An Analysis of Market Variability Trends Among Copper Grounding Products
Lora Aboulmouna | Copperweld
Jeff Jordan, MBA, P.E. | Copperweld
The industry standard for copper grounding conductors vary from IEEE to ASTM, which may not be harmonized. Copper wire may meet the minimum requirements on one spectrum under ASTM manufacturing standards, but falls short on IEEE Standard 80 for fault current rating. A sample size was reviewed from varying copper manufacturers and compared a spectrum of requirements to give an industry analysis.
Transformer On-line Dissolved Gas Analysis Monitoring
Qasim Aziz, P.E. | CenterPoint Energy
Gautam Sonde | CenterPoint Energy
This paper presents feasibility analysis for installation and commissioning of condition-based online monitoring on CenterPoint Energy's fleet of in-service substation class transformers. Dissolved Gas Analysis (DGA) is a powerful condition monitoring technique for detection of developing faults within oil filled assets such as transformers. Trending of historical DGA results helps diagnose a fault in a timely manner therefore preventing a transformer failure. This paper is an effort to provide feasibility analysis regarding deployment of on-line DGA monitoring on in-service fleet of CenterPoint Energy Houston Electric (CEHE) substation class transformers. CEHE has several in-service substation transformers in its fleet with many units already installed with online monitoring sensors but not commissioned yet. Feasibility analysis described in this paper discusses both technical and financial aspects of installation of condition-based on-line monitoring.
Role of Power Factor Testing and Dielectric Frequency Response Testing in Bushing Health Assessment
Sanket Bolar | Megger
Sameer Kulkarni, P.E. | Megger
Unlike most components in a transformer, the bushings are exposed to the elements and undergo wear and tear as part of normal ageing. While it may not be possible to sample bushing oil in most cases, capacitance and power factor of the bushings can be measured periodically to assess the health of the bushings. While power factor testing at line frequency has been done traditionally, the focus is starting to shift to observing the power factor behavior at varying signal frequencies by using a technique called Dielectric Frequency Response (DFR). Through this paper, the reader will get a deeper understanding of power factor testing on condenser bushings. The added value that DFR provides in bushing health assessment will be highlighted through field measurements and case studies.
Stuart Borlase, P.E. | GE Grid Solutions
Michael Janiga, P.E. | GE Grid Solutions
Rich Hunt, P.E. | GE Grid Solutions
The IEC 61850 station bus standard for substation communications has been in use worldwide in multi-vendor environments since the early 2000s for various applications, such as controls, interlocking, and blocking. The basic building block of a digital substation is the IEC 61850-9-2 sampled values (SVs) process bus standard, which exchanges distributed I/O measurements among devices in the substation. SVs have been available since 2009 but are yet to gain widespread popularity.
This session provides a high-level overview of digital substation technologies and solutions, including a comparison of digital and conventional substations, the business case for digital substations, and use of the IEC 61850 process and substation bus protocol standards as an enabler for digital substations. The session will also include practical considerations for designing, engineering, constructing, testing, operating and maintaining a digital substation, with examples of digital substation deployments.
2018 Colorado City Major Storm Event: Oncor Restoration Effort
Brandon Campbell | Oncor Electric Energy
Jerry Murphree | Oncor Electric Energy
Josh Holder | Primoris T&D
To present upon the extensive damage inflicted, immediate responses employed, and lessons learned throughout the restoration efforts following the June 7th/8th, 2018 major storm event near Colorado City, TX. Details will also include the interesting failure patterns and analyzing techniques utilized to research the effects.
Do's and Don'ts of Power Factor Testing
Dinesh Chhajer, P.E. | Megger
Charles Nybeck | Megger
Power Factor (PF) testing is used to identify and detect insulation related problems for various electrical assets. PF test when performed correctly provides valuable diagnostic information that can be analyzed and trended throughout the life of the insulation to detect any abnormalities and dielectric failures.
The paper will talk about the best recommended field practices to perform the test effectively and obtain reliable and accurate measurements. It will focus on field aspects that can impact the measurements such as selection of correct test voltage, effect of grounding and guarding, effective measurement of insulation oil temperature and temperature correction of PF readings, position of on load tap changer, effect of humidity and bushing surface contamination and adverse effect of electrostatic interference and noise present in HV stations. The paper will provide users a detailed understanding of what to do and what not to do in the field environment when performing PF testing.
