Synchrophasors Electrify Power Transmission

By Kathleen Davis, Senior Editor

The status quo of transmission-monitoring technology at the moment is a bit slow. With phasor measurement units (PMUs) in place, utilities could record system information 30 times to 120 times per second. That’s significantly faster than today’s technology–about 100 times faster, which is a stunning development.

There are a lot of benefits from the PMUs’ time-stamp of each measurement taken. Put together across a region and across a time period, these stamps give an accurate overview of the entire system. Having a more accurate view would allow for more accurate and timely reactions.

Synchrophasors could significantly change the flow of power, making instant reactions possible and accurate preplanning much easier.

For a view of how synchrophasor programs are progressing, POWERGRID International spoke with four interrelated synchrophasor insiders: the Western Electricity Coordinating Council (WECC), Southern California Edison (SCE), PJM Interconnection and the Department of Energy.

So Far: Lessons Learned

Led by the WECC, the Western Interconnection Synchrophasor Program (WISP) is installing more than 350 new or upgraded PMUs across the western U.S. and parts of western Canada. Scheduled for completion in March 2013, this “early warning mechanism,” as WECC labels it, will enable WECC and WISP’s participating entities to take timely blackout prevention action.

Linda Perez, WECC’s program director, applauded how the synchrophasor project has brought them improved system observation tools, but she also noted that sharing data will need some agreed upon rules.

“The most significant lesson learned is the need for a clear, agreed-upon standard for the security, sharing and transfer of synchrophasor data between the participants,” Perez said, calling that aspect “critical” to the project’s success, along with building a solid data-sharing infrastructure between participants.

Vickie VanZandt, WECC’s WISP program lead, added, “The standards for synchrophasor streaming data are relatively new, and continuously evolving. As a consequence, there is a lack of commercial, off-the-shelf synchrophasor products.”

Currently, PMUs with dynamic capability and phasor data concentrators (PDC) aren’t readily available. Vendors take note.

The same applies to software tools to interpret all that data PMUs pull in. This slice of software, too, is fairly new and untried in this synchrophasor arena. As WECC better understands the system and its capabilities, it can better inform vendors about product and software needs.

Research in this area also continues, with efforts to develop new applications, tools and technologies, according to VanZandt, and that will bring a number of benefits when all the research comes to a commercial fruition.

“When deployed and commercialized in the nation’s control centers, these new synchrophasor elements will enhance the reliability of the entire grid, provide a more robust and diverse power supply, and will strengthen the U.S. patent portfolio,” she said.

SCE has PMUs at most major 500 kV and 230 kV substations. The utility monitors over 20 PMUs receiving about 150 phasors of data at 30 samples per second for each phasor. SCE may install up to 80 PMUs as part of the WECC synchrophasor project.

Anthony Johnson, consulting engineer with SCE, says the utility’s major project lesson is that the grid is more complex than they thought.

“The electrical grid is more complicated than the models and EMS systems present to us,” he said.

Noting that synchrophasor technology is laying out a much more layered, detailed view of the system, Johnson tied it to the evolution of other data-heavy digital maps like Google Earth.

“If the map has been recently updated with a new picture, a huge amount of detail was available,” he said. “However, if it was from an earlier picture, the details are not available, and it’s a blur as you zoom in.

“The synchrophasor technology is the modern picture; the EMS data is the older picture.”

PJM and its members are still implementing the synchrophasor technology, said Chantal Hendrzak, director of applied solutions. With a plan to put PMUs across 80 extra-high-voltage substations by the end of 2013, the current transitional phase is already seeing progress in using the data for post-event analysis.

“We’ve also started to collect baseline the data to establish an operating picture of what is normal so we can then start to identify the exceptions,” Hendrzak said.

In the lessons arena, Hendrzak said, “Not all vendor equipment operates the same.” PJM is learning the nuanced differences in how different equipment collects, calculates and transmits data.

“Data measurement, as well as collection systems and associated standards, are going through rapid changes for this evolving technology, so deployment of a production-grade system is a challenging task,” she said.

