Electric Power Network Efficiency and Security (EPNES) 1 THE USE OF MICROMECHANICAL SWITCHES IN A...

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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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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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Micro-switch based Micro-switch based

Circuit Breaker Concept Circuit Breaker Concept

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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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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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Switching string operation Switching string operation

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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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Operation of Switching Strings Operation of Switching Strings Connected in ParallelConnected in Parallel

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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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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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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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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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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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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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System RealizationSystem Realization

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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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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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Reduced scale circuit breakerReduced scale circuit breaker

SwitchDiode String 1

String 2

Control solenoid

Switching string

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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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Reliability CalculationReliability Calculation

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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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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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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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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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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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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..

Electric Power Network Efficiency and Security (EPNES) 1 THE USE OF MICROMECHANICAL SWITCHES IN A...

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