Rapid Pressure Rise Relays Concept, Construction, Application & Testing
Emilio Morales Cruz | Qualitrol
Internal arcing in an oil-filled power transformer can instantly vaporize surrounding oil, generating gas pressures that can cause catastrophic failure, rupture the tank, and spread flaming oil over a large area. This can damage or destroy other equipment in addition to the transformer and presents extreme hazards to workers and the environment. The sudden Pressure Relays utilize sudden changes in internal transformer pressure to sense internal faults caused by arcing and then with its control circuit de-energize the transformer and/or provide an alarm. High level internal faults are detected sooner than the sudden pressure relays by other electrical relays, but they are somewhat unique in that they can sense low level internal faults that are often not able to be identified by conventional protection schemes. Sudden pressure relays are designed to not operate for steady state (temperature, vibration, mechanical shock, or pump surges) or non-fault changes in these parameters.
Maximizing Existing Infrastructure for Transmission Line Reconstruction and Growth
Kirby Davis | Power Engineers
John Owen | Oncor Electric Delivery
To safely serve the growth of Dallas, rebuilding Oncor's 35-year old Northaven-Renner 138kV double circuit transmission line was needed. Routing through Dallas County, the 10-mile line had to contend with a myriad of design constraints from reusing existing foundations built into the Dallas North Tollway's retaining wall to shifting existing lattice towers to installing specialized conductor to provide the required 3000 amp capacity. This paper will discuss the solutions utilized to successfully upgrade a large transmission project in a congested urban area.
Ameren's 237' River Crossing Towers - Structural and Wind Engineering
Lauren Dixon, P.E. | Ameren Transmission
Hock Lim | Sabre Industries
Thomas Mara, Ph.D., P.E. | BLWTL
Ameren wanted to pursue a tubular tower option to serve as a template for future storm restoration for river crossing towers due to the reduced number of members and connections and the predicted cost savings during construction. A taller tubular structure brought about concerns to be addressed during design, including the potential for vortex-induced vibrations (VIV) due to higher sustained wind speeds and lower turbulence levels in the upper portion of the tower. In Sabre's initial design, prior to dynamic modelling and testing, calculations of member natural frequencies and avoidance of approximate VIV frequency ranges were considered. The Boundary Layer Wind Tunnel Laboratory delivered site-specific wind climate studies, finite element modeling of local members and the full tower, modal analysis, and wind tunnel tests of sections and the full tower, to provide Ameren and Sabre with a high level of confidence in Sabre's structural design to resist VIV.
Lubbock Power & Light (LP&L) The ERCOT Solution
Kenneth Donohoo, P.E. | Electric Power Engineers, Inc.
Cole Dietert, P.E. | Electric Power Engineers, Inc.
It is not a common activity to switch from one interconnect to another separate interconnect. It is a significant task including many markets, technical, modeling, studies, planning, operations, switching and compliance activities. The integration is anticipated to take place in June 2021 pending the completion of transmission lines and substations required to make the transition.
Electric Power Engineers, Inc. (EPE) has been working with LP&L since late 2018 to integrate them into the ERCOT Interconnection. Our presentation will provide information and what we have learned by performing the following tasks related to the integration:
Phased Array UT is Now in the AWS D1.1 Code - What Will That Change for NDT of Pole Welds?
Garrett Ehler | Texas NDT Academy
Advances in Nondestructive Testing technology will enable fabricators and quality teams to more accurately and consistently find and repair defects in the complex weldments used in utility structures. None more so than the advancements made in Ultrasonic Testing (UT). Unfortunately, many codes and standards struggle to keep up to date in comparison to the rate at which technology advances. Phased Array Ultrasonic Testing (PAUT) is a prime example of technology that has been available for some time and until now, was not formally written into the AWS D1.1/D1.1 Structural Welding Code-Steel. With the 2020, 24th Edition of the welding code release, PAUT is now directly addressed in its Normative Annex H with full details regarding equipment, calibration, scanning and evaluation.
This paper will discuss the areas in which PAUT will likely greatly increase the accuracy and probability of detection of flaws in welds on critical infrastructure elements and how PAUT will be utilized.
Safety in Equipotential Zones
Dale Gaddis | YAK ACCESS
Creating safe work environments for electrical workers is of extreme importance. An area that plays a key role in this are equipotential zones. Per OSHA, an equipotential zone is a zone in which the worker is protected from electrical shock from differences in electrical potential between objects in the work area. In order to successfully create these safe work zones, we need to identify the current methods being used within the industry, how they are being used and at what specific work sites. Furthermore, it's important to follow both the OSHA and IEEE guidelines to properly establish the safest equipotential zone. In this talk, we will cover the basics of setting up these zones according to standards and ensuring the highest safety standards while also looking at equipotential grounding grates and other methods to improve these areas.
