swgr seminar@eng aus-1

Technology Past, Present & Future for Medium Voltage Vacuum Switchgear

Kazuhiro Matsuo

2009 Lecture Program of the Joint Electrical Institutions Sydney Engineers Australia, IEEE, IET

10th September, 20092The Joint Electrical Institutions Sydney

●Contents

◆Application and Composition

◆Characteristics of Vacuum

◆Vacuum Interrupter( VI )・VI Configuration・Insulation in Vacuum・Arc Control Technology・Reliability and Quality Control

◆Vacuum Circuit Breaker (VCB)・VCB Configuration・Mechanical Characteristics・Special Application

◆Solid Insulated Switchgear (SIS)・Introduction of Insulation material

◆Toward The Future

●Contents

◆Application and Composition

◆Characteristics of Vacuum

◆Vacuum Interrupter( VI )・VI Configuration・Insulation in Vacuum・Arc Control Technology・Reliability and Quality Control

◆Vacuum Circuit Breaker (VCB)・VCB Configuration・Mechanical Characteristics・Special Application

◆Solid Insulated Switchgear (SIS)・Introduction of Insulation material

◆Toward The Future


Medium Voltage; up to 84kV Vacuum Switchgear Application

Power plant system Power distribution system

Transportation system

Factory system

Buildings systemGeneral supply

system


7.2kVMetal-Clad Switchgear

24kV Spot network system

7.2kVJIS standard power distribution switchgear

Air insulated SWGR

SWGR component

22-77kVCubicle type Gas Insulated Switchgear

Vacuum Circuit Breakers

7.2kV-63kANuclear and thermal power station

3.6-24kV VCB

36kVVCB

36kVFor electric

railway

Thermal relayMulti-function

motor protection relay

Local monitor

Sensor technology

Digital Technology

Computer Technology

66/84kV Compact Cubicle type Gas Insulated Switchgear

36kVSolid Insulated switchgear

Multi-function relay for switchgear

Gas, Solid insulated SWGR

Protection, Control, Monitoring system

Vacuum Interrupters

Medium Voltage Vacuum Switchgear Composition


To extinguish arc – to interrupt current

Ex. flame of a candle….to extinguish flame

・Blast・・

・Extend ・・

・Pour liquid (water..)・・

・Choke off ・・

Candle


Ambient liquid, gas,..Oil

SF6Air

Conductor Conductor

Current flow

Arc

Vacuum

Moving

OCB･･Oil Circuit BreakerACB･･Air Circuit BreakerABB･･Air Blast Circuit BreakerGCB･･Gas Circuit Breaker (SF6)VCB･･Vacuum Circuit Breaker

To extinguish arc – to interrupt current


•Environmentally friendly

SF6 was placed on the list of greenhouse gases under the KyotoProtocol in 1997.

•Low flammability

・High insulation capability

Characteristics in Vacuum


10-2 10-1 1 10 102 103 104 105

30

10

3

1

0.3

Pressure (Pa)

Bre

akdo

wn

Volta

ge (k

V)

Atmospheric Pressure

Characteristics in Vacuum (Paschen’s Curve)

Breakdown Voltage vs. Pressure

Pressure of actual products is 10-5Pa order.


10-2 10-1 1 10 102 103 104 105

30

10

3

1

0.3

Pressure (Pa)

Bre

akdo

wn

Volta

ge (k

V)

Characteristics in Vacuum

103 m3X109 /cm310-5 Pa

10-1 m3X1013/cm310-1 Pa

10-5 m3X1017/cm3103 Pa

Mean free path (N2)Molecular Pressure


0 20 40 60 80 100 120 140 160 180Distance (mm)

175

150

125

100

75

50

25Impu

lse

With

stan

d Vo

ltage

(kV)

VacuumAbs. 0.1MPa SF6

Air

Withstand Voltage Characteristic by Insulation Media

Normal contactStroke in vacuum Air

Insu

latio

n

SF6 Vacuum

13

7

Vacuum Insulation Capability


Arc behavior taken by high-speed camera

Current Interruption in a Vacuum interrupter(The Case of Axial Magnetic Field Electrodes)

Voltage Wave

Current Wave

ContactSeparation

Close Open

ZeroCurrent

→Time


→R

ecov

ery

volta

ge [k

V]

Time after zero current [μs]

極間の過渡回復電圧

Current InterruptionVoltage Wave

Current Wave

ContactSeparation

Zero Current →Time

Transient recovery voltagebetween contacts

→Vo

ltage

→Time

Vacuum

Characteristic of recovery voltage

Characteristics of Recovery Voltage by Insulation Media

Current Interruption


Transition of Circuit Breakers

OCB

ABB

GCB

MBB

VCB

Introduction

DeclineDiffusion

AD

Reference: 遮断器＆断路器のメンテナンス入門オーム社

Transition of production


History of Vacuum Circuit Breakers

Vacuum Switch(7.2kV 100A 50MVA)

1965Vacuum Circuit Breaker(7.2kV 600A 150MVA)

