Latest Overhead T&D Articles

Critical energy storage ensures uptime with UPS systems, battery backup, and microgrids, stabilizing renewables and grid resilience through frequency regulation, peak shaving, and long-duration solutions for hospitals, data centers, and industrial facilities.

What Is Critical Energy Storage?

Systems that provide guaranteed power continuity and grid support using UPS, batteries, and microgrids.

✅ Ensures uptime for critical loads during outages

✅ Stabilizes grids via frequency regulation, peak shaving

✅ Integrates renewables with storage, UPS, and microgrids

Upgrading and deferring existing wires and substations may be the most common application of battery storage utilized for transmission and distribution. However, batteries also provide a range of solutions designed to maximize the lifetime of T&D infrastructure. Also referred to as T&D asset optimization, these energy storage systems (ESSs) are designed to enhance the efficiency and effectiveness of existing T&D assets to provide electricity in a given service territory. Ensuring that these systems are reliable is critical to the effective operation of electricity throughout a given service territory.
Navigant Research anticipates that a cumulative 35.5 GW of new energy storage will be built for critical infrastructure through 2027. Approximately 25% of this storage capacity is expected to directly address T&D issues. Mission critical installations require systems that deliver continuous electrical service with high power quality to the grid. Such installations also require facilities like large data centers, telecom operations, financial services centers, hospitals and complex manufacturing operations. This market segment is growing and can be addressed by a variety of system design topologies that can deliver high-fidelity electricity.
There exist a variety of specific drivers that have led utilities around the world to deploy ESSs to improve operations in T&D infrastructure. Local grid conditions and utility preference have a significant impact on the likelihood that storage systems will be developed to defer T&D upgrades. Specifically, there are three key issues that ESS help mitigate in this market. For readers new to system architecture, the fundamentals of power distribution help explain how storage eases bottlenecks across feeders.

Reliability
The primary driver for utilities pursuing reliability improvements—with or without energy storage—is the need to enhance the reliability of energy supply for their customers. ESSs enable this by either avoiding local outages that may originate on the feeder where an ESS is deployed or islanding the feeder and maintaining power supply for customers. Improving reliability is a concern for commercial and industrial (C&I) customers, who often place a premium on reliability as they risk significant financial losses from an outage. To understand the impact of grid outages for customers, analysts and utilities calculate the value of lost load (VOLL), which represents the cost of going without power for a certain period. For a homeowner this cost is minimal, more of an inconvenience than a major economic impact. However, for C&I buildings, the VOLL in the United States is estimated to average around US$20,000/MWh, according to a 2014 study from The Brattle Group. With the increasing cost-effectiveness of distributed energy resources and independent energy procurements allowing large companies to defect from their local utilities, maintaining reliable service is a critical concern for grid operators. In outage-prone zones, deploying a microgrid can maintain service while upstream faults are cleared.

Congestion and Curtailment
Transmission line congestion is a frequent issue faced by grid operators around the world. Transmission congestion issues can occur in both urban and rural areas and may be driven by either renewable or conventional energy generation. Congestion is caused when increased demand for electricity during peak periods outpaces the available transmission capacity. This issue is frequently the result of generation facilities being located far from load centers, with limited bandwidth to transfer energy from generation to load centers. During peak demand periods (that is, when wires heat up), congestion on transmission lines can result in insufficient energy to serve load, instability on the transmission network and increased costs for load-serving utilities. Although congestion issues on the transmission network receive the most attention, congestion can also occur on the electricity distribution system when existing infrastructure is unable to serve peak demand in each area. This situation is often exacerbated by high penetrations of variable distributed generation, such as solar PV, wherein fluctuating output leads to rapid changes in demand for electricity at the grid edge. As utilities integrate more distributed energy resources, storage can buffer variability at the grid edge.

Load Growth
Overall load growth rates have decreased or remained flat in the US and other developed economies in recent years; however, the dynamics of peak demand periods on the grid continue to evolve. Some utilities are experiencing decreasing overall load growth rates yet have increasing growth in their peak demand. Furthermore, the duration of peak demand is growing in many areas, moving from the traditional two to four-hour peak period to well over four or even eight hours in some locations. This trend is being exacerbated by the rising penetration of solar generation, particularly in hot climates. According to utility Arizona Public Service, hot summer temperatures above 100°F combined with decreasing solar generation in the evening result in six to seven-hour peaks across their system to cover air conditioning usage. Advanced smart grid controls can stretch capacity during extended peaks without immediate wire upgrades.

What Types of Technologies Fit?
There are key advanced battery technologies that have the optimal characteristics to serve critical loads in high fidelity settings. These technologies are judged by metrics including the following:

• Power and Energy Density
• Lifespan
• Cost
• Operation and Maintenance Requirements
• Physical Size/Housing Requirements

While there are several technologies that have attractive profiles across the above criteria, there are three key technologies that are poised to have a substantial impact on the backup power market.

Li-ion
Lithium ion (Li-ion) batteries have good energy and power densities, round-trip efficiency and life cycle expectations, making them particularly well-suited for power-intensive critical infrastructure applications. Li-ion batteries have emerged as the leading technology for both utility-scale and C&I energy storage applications because of their flexibility and availability through mass production, pushing them further down the experience curve than other advanced batteries. Several leading vendors—including LG Chem, Samsung SDI, Panasonic and BYD—have rapidly expanded manufacturing capabilities in recent years, contributing to the falling costs of  the technology. For project timelines, anticipating costly interconnection delays helps developers align procurement and commissioning.