Performance Evaluation of Joint Use Transmission Structures
Aaron Haithcock | MESA Associates, Inc.
Transmission structures carrying high-voltage electrical lines are also often used to support communication equipment owned by telecom companies. This constitutes a dual or joint use of a structure whose primary purpose is for power delivery. The performance criteria for each of the dual purposes is governed by different standards (ex: NESC vs TIA) and this has often needed an engineering effort to reconcile different conflicting design approaches and therefore different structural reliabilities. This article examines some of those criteria and discusses challenges faced by engineers dealing with dual-use structures. The issues are illustrated by means of a small design example involving a tubular steel pole.
Review of Integrating and Controlling Distributed Energy Resources
Rekha Jagaduri | HDR Inc
With the focus on decarbonization of the electric grid, renewable technologies, such as solar, wind, and energy storage, are taking predominance. These technologies, when paralleled with traditional energy resources, can provide reliable power to rural and remote communities with weak utility infrastructure. This paper presents control strategies to integrate inverter- based resources with traditional generation, such as diesel and gas generators. Energy storage is presented as a primary resource to reduce the variability of renewable sources, such as photovoltaic and wind generators. An active power control algorithm with voltage stabilization is presented, along with fast- acting islanding schemes, to effectively detect a failing grid while maintaining anti-islanding required by utilities. Finally, protection challenges of integrating inverter -based low inertia resources are also presented.
Using Real Time DER Data to Improve Utility Operations
Thilo Janssen | Bandera Electric Cooperative
Joshua D. Rhodes, Ph.D. | IdeaSmiths LLC
Utilities are just now understanding the value of real time distributed energy resources (DERs) and behind the meter load data. Bandera Electric Cooperative (BEC) has been monitoring real time data from its members' DER installations for almost four years and has quantified some of the benefits to the Utility. This paper introduces Apolloware, a cloud-based, Behind-the-Meter (BTM), software platform developed by BEC for just that purpose. We explain how the system works and present a case-study in the use of Apolloware's data streams that allowed BEC to better assess the value of distributed solar PV systems on their network. This paper not only quantifies the financial benefits of DERs to a Utility through Four Coincident Peak (4CP) charge and system loss reductions, but also describes how having access to real time DER and BTM data through the Apolloware platform can improve a wide range of utility operations including Customer Service, power quality issues, and enhanced outage management.
Monitoring of OH Transmission Lines
Albert Kurz | MOSDORFER
Matej Kovač | MOSDORFER
Conventional rating of power lines is based on seasonal, worst-case scenarios which often leaves high reserves in the grid, resulting in significant economic losses. With today's technology and computational capacity, the future of power line ampacity determination has a novel and completely different approach. System operators (TSOs, DSOs) are now implementing different technologies to efficiently and safely optimize energy flows. Dynamic Line Rating (DLR) is a huge opportunity to safely extract more capacity from existing overhead lines, without large investments like building new overhead lines. Advanced sensors in connection with algorithms based on the latest mathematical models allows users to increase line capacity for a more reliable, cost-effective and green grid.
Professional Ethics - Texas Board of Professional Engineers
Lance Kinney, Ph.D., P.E. | Texas Board of Professional Engineers and Land Surveyors
Texas Board of Professional Engineers and Land Surveyors - Professional Practice Update/Ethics: Updates on engineering ethics and Code of Conduct, Board Activities, rule and statutory changes, and general updates on Board initiatives.
Reducing Transformer Current Inrush through Residual Flux Analysis and Precision Switch Closing
Toby Landes, P.E. | Valquest Systems
This presentation discusses mitigating transformer inrush currents by calculating residual flux in each leg of a transformer and closing each phase switch at the precise voltage that matches that flux.
Wideband Voltage Sensors for The Modern Substation
Theo Laughner, P.E. | PowerGrid-RX, Inc
Bob Elliott | PowerGrid-RX, Inc
The addition of power electronics to the power system has resulted in a significant increase in harmonic injection. Many power electronic systems operate at switching frequencies in the kilohertz range. However, most modern voltage sensing technologies do not have good frequency response above 600 hertz. This paper describes technologies that enable wide-band sensing of voltage within the power system. Better visibility of the higher frequencies enables utilities to better understand the impacts of harmonic flows on their system. More importantly, this enables utilities to understand their compliance with nationally recognized harmonic standards like IEEE 519 and IEC 61000-4-3.
