Control Room Solutions Task Team

An oscillation was observed in the frequency and voltage data from a single PMU in an area with several PMUs.  The map below (see Figure 1) shows the relative location of three PMUs on the NPPD system.  A significant customer (steel mill) is physically located somewhere near the end of the word “Antelope” on the map.  Some wind farms were recently added in the same area with a point of interconnect at the Antelope location. 

A post-event analysis was conducted by ERCOT engineers for a compound event on the grid. In the process of analyzing a loss-of-generation event using PMU data, ERCOT engineers discovered other disturbances immediately before the loss of generation. This triggered a more in-depth analysis of these disturbances.

The event began with a phase-to-ground fault (determined by PMU frequency and voltage), which was followed by three separate frequency ramps. Since SCADA telemetry indicated that only the third frequency ramp was caused by a generator going offline, ERCOT requested information from the operator of the power plant about a possible load rejection/imbalance event. The operator confirmed that the load imbalance had indeed happened while the TSP in the area confirmed the occurrence of the fault as well as a relay mis-operation in response to the fault at the Point of Interconnection (POI) of the generating station.

ATC implemented a back to back HVDC system in 2014 and a Static Var Compensation [SVC] system in 2017. We have SCADA data available from each site scanning every 4 seconds and we also have high speed fault recording at both sites but neither of these data sources provided a picture of the dynamic response of the devices to system events that was readily available.

Phasor Measurement Units were installed at both of these facilities to monitor the net output for each. As events occur the equipment response is reviewed, and oddities are investigated. The following plots show the response of each device to a significant double circuit trip event on the system as reference. Note that the SCADA data for each is also included and while it provides information on the general operation of the device the dynamic attributes are hidden.

This paper describes how synchrophasor technology can be used in the Real-time Operations Horizon to determine the origin, nature and severity of disturbances on the electric power system.

Specifically, this paper considers how synchrophasor data and their application can be used by System Operations staff to analyze power system disturbances in near real-time and identify actions that can be taken to isolate faulted/failed equipment to return the electric system to an acceptable operating state.

The paper also identifies potential benefits to the utility organization in the areas of Operational Performance, Safety, Reliability, and Cost.

This paper describes certain functional entity roles and responsibilities related to oscillation detection monitoring, considers how synchrophasor technology may be used to identify actual oscillation events or issues, and describes some of the related commercial applications that are currently available to the industry to perform these tasks. This paper describes applications for which the NASPI CRSTT received information from application users or vendors and may be updated to include additional applications as new information is provided.