Flow
Flow batteries are advantageous because they can store chemical energy for long periods of time by simply adding more tanks of liquid electrolyte. This makes them favorable for low cost, long-duration applications that require shifting of multiple hours’ worth of energy from one time of day to another. They are generally safer than Li-ion batteries as thermal management is not required. They also have little to no depletion of active materials over time, giving them greater life cycle expectancies than other battery types. This benefit is magnified by the fact that many flow batteries use inexpensive materials, vanadium being the primary exception.

Hybrid Battery/Fossil Generator
Hybrid battery-fossil fuel technology can be especially flexible as a grid or building asset and is increasingly being recognized as a tool to improve the efficiency, flexibility, and resiliency of existing fossil fueled power systems. In the same way a hybrid car uses battery storage to improve efficiency and reduce fuel consumption, an ESS integrated with conventional power can result in significant fuel savings while improving the system’s overall resiliency. Additionally, critical facilities with the need for long-duration guaranteed power (for example, 12-, 24-, or 72-hour needs) often are required by legislature to have diesel generators onsite. Pairing storage with improved overhead switchgear can further enhance fault isolation and reduce restoration times.

What Should Stakeholders Do to Prepare?
Utilities should work with vendors and project developers to offer solutions tailored to their customers’ specific needs. The most viable early projects may be smaller in capacity and specifically target a T&D issue a utility is experiencing. Smaller problems are more likely to be accepted by utilities and regulators due to the lower risk involved. Additionally, vendors should focus on providing standardized, modular systems that can be scaled to meet the required capacity for projects now and in the future. By starting small with modular systems, additional capacity can always be added as needed. Once utilities and regulators become comfortable with ESSs for T&D deferral, small modular systems will be easier to replicate in new locations and with new customers.
Storage providers need to determine how to structure their business models to take advantage of additional revenue streams while ensuring the reliability of core T&D optimization benefits. This challenge will require input and collaboration between project developers and integrators, software providers, utilities and market regulators to determine the best-fitting solutions. Storage industry stakeholders should be actively involved in ongoing regulatory processes to ensure that the full benefits of the technology are well understood.

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• Transmission And Distribution Channel

Direct current technology delivers efficient DC power distribution via rectifiers, converters, and power electronics, enabling microgrids, energy storage, HVDC links, photovoltaics, and electric vehicle charging with reduced losses and improved reliability.

What Is Direct Current Technology?

Direct current technology uses one-way flow and power electronics to enable efficient DC distribution and control.

✅ Unidirectional conduction for stable voltage and reduced conversion losses

✅ Power electronics: rectifiers, DC-DC converters, inverters, protection

✅ Applications: HVDC links, microgrids, EV charging, PV and battery systems

Direct current (DC) is the preferred technology for moving large amounts of power across long distances. DC results in overall higher efficiency and reliability than an equivalently-sized alternating current (AC) system moving the same amount of power.

The Advantages of DC

More efficient: Over long distances, DC transmission can move more power with less electrical losses than an equivalent AC transmission line. For foundational context on grid-scale power flows, see electricity transmission basics to understand how DC and AC corridors are planned.

Lower Cost: Higher efficiency means a lower transmission cost, helping renewable energy compete against other power sources. Advances in overhead switchgear innovation can also drive capital and operating savings across long routes.

Improved Reliability: HVDC transmission can enhance system stability, allow the operator complete control over power flow, and facilitate the integration of wind from different resource areas. These characteristics align with smart grid strategies that require precise controllability and resilience.

Smaller Footprint: DC transmission lines require narrower right-of-way footprints, using less land, than equivalent AC lines. Planning and design of overhead transmission lines further influence corridor width, clearances, and visual profile.

The major advantage of DC power lines is their efficiency—less energy is lost as it is transmitted and there is no need for reactive compensation along the line. Because DC (Direct Current) flows steadily through the wires without changing direction many times each second and through the entire conductor rather than at the surface, DC (Direct Current) transmission lines typically lose less power than AC transmission lines. By comparison, AC transmission lines must manage reactive power and frequency-related effects over distance.

How HVDC Works

Historically, the transfer of electricity between regions of the United States has been over high voltage alternating current (AC) transmission lines, which means that both the voltage and the current on these lines move in a wave-like pattern along the lines and are continually changing direction.  In North America, this change in direction occurs 60 times per second (defined as 60 hertz [Hz]).  The electric power transmitted over AC transmission lines is exactly the same as the power we use every day from AC outlets, but at a much higher voltage. From bulk transmission, electrical distribution systems step and route energy to neighborhoods and facilities.

Unlike an AC transmission line, the voltage and current on a direct current (DC) transmission line are not time varying, meaning they do not change direction as energy is transmitted.  DC electricity is the constant, zero-frequency movement of electrons from an area of negative (-) charge to an area of positive (+) charge.

The first commercial electric power system built by Thomas Edison in the late nineteenth century carried DC electricity, but given some early advantages, AC power eventually became the primary power system in the United States.  Some of these advantages are no longer applicable (e.g., technology has advanced to allow efficient conversion from AC to DC), and DC transmission is the preferred solution for moving large amounts of renewable power over long distances.

