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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
THE USE OF THE USE OF MICROMECHANICAL SWITCHES MICROMECHANICAL SWITCHES IN A POWER CIRCUIT BREAKIN A POWER CIRCUIT BREAKERER
Esma Gel, Gerald T Heydt, Esma Gel, Gerald T Heydt,
Norma Faris Hubele, George G KaradyNorma Faris Hubele, George G Karady
Arizona State University, Tempe, AZ, Arizona State University, Tempe, AZ, USAUSA
PSERC
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
MOTIVATIONMOTIVATION No major change in CB design in many yearsNo major change in CB design in many years
Large moving components and sizeLarge moving components and size
Need for vacuum or SF 6 enclosureNeed for vacuum or SF 6 enclosure
No synchronous switchingNo synchronous switching
Application of electronics components Application of electronics components and MEMS switches allow miniaturization and MEMS switches allow miniaturization and zero current switchingand zero current switching
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Micro-switch based Micro-switch based
Circuit Breaker Concept Circuit Breaker Concept
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Conceptual circuit diagram for an ac Conceptual circuit diagram for an ac circuit breakercircuit breaker
Positive Switch Negative SwitchMicro-switch
Diode Snubber circuit
Circuit breaker contains two switches• Positive switch operates in the positive cycle•Negative switch operates in the negative cycle
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Switching string assembly Switching string assembly with several strings with several strings connected in parallel. connected in parallel. (Positive switch only(Positive switch only))
Voltage rating is increased by Voltage rating is increased by switching additional units in switching additional units in seriesseries
Current rating is increased by Current rating is increased by switching additional units in switching additional units in seriesseries
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Switching string operation Switching string operation
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
LoadPositiveswitch
Negativeswitch
Positive cycle
Leakage current turns on the diodes inthe positive switch
Negative switch blocks the loadcurrent
Switches are closed in thepositive cycle
LoadPositiveswitch
Negativeswitch
Negative cycle
Diodes carry the load current after zero crossing.
Closed positive switches carry the loadcurrent
Negative switches are closed withoutovervoltage
Illustration of circuit breaker closing.
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ShortcircuitPositive
switchNegative
switch
Negative cycle
Positive switches are open. The diodesinterrupt the current after zero crossing
ShortcircuitPositive
switchNegative
switch
Positive cycleSwitches are open in the positive cycle.The current is transferred to the diodes
Negative switches are open without currentinterruption
Negative switches are closed
Illustration of current interruption.
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Operation of Switching Strings Operation of Switching Strings Connected in ParallelConnected in Parallel
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Short circuit current
Voltage across the NegativeSwitch
Short circuit current is interrupted at the end of the positive cycle
Voltage acrosspositive switch
Current transfer to thediode
PSPICE simulation of circuit interruption
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Equivalent circuit of Equivalent circuit of a switching stringa switching string
Closed switches equivalent is Closed switches equivalent is the contact resistancethe contact resistance
Open switches equivalent is the Open switches equivalent is the diode voltagediode voltage
ki Vdiode(n - ki ) Rcontact
Closedswitches
Openswitches
n number of switches in a stringki number of switches off in a string
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Shortcircuit
(n - ki ) Rcontact ki Vdiode
Ishort
N number of stringsn number of switches in a stringki number of switches off in string
A
Equivalent circuit modeling the non- simultaneous operation of the switches.
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Current distributions Current distributions when all string except when all string except one is turned on with one is turned on with one millisecond delayone millisecond delay. .
A. Inductive load currentA. Inductive load current
B. The closing of all switches B. The closing of all switches in string 1 eliminated the in string 1 eliminated the diodes and inserted the diodes and inserted the contact resistancescontact resistances
C. Simultaneously the current C. Simultaneously the current of the other two strings of the other two strings reduced to zero, because the reduced to zero, because the diodes become reverse diodes become reverse biasedbiased..
Total current
Diodecurrent
Diodecurrent
Switches instring 1 on
All switchesare on
100%
68.72%
- 31.45%
A
B
C
Simulation of switch closing
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Current distribution Current distribution during current during current interruption. interruption.
A). String current when one A). String current when one string is turned off with 1 string is turned off with 1 msec delay.msec delay.
B) String current when all B) String current when all strings except one is turned strings except one is turned off with 1 msec delayoff with 1 msec delay..
The short circuit current is The short circuit current is interrupted with a half cycleinterrupted with a half cycle A
100%
28.3%
36.4%
B
100%
67.6%
27.5%
Simulation of switch opening
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Current injection circuit for interruption of DC current. Current injection circuit for interruption of DC current.
