Phasor Measurement Units
Hesen Liu, Minh Nguyen, Ryan Russel, Mathew Stinnett,
Micah Till, and Nicholas Zamudio
Nicholas Zamudio
HISTORY AND BASIC THEORY
Definition of Phasors
• A phasor is a way of representing a
sinusoidal function
• Utilizing Euler’s Formula, a phasor maps a
sinusoidal function to the complex plane
• The use of phasors, as well as the
introduction of the term, in electrical
circuits can be traced back to a paper
written in 1893 by Charles Proteus
Steinmetz
General Theory of Synchrophasors
• Within a given power system, synchrophasors
allow the measurements of circuit properties.
• A phasor measurement unit (PMU) is used to
calculate synchrophasors
• PMUs were invented by Dr. Arun G. Phadke and
Dr. James S. Thorp at Virginia Tech in 1988.
• Macrodyne built the first PMU in 1992
• The PMUs measure real time circuit properties
with respect to a time reference provide via a GPS
system.
• Phasors will either represent three-phase voltage
or current, and therefore will require three
separate electrical connections.
Phasor Networks
• A typical phasor network consists of PMUs,
PDCs (phasor data concentrators), and
supervisory control and data acquisition
system at a central control facility.
• Phasor data collected either on-site or at
centralized locations utilizing data
concentrator technologies. This data is sent
to regional monitoring system maintained by
the local independent system operator.
• PMUs connects to PDCs which sends data to
either SCADA or WAMS servers
Architecture of Wide Area Network
• Wide area measurements systems were first
developed in 2000 by the Bonneville Power
Administration.
• A definition of WAMS was introduced by Hauer
from BPA/Pacific NW National Labs: “The WAMS
effort is a strategic effort to meet critical
information needs of the changing power system”.
• Typical wide area measurement system (WAMS)
utilizes a reliable communication system that
connects power stations, network control centers,
and sub stations.
• Consists of three fundamental processes: data
acquisition, data transmission, and data
processing.
Applications of Phasor Networks
• Used for power system automation (smart
grids)
• Load control to manage power delivery
• Fault detection (preventing outages)
• Wide are measurement and control
Mihn Nguyen
STATE OF THE ART DESIGNS
8
System Design Overview
• PMU technology is designed to provides phasor (both
magnitude and phase angel) information in real time.
• PDC is designed to synchronize and collect real time
phasor data streams for use by Synchrophasor
applications.
• The data is then transmitted to a regional monitoring
system which normally maintained by the local
Independent System Operator (ISO).
• ISO will monitor phasor data from individual PMU’s.
• The monitoring system is a designed to provide
accurate means of establishing controls for power flow
from energy generation sources.
• Phasor Data Concentrator (PDC
PMU
PDC
SOC
Schweitzer (SEL Inc.)
.
SEL offers many different PMU products for different
purposes. They consists of Relays with PMU capability and
Standalone PMU’s
Price Range $1000 - $5000
Key Benefits of their PMUs
•
•
•
•
•
.
Offer many different PMU products for different purposes
Lower Prices
Flexible Communications/Designs
High-Speed, Secure Line Current Differential Protection
Synchrophasor Measurements to Increase Asset
Utilization
• UseIEEE C37.118 format with 1–60 messages per
second or SEL Fast Message format for interleaved
communications. Apply direct relay-to-relay
synchrophasors for wide-area-based control without
additional devices
GE Multilin
Price Range $8000 - $15000
Key Benefits of their PMU designs
• High-speed inter-relay communications
• Ambient temperature monitoring with alarm
• Five zone quad or mho, phase and ground
distance protection
• Reliable and secure protection on lines
equipped with series compensation
• Exceeds the latest IEEE C37.118 standard for
PMU measurement devices with a TVE of less
than 1%, Protection and Metering class
synchrophasors and multi-cast IEC 61850-90-5
support
ABB
• ABB offers only standalone phasor
measurement units
Key Benefits of their PMU designs
• Protective relay technology and EMC noise
• Frequency, frequency error, and rate of change
of frequency
• Synchrophasor data streaming per IEEE
C37.118 and IEEE 1344 standard
• Built-in GPS clock module for synchronized
sampling of terminals in different substations
• Flexible system configuration through integrated
protection and control in one IED
• Order form, so you can customized your PMU to
your suited needs
Ryan Russell
IMPACTS OF PMUS
Benefits
•
•
•
•
Real-Time Analysis
Wide Area Monitoring Systems (WAMS)
Improve control/efficiency
Failure Analysis
Real-Time Analysis
• Synchrophasors allow operators to track
current and voltage levels in phase in real
time
Wide Area Monitoring Systems (WAMS)
• Improve power system operation
• Maximize transmission line power
• Reduce the risk of failure
Improve control/efficiency
• EMS software can fix problems without
operator present
Failure Analysis
• 2003 East Coast
Blackout
• Synchrophasors allow
operators to see how
the failure occurred
Disadvantages
• Cost
• Requires outages to install
Cost
• Synchrophasors - $2,000-3,000
• N60 Network Stabilizer - ~$8,000
• Software