Clean Line’s HVDC transmission lines projects will deliver power from new, renewable energy resources.  These resources will be AC generators, as is normally the case, and their energy will be transmitted along collector lines.  These collector lines will then be connected to a substation where the power will be collected and the voltage will be transformed from the voltage of the collector lines to a common voltage (such as 345,000 volts).  The power will then be converted to DC, a process known as rectification, using power electronic switches called thyristors.  The power will then be transmitted several hundred miles along a set of conductors called a transmission line before getting converted back to AC, a process known as inversion, again using thyristors as the switching devices.  After the DC power is converted back to AC it is transformed to the common voltage of the grid to which it is being connected (e.g. 500,000 volts or 765,000 volts, in the case of Clean Line’s projects).  This power is then distributed via the interconnected grid by the local utilities to homes and businesses.  See below for an illustration of this process.
  Once inverted and synchronized, the power enters local power distribution for last-mile delivery and metering.

The History of DC Transmission

The development of direct current (DC) transmission dates back to the 1930’s and has been a proven technology since the first major installations in 1954.  Over the last 40+ years, DC Projects have shown to offer significant electrical, economic, and environmental advantages when transporting power across long distances, where there has been a veritable boom in the use of DC to tap energy resources in remote portions of the country and bring the energy to consumers in more heavily populated areas.  Among those direct current lines is the Pacific DC Intertie, which has been in operation for over 30 years.  Operating at ±500 kilovolts, the line is capable of transmitting up to 3,100 MW of power.  In terms of operating voltage and capacity, the Pacific Intertie is similar to the Clean Line transmission line projects, which will operate at ±600 kilovolts and deliver up to 3,500 MW of power.

Currently there are more than 20 DC transmission facilities in the United States and more than 35 across the North American grid.

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• Transmission And Distribution Channel

How Overhead Switchgear Innovation Cost Effectively? Advanced medium-voltage reclosers, vacuum interrupters, and SCADA-enabled smart sensors enhance reliability, reduce arc-flash risk, cut lifecycle maintenance, and optimize distribution networks for grid modernization and predictive maintenance.

How Overhead Switchgear Innovation Cost Effectively?

Deploy SCADA-ready reclosers, vacuum tech, and sensors to boost reliability, cut OPEX, and extend asset life.

