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Point-on-Wave Controller Developed for
Circuit Breaker Switching
J. A. Jardini, R. P. Casolari, G. Y. Saiki, M. Masuda, , L. C. Magrini, R. M. Jacobsen
Abstract - The controlled switching of circuit breakers has shown
to have a highly satisfactory performance for the reduction of
electric transients in the electrical grid while maneuvering circuit
breakers. A controlled switching device was developed for the
utilization in the energization and de-energization of unloaded
transmission lines as well as in the disconnection and subsequent
energization of unloaded power transformers. The device was
developed using a DSP (Digital Signals Processing) system which
resulted from an R&D project between the University of São
Paulo and the Electric Power Utility Company ECTE (Empresa
Catarinense de Transmissão de Energia S.A.) that belongs to the
TBE (Transmissoras Brasileiras de Energia) group.
Index Terms – Circuit breaker controlled switching, Transformer Inrush Currents Elimination, Overvoltage, COMTRADE,
DSP
I. INTRODUCTION
Controlled switching is usually utilized by electronic devices
so as to facilitate the contact operations of the switching
equipment on a predetermined point in relation to a reference
electric signal.
The monitoring of the opening refers to the contact separation
control technique of each pole of the circuit breaker in relation
to the current phase angle, thus, controlling the arc time to
minimize the stresses in the power system components.
Similarly, these stresses can be minimized by using the controlled switching for monitoring the closing time in relation to
the system voltage waveform.
Such controllers are used for the interruption of small inductive currents, switching of capacitor banks and transmission
lines as well as in the energization of power transformers.
This paper will deal with the closing time control of circuit
breakers for the maneuvers described next:
• energization and de-energization of the 525 kV transmission line linking Blumenau and Campos Novos;
• energizaton of the third 525/230 kV Blumenau transformer.
In the cases of energization and de-energization of transmisJ. A. Jardini – Polytechnic School of Universidade de São Paulo, Department de Engineering, Energy and Electric Automation – ([email protected])
Ronaldo P. Casolari – Polytechnic School of Universidade de São Paulo,
Department de Engineering, Energy and Electric Automation –
([email protected])
Gerson Y. Saiki – Polytechnic School of Universidade de São Paulo, Department de Engineering, Energy and Electric Automation –
([email protected])
Mario Masuda – Polytechnic School of Universidade de São Paulo, Department de Engineering, Energy and Electric Automation – ([email protected])
L. C. Magrini – Polytechnic School of Universidade de São Paulo, Department de Engineering, Energy and Electric Automation –
([email protected])
Rogério M. Jacobsen - Transmissoras Brasileiras de Energia (TBE)
([email protected])
978-1-4244-1904-3/08/$25.00 ©2008 IEEE
sion lines, the objective of the controlled switching is to reduce the overvoltages resulting from those maneuvers. As for
the power transformers energization, the objective is to reduce
the inrush currents that appear following its energization.
Also, the basis and development specification of a controlled
switching device utilizing a digital signals processing (DSP)
system will be presented.
The controlled switching device was developed for the Blumenau substation at ECTE. The system components in red
color, shown in Fig. 1, pertain to the ECTE Company.
Figura 1 - ECTE System (C. Novos/Blumenau 525 kV
Transmission Line and the third power transformer)
A. Energization of the Transmission Line
The controlled switching device will be used for energization
of unloaded transmission line. The studied line links Blumenau and Campos Novos and has 252.5 km of extension at
525 kV. The circuit breaker used in the substation of Blumenau is monopolar.
The time when the voltage passes through zero, will present
the least overvoltage in the circuit breaker.
B. De-energization of the Transmission Line
The system used for the de-energization of unloaded transmission line was the same case of line energization (figure 1).
As there are no special devices to drain the residual load at the
opening of the transmission line, the maneuvering is made in
presence of residual loads in the three phases. After the opening of the transmission line, the device determines the polarity
of the residual loads in each individual phase. The best deenergization times are the voltage peaks at the source side.
The polarity of those peaks must be the same as the residual
load in each individual phase.
C. Transformer Energization
The controlled switching of transformers has the objective of
reducing the inrush currents that appear when the transformer
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is energized. By choosing appropriate times for energization
of the transformer, there will be a great reduction of those
currents that are responsible for the harmonic generation,
stress in some equipments and bad operation of protection
systems.
The present project used the energization strategy that takes
into account the residual flux resulting from the precedent
opening. Within that strategy, the delayed energization was
used. The first phase to be energized is the one with greater
residual flux in absolute value. This is advantageous because it
allows the energization at low values of the source voltage,
imposing a less voltage stress in the transformer at the energization time. That phase is energized at the time in that the
residual flux is equal to the prospective flux of that phase. The
prospective flux is the one that would exist in each phase in
case of absence of the desenergization.
