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7/30/2019 Use of Synchronized Phasor Measurement System for Monitoring
Operation of electric power systems has become increasingly complex as the load growth
continues and additional market forces are coming into play. Deregulation and demand for
renewable and distributed resources is putting additional challenges in maintenance of the
reliability. On the other hand, the demand for higher reliability and power quality is increasing as
the industrial consumers add power electronics driven sensitive loads. Also, under the competitivederegulated market conditions, the utilities are finding it more difficult to plan and upgrade the
transmission systems as in the past and are unable to keep up with the growing loads and the added
generation. The power systems have also become so inter-dependent that the events in one area can
cascade and have significant impact on other remote areas. This was recently witnessed in
Northeast US blackout, which occurred on August 14, 2003. This change in the industry is putting
pressures and development of new tools to monitor wide area system stability and reliability is
becoming very essential.
The advances in the field of communications, computers and Global Positional System(GPS) technologies have enabled the development and use of Synchronized Phasor Measurement
technology in monitoring and managing dynamic system security of large power systems [Ref. 1-
5]. Southern California Edison (SCE) Co., which is part of the Western Electric Coordinating
Council in United States, has been working on the “Synchronized Phasor MeasurementTechnology” for last twelve years and has made substantial development in tools for visualizing
and analyzing the system dynamics. SCE has now a fairly good SPMS system installed at its key
locations and has installed a network of Phasor Measurement Units, Phasor Data Concentrators, a
high speed reliable fiber optic communication system and suitable data storage servers to collect
the phasor data. SCE also exchanges data from a Phasor Data Concentrator installed by Bonneville
Power
SCE Synchronized Phasor Measurement System (SPMS)
As a result of a large-scale WECC disturbance in August 1996, SCE began moreaggressively researching wide area measurement technologies. The initial goal of this effort with
WECC and EPRI was to monitor and analyze system events or disturbances. Since that time, SCEhas installed eighteen phasor measurement units (PMU) at all of its major 500kV and 230kV
substations, two BPA Phasor Data Concentrators, recorded data for most WECC events (since
1996), developed an off-line analysis tool for planning and operator training (Power System
Outlook), and a real-time operations tool (SCE SMART®) that is deployed in SCE’s Grid Control
Center. Figure 1 shows the Phasor Measurement units installed with in SCE. The Phasor Data
Concentrators are installed in SCE Grid Control Center in Alhambra.
SCE is currently working with the California Independent System Operator (CAISO) to receive
reliable data that CAISO collects from other WECC entities. SCE has a limited capability link
with Bonneville Power Administration (BPA) to exchange information with one of the main power
stations in BPA’s territory. This link is essential for determining North-South power flows and
WECC system stress conditions. The quality of this link is adequate for RD&D, but unfortunately,
does not satisfy the reliability requirements necessary for operations. SCE is working with otherWECC entities to improve data interchange.
SCE believes that this Synchronized Phasor Measurement (SPM) technology has potentialto reduce blackouts in future, provide full visibility of the entire system to operators and is needed
to monitor all essential dynamics that occurs in the power system. It is fast enough to providecapability of closed loop wide area control which may become essential in future power systems.
7/30/2019 Use of Synchronized Phasor Measurement System for Monitoring
Figure 1: Phasor Measurement units installed in SCE (as of 2007)
SCE Program Capabilities –present and future (proposed)*:
Currently the two programs developed by SCE have the following capabilities.Additional capabilities, not underlined in the list, will be added in future.
P ower S ystem Outlook program ( PSO ) - Off-line Applications:
Presently available Monitoring system stress (Phase angle separations)
Monitoring voltage support at critical locations
Post disturbance analysis (what operated correctly or incorrectly) Monitoring modal oscillations and modal damping
Monitoring dynamic power swings
Future planned enhancements
Model validation/establishing limits using off-line analysis tools
System status summary
Monitoring machine excitation and governor systems
System Voltage and reactive power management
Pattern recognition and AI tools for quick event analysis
System load response to voltage and frequency variations
S ynchronized M easurements and A nalysis in Real T ime ( SMART )
Presently available
Monitoring system stress (Phase angle separations)
Monitoring voltage support at critical locations Monitoring path flows, frequency, df/dt
7/30/2019 Use of Synchronized Phasor Measurement System for Monitoring
Post disturbance analysis (what operated correctly or incorrectly)
Operator Training tools – replay of past events Planning and Operational capability – replay of future simulated events
Future planned enhancements
Alarms and system flow views Monitoring modal oscillations and modal damping
Model validation/establishing limits using off-line analysis tools System Voltage and reactive power management
Pattern recognition and AI tools for quick event analysis
System load response to voltage and frequency variations
* The underlined applications are already available in the above programs
SCE Power System Outlook Program (PSO)
Power System Outlook was developed in 2000, to understand the data captured by SCE’s
SPMS and provide information usable for engineering and planning. The software provides off-line viewing and playback capabilities for data captured on all monitored circuits and features the
ability to determine: currents, power, reactive power, frequency/frequency deviation, df/dt at allPMU locations, phase angle difference from selectable bus reference, percent deviation for voltage,
current, power, reactive power and a voltage phasor display. More recent additions to the list
include: modes of oscillations, damping of identified modes, time constant for identified modes,
relationship analysis, data extraction into Microsoft Excel®
files, power in specific frequency band
(time domain), power vector replay at PMU location, and viewing and validation with GE’s PSLF
simulated events. The capabilities of PSO have enabled SCE’s engineers to better understand what
the phasor data means and have led directly to the development of a real-time system operations
tool with analytical capabilities. The tool is also being utilized in the studies for incorporating
4500 MW renewable wind generation. Future applications of this technology will include
intelligent control of bulk power components, remedial action schemes, and eventually, closed-loop control.