PJM, SCE and WECC are all a part of the Department of Energy’s (DOE’s) Smart Grid Investment Grant (SGIG) projects funded under the American Recovery and Reinvestment Act (ARRA) and managed by the DOE’s Office of Electricity Delivery and Energy Reliability. (SCE is part of WECC’s WISP program.)

Phil Overholt, the DOE’s transmission R&D program manager, touted the wide-area grid visibility across the entire U.S. that the synchrophasor projects like PJM’s and WECC’s will allow.

“Across the U.S., these projects and others are helping independent system operators, transmission companies and other utilities get a faster, more accurate window into the status of the grid, allowing them to respond more quickly and effectively to disruptions,” Overholt said. “Enhancing situational awareness is a critical component of grid modernization.”

The data itself will teach a few lessons to participants, including grid dynamics and an ability to follow deterioration of grid conditions by tracking the rate of change in real time.

“These capabilities can prevent or limit the extent of major blackouts, and support the integration of variable output renewable resources,” Overholt said.

As for lessons from the implementations themselves, Overholt pointed out two major positive items. First happy lesson: Participants have been able to “install more PMUs than originally proposed because the cost of installation is less than estimated.”

Second, even without being a finished set of projects (and with a limited number of PMUs), Overholt has heard from engineers who already are able to use archived data immediately after a grid disturbance for preliminary event analysis.

According to Overholt, in the past this analysis took days. In the future, it may take mere moments.

Next Steps

What’s next for these interconnected entities? All are moving forward, though some are emphasizing installations while others put the focus on applications.

“It is important to note that installing the technology across the country will require an enormous effort to build a system that can accurately collect, organize and share a huge amount of time-synchronized information,” Overholt said. “Ensuring that data provided by the system is accurate and valid may require two to three years and will constitute an essential first step, as applications for the data that will be used by system operators are developed.”

For WECC, good planning has laid the groundwork for a smart synchrophasor future. They developed criteria and identified places and people early in the process.

Independent system operators and reliability coordinators were all included from the beginning, and WECC projects that all the PMUs will be in place by the March 31, 2013, grant deadline laid out with their ARRA funding.

Additional PMUs are in the works as well–more than originally planned.

“The intent is to transfer the technology from a research environment to production, culminating in full commercialization,” Perez said.

Southern California Edison will be looking into the details of design and system implementation starting in January 2012, Johnson said. And it expects to start factory acceptance testing in the second quarter of 2012. That synchrophasor project is humming right along.

PJM plans on continuing synchrophasor installation with its participating members in 2012, along with investigating and developing applications for both visualization and analysis. In addition, Hendrzak noted that they will expand to involve the operations team in user interface development and may require new generation projects to install phasor measurement devices.

“DOE is also working to develop applications that use synchrophasor data to assist transmission owners and operators in planning and operating the grid,” Overholt said when asked about the next step in the overall PMU onslaught.

Right now, the first applications software is available, which provides display and visualization of PMU data in near real-time. Other software can perform data analysis to identify potentially dangerous oscillations, which, Overholt said, “were not visible with the slower SCADA monitoring.”

Synchrophasors of the Future

WECC believes that PMUs are very important to monitor and improve the reliability of the Western Interconnection, making synchrophasors a future reality, not a future fantasy.

“Control actions based on high-resolution synchrophasor signals are an essential part of the smart grid,” Perez said.

Johnson sees synchrophasors as one of many “base technologies” critical to the smart grid effort, as Perez noted.

Johnson equates the importance of synchrophasors for a smarter transmission system to the place of smart meters within the smart grid.

“For distribution systems, it is generally acknowledged that the smart meter is a key technology. While it is possible to have a distribution smart grid without a smart meter, the smart meter is an enabler of distribution smart grid solutions. The synchrophasor data does the same thing to the transmission smart grid,” he said.

DOE’s Overholt agreed, calling synchrophasors “essential at the transmission level,” and even predicting growing value at the distribution level with the growing renewable integration issues and a need to keep up with “changing grid parameters.”

Hendrzak looks to the details that synchrophasors provide, such as time-synchronized measurements “enabling interconnectionwide area situational awareness to a level not feasible with the existing technology.” In addition, there are better models that this data will allow, making for more accurate simulations.

Models and distribution options aside, in the near future, synchrophasors are all about transmission. And smart transmission is bound to be all about synchrophasors.