For the remaining phases, different approaches can be used to
reduce or to eliminate the core saturation, taking the net and
the circuit breaker characteristics into account. An approach
that has been studied and applied with success is the closing of
the two remaining phases at the same time, some half-cycles
after the passage through voltage zero of the first phase, once
the residual flux in the other two phases is eliminated quickly
in some cycles and a flux occurs called dynamic, which is the
flux generated by the energization of the first phase. In a real
application, a delay of 4.5 cycles has been used with success.
Based on the methodology of the delayed energization, the
project adopted as follows:
"Initial Energization of the phase with greater residual flux (in
absolute value) at the time in that the residual flux is same as
the prospective one. The 2 remaining phases will be closed
after 4.5 cycles, simultaneously, when the dynamic flux is the
same as the prospective one."
The residual and dynamic fluxes are obtained through the
voltage integration beside the 525 kV of the transformer soon
after the circuit breaker. Thus, the prospective flux is obtained
through the voltage integration beside the source, in other
words, before the circuit breaker.
II. CONTROLLED SWITCHING DEVICE
A. Hardware Architecture
The selected hardware for the controlled switching device has,
as a basic characteristic, the capacity to support the acquisition
and treatment of at least 320 samples per cycle of six analogical channels in a way to provide an inferior error to 20 electric
degrees.
Those requirements are not complied by most of the commercialized industrial computers, which led to the development of a hardware based on the C6000 technology of Texas
Instruments. From that DSPs family, the TMS320C67x generation was chosen, whose 32-bit processor operates at 225
MHz and incorporates resources of floating point. The manufacturer commercializes a "starter kit" denominated
TMS320C6713 DSK, which was used as a basis for the hardware development.
This TMS320 family is built on the VelociTI architecture.
It presents a high performance architecture and very long
instructions (VLIW) developed by Texas Instruments, which
make of these devices an excellent choice for multichannel
and multifuction applications, ideal for applications of high
performance through a parallelism growth increase.
The CPU core of the TMS320C6713 platform consists of 8
functional units (two multipliers and six ULAs) and 32 general
purpose recorders with words of 32 length bits. These devices
are developed with a data memory and with an on-chip program that can be set up as cache memories. The peripherals
include improved controllers for direct access to the (EDMA)
memory, power-down logic, interfaces for external memories
(EMIF), multichannel buffered serial ports (McBSP), host
interface (host-port) (HPI) and timers.
The TMS320C6713 DSK kit has 16 Mbytes of SDRAM
and 512 Kbyte flash and has a dedicated busbar (busbar
EVM), through which several input and output peripherals can
be linked. Through this busbar high-speed AD converters can
be linked operating at up to 2Mhz of acquisition per channel,
and up to four channels. Specific circuits with several AD
converters can also be mounted as well as digital inputs, digital outputs, and also interfaces of serial communication of
high-speed.
The TMS320C6713 DSK kit incorporates besides the processor, devices required by DSP, such as, feeding circuit, timers, external memory, among others, providing the possibility
of optimized execution of the project. This processing platform also includes audio input and output, connected to a 16
bits audio codec, parallel port for communication with the
computer and connectors for the connection of expansion
plates.
They were incorporated to the analogical and digital interface plates kit that provides six inputs under voltage (0 to
130Vac) and six isolated current inputs (4 to 20ma) besides
sixteen opto-digital inputs coupled dry contact type, and six
digital voltage outputs implemented through IGBT's (Insulated
Gate Bipolar Transistor). These six outputs power the opening
reels and closing of each circuit breaker poles.
The IGBTs are interconnected to the DSP through optical
coupling, which should be connected to an external source of
up to 125Vcc for powering of loads with current of up to 25
Amperes. The IGBT switching time is about 50 to 100 microseconds, however the time in order for the operation current to
set down depends on the load to be energized.
B. Software Architecture
The programming is made in C language, through a tool of
the manufacturer denominated Code Composer. This tool runs
in MS Windows environment enabling the development and
debugging of the code in high environment level, with resources for compilation of the code source developed and
unloading of the binary code generated for the DSP via USB
port.
The developed software uses functional parameters, constant and processing keys that are stored in flash and are recovered in the beginning of the processing. It was developed
in Visual Basic; a set-up tool that enables the user, in a laptop
or interlinked PC to the DSP via serial port, to consult or alter
any values of the parameters or coefficients of the formulas
without the need to understand the DSP particularities nor its
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memory mapping (figure 2).
