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Final Blackout Report Chapter 5 5.
How and Why the Blackout Began in Ohio
Summary
This chapter explains the major eventselectri-
cal, computer, and humanthat occurred as the
blackout evolved on August 14, 2003, and identi-
fies the causes of the initiation of the blackout.
The period covered in this chapter begins at 12:15
Eastern Daylight Time (EDT) on August 14, 2003
when inaccurate input data rendered MISOs state
estimator (a system monitoring tool) ineffective.
At 13:31 EDT, FEs Eastlake 5 generation unit trip-
ped and shut down automatically. Shortly after
14:14 EDT, the alarm and logging system in FEs
control room failed and was not restored until
after the blackout. After 15:05 EDT, some of FEs
345-kV transmission lines began tripping out
because the lines were contacting overgrown trees
within the lines right-of-way areas.
By around 15:46 EDT when FE, MISO and neigh-
boring utilities had begun to realize that the FE
system was in jeopardy, the only way that the
blackout might have been averted would have
been to drop at least 1,500 MW of load around
Cleveland and Akron. No such effort was made,
however, and by 15:46 EDT it may already have
been too late for a large load-shed to make any dif-
ference. After 15:46 EDT, the loss of some of FEs
key 345-kV lines in northern Ohio caused its
underlying network of 138-kV lines to begin to
fail, leading in turn to the loss of FEs Sammis-Star
345-kV line at 16:06 EDT. The chapter concludes
with the loss of FEs Sammis-Star line, the event
that triggered the uncontrollable 345 kV cascade
portion of the blackout sequence.
The loss of the Sammis-Star line triggered the cas-
cade because it shut down the 345-kV path into
northern Ohio from eastern Ohio. Although the
area around Akron, Ohio was already blacked out
due to earlier events, most of northern Ohio
remained interconnected and electricity demand
was high. This meant that the loss of the heavily
overloaded Sammis-Star line instantly created
major and unsustainable burdens on lines in adja-
cent areas, and the cascade spread rapidly as lines
and generating units automatically tripped by pro-
tective relay action to avoid physical damage.
Chapter Organization
This chapter is divided into several phases that
correlate to major changes within the FirstEnergy
system and the surrounding area in the hours
leading up to the cascade:
u
Phase 1: A normal afternoon degrades
u
Phase 2: FEs computer failures
u
Phase 3: Three FE 345-kV transmission line fail-
ures and many phone calls
u
Phase 4: The collapse of the FE 138-kV system
and the loss of the Sammis-Star line.
Key events within each phase are summarized in
Figure 5.1, a timeline of major events in the origin
of the blackout in Ohio. The discussion that fol-
lows highlights and explains these significant
events within each phase and explains how the
events were related to one another and to the cas-
cade. Specific causes of the blackout and associ-
ated recommendations are identified by icons.
Phase 1:
A Normal Afternoon Degrades:
12:15 EDT to 14:14 EDT
Overview of This Phase
Northern Ohio was experiencing an ordinary
August afternoon, with loads moderately high to
serve air conditioning demand, consuming high
levels of reactive power. With two of Clevelands
active and reactive power production anchors
already shut down (Davis-Besse and Eastlake 4),
the loss of the Eastlake 5 unit at 13:31 EDT further
depleted critical voltage support for the Cleve-
land-Akron area. Detailed simulation modeling
reveals that the loss of Eastlake 5 was a significant
factor in the outage later that afternoon
with Eastlake 5 out of service, transmission line
G U.S.-Canada Power System Outage Task Force G August 14th Blackout: Causes and Recommendations G
45 loadings were notably higher but well within nor-
mal
ratings.
After
the
loss
of
FEs
Har-
ding-Chamberlin line at 15:05 EDT, the system
eventually became unable to sustain additional
contingencies, even though key 345 kV line load-
ings did not exceed their normal ratings. Had
Eastlake 5 remained in service, subsequent line
loadings would have been lower. Loss of Eastlake
5, however, did not initiate the blackout. Rather,
subsequent computer failures leading to the loss
of situational awareness in FEs control room and
the loss of key FE transmission lines due to con-
tacts with trees were the most important causes.
