2017 Research Portfolio

Power Delivery and Utilization - Transmission

Program 40 - Grid Planning

Last Updated: 14-Jun-2016
Program Description

Traditional power system planning methods and tools are increasingly challenged in today’s power system environment. Transmission owners and operators not only need to plan for future demand growth and increasingly uncertain generation portfolios, but also to provide transmission services based on distributed resources and central generation resources that include significant portions of variable generation (VG) technologies that are often remote from load centers and have significantly different dynamic behavior from synchronous generation. The challenge of meeting reliability requirements with the changing landscape and increasing levels of uncertainty may necessitate adjusting and augmenting transmission planning criteria and methods.

Transmission planners are also increasingly tasked with considering deeper and varied contingencies requiring screening of many more potential contingencies and prioritizing the contingencies for more detailed analysis. They also need to plan the system to withstand “special” circumstances such as the impacts of geomagnetic disturbances, electromagnetic pulses, and various physical security attacks on system reliability, and non-traditional impacts such as high levels of harmonic distortion. Some of these more advanced contingency analyses also require consideration of breaker-node representation and closer coordination and explicit integration of protection system models in planning models.

Resource planners are also increasingly challenged as environmental regulation forces the retirement of some conventional generation, as supply resources become more variable and uncertain, and as distributed and demand-side resources become more viable. Additionally, demand response and extreme temperatures in traditionally shoulder load periods are increasing the uncertainty in load levels at specific points in time. As a result, resource adequacy planning methods may require more consideration of the operational uncertainties associated with renewable energy and load forecast errors.

Research Value

The mission of EPRI's Grid Planning research program is to support the development and validation of planning study models, planning processes and frameworks, and reliability assessment analytics that will be required to build a reliable and economic transmission grid that integrates an evolving generation mix to supply an increasingly complex load that can also act as a system resource. The Grid Planning program directly supports EPRI’s Research Imperative #3 “Integrated Power System and Environmental Modeling Framework.” This is accomplished through a collaborative process in which EPRI works with utility and independent system operator (ISO) members and other stakeholders to identify existing research gaps and associated project needs that would provide value to society and EPRI members. Once identified, the EPRI Grid Planning team of technical and project management experts works with members and the world’s foremost experts in related research areas to structure and conduct specific projects that create value by delivering a combination of research results that provide value in the near-term, mid-term, and long-term. Finally, this value is transferred to members through collaborative advisory and task force interactions, workshops and webcasts, and specific applications and demonstrations of the developed methods and tools.

 

Approach

EPRI's Grid Planning research program delivers value by using the shared experiences and understanding of its utility and ISO members, in conjunction with the expertise of EPRI's staff and network of worldwide contractors. The program conducts research projects that lead to innovative methods and tools used by system planners. EPRI's Grid Planning program also engages with external industry standards groups, regulatory agencies, and other research efforts to ensure that the EPRI research program is building upon and leveraging broader stakeholder efforts and advancing the state-of-the-art.

For research areas where the developed deliverables are of value to EPRI members only if embraced by the larger stakeholder community, for example as with the development of new models that need to be adopted in commercial analysis packages, EPRI works to engage in industry efforts and share research publicly to drive society and all stakeholders to the desired path. The EPRI research program also strives to provide near-term, mid-term, and long-term value from each research project. For example, the 2016 the Grid Planning research program will deliver new prototype tools for generating and screening new contingency types and guidelines for conducting GMD studies, while also investigating methods and tool through which risk-based analysis methods can be integrated with existing planning processes to address the increasing levels and sources of uncertainty that will increasingly impact system planning in the future.

The research in the Grid Planning program addresses five primary areas:

  1. Model Development, Validation, and Management
  2. System Protection Methods & Tools for Planning
  3. Risk-Based System Planning
  4. Special Planning Study Methods and Tools
  5. Advanced Power Flow and Contingency Analysis Methods and Tools

 

Accomplishments

The Grid Planning program delivers valuable information that helps its members, other electric power stakeholders, and society in numerous ways. Some examples include the following:

  • System-Wide Protection Evaluation Macro Tool (3002006864): This deliverable provides a macro that integrates into a commercial short circuit analysis software tool to allow the user to configure aspects of a system-wide short circuit study and then execute the simulations and report on the results. Based on the configuration from the user, the macro identifies protection systems which may mis-operate allowing the user to identify potentially incorrect relay settings prior to mis-operation occurring.
  • Categorizing Line TOV Values for Determining Minimum Approach Distances (3002004444):  This report documents a technical basis for characterizing transient overvoltage values (TOV) that drive the minimum approach distances for conducting live-line work. The report summarizes the maximum TOV magnitudes expected for various line characteristics and associated operational practices.
  • Power Plant Parameter Derivation (PPPD) Version 5.0 (1025786):  The PPPD software uses measured synchronous generator responses to system disturbances to validate the generator, excitation system, and governor control system transient stability models. This tool allows transmission generation owners to perform ongoing model validation as system disturbances occur to support system reliability and to comply with emerging North American Electric Reliability Corp. (NERC) requirements to periodically validate the generator models.
  • Enhancing and Testing Fast Fault Screening (FFS) Methodology (1024271) and Fast Fault Screening for Transient Stability Studies (1021928):  These technical updates present methodologies developed in the Grid Planning program for fast prediction of the most severe three-phase fault locations for transient and voltage stability studies and then ranks them in order of severity to support reliability and more efficient compliance with NERC TPL standards.
  • Comprehensive Load Modeling for System Planning Studies (1015999):  This technical report covers both measurement-based and component-based load modeling. It also contains a guide to comprehensive load modeling for planning studies and detailed laboratory test results of select load components, such as air conditioners, compact fluorescent lighting, and high-definition televisions. It also includes the results and insights of measurement-based load model parameter derivation modeling research.
  • Transmission Contingency and Reliability Evaluation (TransCARE) (1022353):  This software provides a comprehensive framework for computing reliability indices for transmission networks, identifying worst-case contingencies and impacts of remedial action schemes, analyzing costs and benefits for various transmission upgrade options, studying the impacts of variable generation on system reliability, and analyzing extreme events, as well as performing NERC compliance studies.

 

Key Activities

In 2017, EPRI's Grid Planning research program will focus research on the following objectives:

  • Develop and validate static and dynamic models of system components such as HVDC and loads, including completion of the VSC HVDC dynamic models that can be used in system planning studies. Additionally, methods for system-wide model validation based on measurements will be applied, evaluated, and revised.
  • Develop methods and tools for system protection engineers to assess the performance of protection schemes to identify and mitigate potential mis-operations. Additionally, provide guidance and tools for transmission planners to determine to what extent protection systems may need to be explicitly represented in planning models for various study types.
  • Develop probabilistic and risk-based planning methods and tools incorporating all sources of system uncertainty and metrics, criteria, and a framework for making investment decisions based on the probabilistic analysis results.
  • Develop guidelines for conducting planning studies for ensuring reliable operation of the transmission system during geomagnetic disturbances (GMD) and develop models and tools to support GMD-driven harmonic assessments.
  • Develop methods and guidance for modeling and evaluating general transmission harmonic distortion which might result from increasing power electronic load and high levels of inverter-based resources.
  • Develop guidelines and models to support time-domain transient study assessments such as temporary overvoltage (TOV), transient recovery voltage (TRV), and general switching studies.
  • Develop methods and tools for synthesizing advanced contingencies such as stuck breaker or internal bus faults, as well as methods and tools for screening and prioritizing these contingencies for more detailed study.
Estimated 2017 Program Funding
$4M
Program Manager
Daniel Brooks, 865-218-8040, dbrooks@epri.com
Non-EPRI Members: Contact Program Manager - Daniel Brooks; 865-218-8040; dbrooks@epri.com
Last Updated
  • P40.016: Model Development, Validation, and Management
    • P40.016: Planning Study Model Development and Management
      14-Jun-2016

      Planning the transmission system to reliably perform under anticipated future operating scenarios requires models that faithfully represent the behavior of the interconnected system, which requires that the development and validation of models of the various components comprised by the system.  With the emergence of new generation and transmission technologies and the ever-increasing complexity of loads that respond dynamically to power system changes, there is a clear need to improve component and system dynamic models:

      1. The need for continued development and improvement of models for various power system components (particularly improving aggregation of loads etc.) and advanced technologies such as HVDC.
      2. The need to continue to explore improvements in procedures and methods for system wide model validation.

      This project aims to work on these two tasks, and is a continuation of previous EPRI research in this area.

  • P40.018: Transmission Line Protection Support Tools
    15-Jun-2017

    The optimal performance of protection relays is critical to the safe, reliable and stable operation of modern power systems. When a disturbance occurs on a power system the protection systems should act in concert to isolate faulted equipment while maintaining the stability of the power system and minimizing power outages. Protection systems have grown in complexity, speed and reliability since the early days of power systems and modern relays have the capability to provide very reliable and selective fault detection and isolation. However, the optimal application of these capabilities presents a key challenge to modern protection engineers.