Arc Flash Hazards and Electrical Safety
Wei-Jen Lee, Ph.D., P.E. | The University of Texas at Arlington
Though electrical incidents represent a relatively small percentage of all work-related incidents; they are disproportionately fatal. In the case of burn injury, it may result in extended hospitalization and rehabilitation. According to NFPA 70E, approximately 5 to 10 arc flash explosions occur on the job every day in the United States. Proper protection is the key to reduce casualties during these incidents. IEEE 1584 and NFPA 70E are developed to protect the safety of the workers. With the better understanding of the arc flash phenomena, several areas in the IEEE Std. 1584-2002 need further research, testing validation, and revision.
The IEEE and the NFPA (National Fire Protection Association) have joined forces on an initiative to fund and support research and testing to improve the understanding of arc flashes. The results of this collaborative project will provide information that will be used to improve electrical safety standards, predict the hazards associated with arcing faults and accompanying arc blasts, and provide practical safeguards for employees in the workplace. The identified areas include but are not limited to: 1) Heat and Thermal Effects, 2) Blast Pressure, 3) Sound, and 4) Light intensity.
The following topics will be covered in this tutorial:
Risk Mitigation Planning for a Successful EPC Project
Ajay Mallik, P.E., P.Eng. | SANPEC Inc
Michael Foster, P.E., P.Eng. | Dashiell Engineering
Casey Miller, P.E., P.Eng | Dashiell Engineering
In this age of increasing dependencies on reliable power and resilient grid system to support our economic development, new high voltage electrical transmission lines are continually being required to transport electricity longer distances. Many utilities and merchant developers are looking towards cost effective EPC business models to meet the transmission infrastructure demands. EPC model requires the contractor to be responsible for ensuring all industry and material standards are adhered to in their scope of work, this required developing robust ITP's (Inspection Test Plan) and source inspection plans to ensure quality and complete products were delivered on time. The objective of this paper will be to present a case study towards a recent successful EPC project for the Alberta Power Line 500kV WFMAC. The WFMAC project was a competitively bid 510 km 500kV transmission line which included routing, siting, permitting, design, procurement, construction, and operation for 35 years.
A Field Study on Suspended Weights to Secure Steel Davit Arms
Diaaeldin Mohamed, Ph.D., P.E., PMP | Valmont Industries Inc
William J. Reisdorff, Jr., P.E. | Valmont Industries Inc
The wind-induced response of structures has been a significant subject of engineering research over the past 40 years. Tall, slender buildings, chimneys, antenna towers, and transmission structures (e.g. guyed-V tubular towers, T-poles and H-frames) can be subjected to wind-induced vibration that results in an excessive vibration response, potential fatigue damage and even collapse. Dampening of steel transmission arms helps to prevent an arm from vibrating in the wind, and typically only needs to be done when conductors and insulators have not yet been installed. Industry guidance recommends that all unloaded arms be secured, immediately after the arm is installed to mitigate the damage induced by Vortex Induced Vibration (VIV), by hanging weights at the tip of the steel davit arms. The details of suspended weights in this guidance are nonspecific. This paper presents a numerical and experimental analysis of unloaded T-pole with six davit arms.
Battery Testing Standards and Best Practices
Volney Naranjo | Megger
Daniel Carreño | Megger
The design and operation of substations for electrical transmission and distribution systems must consider stationary batteries, as the means to provide backup DC power for the operation of protection and control devices. Following proper practices for the installation and maintenance of these systems ensure the maximum benefit from the battery and the reliability of any electrical system. However, despite existing regulations and standards, batteries are not always installed, maintained and tested as required.
Guides and standards from IEEE, NETA, NFPA and NERC prescribe different aspects related to the installation and maintenance of lead acid batteries. Each document contains pieces of information that need to be considered when scheduling and performing a battery test in the field, however navigating through them could be confusing.
Conductor Properties & Sag Effects: A Comparison Between Traditionally Accepted and Manufacturer Values and an Innovative Approach to Combat the Difference
Gokul Narayanan, P.E. | ASEC Engineers, Inc.
Ben Averill, P.E. | ASEC Engineers, Inc.
Jackson Vick, P.E. | LCRA
The need to accurately model transmission infrastructure has increased significantly. Fortunately, cable manufacturers have adapted to the needs through R&D and providing accurate data on conductor properties. A significant disconnect still exists with the utility and consulting industries still relying heavily on inaccurate data in their design practice. The public data being utilized was created from tests performed over 50 years ago. These Generic Non-Linear files used can cause a measurable discrepancy in the designed versus installed conditions of a Transmission Line.
