DIMACS Workshop on Algorithmic Decision
Theory for the Smart Grid
Real-time Data for System
Protection and System
Restoration
James T. Reilly
Consultant
October 26, 2010
Synchrophasors
 Synchrophasor is short for:
Synchronized Phasor
 A mathematical quantification
of the electric system,
synchronized to an absolute
time source
 Voltage and current phasor
data is retrieved from key
points in the power system
many times each second
Synchronized Measurements
Location 2
Location 1
Phase angular difference between the
two can be determined if the two local
clocks are synchronized.
Synchronizing pulses obtained from
GPS satellites.
Synchrophasor Data
Visualization Views
Control Room
Regional Transmission Organization
Use of PMU Data: Two Examples
 Houston Blackout
 Hurricane Gustav
Houston Blackout
 Houston Blackout
On June 15, 2005 in Houston (and southern
Louisiana), 11 PMUs were recording PMU
data, each reading was 74 measurements.
Blackout could have been prevented if system
operators were looking at these data and
understood the importance of phase angle
differences.
Phase Angle Jumping (T-20 min) &
Frequency
Spikes
4:50 PM
5:00 PM
4:56 PM
Frequency “spikes”
as Phase Angle
jumps to 76⁰
Normal Phase angle 30⁰
Phase Angle Jumping (T-10 min)
5:00 PM
Phase Angle difference
continuing to grow.
Diff
120⁰
60⁰
5:10
PM
Frequency Collapse (T-0 min)
5:16 PM
5:10 PM
Frequency becomes
Unstable and Phase
Angle difference
Exceeds 120⁰
Diff
120⁰
Hurricane Gustav
 Hurricane Gustav
Successful intentional islanding and
resynchronization, using PMUs to monitor
frequency.
Entergy System
Hurricane Gustav
Approach
Hurricane Gustav
Landfall
Island Formation
Creation of Gustav Island at 2:49 PM
on 9/1/2008ENT_
Monitoring the Island
Customer outage restoration within the
island was suspended
 Reduces the risk of inadvertently adding more
load than available generation.
 Helps to maintain voltage and frequency control
Monitoring the Island
PMU frequency measurements were
monitored during the life of the island to
identify frequency oscillations within the
island.
Cause of Frequency Oscillations
 Electrical strength of the island was much less
than when connected to the grid.
 Generators within the island automatically
attempting to respond to demand changes at the
same time.
Monitoring the Island
Action taken to prevent frequency
oscillations.
 Placed two of the three generators within
the island on manual boiler control mode
and left the third generator on automatic
boiler control mode.
Frequency Oscillations Observed
Gustav Island Successfully
Resynchronized
Smart Grid
Reliability
System Restoration
Reilly Associates
PO Box 838
Red Bank, NJ 07701
Telephone: (732) 706-9460
Email: j_reilly@verizon.net