    This research aims to address the challenges of balancing protection security, sensitivity, and selectivity through the analysis of protection models not only in traditional protection coordination study tools used by protection engineers, but also in transient stability and contingency analysis tools applied by operations and planning engineers.

    • P40.018: Transmission System Protection Support Tools
      14-Jun-2016

      The optimal performance of protection relays is critical to the safe, reliable and stable operation of modern power systems. When a disturbance occurs on a power system the protection systems should act in concert to isolate faulted equipment while maintaining the stability of the power system and minimizing power outages. Protection systems have grown in complexity, speed and reliability since the early days of power systems and modern relays have the capability to provide very reliable and selective fault detection and isolation. However, the optimal application of these capabilities presents a key challenge to modern protection engineers.

      With more complex and configurable functions comes a longer learning period for protection engineers to fully understand how each function works for each relay and to map out processes for establishing the optimal settings for each new installation. The optimal settings not only take into account prudent coordination of primary and backup protection relays, but also balancing sensitivity of fault detection with security of operation during stressed system conditions. In addition to coordinating primary and backup protection with each other, the protection schemes must also operate fast enough to prevent generator or system instability and perform correctly should instability or other major system disturbance occur. This research aims to address this challenge of balancing security, sensitivity and selectivity through the analysis of protection models not only in traditional protection coordination study tools used by protection engineers, but also in transient stability and contingency analysis tools applied by operations and planning engineers.

      Modern transmission protection relays and other substation intelligent electronic devices (IEDs) provide a wealth of information that may be used for disturbance analysis, evaluating protection system performance and validating power system models. While system studies are used to optimize the configuration and setting of protection relays, they cannot account for relays operating in an unanticipated manner due to internal or external component failure. Prior research in this project has focused on using IED data for determining fault location on transmission lines and validating transmission line impedances. The current research focuses on using data from protection relays and digital fault recorders to analyze protection system performance; this is to both identify and assess those relays that tripped as well as analyzing backup protection relays to ensure that they had detected the fault and were prepared to trip should primary protection fail. The data is further analyzed to accelerate the root-cause identification of power system disturbances and aid system operator decision and corrective actions.

  • P40.023: Special Planning Study Methods and Tools
    13-Jun-2016

    This research project provides for R&D to address special planning studies for addressing specific issues that must be considered in the broader planning process. In 2016, research was conducted to aid planners in conducting studies to evaluate the impacts of Geomagnetic Disturbances (GMD) on system reliability and to provide a guidance on modeling and simulating transmission harmonic impacts and guidelines for conducting transient recovery voltage (TRV) and temporary overvoltage (TOV) studies.  In 2017, this project will focus on potential transmission harmonic distortion associated with harmonic injections for transformers during a GMD event or from other drivers such as high levels of inverter-based resources.  Additionally in 2017, research will continue to provide guidance on modeling and simulation-based time-domain transient studies that may be required for transmission planning.

    • P40.023A: GMD Vulnerability Assessments - Harmonics Analysis
      14-Sep-2016

      During geomagnetic disturbance (GMD) events, magnetic field variations at the earth’s surface drive low-frequency electric currents along transmission lines and through transformer windings to ground.  These geomagnetically induced currents (GIC) cause half-cycle saturation of transformers leading to harmonic generation, increased reactive power losses, and heating of transformer windings and structural components. The combination of protection system misoperation due to harmonics and increase in reactive power absorption can result in voltage collapse.  This phenomenon was experienced in March 1989 when the Hydro Quebec network experienced voltage collapse when seven static var compensators were removed from service when their protection systems operated due to their sensitivity to harmonics. Additionally, harmonics created by half-cycle saturation have the potential to affect the operation of both synchronous and inverter-based generation.  Effects on synchronous generators, although to a lesser degree, were experienced during the March 1989 event.

    • P40.023B: Transmission Harmonics Analysis Methods and Tools
      14-Jun-2016

      Voltage and current harmonics have been present on power transmission systems since their earliest days. Historically, the topic has been of primary interest on distribution and industrial power networks where distorting loads and loads sensitive to harmonics are both commonly found. For many transmission systems, however, the issue of harmonics was less often the focus of attention except in the case of large non-linear loads like arc furnaces or distorting power electronics devices like SVC or HVDC. Even for such cases where the harmonic emissions are from a single source or a small number of sources at a single substation there are many challenges to the accurate development of transmission models and performing the necessary analysis and interpretation of the results.