1 User - $1,500
Site License - $45,000-60,000
• PMU installation - $100,000 – 200,000
Requires outages to install
• Scheduled outages to install system

Takes lots of time and money
Mathew Stinnett
RESEARCH AND
DEVELOPMENT
Today’s Restrictions
•
•
•
•
Grid coverage
Outages required for installation
Lack of control applications
Collaboration between academia and
industry
Tomorrow’s Vision
• Installation of PMU’s across the grid
• Cheaper and more efficient PMU’s
• Cooperation between industry and
academia
Micah Till
PMU APPLICATIONS
The Tennessee Valley Authority
• Provided funding for initial PMU research
• Early adopter of PMU technology on the
grid
• Creator of superPDC phasor data
concentrator

Software is now openPDC owned by GPA
• Acting national PMU data repository


Collects data from over 100 PMUs
Receives over 4 GB for every 3 hour period
The North American SynchroPhasor Initiative
• NASPI is a collaborative effort between
the DOE, NERC, industry stakeholders,
and researchers
• Provides a forum to discuss
synchrophasor research, implementation,
and application tools
• Funding officially ended but additional
meetings have been scheduled due to
popular demand
The Frequency Monitoring Network
• PMUs were developed at VT in the late
1980s
• From 2000 to 2003 researchers worked to
develop an FDR


Single-phase distribution measurements
High accuracy surpassing most PMU devices
• Simple installation



120 V AC outlet
GPS Antenna
Internet connection
The Frequency Monitoring Network
• Established 2004
• Over 100 PMUs
installed across
American grids
• Over 80 in EI
• Event triangulation
• Oscillation mode
identification
• Disturbance Scenario
reconstruction
• Tool for NERC
frequency response
compliance
The Frequency Monitoring Network
Hesen Liu
RELATED RESEARCH PAPERS
Published in IEEE Transactions on Smart Grid, in 2010
WIDE-AREA FREQUENCY MONITORING
NETWORK (FNET) ARCHITECTURE AND
APPLICATIONS
Brief Ideas
• Why does the power system need WAMS?
Wide-area monitoring systems (WAMS) utilizing synchrophasor
measurements can help with understanding, forecasting, or even controlling
the status of power grid stability in real-time.
• What is FNET?
A power system frequency monitoring network (FNET) was first proposed in
2001 and was established in 2004. As a pioneering WAMS, it serves the
entire North American power grid through advanced situational awareness
techniques, such as real-time event alerts, accurate event location
estimation, animated event visualization, and post event analysis.
• What kinds of measurement data can be collected from FNET?
Three kinds of data: Frequency data, Voltage data and Angle data.
The sampling rate: 10 points in one second.
Building blocks of the FNET system
FNET Applications
• FNET applications can be divided into
real-time applications and non-real-time by
their response time frame. Real-time
applications require response within
seconds or even subseconds after
receiving the data, while non-real-time
applications have more flexible timing
requirements.
1st Application
• Frequency Monitoring Interface
The frequency monitoring interface module
is one of the real time applications.
FDR
Selection
Channel
GUI
interface for
display
Data Query
Window
2nd Application
• Event Trigger and Event Location
•
•
The FNET event trigger module detects such phenomena by continuously scanning
the incoming FDR records; thus, it is located in the real-time application layer. The
scanning window calculates the derivative of 10 s worth of data.
The event location method is based on a geometrical triangulation algorithm making
use of the time difference of arrival (TDOA).
3rd Application
• Interarea Oscillation Trigger
Power system oscillations can be associated with events such as generation trips and
load shedding, but they can also be ambient. The FNET system creates a separate path
for treating the oscillation data. Because of the high accuracy that FNET possesses on
measuring system dynamics, power system oscillations can be monitored from both
FNET phase angle recordings and FNET frequency recordings.
Frequency oscillation monitoring by
FNET
Angle oscillation monitoring by
FNET
4th Application
• Interarea Oscillation Modal Analysis
The interarea oscillation modal analysis module starts functioning after receiving
oscillation data from the oscillation trigger. The matrix pencil approach, because of its
robustness to noise, is used as the signal decomposition tool for modal analysis.
5th Application
• Event Visualization
Frequency disturbance events have a geographically distributed impact, as the
electromechanical waves propagate throughout the power system in time and space. It
is therefore beneficial for the grid operators to have intuitive visualization of the
cascading response.
5th Application
6th Application
• Web Service
The FNET Web service integrates visualization components such as a frequency table
display, map display, and map gradient. It provides an educational platform for
researchers, grid operators, and regulators to better understand the power system
status in a wide-area perspective.
Summary
• The FNET system was originally built as a power grid wide area
monitoring system specifically applied to frequency monitoring. The
FNET system’s potential for power system dynamic monitoring,
stability estimation, real-time control and smart grid solutions are
currently being explored.
QUESTIONS?