Invisible smarts: let's talk synchrophasors

Phil Carson | Mar 30, 2010


A little-noticed piece of news slid past me last week, which is somehow appropriate for topics such as synchrophasors.

NERC and CAISO signed a DSA as part of NASPI.

Sorry to do that to you. I just wanted to make the point that a litany of acronyms often disguises an interesting story.

Let me present that again: The North American Electric Reliability Corporation and the California Independent System Operator signed a data-sharing agreement as part of the North American Synchrophasor Initiative.

NASPI's mission is to improve the grid's reliability through wide area measurement and control, which contributes to situational awareness. That, in turn, lies at the core of the smart grid: actionable intelligence that could prevent cascading blackouts.

For NASPI project manager Alison Silverstein, the agreement signed last week is a big deal. Prior to the NERC-CAISO agreement on data-sharing, such an exchange took place between two interested parties on a one-to-one basis. That approach created "an Achilles heel and logistical nightmare," Silverstein told me yesterday. To assist in preventing cascading blackouts across various transmission facilities, of course, PMU data must be widely shared.

With the advent of federal investment grants that will accelerate PMU deployment and programs such as the Western Electricity Coordinating Council's Western Interconnection Synchrophasor Project (the WECC WISP - gotcha!), the data-sharing conundrum had to be solved.

So the agreement signed last week is based on NERC's operating reliability data (ORD) agreements and standard non-disclosure agreements (NDA). It places NERC at the center of a one-to-many signatory model.

"When one entity involved in PMU data signs an agreement with NERC, they become a partner and qualified to share and protect data with everyone else who signed that agreement," Silverstein said. "NERC plays role of 'counter-party.'"

NERC expects to roll-up more transmission system owners and operators in coming weeks, according to the organization's announcement last week.

Perhaps a quick dive here will help readers visualize or otherwise get their head around the PMU value chain.

Synchrophasors, aka phasor measurement units, or PMUs, have been upgraded with the advent of civilian use of the global positioning system (GPS) to provide near-real time data on wide areas of the grid and its behavior. Before that, PMUs provided forensic data on past events such as blackouts. Today, they can provide the basis for making decisions that could prevent blackouts.

PMUs measure grid conditions about 30 times per second, a considerable improvement over the once per four seconds possible in the past. Each measurement is "time stamped" using GPS so that different utility grids in an interconnection can be compared and realigned. Those comparisons are expressed in degrees, as in a compass bearing. If two interconnected grids are seriously out of phase, for example, there may be trouble ahead and PMUs can provide operators with timely data to suggest a correction.

PMUs can be discreet, dedicated devices installed at the substation or they can be digital fault recorders (DFRs) or relays already in place and optimized to provide analogous data. So the patchwork of grids that make up a major interconnection such as the Western Interconnection already have some PMUs in place. Now, more than 800 additional PMUs will be added to the North American bulk power system over three years using federal investment grants.

The transmission operator employing PMUs collects the raw data and "pushes it up" to a regional data concentrator (CAISO in West, TVA in East, e.g.) that archives and time-aligns the data. That data is fed to applications that translate it into actionable intelligence such as the Real Time Dynamics Monitoring System (RTDMS), a phasor application platform.

NASPI is funded by DOE and NERC to advance PMU use and its value and to accelerate commercialization to improve grid reliability.

In the big picture, all three of the nation's major interconnections are involved in PMU implementation via local transmission entities, Silverstein said. All seek reliability improvements and real-time situational awareness, while focusing as well on regional interests.

The Eastern Interconnection has about 100 PMUs installed and in one example, PJM Interconnection will use an investment grant to further PMU use. PJM is focused on major transmission pathway congestion management, too.

The Electric Reliability Council of Texas (ERCOT) is looking at the integration of renewable energy. WECC is looking at planning applications, renewable energy integration and major transmission pathway congestion management.

Meanwhile, Silverstein added, there's a "frenzy of effort" on technical standards development so that data sharing works in the real world as well on the paper signed last week between NERC and CAISO.

Okay, I used only a dozen acronyms today. What once was designed to help can also hurt. Where's the line, dear reader? And what can you add to the synchrophasor discussion?

Phil Carson
Intelligent Utility Daily





Related Topics



Phil, thanks for finally focusing attention on Smart Grid elements that have heretofore been out of the limelight.  Finally having real-time data about the actual state of the grid rather than estimates is going to be a big step forward.