“While it is possible to have a transmission smart grid without synchrophasors, the synchrophasor is an enabler of the transmission smart grid. Without the enabling technology, the success of smart grid applications would be much more difficult,” Johnson said.

A PRIMER ON SYNCHROPHASORS

What is a synchrophasor, exactly?

The term synchrophasor is “a calculated measurement of the magnitude and phase angle of voltage or current between two points on the grid, time-synchronized against GPS,” said Alison Silverstein, North American Synchrophasor Initiative’s (NASPI) project manager.

What else is involved?

Synchrophasor data/phasor data: a broad set of grid condition data collected at high speed (30-120 samples per second) and time-synchronized.

Phasor measurement unit (PMU): the device that collects phasor data.

What does it mean when people say they are “putting in a synchrophasor system?”

“They’re installing PMUs (or upgrading existing relays) in substations, building or leasing a high-speed communications network, installing local and control room phasor data concentrators to process, archive, and pass on the time-synchronized data coming out of PMUs, and buying (or building) phasor data applications starting with wide-area monitoring and visualization for real-time situational awareness,” Silverstein said.

What’s the most important piece of data that PMUs offer?

Linda Perez, WECC program director, chose three:

  • Data that identifies when the damping of the power system is a reliability risk.
  • Data that is used to validate and improve power system component models, such as generators and transformers, for planning and operational studies. These studies are used to predict power system behavior, set near- and longer-term operating limits and to form the basis of transmission infrastructure expansion plans.
  • Data to assess power angles, which are important indicators of system stress. Because PMUs provide high-resolution, time-synchronized measurements, they have a significant advantage over traditional SCADA measurements.

What will synchrophasors do for the transmission system?

Phasor data will let operators manage the grid “with greater reliability, help them identify and avert potential reliability problems before they get out of control, and help to integrate intermittent renewable generation while getting more transmission out of the grid we’ve got,” Silverstein said.

Where are current synchrophasor projects under way?

SGIG funding has launched 10 transmission synchrophasor projects since the awards were announced in 2009. The projects involve 57 utilities and grid operators and 850 networked PMUs. (The DOE estimates that by 2013 PMUs will be at work in nearly all U.S. regions.)

Together the projects make up the single-largest synchrophasor effort ever undertaken, according to NASPI and the DOE, including:

  • American Transmission Co., Wisconsin (two)
  • Duke Energy, North Carolina
  • Entergy Services, Louisiana
  • ISO New England, Massachusetts
  • Midwest Energy, Kansas
  • Midwest Independent System Operator, Indiana
  • New York ISO, New York
  • PJM, Pennsylvania
  • WECC, Utah

What advice would you give utilities or other entities just beginning a PMU project or installation?

Perez, WECC: Utilities and other entities need to plan enough time to work through data sharing and other institutional issues to be able to use the PMU data. However, the PMU installation, in and of itself, is not complicated. It is akin to the installation of a protective relay or digital fault recorder.

Johnson, SCE: The first thing to figure out is: What applications do you want to implement? The answer to that question will define where you need to place synchrophasor equipment and what the supporting architecture needs to be. The applications range from simple visualization to advanced control applications and anywhere in-between.

Overholt, DOE: Install a few PMUs at key locations on the system, a phasor data concentrator to collect and archive PMU data, and visualization software for engineers and operators to view the data. For technical assistance they can contact NASPI, and access DOE Smart Grid Investment Grant (SGIG) data on build metrics, DOE support resources and colleagues at other utilities. In addition, SGIG impact metrics provided by each grant recipient will show the system benefits derived from implementation of their synchrophasor networks.

Hendrzak, PJM: Indentify and plan for the install locations carefully in order to ensure the highest possible coverage of the entire transmission system. Ensure all cyber security issues are addressed; involve security experts from the very beginning. Ensure representatives from multiple operations areas are involved in the analysis, design and implementation of the system; it is not just an IT project. Not all vendor equipment operates the same; confirm that the vendor equipment operates as expected and verify interoperability and scalability of the data systems. Capture the configuration data and details about each phasor unit and its installation and plan to keep this data up-to-date; this is useful when analyzing measurement results.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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