by Jorge Miguel Ordacgi F ilho, ONS, Brazil
The Brazilian Blackout
Blackout Watch
36
Brazilian Blackout
2009
Blackout Watch
Brazil benefited from correct
performance of islanding schemes.
On November 10th, 2009, at 10:13 PM, Brazilian National
Interconnected System (NIPS) was submitted to a significant
disturbance that caused the interruption of 40% of its load.
The disturbance was triggered by the automatic disconnection
of 765 kV transmission line (TL) Itaberá-Ivaiporã #1, #2 and
#3 under adverse weather conditions. The lost of the three
circuits imposed 5,564 MW generation rejection at Itaipu
60 Hz Hydro Plant, as well as tripping of the remaining 525
kV, 500 kV, 230 kV and 138 kV circuits of South-Southeast
Interconnection, rejecting 2,950 MW additional power flow
from South to Southeast, and the tripping of the HVDC link
(two ± 600 kV bipoles in parallel with the three circuit 765 kV
TL) which were loaded with 5,329 MW. This were followed
by other disconnections, leading to a total load interruption of
24,436 MW (40%) along NIPS, distributed as listed below:
Southeastern Region: 22,468 MW
Central-Western Region: 867 MW
Southern Region: 104 MW
1 NIPS Conditions at 10:13 PM
Hydro Generation
Thermal Generation
Wind Generation
Total Power Exchange
Load
Values in MW
Hydro Generation
1,825
Thermal Generation
0
Total Power Exchange - 2,090
Load
3,915
2,090
North
8,174
30
80
- 683
8,967
683
Northeast
2,773
5,328
Southeast/
Center-West
50
60
Hydro Generation
57,333
Thermal Generation
530
Wind Generation
14
Total Power Exchange 2,950
Load
9,656
5,560
ITAIPU
Binacional
0
Argentina
PAC.MARCH.2010
8,515
Sul
2,955
Hydro Generation
35,802
Thermal Generation
621
Nuclear Generation
1,637
Total Power Exchange - 177
Load
38,237
NIPS
Hydro Generation
Thermal Generation
Wind Generation
Nuclear Generation
Load
57,863
1,231
1,637
44
60,775
Northeastern Region: 802 MW
Northern Region (Acre and Rondônia States): 195 MW
NIPS operating conditions right before the disturbance
are summarized in Figure 1. This summary will be easier to
understand with the aid of NIPS map presented on Figure
9 of the paper “Wide Area Protection Systems in Brazil” in
2009 PAC World Autumn Issue.
The disturbance was started by a phase B to ground fault
on 765 kV TL Itaberá-Ivaiporã #1 inside Itaberá Substation
(t0). At t0+13.5ms, with the first fault still present, another
single phase to ground occurred, this time involving phase C
of 765 kV TL Itaberá-Ivaiporã #2. In a sequence, at t0+17ms,
still with the two precedent faults present, a third single phase
to ground occurred on phase A of Itaberá 765 kV busbar,
section A (double bus with breaker and a half arrangement).
So, the faults occurred almost simultaneously inside TL
765 kV Itaberá-Ivaiporã #1 and #2 and section A of Itaberá
765 kV busbar, and remained present for a few moments,
imposing to NIPS a three phase to ground fault at Itaberá
Substation up to when the individual short-circuits were
cleared by automatic tripping of the faulted components.
The fault on 765 kV TL Itaberá-Ivaiporã #1 was cleared
at both terminals by the operation of main1 and main 2
protections, which are based on the travelling wave principle.
The fault on 765 kV TL Itaberá-Ivaiporã #2 was cleared at
both terminals by the operation of directional overcurrent
functions associated to teleprotection schemes. The fault on
section A of Itaberá 765 kV busbar was cleared by differential
protection operation. Instants after the clearing of this last
fault, the instantaneous residual overcurrent protection
of the shunt reactor directly connected (by switch – no
breaker) to Ivaiporã terminal of 765 kV TL Itaberá-Ivaiporã
#3, leading to the disconnection of this transmission line,
thus interrupting totally the connection between Itaberá and
Ivaiporã Substations.
At Itaipu 60 Hz Hydro Plant, five of nine generating units
were tripped (the tenth unit was out of service), rejecting
3,100 MW of generation by operation of the 765 kV Trunk
Wide Area Protection Scheme (WAPS), due to the triple
contingency between Itaberá and Ivaiporã Substations,
thus promoting islanding and preservation of the Southern
Subsystem. As a consequence, 500 kV TL Bateias-Ibiúna
#1 e #2 were tripped because of overload and power swing
between Southern and Southeastern Subsystems, with a
frequency increase up to 63.5 Hz in Southern Subsystem
and a frequency decrease down to 58.3 Hz in Southeastern
37
Subsystem. Moments after the events mentioned so far,
mainly in Rio de Janeiro and Espírito Santo States, there were
tripping of generating units and many transmission lines, as a
consequence of the power swing experienced by NIPS. Figure
2 describes the main sequential disconnections that led NIPS
to a partial blackout.