Figure 2: SCE Power System Outlook - Modes of Oscillation, Damping and Time
Constant for the August 4, 2000 dynamic event. The event had low dam-ping for
the WECC North-South oscillatory mode.
7/30/2019 Use of Synchronized Phasor Measurement System for Monitoring
and PSO are highly advanced software packages, they continue to be
part of SCE’s Research, Development and Demonstration portfolio, and are not commercialized
products. These products and the recorded events have enabled SCE to better understand its
system and WECC system characteristics. SCE has freely provided PSO to electric utilities,independent system operators and universities to encourage the development of advanced systems
technologies. Nonetheless, more RD&D is essential to fully understand and utilize the data
provided by phasor measurement units and other time-synchronized devices. SCE is committed to
advancing this effort and invites others to participate in this endeavor.
Note/Disclaimer
This paper represents the views of theirs authors and does not necessarily represent the
views of Southern California Edison Co. or its parent organization Edison International.
References:
[1] Phadke, A. G. Ibrahim M, Hibka, T., “Fundamental Basis for Distance Relaying withSymmetrical Components”, IEEE PA&S Transaction, Vol. PAS-96, No.2, March/April, 1977.
[2] Missout, G., Beland, J., Bedard, G., Lafleur, Y., “Dynamic Measurements of the Absolute
Voltage Angle on Long Transmission Lines”, IEEE Transaction, PA&S, November, 1981.
[3] Phadke, A. G., Thorp, J.S., Adamiak, M.G., “A New Measurement Technique for Tracking
Voltage Phasors, Local System Frequency and Rate of Change of Frequency”’ IEEE PA&S
Transaction, Vol. PAS-102 No.5, May, 1983,pp 1025-1038.
[4} Schulz, R.P., Van Slyck, L.S., Horowitz, S.H., “Potential Applications of Fast PhasorMeasurements on Utility Systems”, IEEE PICA, 1989.
[5] Phadke, A.G., “Synchronized Phasor Measurements In Power Systems”, IEEE Computer
Applications In Power, Vol. 6, Number 2, pp 10-15, April, 1993.
[6] R. L. Cresap and W. A. Mittelstadt, “Small Signal Modulation of the Pacific HVDC
Intertie”, IEEE Trans. PAS, Vol. 95, pp. 536 - 541, 1976.[7] R. L. Cresap and J. F. Hauer, “Emergence of a new swing Mode in the Western Power
Systems”, IEEE Trans. PAS, Vol. PAS 100, April 1981, pp. 2037- 2045.
Bharat Bhargava
Mr. Bharat Bhargava is a Consulting Engineer in the Technology Integration group of
Transmission and Distribution Business Unit of Southern California Edison Company in Rosemead,
California, where he has worked for the last thirty years. He is actively involved in phasor
7/30/2019 Use of Synchronized Phasor Measurement System for Monitoring
measurements, transient analysis of power system, SSR studies, System Dynamics studies, Power
Quality, Railway Electrification, capacitor switching and Insulation Coordination studies, etc.
Mr. Bhargava graduated from Delhi University in 1961 with a Masters from Rensselear
Polytechnic Institute in 1976. He worked with the UP State Electricity Board in India from 1961 to
1975. Mr. Bhargava is a Senior Member of PAS, IAS Communication and Vehicular Societies of
IEEE and a Member of CIGRE.
Armando Salazar
Mr. Armando Salazar is a research engineer in the Engineering Advancement Group of
Southern California Edison (SCE) working in the Synchronized Phasor Measurement System project.
He received his Electrical Engineering degree in Power Systems from the National University of
Colombia. Before joining Edison, he was an Energy Consultant in South America. For 6 years, he
worked for the Latin American Energy Organization (OLADE). He also worked for the Bogotá
Power Company (EEB). Currently he is pursuing his Master degree in Power Systems at Kansas StateUniversity (KSU). He is an IEEE Member and a registered professional Electrical Engineer in the