✅ Medium-voltage reclosers and sectionalizers lower fault costs

✅ Vacuum interrupters reduce maintenance and minimize arc-flash hazards

✅ SCADA, IoT sensors enable predictive maintenance and uptime

BACKGROUND
Achieving many of the globe’s top priorities depends on an unprecedented expansion of electric generation capacity. A report released last year by the Electric Power Research Institute (EPRI), for example, forecast that achieving net-zero carbon emissions in the U.S. by mid-century would require a nearly 500 percent increase in electricity generating capacity.
A decarbonized future powered largely by renewable electricity generation depends on a reliable grid, especially the transmission grid. A new report by the National Academies of Science, Engineering, and Medicine in the U.S. laid out a blueprint for achieving 2050 net-zero goals, and strengthening and expanding the transmission system was a key component because the transmission system is so important both to integrating renewables and delivering clean energy to where it is consumed. The reliability of the transmission and sub-transmission grid is particularly vital as clean electricity is increasingly relied on to fuel transportation, heating and cooling, and manufacturing and industrial processes. Indeed, the ability to sectionalize and reroute power when an outage hits the sub-transmission system has an outsized impact on reliability because high-voltage grids serve so many homes and businesses. As planners modernize regional networks, an understanding of electricity transmission principles helps explain how long-distance power flows and interconnections support resilience.
The high costs and environmental impacts of status quo solutions
G&W Electric’s Viper®-HV overhead switchgear solution is an important innovation in efforts to simultaneously reduce utility operating expenses (OPEX), improve sub-transmission grid reliability, and integrate more renewables. The genesis of the Viper-HV switching solution was when two utilities approached G&W Electric, one of the U.S.’s largest recloser and switchgear manufacturers, with the request that the company develop a 72.5 kV recloser able to switch and sectionalize sub-transmission power lines to maintain reliability. Deployed on critical transmission lines, such devices expand sectionalizing options without the footprint of new substations.
The reason the utilities and the wider industry were so keen on an overhead solid dielectric solution able to enhance sub-transmission grid reliability was because existing options were inadequate – especially because the sub-transmission system needs both the ability to sectionalize the grid to maintain reliability when faults occur and because it demands advanced monitoring to quickly detect, locate, and respond to outages. Historically, sectionalizing the sub-transmission grid has been handled by motor-operated switches that were insulated either by air or gases such as SF6. Because these products are mechanical devices, they require frequent inspection and maintenance. Not only does this put stress on already tight utility OPEX budgets and a workforce stretched thin by retirements, mechanical devices exposed to the elements can also fail. Utilities increasingly pair such equipment with distribution automation strategies to accelerate fault isolation and service restoration.
Overhead switchgear innovation drives desired and unexpected sub-transmission grid benefits
Development of the Viper-HV overhead switchgear solution took years, with significant input from customers and industry experts. But the advances made deliver important benefits to sub-transmission grid reliability and intelligence, along with improved costs. Indeed, the Viper-HV is a solid dielectric overhead switchgear solution that can respond quickly to temporary faults and deliver the sectionalizing the utilities originally requested, as well as serving as a creative alternative to circuit breakers and bringing reclosing capabilities where applicable. These capabilities align with broader smart grid objectives that emphasize pervasive sensing, coordinated control, and adaptive protection.
Manufactured with a robust, proprietary, time-proven process, the Viper-HV solution is made to solve several pressing sub-transmission grid reliability and cost concerns. For example, it is made to complete a minimum of 10,000 operations without any need for maintenance – which delivers relief to utility OPEX budgets and frees up limited staff for other tasks. Reduced maintenance cycles also streamline power distribution workflows and spare-parts planning for field crews.
Besides providing a low-cost, no-maintenance solution for sub-transmission grid sectionalizing, advanced reclosing technology is important for other reasons as well, including:
Precise location of faults for rapid power restoration
One of the primary challenges facing utilities trying to restore power when there is an outage is finding the fault that caused it. Existing solutions can approximate the location of a fault, which still requires utility personnel to devote precious time to pinpointing its exact location – often in harsh weather conditions – which results in longer restoration times and customer and regulator frustration. The Viper-HV overheard switchgear solution can be equipped with controllers with built-in intelligence enabling precise fault location. The Viper-HV solution includes switching technology plus controllers to include not just impedancebased algorithms but traveling wave fault location determination, which is suitable on longer sub-transmission lines. While most sub-transmission applications are AC, awareness of evolving direct current technology informs protection coordination, converter siting, and interoperability decisions.
Rapid and less costly integration of renewables
Many nations are accelerating deployments of renewable energy to reduce greenhouse gas emissions and achieve ambitious decarbonization targets. Distributed energy resources (DERs) like solar and wind increasingly connect to the transmission and sub-transmission grid – especially when an extra transmission line is added to existing infrastructure to take advantage of an advantageous renewable energy location. DERs introduce complexity to the grid, including more frequent switching than is normal on sub-transmission feeders. The Viper-HV technology, since it was certified as a recloser with 10,000 operations capability, is more suitable than traditional motor operated switches. Furthermore, the form factor of the Viper-HV overhead switchgear is easier to install than other solutions. Pairing sectionalizing schemes with strategically sited critical energy storage can further smooth variability and enhance grid stability during switching events.
Removes need to add expensive and time-consuming grid infrastructure
Another significant benefit of advanced overhead switchgear technology: it can avoid the necessity to add new substations. In cases when a new feeder and circuit breaker need to be added to a sub-transmission system substation, the Viper-HV overhead switchgear solution can increase the speed and lower the cost. That’s because traditional circuit breakers need to be ground-mounted on a concrete pad, which takes up space many substations don’t have and involves permitting that can take a lot of time. By contrast, the Viper-HV overhead switchgear solution can be mounted on the already grounded metal frames most substations have available. This takes no additional space and doesn’t require a time-consuming permitting process.
Advances in technology are essential for increasing the reliability and resiliency of the sub-transmission grid. At the same time, these technologies must lower, rather than elevate, the total overall costs including all aspects of the installation and lifecycle costs (i.e. maintenance, replacement). Sophisticated overhead switchgear technology provides a budget-friendly option for enhancing reliability, resiliency, and helping to green the power grid.
 

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• Transmission And Distribution Channel

Power line carrier communication enables data transmission over electrical power lines for grid automation, SCADA telemetry, and protective relaying, using coupling capacitors, line traps, and narrowband modulation to support substation monitoring and smart grid control.

What Is Power Line Carrier Communication?

A narrowband method sending control, protection, and telemetry data over power lines using coupling and line-trap equipment.

✅ Uses coupling capacitors and line traps to inject and isolate signals

✅ Supports SCADA, teleprotection, and substation automation traffic

✅ Typically narrowband FSK/PSK; robust against high-voltage noise

Power line carrier communication (PLCC) is a vital technology for electrical professionals to understand in today's evolving energy landscape. By utilizing existing power lines for data transmission, PLCC offers a cost-effective and reliable communication solution for a wide range of applications within industrial, commercial, and institutional power systems. In transmission engineering contexts, PLCC must account for impedance characteristics of overhead transmission lines to maintain carrier signal integrity across long spans.

Let's explore the evolution of PLCC, its crucial role in smart grids, its advantages compared to alternative communication technologies, the cybersecurity challenges it faces, and its integration with SCADA systems. By understanding these key concepts, we can harness the power of PLCC to enhance the efficiency, reliability, and security of modern power systems. These concepts align closely with the principles outlined in smart grid architectures that emphasize interoperability and resilience.

Power line carrier communication has emerged as a versatile and essential technology in modern industrial, commercial, and institutional power systems. By leveraging existing electrical infrastructure for data transmission, it offers a cost-effective and reliable solution for a wide range of applications. Within utility operations, PLCC complements core power distribution practices by enabling telemetry and control without new cabling.

