Reference Information
Key information from reference documents and guides (e.g.) or succinct descriptions of concepts (e.g. what is risk and how do I visualize it)
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Research & Technical Content
Key takeaways, results from ongoing research tasks, and how they are applied.
1 - Research Result Summaries
Latest results from ongoing tasks
EPRI Approach to Corrosion Monitoring
Corrosion on utility assets often represents risk to the utility, personnel and the general public due to loss of structure, conductor or hardware strength. The effects of corrosion vary with the location and design of the circuit while the severity varies with the environment.
Innovative Cathodic Protection Application for Transmission Tower Concrete Foundations
Heavy wire tension loads from transmission towers are often transferred to the soil through concrete foundations. The foundations may be exposed to harsh environments resulting in corrosion of the reinforcing steel, internal stresses in the concrete and ultimately concrete degradation.
Corrosion Monitoring System (CMS) The Corrosion Monitoring System (CMS) has migrated from a research tool into a standalone data collection system to help us understand corrosion anomalies and monitor “at risk” structures. The CMS has its own power supply, data collection, cellular connection and a host of atmospheric and subgrade sensors to identify changes in both the environment and the degradation rate of the asset. That data may be used to model conductor degradation, ground grid degradation or any asset in atmospheric or soil exposure. Perhaps the greatest benefit of deploying the CMS is understanding severe types of corrosion such as stray current or circulating current corrosion.
1.1 - Corrosion Monitoring System
Originally designed as a research tool but has now found a home in monitoring “at risk” structures and anomalies that remain unexplained. The Corrosion Monitoring System (CMS) is a self-contained system that has power management, power supply, data storage, cellular connectivity and may be expanded to collect both atmospheric and subgrade data (see Figure 1).
Figure 1: The Corrosion Monitoring System installed at the Charlotte Campus in the underground test facility
The objectives of deploying the CMS is threefold, the first is to understand why assets degrade but also discriminate between corrosion types, the second is to locate suspect areas containing “at risk” assets and the third is to provide environmental data to support degradation models. Models consist of the following data and may be easily charted to trend both corrosion rates but also changes in subgrade and atmospheric weather (see Figure 2). The corrosion rates may be gathered for steel, zinc and copper for subgrade models or steel, zinc, aluminum, and copper in atmospheric models (see Figure 3).
Figure 2: The Corrosion Monitoring System Dataset for Atmospheric and Subgrade Monitoring
Figure 3: Algorithm for Substation Ground Grid Corrosion Monitoring and Installation Methods
EPRI has developed extensive atmospheric and soil corrosivity maps that may be augmented using data from the CMS data sets. Many departments within the utility may then use this new information for more accurate and informed life cycle decisions (see Figure 4).
Figure 4: Atmospheric and Soil Corrosivity Maps with Severity Categories for Corrosion
The CMS data sampling rate may be set for a very high- or low-resolution dependent upon the application and how often the anomaly or environment changes. Figure 5 illustrates a Corrosion Monitoring System collecting subgrade data to determine if a cathodic protection system is performing properly and meeting the acceptance criteria of -850 mV or 100 mV shift.
Figure 5: Monitoring a Cathodic Protection System using a CMS
Reviewing the chart, we may see that all of the bonded coupons are polarized more negative than -850 mV which is the acceptance criteria recommended by AMPP (formerly known as NACE). This polarization level allows the stake owners to determine that their asset is well protected and may provide many years of service.
2 - Reference Information
Key information from reference documents and guides (e.g.) or succinct descriptions of concepts (e.g. what is risk and how do I visualize it)
Determining End of Life for Transmission Line Assets and Substations Screening a service territory for “at risk” structures allows a utility to prioritize and optimize many of the life cycle decisions for both transmission and substation assets.
Selection and Application of Coatings Coating system degradation may occur due to exposure to environmental factors such as UV, temperature, salts, and precipitation, perhaps leading to corrosion-related damage of assets. EPRI evaluates new and emerging coating systems through laboratory testing to determine performance in various environments. Use the link above to access the performance summary tables of coating systems tested in the EPRI Coatings for Corrosion Control Project and common coating system application notes.
3 - Videos
Updates on tasks or tests
Subgrade Corrosion Map Update Screening your service territory for structures at risk has become an important tool for asset managers, engineers and maintenance crews. GIS Enabled, Subgrade corrosivity maps allow utility personnel to query circuits with severe corrosion and proactively manage the degradation due to soil exposure.
Coating System Selection and Application: Case Study Update: Coating system formulations evolve and change due to environmental restrictions and performance improvements. Evaluation by a third party is key to understand if the repair coatings are compatible with the old coating system and if the coating will perform well in different environments. The EPRI Coating Selection and Application library is migrating to a WebApp on the Transmission Resource Center so that utilities may quickly review more than 80 coating formulations and select the appropriate one for the utility needs.
Cathodic Protection and the Effects of Stray Current: In many cases the voltage level of stray currents that are found within the ROW fall below the safety criteria for touch and step potentials, so it is ignored and the effects are not well understood. This can be a fatal flaw in the asset management processes and discharge current may severely reduce the service life of a structure. This video demonstrates the concepts of anodic and cathodic interference and how we may identify each source to mitigate the stray current interference.
3.1 - Cathodic Protection and the Effects of Stray Current
In many cases the voltage level of stray currents that are found within the ROW fall below the safety criteria for touch and step potentials, so it is ignored and the effects are not well understood. This can be a fatal flaw in the asset management processes and discharge current may severely reduce the service life of a structure. This video demonstrates the concepts of anodic and cathodic interference and how we may identify each source to mitigate the stray current interference.
3.2 - Coating System Selection and Application: Case Study Update
Coating system formulations evolve and change due to environmental restrictions and performance improvements. Evaluation by a third party is key to understand if the repair coatings are compatible with the old coating system and if the coating will perform well in different environments. The EPRI Coating Selection and Application library is migrating to a WebApp on the Transmission Resource Center so that utilities may quickly review more than 80 coating formulations and select the appropriate one for the utility needs.
3.3 - Subgrade Corrosion Map Update
Coating system formulations evolve and change due to environmental restrictions and performance improvements. Evaluation by a third party is key to understand if the repair coatings are compatible with the old coating system and if the coating will perform well in different environments. The EPRI Coating Selection and Application library is migrating to a WebApp on the Transmission Resource Center so that utilities may quickly review more than 80 coating formulations and select the appropriate one for the utility needs.