The openings or closings led by the equipment have an algorithm summary, as well as the wave form of the voltages
and currents along the maneuvering, registered for later analysis. The wave form can be later extracted and saved in
COMTRADE format, in the user's machine, through the set-up
program.
Figura 2 - Set-up program screen
C. Algorithm
In order to minimize the transitories resulting from the circuit breakers powering maneuvers, there is a need that they
occur in certain intervals of voltage angle (for each phase).
The first parameter considered in the algorithm of the system
is the interval of the angle of the voltage of each phase, so that
the switching time of each pole of the circuit breaker is located
within the intervals of the voltage angle. For the powering to
occur within these specified intervals, the opening and closing
times were considered (operation times) of the circuit breakers
supplied by the manufacturer.
Additionally, the circuit breakers operation time, independent of the interruption system and of the type of operation
mechanism, varies depending on certain service parameters:
• With the control voltage reduced in the reel of the circuit
breaker, there is less available energy to change the commands of electric control for a mechanical action. The operation is prolonged independently. (Valid for all types of
drivers);
• Altering the hydraulic pressure in the hydraulic drivers, a
change in the available energy occurs in order to execute
the switching movement;
• The environment temperature is the most complex influence parameter. The electric resistance of the operation
reels, the viscosity of the oil and the SF6 gas pressure are
dependent of the temperature. Besides, there is expansion
of the powering rods and porcelains. All these parameters
influence the operation time of different modes.
In an extreme condition, each of these 3 parameters can alter the operation time in milliseconds order. The compensation
of the variation of these parameters was also considered in the
algorithm of the system. Each of these parameters is monitored through sensors associated to the system.
In regard to the energization algorithm of the transmission
line, as verified in simulations to the 3 phases, they should be
closed in the interval of the voltage wave within -30º and +30º
of each phase, central value equal to 0º, in other words, at the
time in which the voltage in each phase is going through zero
(sinusoidal wave). For the identification of the passage
through zero, with positive derivative, the moment in that an n
reading is bigger than zero and the readings n-1 and n-2 are
smaller or same to zero is identified.
The powering of the circuit breaker can be requested in any
point of the voltage wave, through an external command.
Starting from this command, the system will identify the moment of the passage through zero of the voltage wave of one
of the system phases beside the source. In relation to this instant, the moment in that the circuit breaker must be powered
will be calculated, taking the circuit breakers nominal operation time into consideration, compensated with the service
parameters presented previously. The nominal operation time,
corrected according to the current conditions, can be considered as a delay that should be counted so that the opening or
closing is really concluded at the moment of the passage
through zero of the voltage wave. The same procedure is made
for the other phases taking the difference in phases of 120º and
240º into account.
As for the de-energization of the transmission line (Without
Reactor) the best times for de-energization occur when the
voltages in the side source, in each phase, reach the values of
the residual voltages of the respective phases, with an acceptable interval of ±30º around this excellent value. In this case
the voltage of a system phase is monitored beside the source,
as well as the voltages in the three phases of the system beside
the line (before and after the LT opening). Based on this premise, the controller calculates the necessary delay times for each
phase to be de-energized in the excellent point of the voltage
wave. Also taking into account the additional times related to
the circuit breaker operation and to the operation voltage
variations of the closing reel, the oil pressure and of the environment temperature.
In the Transformer Energization, the excellent moment occurs when the magnetic fluxes beside the transmission line
(prospective) and beside the transformer (residual) are the
same, for the phase that presents larger residual flux in absolute value. And the two remaining phases should be energized
4.5 cycles after the first phase, simultaneously.
The magnetic flux is proportional to the integral voltage, to
avoid displacement in relation to zero. The voltage integration
must start at the moment in that it is at its maximum, and,
therefore the magnetic flux is zero. For the identification of
the maximum voltage instant, a similar function to the identification function of the passage through zero is used. The
function basically determines the moment in which the signal
presents a superior value to 90% of the maximum value verified in the previous cycle, and in which the voltage (n+1)
<voltage (n) and voltage (n-1) <voltage (n).
The calculation of the excellent instant also takes into account the additional times related to the operation of the circuit breaker and to the variations of the voltage of the closing
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reel operation, the oil pressure and the environment temperature.
D. Acquired signals
The DSP analogical ports are connected to the following
substation signals:
• Voltage in Pole A, in busbar B of the substation beside the Transmission Line
• Voltage in Pole A, in busbar beside the high voltage
of the transformer
• Voltage in Pole B, in busbar beside the high voltage
of the transformer
• Voltage in Pole C, in busbar beside the high voltage
of the transformer
• Signal AC representing the unloaded current of the
transformer in phase A.