Evolution of PLCC in Power Distribution

Power line carrier communication has come a long way from its early days of simple signaling and control functions. Initially, it relied on narrowband carrier frequencies transmitted over high voltage power lines. To achieve this, systems employed coupling capacitors, which provide high impedance to power frequency while allowing the passage of higher carrier frequencies. This ensures that the carrier signals do not interfere with the power flow. Furthermore, wave traps, also known as line traps, were installed to prevent the carrier signals from propagating beyond the desired sections of the power line, effectively creating a trap line for the communication signals. These early systems, often employing band pass filtering to further isolate carrier signals, were primarily used for basic communication between substations and protective relaying. However, with the rise of smart grids and advanced automation needs, PLCC has evolved to encompass broadband technologies, enabling higher data rates and supporting a wider range of applications. This evolution has been driven by advancements in signal processing, modulation techniques, and the development of sophisticated PLC terminal equipment. Design considerations also differ from direct current technology where coupling, filtering, and insulation coordination require different approaches.

Applications in Smart Grids

Power line carrier communication plays a crucial role in enabling the functionalities of modern smart grids. By providing a communication backbone for various grid devices, PLCC facilitates real-time monitoring and control of the power system. This includes applications like demand response, where it enables dynamic pricing and load control to optimize energy consumption. Moreover, it supports voltage control by allowing for real-time adjustments to maintain grid stability. It also aids in fault location by providing precise information about the location of disturbances, enabling faster restoration of power supply. PLCC can also coordinate distributed energy resources such as rooftop solar and battery inverters for local balancing and protection schemes.

PLCC vs. Alternative Communication Technologies

While it offers numerous advantages, it's essential to compare it with other communication technologies used in power distribution. Wireless communication, for instance, offers flexibility and ease of deployment but can be susceptible to interference and may have limited range, potentially impacting signal to noise ratio. Fiber optic communication provides high bandwidth and security but can be expensive to install, especially in challenging terrains. Coaxial cable, while offering a balance between cost and performance, may not be as readily available as existing electrical infrastructure. However, coaxial cables play a critical role within systems themselves, as they are often used to connect the equipment to the coupling capacitors, efficiently carrying the high-frequency carrier signals with minimal loss. PLCC, with its cost-effective utilization of existing power lines, often proves to be a compelling choice, particularly for applications requiring wide coverage and reliable communication in industrial settings. At the feeder level, advancements in overhead switchgear complement PLCC by enabling faster sectionalizing and restoration decisions.

Cybersecurity Challenges and Solutions

As power line carrier communication systems become more integrated into critical power infrastructure, ensuring their cybersecurity is paramount. PLCC is vulnerable to cyberattacks that can disrupt operations, compromise data integrity, and even cause widespread power outages. To mitigate these risks, robust security measures are essential. Encryption techniques protect sensitive data transmitted over PLCC channels, while authentication mechanisms prevent unauthorized access to the system. Intrusion detection systems continuously monitor the network for suspicious activity, enabling prompt response to potential threats. By implementing these security solutions, power systems can enhance the resilience of their infrastructure against cyberattacks. As utilities deploy more critical energy storage systems, securing PLCC channels that supervise these assets becomes increasingly important.

Integration with SCADA Systems

Power line carrier communication seamlessly integrates with SCADA systems, enhancing their functionality and providing real-time data for grid monitoring and control. SCADA systems rely on communication networks to gather data from remote terminal units (RTUs) and intelligent electronic devices (IEDs) located throughout the power system. It acts as a reliable and efficient communication channel for transmitting this data to the central control center. This real-time information enables operators to monitor grid conditions, detect anomalies, and take corrective actions promptly. The integration with SCADA systems improves situational awareness, facilitates faster response times, and enhances the overall efficiency of power distribution operations. Furthermore, by utilizing PLCC for communication, SCADA systems can leverage the inherent protection offered by devices like protective relays and wave traps, enhancing the overall system reliability.

Leading Questions:

What are the core advantages?

Power line carrier communication leverages existing electrical infrastructure, making it cost-effective. It offers wide coverage, especially in remote areas, and the inherent robustness of power lines ensures reliable communication even in harsh environments.

How does it contribute to smart grids?

PLCC enables essential smart grid features like demand response, voltage control, and fault location, contributing to optimized energy consumption, grid stability, and efficient power restoration.

What are the main challenges?

Signal attenuation and noise over long distances, electromagnetic compatibility issues, cybersecurity vulnerabilities, and ensuring interoperability between different PLCC equipment are some of the challenges.

How do narrowband and broadband technologies differ?

Narrowband PLCC typically uses lower carrier frequencies and is suitable for longer distances and applications like SCADA and protection relaying. Broadband PLCC, with its higher data rates, caters to modern applications like smart metering and grid automation.

What are the future trends?

Advanced signal processing techniques, integration with IoT devices, enhanced cybersecurity measures, and applications in electric vehicle charging infrastructure are some of the future trends shaping the evolution of PLCC.

Related Articles

• Transmission And Distribution Channel

Ac transmission lines deliver alternating current across the power grid using high voltage, overhead conductors, and insulators, controlling reactive power, impedance, and corona effects to minimize losses, improve efficiency, and ensure reliable long-distance electricity transmission.

What Are AC Transmission Lines?

Ac transmission lines carry high-voltage AC power long distances with minimal losses.

