTAGE DROP TO SIZE CONDUCTORS
Do you need to calculate the voltage drop for a specific circuit length or size conductors to meet the voltage drop limit of 3% per NFPA 70® NEC®? Southwire’s calculator tool includes copper & aluminum options, commercial & residential applications, 60, 75, or 90°C ratings, and single vs. 3-phase systems. Installation methods feature overhead lines, direct burial, and steel vs. non-steel conduit.
REJUVENATE CABLE TO EXTEND LIFE
Aging dielectric cables with growing water trees can be restored close to their original state by utilizing the one of the world's only cable rejuvenation services. Our patented rejuvenation technology injects silicone fluid into cables via the conductors. Then, the liquid migrates out to the conductor shield and insulation. This process raises the breakdown strength of the insulation, extends service life, and boosts reliability of old circuits without costly replacement.
MODEL AMPACITY TO AVOID OVERHEATING
Recently, more copper conductors instead of aluminum have been specified due to the high ampacity required for infrastructure expansions, such as EV and data centers, to meet the growing power demand. Using general ampacity data from a code book might not be sufficient. Southwire offers comprehensive ampacity studies to verify the maximum current-carrying capacity for cables under complex installations and unique environmental conditions. Factors such as burial depth, cable layout, heat sources, and soil thermal resistivity play a critical role in ampacity.
CALCULATE PULLS TO PREVENT DAMAGE
Conduct cable pull calculations in advance to evaluate the routings, coefficient of friction (CoF) for different jacket materials, pull distance, number of bends, and the angle of each bend.