1966


0

5

10

15

20

1975 1980 1985 1990 2000

Year

A/mm2

Glass EnvelopeSpiral + CuTeSe

Ceramic Envelopewith pipe

AMF + CuTeSe

AMFCuCr50

Improvement of AMF & Shield

New Electrode+ CuCr25

Cap

acity

per

uni

t (A

rea

of e

lect

rode

)

Progress on Interrupting Capacity(24kV-25kA Rating)


•High Voltage application

•High Current Interruption

Technical Progress on Vacuum Interrupters

•Compact Design at Same Rating

Insulation in Vacuum

Arc Control


Dielectric Breakdown Mechanism in Vacuum

The field emission is generated from the micro-protrusion on the cathode surface

micro-protrusion

Hypotheses have been proposed;

Field Emission HypothesisField Emission Hypothesis

CATHODE

ANODE

CATHODEANODE

CLUMP

VAPORIZATION↓

ＢＲＥＡＫＤＯＷＮ

Clump is a contamination of micro-particle on the electrode surface.

Clump is accelerated by electrostatic power.

Clump Clump HypothesisHypothesis


Surface roughnessMachining

Electrochemical buffing treatment

◇ Electrochemical buffing treatment＋ Machining

Number of voltage application

Bre

akdo

wn

volta

ge [k

V]

Comparison of conditioning effect between machining and electrochemical buffing electrodes

Base material

Melted layer

25μm

Conditioning Effect Conditioning Effect –– what is conditioning effect ?what is conditioning effect ?

Cross-section after conditioning


CauseCause of conditioning effectof conditioning effect


Bre

akdo

wn

field

str

engt

h E b

(kV/

cm)

Effective area Seff (cm2)

Stainless steelCopper

Stainless steelCopper

Sphere-sphereRing-ringVacuum interrupter modelRod(R5)-planeR0d(R5)-planeCylinder-plane

Coaxial cylinder

Stainless steel:

Copper:

Effective area Seff = more than 90% of maximum field strength

Area Effect of Breakdown Field Strength in vacuum


Electrical potential distribution

Electrical field distribution

Example of electrical field analysis of vacuum interrupter

Electrical Field Analysis of Vacuum interrupter


Size Reduction of 72/84kV Vacuum InterrupterSize Reduction of 72/84kV Vacuum Interrupter

Vacuum Circuit Breaker for C-GISThe volume of C-GIS is

reduced to traditional half.


Anode

Arc concentrate in cathode (anode) spot

Control arc not to be concentrated increases capability of interruption

Arcing plasma;Ion and electron

Arcing in Vacuum

Cathode spot (μm in order)：Supply plasma by melting cathode electrode

Cathode

Metal vapor emittedcontinuously

Arcing Characteristic in Vacuum

Heating rising

Arc Behavior

Re-ignition


Axial Magnetic Field Method

Spiral

Arc Contact

Coil

CurrentMagnetic Field

ARC

Contrate

Arc

Major Electrodes in the world

Magnetic Driven Method

Contact

Coil


Arc

Magnetic Driven Method

Spiral

Current Flow in Coil

Force against Arc

Typical Configuration

A A

A - ASide section


Generate Axial Magnetic Field by current in coil(Parallel flux to arc)

Axial Magnetic Field Method

Contact

Coil

Current

Typical Configuration

Current Flow in Coil

Magnetic Field

Magnetic Field


Cathode

Anode

•Electrons and Ions are trapped by magnetic line

•Arc is captured within spaces between contacts

•Arc root spread uniformly

Axial Magnetic Field Electrode

Magnetic Field

Spread Uniformly Arc


Magnetic Field Analysis(ELKTRA)

Eddy Current Consideration in 3D

Example of Analyzed Results

Electrode Designing

13.8kV-100kA Type VGB2 VCB

- Largest Vacuum Interrupting Capability in the World -

Large Current interruption

VCB Front ViewVacuum Interrupters


Reliability of Vacuum Interrupters

•Quality Control on Vacuum leakage

•Measurements of Vacuum pressure


Quality Control for Vacuum Life

Inte

rnal

Pre

ssur

e

Internal Pressure Change

Measurement of Internal Pressure

Target life

Critical PressureTolerance

ExpectedVacuum Life

A: Pressure Change caused by Gas Evolution B: Pressure Change caused by leakage

PASS

DEFECT

A

B

C=A+B

Shortage time


Measurement of Vacuum

Source for Magnetic Field

High Voltage DC

Micrometer

Arc Shield

ElectrodeMovement of Electron

Direction of Electrical Field

Magnetic Field from Outside

Principle

Apply Magnetic Fieldand Electrical Field

Increase Path of Electron

Dissociation by Electron

in Collision with Particle

Proportional Current to

Particle (Vacuum pressure)

swgr seminar@eng aus-1

Documents

sf6 vacuum

kv vcb

kv solid insulated switchgear

pressure pa breakdown

kv metalclad switchgear

insulation air

configuration insulation

rating insulation