✅ Typical voltages: 69 kV to 765 kV; higher reduces I2R losses

✅ Requires reactive power compensation: shunt capacitors, SVC, STATCOM

✅ Design factors: conductor bundling, corona control, insulation coordination

Three-phase electric power systems are used for high and extra-high voltage AC transmission lines (50kV and above). The pylons must therefore be designed to carry three (or multiples of three) conductors. The towers are usually steel lattices or trusses (wooden structures are used in Germany in exceptional cases) and the insulators are generally glass discs assembled in strings whose length is dependent on the line voltage and environmental conditions. One or two earth conductors (alternative term: ground conductors) for lightning protection are often added to the top of each pylon. For background on material properties, the electrical insulator overview provides relevant design considerations.

Detail of the insulators (the vertical string of discs) and conductor vibration dampers (the weights attached directly to the cables) on a 275,000 volt suspension pylon near Thornbury, South Gloucestershire, England. In some countries, pylons for high and extra-high voltage are usually designed to carry two or more electric circuits. For double circuit lines in Germany, the “Danube” towers or more rarely, the “fir tree” towers, are usually used. If a line is constructed using pylons designed to carry several circuits, it is not necessary to install all the circuits at the time of construction. Medium voltage circuits are often erected on the same pylons as 110 kV lines. Paralleling circuits of 380 kV, 220 kV and 110 kV-lines on the same pylons is common. Sometimes, especially with 110 kV-circuits, a parallel circuit carries traction lines for railway electrification. Additional context on span lengths, conductor bundles, and right of way is covered in this transmission lines reference for practitioners.

High Voltage DC Transmission Pylons

High voltage direct current (HVDC) transmission lines are either monopolar or bipolar systems. With bipolar systems a conductor arrangement with one conductor on each side of the pylon is used. For single-pole HVDC transmission with ground return, pylons with only one conductor cable can be used. In many cases, however, the pylons are designed for later conversion to a two-pole system. In these cases, conductor cables are installed on both sides of the pylon for mechanical reasons. Until the second pole is needed, it is either grounded, or joined in parallel with the pole in use. In the latter case, the line from the converter station to the earthing (grounding) electrode is built as underground cable. Engineers can review converter topologies, pole configurations, and control methods in the direct current technology guide to inform design choices.

Guidance on electrode placement, resistivity, and corrosion protection is summarized in the grounding electrodes overview relevant to HVDC return paths.

Raliway Traction Line Pylons

Pylons used for single-phase AC railway traction lines are similar in construction to pylons used for 110 kV-three phase lines. Steel tube or concrete poles are also often used for these lines. However, railway traction current systems are two-pole AC systems, so traction lines are designed for two conductors (or multiples of two, usually four, eight, or twelve). As a rule, the pylons of railway traction lines carry two electric circuits, so they have four conductors. These are usually arranged on one level, whereby each circuit occupies one half of the crossarm. For four traction circuits the arrangement of the conductors is in two-levels and for six electric circuits the arrangement of the conductors is in three levels. With limited space conditions, it is possible to arrange the conductors of one traction circuit in two levels. Running a traction power line parallel to high-voltage transmission lines for threephase AC on a separate crossarm of the same pylons is possible. If traction lines are led parallel to 380 kV-lines, the insulation must be designed for 220 kV because, in the event of a fault, dangerous overvoltages to the three-phase alternating current line can occur. Traction lines are usually equipped with one earth conductor. In Austria, on some traction circuits, two earth conductors are used. Integration with substation feeders and sectioning posts must align with the power distribution practices used along the route.

Types Of Pylons

Specific Functions:

• anchor pylons (or strainer pylons) utilize horizontal insulators and occur at the endpoints of conductors.
• pine pylon – an electricity pylon for two circuits of three-phase AC current, at which the conductors are arranged in three levels. In pine pylons, the lowest crossbar has a wider span than that in the middle and this one a larger span than that on the top.
• Twisting pylons are anchor pylons at which the conductors are “twisted” so that they exchange sides of the pylon.
• long distance anchor pylon

A long distance anchor pylon is an anchor pylon at the end of a line section with a long span. Large gaps between pylons reduces the restraints on the movement of the attached conductors. In such situations, conductors may be able to swing into contact with each during high wind, potentially creating a short circuit. Long distance anchor pylons must be very stably built due to the large weight of the exceptionally long cables. They are implemented occasionally as portal pylons. In extreme cases, long distance anchor pylons are constructed in pairs, each supporting only a single cable, in an effort to reduce the strain of large spans.

Branch Pylon: In the layout of an overhead electrical transmission system, a branch pylon denotes a pylon which is used to start a line branch. The branch pylon is responsible for holding up both the main-line and the start of the branch line, and must be structured so as to resist forces from both lines. Branch pylons frequently, but not always, have one or more cross beams transverse to the direction of travel of the line for the admission of the branching electric circuits. There are also branch pylons where the cross beams of the branching electric circuits lie in the direction of travel of the main line. Branch pylons without additional cross beams are occasionally constructed. Branch pylons are nearly always anchor pylons (as they normally must ground the forces from the branch line). Branch pylons are often constructed similarly to final pylons; however, at a branch pylon the overhead line resumes in both directions, as opposed to only one direction as with a final pylon.

 Anchor Portal: An anchor portal is a support structure for overhead electrical power transmission lines in the form of a portal for the installation of the lines in a switchyard. Anchor portals are almost always steel-tube or steel-framework constructions.