• Signal DC from 4 to 20mA representing the hydraulic pressure in Pole A
• Signal DC from 4 to 20mA representing the hydraulic pressure in Pole B
• Signal DC from 4 to 20mA representing the hydraulic pressure in Pole C
• Signal DC from 4 to 20mA representing the environment temperature
• Signal DC from 4 to 20mA representing the Auxiliary Service Voltage.
The voltage inputs and alternating current are acquired at a
20 kHz rate per channel, while the ones from 4 to 20 MA are
swept at a 1 kHz rate per channel.
The following digital information is collected at a 1 kHz
frequency per channel;
• Contact Condition 52A (NA) of the Circuit breaker
• Contact Condition 52B (NF) of the Circuit breaker
• Contact Condition 52A (NA) of the Circuit breaker
• Contact Condition 52A (NF) of the Circuit breaker
• Closing Command Condition given by the User to
the Circuit Breaker
• Closing Command Condition given by the User to
the Circuit Breaker
The developed equipment also offers a port for synchronization with a unique time base according to the IRIG B standard.
III. TESTS
Initially powering simulated tests in laboratory, without the
physical presence of a circuit breaker, stimulating the switching device starting from a giga of tests, and using some of the
digital inputs of the device to indicate the change of condition
of the opening and closing IGBT outputs. These inputs would
be normally used to verify the status of the circuit breakers.
Once linked to the equipment, the developed software is
continually collecting all of the analogical and digital signals,
but only save the samples once the circuit breaker powering
command is detected.
Figura 3 - Test in the Blumenau substation
The analogical and digital greatness of interest are registered starting from the command for the beginning from the
maneuver up to the alteration of the contacts 52 a and b of the
circuit breaker, which signalize the end of the operation.
Later tests were made in field, in the Blumenau substation,
with the objective of verifying the precision of the algorithms
of the system during the opening and closing operations of the
circuit breaker DJ1050 (Alston FX500KV) that belongs to the
Transmission Line that links Blumenau to Campos Novos
circuit breaker and half set-up). This test was made with the
unloaded circuit breaker, in order to avoid that bad eventual
operation of the device that could cause disturbance in the
substation.
In a first moment the measures made by the sensor ones
were validated comparing them with the values originating
from other sensors already existent in the substation. Several
tests were accomplished for gauging the mathematical models
that determine the times of closing and opening of the circuit
breaker in real conditions of operation in field.
As example one of the tests is introduced for the closing of
the circuit breaker. In figure 1, the times corrected for the
closing of each of the poles are presented, calculated by the
device.
After verifying the coherence between the closing and
opening times, calculating from the greatness measured by the
sensors, a closing test was accomplished for the verification of
the powering instants of the IGBTs, and the results registered
in the COMTRADE file, susceptible to be analyzed by any
software and upon the oscillographics produced by other
equipments of SE.
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Table 1- Powering Times
Greatness
Device
Pressure in Phase A (Bar)
361,9258
Pressure in Phase B (Bar)
356,1741
Pressure in Phase C (Bar)
360,9806
Auxiliary Service Voltage (V)
132,26
Environment Temperature (Celsius)
32,58
Phase A Closing Time (µs)
Phase B Closing Time B (µs)
Phase C Closing Time (µs)
19340,14
19650
19274,17
Figure 4 presents the oscillographics regarding the accomplished test, the tables presented are related to phase A voltage
(the source side); voltages of phases A, B and C (the transmission line side); hydraulic pressures of the poles of phases A, B
and C; environment temperature and feeding voltage of circuit
breakers powering reels. As onc can observe in the oscillographics related to the test, after the duration of the maneuver calculated for pole A (19.34 ms), a passage through voltage zero occurred in pole A. The duration has as an initial
referential, the powering instants of the IGBT's, which were
highlighted in the oscillographics presented. Regarding the
other phases the respective powering difference in phases of
120º and 240º were verified.
As one can observe in the oscillographics regarding the
test, after the duration of the maneuver calculated for pole A
(19.34 ms), it happened a passage for the voltage zero in the
pole A. The duration has as an initial referential the powering
instants of the IGBT's, which were highlighted in the oscillographics presented. Regarding the other phases the respective powering difference in phases of 120º and 240º were
verified. .
IV. CONCLUSIONS
The project of circuit breakers powering lasts for four
years, which is in the beginning of the third year, with the
development and tests of the device prototype for closing
maneuvers. The equipment is being submitted to performance
tests and validation to evaluate the adherence of the implemented mathematical models. The subsequent phase of the
project will contemplate maneuvers of the circuit breaker in
normal operation conditions, complementing the necessary
requirements for complete approval of the powering device.