Rectifier
High voltage thyristorswitch
Blockinginductance
Currentinjection
DC loadcurrent
Switching stringassembly
DC current interruption requires current injection:
•Charge capacitor produces current oscillation.•During the negative cycle the switches are opened•At zero crossing the diodes interrupts the current
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
System RealizationSystem Realization
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
The coil under the switch is The coil under the switch is energizedenergized
The generated magnetic The generated magnetic field moves the permanent field moves the permanent magnet towards the basemagnet towards the base
This closes the contactThis closes the contact
The problem is that the The problem is that the insulation has to withstand insulation has to withstand 7.2 kV between the contact 7.2 kV between the contact and the magnetand the magnet..
No switch is available to No switch is available to meet with this requirementmeet with this requirement
Permanentmagnet
Silicon DioxideBridgeInsulator
MagneticCore
Coil
Conduction path
Bridge
Insulatingarm
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
ASU started to develop ASU started to develop MEMS switches for this MEMS switches for this circuit breakercircuit breaker
A matrix contains 4 x 4 = 16 A matrix contains 4 x 4 = 16 switches is being studiedswitches is being studied
Several sample has been Several sample has been built and testedbuilt and tested
This matrix permits the This matrix permits the formation of 4 switching formation of 4 switching strings with 4 MEMS strings with 4 MEMS connected in seriesconnected in series
1175 m
1328 μm
4 x 4 Matrix of switches using aluminum metalization
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Reduced scale circuit breakerReduced scale circuit breaker
SwitchDiode String 1
String 2
Control solenoid
Switching string
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
The technical data of the developed The technical data of the developed small scale circuit breakersmall scale circuit breaker
Rated current:Rated current: 8 A steady state8 A steady stateInterruption current:Interruption current: 50 A for a half cycle50 A for a half cycleRated voltage:Rated voltage: 4000 V4000 VBIL:BIL: 95 kV95 kVNumber of switches in series in a single string:Number of switches in series in a single string: 1010Number of strings in parallel:Number of strings in parallel: 88
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Reliability CalculationReliability Calculation
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
CLOSED
CLOSED OPEN
OPEN
S=2
S=0
S=3
S=1
p2(I) p0(V)
q3(I)
q1(V)
1
1
Failed Operational
RELIABILITY ANALYSIS
•States of an individual switching unit
•Most probable failure mode is in closed condition
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
Expected Lifetime = 259
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
0 500 1000 1500 2000 2500 3000
Number of Switching Operations
Pro
bab
ilit
y
Lifetime distribution for qmin = 0.001.
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
ConclusionsConclusions The study proved that the micro-The study proved that the micro-
switched based medium voltage circuit switched based medium voltage circuit breaker is feasiblebreaker is feasible..
It offers small size, zero current It offers small size, zero current switching and interruption of short circuit switching and interruption of short circuit current within a half cyclecurrent within a half cycle..
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
The specific results are:The specific results are: Development of novel concept for CB’s using switching matrix Development of novel concept for CB’s using switching matrix
and switching string.and switching string. Development of a method to analyze the effect of none Development of a method to analyze the effect of none
simultaneous operation of switches in a switching string simultaneous operation of switches in a switching string assembly.assembly.
Reliability analysis of switching matrix.Reliability analysis of switching matrix. Building of a proof of principles switching string assembly to Building of a proof of principles switching string assembly to
experimentally proof the validity of the concept.experimentally proof the validity of the concept. Proposal for development of a new type of MEMS device and Proposal for development of a new type of MEMS device and
the specification of the new device.the specification of the new device. Development of a novel analytical model for the reliability Development of a novel analytical model for the reliability
analysis of the switching matrix.analysis of the switching matrix.
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
FUTURE WORKFUTURE WORK Finalization the analytical technique for operation of large Finalization the analytical technique for operation of large
switching matrixesswitching matrixes,,
Improvement of reliability analysis and Improvement of reliability analysis and
Testing the proof of principle switching assemblyTesting the proof of principle switching assembly..
Detailed design of the MEMS based switchDetailed design of the MEMS based switch
Implementation of the educational objectiveImplementation of the educational objective
PROBLEMPROBLEM Lack of suitable MEMS device in the marketLack of suitable MEMS device in the market
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Electric Power Network Efficiency and SecurityElectric Power Network Efficiency and Security(EPNES) (EPNES)
AcknowledgementAcknowledgement The authors would like to acknowledge the The authors would like to acknowledge the
support of NSF and the Navy. support of NSF and the Navy. The authors thank to Prof B. Kim of ASU andThe authors thank to Prof B. Kim of ASU and Graduate students: Mr. Neil Shah, Daniel S. Graduate students: Mr. Neil Shah, Daniel S.
James II and Rahim Kasim for their James II and Rahim Kasim for their contributioncontribution..