 Termination Pylon: Anchor pylons or strainer pylons utilize horizontal insulators and occur at the endpoints of conductors. Such endpoints are necessary when interfacing with other modes of power transmission (see image) and, due to the inflexibility of the conductors, when significantly altering the direction of the pylon chain. Anchor pylons are also employed at branch points as branch pylons and must occur at a maximum interval of 5 km, due to technical limitations on conductor length. Conductors are connected at such pylons by a short conductor cable “strained” between both ends. They often require anchor cables to compensate for the asymmetric attachment of the conductors. Therefore, anchor pylons tend to be more stably built than a support pylon and are often used, particularly in older construction, when the power line must cross a large gap, such as a railway line, river, or valley. A special kind of an anchor pylon is a termination pylon. It is used for the transition of an overhead powerline to an underground cable. A termination pylon at which the powerline runs further as well as overhead line and as underground cable is a branch pylon for a cable branch. For voltages below 30kV, pylon transformers are also used. Twisted pylons are anchor pylons at which the conductors are “twisted” so that they exchange sides of the pylon. Anchor pylons may also have a circuit breaker attached to their crossbeam. These so called switch pylons are operated from the ground by the use of long sticks. The attachment of circuit breakers to pylons is only practical when voltages are less than 50kV. Where sectionalizing or protection is required aloft, utilities are adopting overhead switchgear innovations to reduce footprint and maintenance.

Materials Used

• Wood Pylon
• Concrete Pylon
• Steel Tube Pylon
• Lattice Steel Pylon

Conductor Arrangements

Portal Pylon: In electricity distribution, a portal pylon is a type of pylon with which the cross beams on the conductor cables rest on at least two towers. Portal pylons can be made of wood, concrete, steel tubing or steel lattice. They are used in German railroad wiring because of their enormous space requirement as a rule only for anchor pylons, which have to resist high traction power and as bases for lines in switchgears as anchor portals. Their application and clearances are coordinated with prevailing electrical distribution systems standards for safe operation.

Delta Pylon: A delta pylon is a type of support structure for high-voltage electric power transmission lines. The pylon has a V-shapedtop for the admission of the cross beam. Delta pylons are usually established only for one electric circuit, occasionally for two electric circuits. They are used for voltages up to 765 kV. Delta pylons are far more common in the USA, France, Spain, Italy and formerYugoslavia, while in Germany on delta pylons shifted high voltage transmission lines are very rare.

Single-level Pylon: A single-level pylon is an electricity pylon for an arrangement of all conductor cables on a pylon in one level. The singlelevel pylon leads to a low height of the pylons, connected with the requirement for a large right of way. It is nearly always used for overhead lines for high-voltage direct current transmissions and traction current lines. If three-phase current is used, if the height of pylons may not exceed a certain value.

Two-level Pylon: A two-level pylon is a pylon at which the circuits are arranged in two levels on two crossbars. Two-level pylons are usually designed to carry four conductors on the lowest crossbar and two conductors at the upper crossbar, but there are also other variants, e.g. carrying six conductors in each level or two conductors on the lowest and four on the upper crossbar. Two-level pylons are commonplace in former West-Germany, and are also called Donau pylons after the river Danube.

Three-level Pylon: A three-level pylon is a pylon designed to arrange conductor cables on three crossbars in three levels. For two three-phase circuits (6 conductor cables), it is usual to use fir tree pylons and barrel pylons. Three-level pylons are taller than other pylon types, but require only a small right-of-way. They are very popular in a number of countries.

Three-level Pylon: A three-level pylon is a pylon designed to arrange conductor cables on three crossbars in three levels. For two three-phase circuits (6 conductor cables), it is usual to use fir tree pylons and barrel pylons. Three-level pylons are taller than other pylon types, but require only a small right-of-way. They are very popular in a number of countries.

From: Overhead and Underground T&D Handbook, Volume 1, The Electricity Forum

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A fault indicator is an electrical device that detects and displays fault conditions in power systems. Used in distribution networks and switchgear, it improves fault detection, outage response, and grid reliability while supporting predictive maintenance.

What is a fault indicator?

A fault indicator is a monitoring device used in electrical distribution systems to quickly locate fault conditions and improve service reliability.

✅ Detects and displays fault conditions in power lines

✅ Enhances outage response and reduces downtime

✅ Supports predictive maintenance and grid efficiency

Understanding how this device functions and its role in maintaining a reliable power system is crucial for any electrician working in an industrial setting. Let’s explore the core concepts, their various applications, and the benefits they offer in terms of issue location, outage reduction, and overall system reliability. By reading this article, an industrial electrician will gain valuable insights into how a fault indicator contributes to safer, more efficient, and more resilient electrical infrastructure. Fault indicators play a crucial role in distribution automation, where remote monitoring and SCADA integration are essential for enhancing grid resilience.

They play a critical role in modern power systems by providing a rapid and reliable means of detecting and locating disturbances. These devices are essential for minimizing downtime, improving safety, and ensuring the efficient operation of electrical networks. In modern electrical distribution systems, fault indicators provide real-time fault location that speeds up troubleshooting and repair.

A faulted circuit indicator (FCI) is more than a simple signal device; it functions as a reliable circuit monitoring device that helps utilities quickly identify abnormal conditions. Whether used as an overhead line indicator on distribution networks or integrated into underground systems, these tools improve outage response and reduce downtime. When connected to SCADA fault detection platforms, they provide real-time data that supports proactive maintenance and rapid dispatch of crews. As utilities transition toward smart grid monitoring, advanced FCIs play a key role in creating safer, more resilient, and efficient power systems.