Figura 4 - Circuit breaker closing test
V. REFERENCES
[1]
[2]
[3]
[4]
[5]
WG 13.07 “Controlled Switching of HVAC Circuit Breakers: Guide for
Application Lines, Reactors, Capacitors, Transformers”, Part 1,
ELÉCTRA No. 183, Pages 43 – 73, 1999.
WG 13.07 “Controlled Switching of HVAC Circuit Breakers: Guide for
Application Lines, Reactors, Capacitors, Transformers”, Part 2,
ELÉCTRA No. 185, Pages 35 – 37, 1999.
H. Ito “Controlled Switching Technologies, State-of-the-Art”, Transmission and Distribution Conference and Exhibition 2002: Asia Pacific.
IEEE/PES, Pages 1455 – 1460, Vol. 2, 2002
J. H. Brunke, K. J. Fröhlich “Elimination of Transformer Inrush Currents by Controlled Switching. Part I: Theoretical Considerations”, IEEE
Transations on Power Delivery, Volume: 16, Issue: 2 ,April 2001,
Pages: 276 – 280.
J. H. Brunke, K. J. Fröhlich “Elimination of Transformer Inrush Currents by Controlled Switching. Part II: Application and Performance
6
[6]
Considerations”, IEEE Transactions on Power Delivery, Volume: 16, Issue: 2, April 2001, Pages: 281 – 285
Rocha, A. C. Carvalho, J. L. Távora “Manobra Controlada: Modelagem
da Suportabilidade Dielétrica do Disjuntor Durante a Operação de
Fechamento”, XIV SNPTEE, Belém, Brasil, 1997
VI. BIOGRAPHIES
José Antonio Jardini (M’ 1966, SM’ 1978, F’ 1990) was born in São Paulo,
Brazil, on March 27th, 1941. He graduated from Escola Politécnica da
Universidade de São Paulo in 1963 (Electrical Engineering). From the same
institution he received the MSc, PhD, Associate Professor and Head Professor
degrees in 1971, 1973, 1991 and 1999, respectively. For 25 years he worked
for Themag Engenharia Ltda., a leading consulting company in Brazil, where
he conducted many power systems studies and participated in major power
system projects such as the Itaipu hydro plant. He is currently Head Professor
at Escola Politécnica da Universidade de São Paulo, where he teaches power
system analysis and digital automation, and where he leads the GAGTD
group, which is responsible for the study and development of automation
systems in the fields of generation, transmission and distribution of electricity.
He represented Brazil at SC-38 of CIGRÉ and is a Distinguished Lecturer of
IAS/IEEE.
Ronaldo Pedro Casolari graduated in Electric Engineering at the Escola de
Engenharia Mauá in 1972. He received the MSc in 1996 at the Polytechnic
School of São Paulo University. Had his professional development at consulting companies, with projects in the area of power electric systems for companies as Itaipu, Eletronorte, Furnas, Chesf, Cesp and others, with systems
planning, coordination of insulation and electric transitory. At present works
as a consultant at Sao Paulo University with electric transmission and distribution projects.
Gerson Yukio Saiki was born on March 30, 1970, graduate in electrical
engineering for the Polytechnic School of the University of São Paulo in
1997. He obtained his title of Master in electrical engineering for the same
institution in 2001. Currently he works in “GAGTD – Group of Automation
of the Generation Transmission and Distribution of Electric Power”, in the
Department of Energy and Automation of the Polytechnic School of the
University of São Paulo.
Mario Masuda was born on June 25, 1948 in Tupã, São Paulo, Brazil. He
received his B.Sc. degree in Electrical Engineering from the Polytechnic
School at the University of São Paulo, in 1973. From 1973 to 1991, he was
with Themag Eng. Ltda working in the area Power Systems and Automation
& Transmission Lines projects. From 1991 to 1997, he worked independently
executing projects, supervising and teaching courses related to the installation
of fiber optic cables in transmission lines (OPGW). From 1997 to 2002, he
worked at Furukawa and Constructions Ltd., with the latter activities.
Presently, he works as a researcher at GAGTD in the Polytechnic School at
the University of São Paulo.
Luiz Carlos Magrini was born in São Paulo, Brazil, on May 3rd, 1954. He
graduated from Escola Politécnica da Universidade de São Paulo in 1977
(Electrical Engineering). From the same institution he received the MSc and
PhD degrees in 1995 and 1999, respectively. For 17 years he worked for
Themag Engenharia Ltda, a leading consulting company in Brazil. He is
currently a researcher at Escola Politécnica da Universidade de São Paulo GAGTD group.
Rogério Moreira Jacobsen not avaible.