      The power electronics used to interface many modern devices to the power system generate voltage and current harmonics due the switching process to convert power between dc and ac. While such devices were comparatively rare in the past, they have become increasingly prevalent due to the wider deployment of power electronic converters and their application as the interface between energy sources, loads and storage devices and power systems, as well as increased application of FACTS devices such as SVC and STATCOMs. As these devices are spread around the system they cannot necessarily be analyzed in isolation, and so, assessing the net impact of these distributed variable harmonic sources is more challenging. As the location experiencing harmonic distortion may be remote from the source or at a different voltage level the transmission engineer is posed with the question of how much of the network to model. Increasing the size of the model not only increases the time required to collect the required data and set up the study, but also extends the number of operational scenarios (generator dispatches, loads, outages) to consider in order to comprehensively study the network and identify possible breaches of harmonic distortion limits. Furthermore, the types of operational scenarios themselves (peak, valley, shoulder) determine the level of damping in the system and can be more difficult to define with significant local penetration of renewables. In the absence of industry-standard guidelines on modelling transmission systems for harmonics studies a research gap exists for evaluating network model depth and detail in order to accurately capture harmonic phenomena while minimizing model development time.

      With the short-term planning time-lines associated with many new transmission-projects – including FACTs devices, data centers, renewable energy sources and energy storage – it can be more difficult to design flexible harmonics mitigation devices. A harmonics mitigation device designed for the system as it is today may be inadequate or exacerbate future harmonics with unforeseen grid developments. Thus, there can be wide ranging benefits from the development of a standardized design approach for more flexible mitigation devices including such topics as physical layout of filter banks, minimizing component values across the fleet of filter banks on a system to permit re-use and replacement and re-configuration, and the application of active harmonic cancellation devices.

      While some of the issues above have been addressed for distribution and industrial systems, the guidelines and philosophies cannot always be directly translated for application to the transmission system. The aim of this research project is to address those issues for transmission grids and provide clear guidance for the analysis and mitigation of harmonics on transmission systems.

    • P40.023C: Transmission System Switching Transients
      14-Jun-2016

      Switching transients relate to the high frequency transient phenomena that primarily occur after operation of disconnects and circuits breakers, but also after other system disturbances such as the initiation of short circuits. The modelling requirements for switching transient studies are much more onerous than for conventional load-flow studies and are quite different to those models required for stability studies. Allied to this is the fact that only a small portion of the larger network may be modeled in order to ensure that the simulation completes within an acceptable time-frame. As a result engineers are often required to develop bespoke network models on a per-study basis. This can have the consequence that switching transient studies can be time consuming to complete as the engineer collects detailed equipment data and test reports, develops the model, configures the simulation and analyzes the results.

      Transmission systems are seeing greater use of EHV lines, longer underground cables, replacement/upgrade of existing equipment and more connection requests for sensitive loads and generators. In addition to this there are more frequent use of gas insulated switchgear and emerging technologies such as gas insulated transmission lines and superconducting conductors, which have their own challenges for modelling and analysis during switching events. This is leading to transmission planners and transmission engineering designers facing increasing requirements to perform switching transients studies in order to ensure adequate insulation coordination, selection of circuit breakers, sizing surge arrestors, design of opening/closing resistors, choosing between replacing relatively high maintenance opening/closing resistors with surge arrestors or synchronized switching and calculating safe minimum approach distances for live-line work.

      Switching transient studies are computationally challenging. Over the years many simplifying assumptions have been adopted in order to speed up simulation time, but such simplifying assumptions tend to decrease simulation accuracy and result in conservative solutions. These conservative solutions feed into the equipment design process and may result in higher specification equipment, additional mitigation devices or operational limitations. More accurate simulations based around the research undertaken in this project could result in reduced error margins and better optimized designs without sacrificing reliability or safety.

      Technology changes also impact insulation coordination and switching studies. For instance, changing between porcelain or glass string insulators to polymeric types or moving from conventional capacitive voltage transformers (CVT) to optical voltage transformers materially impact on transient overvoltages and insulation coordination, but this may not be obvious at the design stage. Case studies and test simulations will be used to develop criteria or methodologies to flag when switching studies may be required.