Fault Location/Detection

A primary function of these devices is to pinpoint the exact location of a circuit problem. This capability is crucial in complex networks with extensive overhead lines and underground cables. Overhead indicators are strategically placed along power lines to visually signal the presence of an issue. When a disturbance occurs, the indicator activates, providing a clear cue to line crews that enables them to quickly identify the affected section and commence repairs. Underground indicators are installed in cable systems and vaults to detect conditions beneath the surface. This precise location capability reduces the time and effort required to identify and address problems, resulting in faster restoration of service. Utilities that depend on reliable electric power distribution benefit from fault indicators to quickly identify and isolate problem areas.

Technology/Functionality

Modern FCIs sense both magnetic and electric fields to distinguish between normal load surges and true electrical events, enabling directional detection and avoiding false trips. With detection speeds measured in milliseconds, they provide real-time pinpointing. Current sensing remains a common approach, but advanced models also utilize digital signal processing (DSP) to minimize false alarms. Some units feature inrush restraint to prevent tripping during temporary surges. Remote indication capability enables the wireless transmission of data to SCADA systems or control centers, providing operators with immediate insight and facilitating the faster dispatch of crews.

Standards & Features

Leading designs include variable trip thresholds, multiple reset types, and low-pass filtering to minimize misoperations. Many models are hotstick-installable for safety and conform to IEEE compliance standards, ensuring reliability across diverse applications. These features not only enhance accuracy but also reduce maintenance requirements, enabling efficient long-term operation.

Historical Evolution

Since their introduction in the 1940s, these devices have evolved from simple manually reset flags to sophisticated electronic equipment. Early versions required crews to manually reset them after repairs. Over time, automatic reset functionality, LED indicators, and remote communication were added. Today’s smart indicators integrate programmable logic, data logging, and seamless communication with grid monitoring systems, reflecting decades of advancement in line sensor evolution. As electricity transmission networks expand, indicators become increasingly critical in maintaining safety and reducing large-scale outages.

Benefits

The benefits of using these monitors are numerous and far-reaching. By quickly identifying the affected circuit, they significantly reduce outage time, minimizing disruption to customers and businesses. This rapid location capability also enhances the overall reliability of the power system, as it enables faster repairs and restoration of service. They improve safety by enabling quick isolation of the affected section, preventing escalation and hazards to personnel. In wildfire-prone areas, indicators support rapid response strategies that reduce risks associated with downed lines and delayed detection.

Smart Grid Integration

Today’s FCIs are part of broader smart grid monitoring strategies. Integrated with SCADA systems, they provide operators with real-time situational awareness. Some advanced designs incorporate wireless transmitters and receivers that signal directly to protective relays, allowing for rapid and coordinated isolation. This integration improves grid resilience, reduces downtime, and supports predictive maintenance by identifying intermittent or developing issues before they escalate. With the rise of smart grid technologies, fault indicators are evolving into intelligent sensors that enhance monitoring and predictive maintenance.

Comparison of Indicator Types

Analysis

The strong emphasis on line location highlights its critical importance in power system management. Accurately pinpointing the source of a disturbance is paramount for efficient troubleshooting and timely restoration. The increasing adoption of real-time monitoring, inrush restraint, and remote indication demonstrates a trend toward more sophisticated management systems. This technological diversity enables greater flexibility and customization, meeting the specific needs of utilities, industrial facilities, and smart grid operators. In overhead T&D, fault indicators complement devices like the electrical insulator by improving protection against system faults.

Frequently Asked Questions

What is a fault indicator, and how does it work?

It’s a device that detects and signals the presence of an abnormal condition in an electrical power system. It works by monitoring parameters such as current and voltage, triggering an alert when unusual activity is detected. This alert may be visual (flag or LED) or transmitted remotely to a control center.

What are the different types available?

They are categorized based on their application and functionality. Common types include:

• Overhead: Used on overhead lines, typically visual.

• Underground: Designed for cable vaults, often audible or remote.

• Electronic: Offer advanced features like DSP filtering, inrush restraint, and communication.

• Smart/SCADA: Fully integrated into monitoring and relay systems.

How do fault indicators improve power system reliability?

They reduce outage times, support immediate response through remote signaling, and enhance preventive maintenance by identifying intermittent problems before escalation.

What factors should be considered when selecting?

Consider factors such as application (overhead or underground), environmental conditions, functionality (visual vs. remote), accuracy, standards compliance, and installation requirements.

How are they installed and maintained?

Overhead indicators are typically pole-mounted, while underground versions are installed in vaults or directly on cables. Maintenance involves inspections, testing, and cleaning. Electronic units may require battery changes or firmware updates.

Do they ever give false alarms?

Advanced models use DSP filtering, inrush restraint, and directional detection to minimize false indications. Proper placement and settings further improve accuracy.

A fault indicator is an indispensable tool for maintaining the reliability and safety of modern power systems. From their origins in simple visual devices to today’s smart, SCADA-integrated models, their ability to quickly and accurately locate circuit issues significantly reduces outage times and improves overall grid resilience. By understanding their functions, standards, and benefits, electricians and system operators can make informed decisions that strengthen electrical infrastructure and support the transition to smarter, safer, and more efficient networks.

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