The purpose of this research is for the industry to adopt the practice of using the wire files from the cable manufacturer supplying for the project to accurately depict the sag and tension of the conductor, or for the industry to start using a "Wire Buffer" to add to the minimum clearance values during design to account for sag differences that arise using the generic values. Various use cases shall be presented.
Foundation for Success: Optimizing Foundation Designs for Variable Subsurface Conditions
Brian Olson, C.E.G., P.Geo | Quanta Subsurface
Justin Toney, P.E. | Quanta Subsurface
Discussion of the unique program developed to design and install foundations for a 310-mile, 500 kV transmission project in Northern Alberta, Canada. A combination of driven piles, drilled piers, helical piles and grout anchors were installed in vastly differing subsurface conditions for the nearly 1,400 self-supporting guyed steel transmission structures. A condensed construction schedule and relative lack of subsurface information during the design phase led to a detailed geotechnical investigation in parallel with foundation construction to identify conditions and select the ultimate foundation type and design for each structure. Site-specific geotechnical probes were performed at every structure location as the alignment Right-of-Way was cleared for construction. To keep pace ahead of construction, up to five geotechnical rigs were employed simultaneously, sampling to depths consistent with the expected optimal foundation element.
Recommended Design Procedure for Conductor Optimization
Greg Parent, P.E. | Ulteig
Stacey Page, P.E. | Ulteig
Josh Potts, P.E. | Ulteig
James Thomas, Ph.D. | Ulteig
Selection of the conductor size and structure type are the most critical tasks for a transmission line engineer, attempting to optimize the design of a new transmission line. As the conductor increases in size so does the cost of the line. This is due to both the higher costs for a larger conductor and due to the more robust structures that are required to adequately support the larger conductor. However, a larger conductor can significantly reduce electrical losses. Over an entire lifecycle of a transmission line these reductions in electrical losses can be significant and often outweigh the additional capital expense costs. Reducing the conductor's electrical losses can often lower the total transmission line's life cycle costs. This paper will provide a procedure and examples on how to determine which conductor size will minimize the total lifecycle costs.
Minimizing the total transmission line lifecycle costs is often referred to as conductor optimization. This involves both technical engineering and financial modeling. Reliability requirements have traditionally driven the need for new transmission lines that focused on alleviating overloads during contingency scenarios for the lowest lifecycle cost. In a modernized grid, new transmission lines will be driven more by economics which need to be factored into conductor optimization. These factors include reducing system losses and enabling markets to operate with a lower cost of energy so that the market receives a net benefit for investing in the transmission line. This paper will provide an example transmission line and provide example calculation on five different conductor types that will provide adequate levels of thermal ratings, electromagnetic field (EMF), Corona (audible noise and radio interference). These five conductor types will each be analyzed for their own specific capital expenses and lost revenue due to each conductors' specific electrical losses. These values, along with others, will be used in a financial model to determine the conductor which yields the lowest total lifecycle cost.
Avalanche Damage Results in Constructability Improvements
Josh Peterson | Xcel Energy
A spring avalanche damaged an Xcel Energy 230kV transmission line in a remote location in the Colorado mountains and required helicopter access. Xcel Energy has been building lines with mountainous remote access for decades, however construction crews and engineering developed more useful constructability strategies for remote access work. The focus areas for constructability were material selection, rigging attachments, and tools for installation. H-frame structure design was modified to allow for variability in hardware alignment, and structure attachments were added to aid in equipment rigging. This project also spurred the development of a new tool to help the helicopter pilot and lineman guide the top pole sections onto the bottom pole sections. The helicopter guide tool is a set of removable equipment that assist the lineman to better position the pole shaft from the ground and allows the helicopter pilot a larger "goal post" to set the pole section.
TDR-Based Fault Location on Overhead Transmission Lines
Robert Probst | Megger
The application of Time Domain Reflectometer (TDR) on overhead transmission lines rated 69 kV and above is almost unknown in USA. The method is based on the same principle as the application of TDR on power cables. Unlike with power cables, regular TDRs cannot be connected directly to an overhead transmission line, therefore special equipment is necessary. The method was first introduced as a safety tool to verify that no fault condition is present anywhere before switching de-energized circuits back on. Aside from this, its main purpose is to locate fault accurately when common approaches fail, impedance relays are not available or provide inaccurate results for precise fault location. This paper will describe the application of TDRs to overhead transmission lines, as well as the necessary equipment for effective and reliable fault location. Multiple real-world examples are presented, and in the end the reader will have a basic understanding of the technology and its various benefits.