At 14:02 EDT, Dayton Power & Lights (DPL) Stu-
art-Atlanta 345-kV line tripped off-line due to a
tree contact. This line had no direct electrical
effect on FEs systembut it did affect MISOs per-
formance as reliability coordinator, even though
PJM is the reliability coordinator for the DPL line.
One of MISOs primary system condition evalua-
tion tools, its state estimator, was unable to assess
system conditions for most of the period between
12:15 and 15:34 EDT, due to a combination of
human error and the effect of the loss of DPLs Stu-
art-Atlanta line on other MISO lines as reflected in
the state estimators calculations. Without an
effective state estimator, MISO was unable to per-
form contingency analyses of generation and line
losses within its reliability zone. Therefore,
through 15:34 EDT MISO could not determine
that with Eastlake 5 down, other transmission
lines would overload if FE lost a major transmis-
sion line, and could not issue appropriate warn-
ings and operational instructions.
In the investigation interviews, all utilities, con-
trol area operators, and reliability coordinators
indicated that the morning of August 14 was a rea-
sonably typical day.
1
FE managers referred to it as
peak load conditions on a less than peak load day.
Dispatchers consistently said that while voltages
were low, they were consistent with historical
voltages.
2
Throughout the morning and early
afternoon of August 14, FE reported a growing
need for voltage support in the upper Midwest.
46
G U.S.-Canada Power System Outage Task Force G August 14th Blackout: Causes and Recommendations G
Figure 5.1. Timeline: Start of the Blackout in Ohio The FE reliability operator was concerned about
low voltage conditions on the FE system as early
as 13:13 EDT. He asked for voltage support (i.e.,
increased reactive power output) from FEs inter-
connected generators. Plants were operating in
automatic voltage control mode (reacting to sys-
tem voltage conditions and needs rather than con-
stant reactive power output). As directed in FEs
Manual of Operations,
3
the FE reliability operator
began to call plant operators to ask for additional
voltage support from their units. He noted to most
of them that system voltages were sagging all
over. Several mentioned that they were already at
or near their reactive output limits. None were
asked to reduce their real power output to be able
to produce more reactive output. He called the
Sammis plant at 13:13 EDT, West Lorain at 13:15
EDT, Eastlake at 13:16 EDT, made three calls to
unidentified plants between 13:20 EDT and 13:23
EDT, a Unit 9 at 13:24 EDT, and two more at
13:26 EDT and 13:28 EDT.
4
The operators worked
to get shunt capacitors at Avon that were out of
service restored to support voltage,
5
but those
capacitors could not be restored to service.
Following the loss of Eastlake 5 at 13:31 EDT, FEs
operators concern about voltage levels increased.
They called Bay Shore at 13:41 EDT and Perry at
G U.S.-Canada Power System Outage Task Force G August 14th Blackout: Causes and Recommendations G
47
Energy Management System (EMS) and Decision Support Tools
Operators look at potential problems that could
arise on their systems by using contingency anal-
yses, driven from state estimation, that are fed by
data collected by the SCADA system.
SCADA: System operators use System Control
and Data Acquisition systems to acquire power
system data and control power system equip-
ment. SCADA systems have three types of ele-
ments: field remote terminal units (RTUs),
communication to and between the RTUs, and
one or more Master Stations.
Field RTUs, installed at generation plants and
substations, are combination data gathering and
device control units. They gather and provide
information of interest to system operators, such
as the status of a breaker (switch), the voltage on
a line or the amount of real and reactive power
being produced by a generator, and execute con-
trol operations such as opening or closing a
breaker. Telecommunications facilities, such as
telephone lines or microwave radio channels, are
provided for the field RTUs so they can commu-
nicate with one or more SCADA Master Stations
or, less commonly, with each other.
Master stations are the pieces of the SCADA sys-
tem that initiate a cycle of data gathering from the
field RTUs over the communications facilities,
with time cycles ranging from every few seconds
to as long as several minutes. In many power sys-
tems, Master Stations are fully integrated into the
control room,