In consequence of a high rate frequency rise in Southern
Subsystem, 765 kV LT Foz do Iguaçu-Ivaiporã #1, #2 and
#3 were tripped by 765 kV trunk WAPS, isolating Itaipu
60 Hz Hydro Plant, which was, until then, connected to the
Southeastern System. By the same reasons here depicted, the
transmission lines that interconnect Mato Grosso do Sul State
System with Southern and Southeastern Subsystems were
also tripped by their protections, leading this state electric
energy supply to collapse.
With the above mentioned disconnections, there was a
voltage collapse in the Southeastern Subsystem, especially
in São Paulo, disconnecting the HVDC link by operation of
permanent DC undervoltage protection, interrupting a flow
of 5,329 MW, thus isolating Itaipu 50 Hz Hydro Plant from
NIPS. Itaipu 50 Hz Power Plant was operating with nine of
its ten generating units. In case of full load rejection there is a
Special Protection Scheme (SPS) to prevent the occurrence of
very high overfrequencies in the Paraguayan Power System,
by islanding two Itaipu generating units and the Paraguayan
Power System.
Those circumstances took place, as described above, but
the SPS did not operate and the automatic islanding of two
Itaipu 50 Hz Hydro Plant generating units with Paraguayan
Electric System did not occur. So the Paraguayan Power
System remained in parallel with nine Itaipu generating units,
what imposed a significant overfrequency and the subsequent
tripping of the 220 kV interconnecting transmission lines.
The performance of the SPS and its consequences for the
Paraguayan Power System are under analysis by Operation
Brazil-Paraguay Commission. The disturbance caused
collapse in Rio de Janeiro, São Paulo, Espírito Santo and
Mato Grosso do Sul states and thus load shedding by ERAC
(regional distributed underfrequency load shedding scheme),
affecting loads in Northeastern Subsystem and Minas Gerais,
Goiás, Mato Grosso, Acre and Rondônia states, these last two
states after their separation from Southeastern/Center-West
Subsystem.
It is important to note that the disturbance that caused
this blackout was way more severe than the disturbances
that caused 1999 and 2002 blackouts, not only because of
involving three phase to ground short-circuit, but also for
causing the disconnection of the 765 kV Transmission Trunk.
Still, comparatively, the consequences of this event for NIPS
were less severe, as one can ascertain by the preservation
of almost the total load in Southern Subsystem, the whole
load preservation at the National Capital, Brasília (DF) and
by the small amount of load loss in Minas Gerais, Goiás
and Mato Grosso states. In Northeastern Subsystem, the
loss of load was restricted to the amount shed by ERAC’s
operation and the average restoring time was 20 minutes.
It is noteworthy that NIPS fundamentally benefitted of its
islanding schemes proper performance and of its transmission
system enhancement, mainly those involving reinforcement
of interconnections between subsystems.
The average NIPS load restoration time was 222 minutes.
Such a long time was caused by unsuccessful black-start of
hydro plants within the restoration corridors, as well as by
some telecommunication failures. Both problems are already
addressed and will be solved in a short term horizon.
Based on the available data, the severity of the disturbance
was estimated in 90 system.minutes, according to
international methodology of calculation. This is lower than
1999 and 2002 blackouts, which had severities of 111 and
106 system.minutes, respectively.
Jorge Miguel
Ordacgi Filho
took his Electrical
Engineer degree
from Universidade
Federal Fluminense.
During his career as
a protection
engineer with FURNAS, ITAIPU Hydro
and ELETROBRAS he
worked on setting
calculations and
analysis of G&T
systems. He later
joined Brazilian ISO
managing the implementation of SPSs
and now he is involved with Control
Center automation,
SCADA and EMS. He
taught Power System Protection at
Universidade Veiga
de Almeida, and was
the Brazilian
Member of SC B5
(2004/2008).
In 2006 Jorge
received a CIGRÉ
Technical
Committee Award.
He is also Advisor of
PAC World Magazine.
2 Main Sequential Disconnections
500 kV TL
A.Vermelha –Marimbondo
T0 + 1,9s
500 kV TL
A.Vermelha – S.Simão
T0 + 1,4s
Islanding of Paraná and
Paranapanema rivers’
Hydro Plants:
Tripping started at T0 + 0,8 s
Total islanding at T0 + 2,6 s
HVDC link under-voltage
tripping:
Convertors tripping started around
T0 + 2 s (V<48%)
Total tripping at T0 + 8,5 sec
500 kV 345 kV TL
Ouro Preto – Vitória
T0 + 26 minutes
Voltage colapse after
765 kV Trunk
and TL 500 kV
Ibiúna-Bateias #1
and #2 disconnections
500 kV TL Ibiúna-Bateias
#1 e #2
T0 + 0,68 s
PAC.MARCH.2010
The text of the
article is based
on the official
report ONSRE-3-252/2009
“Análise da Perturbação do dia
10/11/2009 às
22:13 Envolvendo
o Desligamento
dos Três Circuitos da LT 765 kV
Itaberá-Ivaiporã”
prepared by
Operador Nacional do Sistema
Elétrico – ONS
(Brazilian ISO).