Design and Construction Considerations Near Renewables
Nate Schrein, P.E. | Burns & McDonnell
David Hancock, P.E. | Burns & McDonnell
Nick Khoury, P.E. | Burns & McDonnell
Annie Wantland, P.E. | AEP
The increase of renewable generation has driven the need for transmission lines to be constructed near or within renewable developments across the US.
Transmission service providers tasked with connecting these generators to the grid often deal with constraints that may be atypical of normal grid transmission projects. The operational needs and reliability requirements of both the transmission provider and generator are also taken into consideration.
This paper will focus on planning, engineering and construction challenges when building transmission lines near renewable generators. On the design and planning side, there are measures that can be taken to mitigate problems that are present with transmission lines near wind or solar plants. Common transmission line and generator construction coordination issues will also be discussed.
The Impacts of NESC 250C Extreme Wind Loading on Structures Less Than 60 Feet
Josh Sebolt, P.E. | Burns & McDonnell
Gemma Haake, P.E. | Burns & McDonnell
The 2017 edition of the National Electric Safety Code (NESC) does not require an extreme wind load to be applied to structures when no part of the structure or attached wires exceeds 60 feet. The only required NESC loading for structures not exceeding 60 feet is a combined ice and wind district loading, commonly referred to as 250B loading, named for the section in which it appears in the NESC. The continental United States is divided into three loading districts, Heavy, Medium, and Light. Heavy is defined as 0.5 inch of ice with 4 pounds per square foot (PSF) of wind at 0 degrees Fahrenheit; Medium 0.25 inch of ice with 4 PSF of wind at 15 degrees Fahrenheit, and Light 0.0 inches of ice with 9 PSF of wind at 30 degrees Fahrenheit. This paper seeks to understand the design impacts to typical wood pole lines optimized for 250B loading when an extreme wind load, as defined in section 250C of the NESC, is applied.
Challenges Associated with Diagnostic Testing of PT/VT Instrument Transformers
Charles Sweetser | OMICRON
This session will focus on both inductive and coupling capacitor (CCVT) PT/VT instrument transformers, including theory and practice. It is important to understand the need, value, and application of comprehensive testing of PT/VT instrument transformers. We will investigate the best practices regarding test procedure, test preparation, and the analysis of the results. Standard electrical field tests such as Power Factor, Cross Check, Exciting Current, and Ratio will be discussed, along with specially selected case studies validating the value that these diagnostic tests bring to testing, and finally assessing, PT/VT instrument transformers.
Case Study: Extending the Life of Austin Energy's Holman-Hillje 345kV Steel Pole Transmission Line
Scott Walton, P.E. | Austin Energy
Wesley J. Oliphant, P.E. | Exo Group LLC
In the late 1970's, Austin Energy constructed a 75-mile, single circuit 345kV transmission line utilizing galvanized tubular steel poles, and galvanized vibratory caissons as the foundation system. The nearly 50-year-old line was designed as a single pole, self-supporting line, and utilized a relatively new (at the time) foundation system for steel poles - vibratory caissons. Over the years, the joint interface between the grout and the pole shaft began to separate, allowing moisture to become trapped and accumulate on the exterior surface of the galvanized steel pole shaft causing corrosion resulting in wall thickness loss on the steel pole at the critical point of fixity to the foundation. This case study will provide the details and importance of the line, the inspection/testing conducted, the engineering assessments made, and the design of the remediation performed by Exo that has potentially extended the life of these critical structures for another 25-30 years.
Design and Construction Solutions for 138kV/69kV Transmission Substation Cut-Ins in a Constrained Footprint
Jelisa Zapalac, P.E. | Burns & McDonnell
Lonnie Sandoval Jr. | LCRA
When updating existing facilities, there are many different considerations that can alter typical design and construction practices. This paper will examine one such project where diverse obstacles required unique solutions.
The project consisted of designing and constructing four 69kV and 138kV transmission line substation cut-ins to ensure the upgrade of an existing 69kV substation for 138kV capabilities. The existing transmission lines had several factors that excluded common design options. No additional easement could be acquired, existing transmission lines could not take extended outages, the substation design required existing routes to be altered, and recent construction allowed for reuse of existing resources.
The resultant design included unique elements in structure geometry and construction sequencing which will be discussed in this paper. The impact of the chosen design includes cost savings, reduced construction schedule, and an overall safe project.
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