  • P40.024: Advanced Power Flow Control, HVDC Planning, and Contingency Analysis Methods and Tools
    15-Jun-2017

    40.024: Advanced Power Flow and Contingency Analysis Methods and Tools (2017)

    Significant changes occurring in the power industry due to retirement of fossil generation, increasing levels of renewable generation and advent of distributed energy resources (DER) pose challenges to future transmission planning. Conventional approaches and tools used thus far may not be sufficient for future planning needs as they are not designed to handle distributed, uncertain generation and load-side resources.

    Also as the nature of power system is changing, it is becoming challenging to assess reliability of transmission systems. The new NERC transmission planning standard TPL-001-4 requires a comprehensive set of contingencies to be evaluated. These contingencies are divided into eight categories. Some of these categories require breaker-node modeling of transmission substations which could be quite involved. Considering all eight categories of contingencies for a practical system could result in quite a large number of contingencies. Evaluating these could be significantly labor and resource intense process especially for time domain simulations for stability assessments. Therefore there is an urgent need to develop methods and tools that can make the process of contingency assessment more efficient and at the same time meet TPL standard benchmarks.

    • P40.024A: Advanced Power Flow and Contingency Analysis Methods and Tools
      14-Jun-2016

      Significant changes occurring in the power industry due to retirement of fossil generation, increasing levels of renewable generation and advent of distributed energy resources (DER) pose challenges to future transmission planning. Conventional approaches and tools used thus far may not be sufficient for future planning needs as they are not designed to handle distributed, uncertain generation and load-side resources.

      Also as the nature of power system is changing, it is becoming challenging to assess reliability of transmission systems. Emerging transmission planning requirements and standards (e.g., NERC TPL-001-4) require a comprehensive set of contingencies to be evaluated. These contingencies include many categories, some of which require breaker-node modeling of transmission substations which can be quite involved. Considering all categories of contingencies for a practical system could result in quite a large number of contingencies. Evaluating these could be significantly labor- and resource-intensive process, especially for time domain simulations for stability assessments. Therefore there is an urgent need to develop methods and tools that can make the process of contingency assessment more efficiently and at the same time meet standard benchmarks.

  • PSET_P40 Unrestricted
    • P40.022: Incorporation of Risk Analysis into Planning Processes
      14-Jun-2016

      The electric power industry is experiencing rapid physical, institutional, and regulatory changes that are increasing uncertainty that may have ramifications for reliability and the cost of providing reliable electric service. The main drivers of these changes are the advent of open transmission access and deregulated energy markets across wider geographic regions, the growing prominence of remote variable generation resources such as wind and solar photovoltaic, demand-side resources such as demand response, residential/commercial PV, and electric vehicles, and evolving environmental regulations and capital/fuel cost changes that are influencing generation fleet.

      These factors are significantly increasing the uncertainty as to future supply resources to be developed, future demand levels that must be served, and the resulting specific generation dispatch and associated power flows that will result. As such, it is becoming more difficult, if not impossible, for planners to evaluate all near- and long-term reliability considerations when considering planning projects. The existing planning processes and tools, which are mostly deterministic, may not be adequate to address these challenges. This may result in a failure to study a particular scenario that may have reliability implications or the tendency to over-build the system to account for the uncertainty. Therefore, there is a need to develop new risk-based analysis methods and tools that can be integrated with existing planning processes to explicitly consider many of these noted uncertainties. Augmenting existing, deterministic-based planning processes with risk-based planning methods may yield a framework that can address the dimensionality introduced by the uncertainties in data and forecasts which cannot be captured in a deterministic framework because an impossibly large number of deterministic studies would be required to assess each possible combination of outcomes. However, there are challenges in incorporating risk-based planning in transmission due to lack of standard methodologies, lack of widespread knowledge among practicing engineers, and lack of data and tools, among other factors. Therefore, there is an industry need for concerted R&D efforts to evaluate potential benefits of including probabilistic methods and accordingly to develop methods, tools, metrics, and data processes to support their integration in the planning process.

      In addition, utilities are increasingly being exposed to threats from natural disasters (hurricanes, tornados, earthquakes, GMD etc.) and man-made events (terrorism, electromagnetic etc.) which can devastate generation, T&D infrastructure, and threaten lives and disable communities. These events typically have quite a low probability of occurrence but can wreck tremendous damage to infrastructure. Given the limited resources and investment dollars available, it is necessary to know which system hardening options can provide most bang for the buck. The existing planning approaches and tools do not lend themselves to analyze and plan for these events and address the challenge of where and how to invest. Therefore, there is a need to develop methods and tools that will enable planners to assess resiliency of grid against such events and make sound investment decisions. This is a new multi-year research effort that will be started from 2016.