The benefits of high-speed streaming time-series data and a high-performance time-series database for grid operations are the topics for this issue of The Synchrowave Report.
Operators around the world have relied on SCADA data to provide visibility into the state of the power system for more than forty years. SCADA measurements come from many devices around the power system, including remote terminal units (RTUs), protective relays, digital fault recorders (DFRs), sensors, and more. SCADA data updates are received once every few seconds.
Newer time-synchronized measurement technology (such as synchrophasors, and streaming point-on-wave data) have resulted in an increase in volume and rate of data available to utilities. These newer measurements provide more than a 100 times the visibility into power system events compared to traditional SCADA.
The additional visibility synchrophasors provide compared to SCADA is shown in Figure 1. The figure shows synchrophasor measurements detecting a growing oscillation at a wind farm that resulted in a trip of the generation. You can also see how the oscillation goes undetected with the SCADA measurements.
Synchrophasors provide operators greater visibility into the power system, but trending this high rate data has challenges. In North America, synchrophasor measurements typically update at a rate of 30 messages/second. The table below shows the number of measurements received from a phasor measurement unit (PMU) over time at 30 messages/second.
|Time Range of Data||Number of Measurements|
|1 minute||1,800 measurements|
|15 minutes||27,000 measurements|
|1 hour||108,000 measurements|
|1 day||2,592,000 measurements|
Now let’s explore the challenge of displaying all that data to an operator (or an engineer). Today, computer monitors can display around 2,000 pixels, and that sounds like a lot, but when an operator wants to look at a trend of 15 minutes of synchrophasor data, the software needs to display 27,000 measurements.
The typical solution is downsampling. In this example, the software can only display 1 measurement for every 14 measurements. For many applications and industries, this might be an acceptable solution, but in the power system, events can change state very quickly and it’s important for the operator to know the full impact of the event. Standard downsampling approaches might mean the event in Figure 2 is displayed to the operator as represented in Figure 3.
As measurement sample rates continue to increase, the challenges described in the previous section will become even more critical. In 2011, SEL developed a high-performance time-series database that addresses these challenges with SEL-5078-2 Synchrowave Central Software. In 2019, SEL released SEL-5702 Synchrowave Operations software with an enhanced high-performance time-series database included.
The Synchrowave high-performance time-series database is based on a folder/file structure, making management of the data simple and intuitive.
The key to ensuring operators never miss critical data as a result of downsampling is a maximum/minimum index that complements the raw data archive, as shown in Figure 5. Synchrowave Operations automatically calculates the maximum and minimum values in time ranges and stores the results in the index portion of the high-performance time-series database.
As utilities around the world introduce synchrophasor visualization to grid operators, it’s important to make sure the operators are seeing the full impact of power system events. In Synchrowave Operations, when an operator views a 15-minute trend, the high-performance time-series database ensures that the maximum and minimum values in the time range are always displayed, as shown in Figure 6.
Synchrowave Operations is not only designed for synchrophasor and streaming point-on-wave data sources, but it also connects to common SCADA databases, such as OSI PI. Bringing synchrophasor data and SCADA data together on one screen can provide additional insight not possible before. Figure 7 shows how an operator can quickly compare synchrophasor and SCADA bus voltage measurements from both ends of a transmission line in Synchrowave Operations.
Recently, Dr. Greg Zweigle—R&D fellow engineer and a member of the Synchrowave team—joined SEL CEO Dave Whitehead on the Schweitzer Drive podcast for an in-depth conversation about SCADA, synchrophasors, and the future of real-time power system measurements. You can listen to the podcast here.
To learn more about Synchrowave Operations and its high-performance time-series database, or for general Synchrowave product questions and support, please reach out to the Synchrowave team at firstname.lastname@example.org.