IEEE Power & Energy Magazine - January/February 2014 - 28

Given the difficulties, the affected utilities and their dedicated
personnel did an admirable job in overcoming those difficulties and
restoring the power system following this historic power outage.
except for middle river. restoration efforts in the area were
complicated by a conductor splice failure on the southington-Frost Bridge 345-kV line, which tripped at 5:44 a.m.
restoration of load was halted from 7 a.m. to noon, though
no additional load shedding was needed. Load restoration
was completed by the evening of 15 August. the norwalknorthport 138-kV cable under Long island sound was not
restored until 24 August, however, due to the loss of cable
insulation pressure.
several lessons were learned from the new england
experience:
✔ some generators were not operating with automatic
voltage regulators (AVrs) in voltage control mode,
which hampered efforts to maintain stability of the
islanded system and maintain voltages within emergency limits.
✔ it was concluded that operators should switch from
tie line bias to flat-frequency automatic generation
control (Agc) when the system becomes islanded.
✔ generator governor response needed to be reviewed.
✔ Frequency and voltage match criteria for the resynchronization of islands needed to be reviewed.
✔ it was found that personnel are needed to transcribe
critical decisions and actions.
✔ communications improvements, such as the ability
to keep a teleconference line between control centers
open continuously, were also recommended.

Ontario
in restoring the system in Ontario, the first steps taken were
to confirm the extent of the disturbance and to activate the
Ontario Power system restoration Plan, which includes
establishing communications with other control areas,
transmission owners, and market participants. Loads that
have top priority in the restoration plan include class iV ac
power to all nuclear sites, critical transmission and generation station service loads, and critical utility telecommunication facilities. the next priority is restoration of customer
loads as necessary to control voltages and secure generators,
and the priority that follows that one is synchronization of
islands to each other and to neighboring power systems.
the Ontario system was completely blacked out, except
for the portion of northern Ontario west of Wawa, two islands
in the vicinity of niagara and cornwall (both of which were
connected to upstate new York), and two other small islands
(one north of timmins and the other on the Ottawa river near
Deep river). transmission was restored from niagara to the
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ieee power & energy magazine

Bruce nuclear generating station starting at 4:42 p.m. the
Ontario restoration paths are depicted in Figure 3. this path
also provided potential for restarting the nanticoke units.
the three available Bruce units were restored from 7:13
p.m. to 9:13 p.m. restoration continued toward the toronto
area, Pickering, and Lambton (on the border with michigan).
controlled customer (load) restoration took place between
London and toronto to balance the transmission system. the
Ontario restoration paths are depicted in Figure 3.
meanwhile, an assessment of the cornwall area was conducted between 4:11 p.m. and 5:15 p.m. starting at 5:15 p.m.,
restoration began westward toward Pickering and Darlington.
At 6:40 p.m., restoration of a path from cornwall to Ottawa
was begun in order to energize critical communication facilities. A Darlington unit was restored at 9:18 p.m. At 10:37 p.m.,
a transmission loop was completed around Lake Ontario.
starting from a small remaining island, at 7:41 p.m. a
path was energized south to timmins. Load was restored,
and the restoration continued south to sudbury. this restoration path reached southern Ontario at 3:43 a.m. on 15
August. northern Ontario was resynchronized to the rest of
the province at Wawa at 5:20 a.m.
immediately following the disturbance, 11 nuclear units
were off-line. these units posed a number of special challenges. Fully powering down these reactors would have left
them all off-line for several days, owing to the complications
of restarting them. it was difficult, however, to maintain
them at minimum power generation levels for the amount of
time required to restore the transmission system and provide
suitable outlets for their power. At Pickering B, the pumps in
the emergency cooling system were unavailable for five and
a half hours. in the end, three of four units at Bruce and one
of four units at Darlington were able to come back online
and support the system after several hours, but the remaining
units were not available for several days. One unit at Bruce
required repairs and was out for nine days, while one unit at
Pickering did not return until two weeks after the initial disturbance. Ontario remained in a state of emergency operation for nine days because of capacity issues. some parts of
Ontario experienced rolling blackouts during this time.
the experience in Ontario provided a number of lessons
learned:
✔ the devices in place to protect equipment operated as
planned.
✔ the development and maintenance of a documented
restoration plan, with training and rehearsals, were
essential investments of time and money.
january/february 2014

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2014