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C O M E T 2 0 1 7W E L C O M E T O A

T E C H N I C A L P A P E R P R E S E N T A T I O N

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B Y J A V I E R M A N T I L L A

“INSULATION ANDSWITCHING IN

ENVIRONMENTALLYFRIENDLY GASES

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J A V I E R M A N T I L L AP R I N C I P A L E N G I N E E R

A B B S W I T Z E R L A N D

A B O U T T H E A U T H O R

Principal Engineer at ABB Switzerland

Holds an M.Sc. in Mechatronics and an M.Sc. in Power Engineering from the

RWTH Aachen University

Ten years experience in high voltage circuit breaker R&D with ABB Switzerland.

Main focus on environmentally friendly technologies.

Expert in CIGRE WG A3.26 and WG A3.32

Senior Member of IEEE

BRIEFBIO

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PILOT INSTALLATIONEWZ ZÜRICH

F irs t H igh -Vo l tage GIS (170 kV / 40

kA) with a l te rna t ive Insu l a t ion - and

Switch in g gas A irP lus™

HV and MV equ ipm ent w ith A irP lus™,

F law less opera t ion s ince August 2015

L E A R N M O R E

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Alternative Insulation and Switching GasesO v er v i ew f r om t h e « C u r r en t Z e r o C l u b » fo r C I G R E S C A 3 ( A u g u s t 2 0 1 6 )

A i r P l u s ™C5 Fluoroketones. Used as an additive to a background gas. Air

for insulation, CO2 for switching. Commercially available under

Novec 5110 from 3M

g 3C4 Nitriles. Used as an additive to a background gas.

Commercially available under Novec 4710 from 3M

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Insu lat ion- and Switch ing ga ses for H igh-Vol ta ge switchgear

G en er a l as p ec t s f o r t h e as s es s m en t o f I n s u l a t i on g as es

T r a d i t i o n a lTechnical functionality

Size / Footprint

Capital expenditure

Reliability and maintenance effort

F u t u r eEnvironmental impact / Global Warming Potential (GWP)

Operational costs due to regulations

Different regulations in different countries / regions

Environmental Impact Functionality

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Sca lab i l i ty

A p p l i c a t i on o f a l t e r n a t i v e g as es i n t h e w h o l e p or t f o l i o

B a s i c A s p e c t slThe insulation performance of alternative gases for AC and

impulse stresses is relative simple scalable

Especially the circuit breaker, but also disconnectors and

grounding switches have to be investigated experimentally due to

the complexity of the switching physics

Knowledge from decades of research with SF6 as Insulation- and

switching-medium have to be assessed for validity with respect to

the new gas mixtureU

n*

In

Product

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Insu lat ion- and Switch ing ga ses for H igh-Vol ta ge switchgear

A B B ’s A i r P l u s ™

P r o p e r t i e sC5-Fluorketones have a boiling-point of 26.5° C and have to be

mixed with a non-condensing buffer gas therefore a

mixture with N2 or CO2 (Circuit Breaker) is necessary

Additional admixture of O2 to avoid soot formation and toxic

decomposition products

Insulation- and switching performance close to SF6 today

achievable for minimum ambient temperatures of -5°C .. +5°C by

using only slightly modified SF6 - products

Typical mixing ratios in HV - applications:

C5-Ketones O2 N2 or CO2

4-7% 8-14% 79-88%

Typical minimum operating pressure around 6-7 bar

N2 or CO2

O2

C5F10O

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Example for new opt imiza t ion areas

T h er m od y n am i c P oy n t i n g E f f ec t [ 1 , 2 ]

D e w p o i n t s h i f tTests in climate chamber to confirm dewpoint

Buffer gas influences C5-vapor, shift of dewpoint

Effect strongly depends on gas properties

AirPlus™ : Shift of dewpoint around -0.7°C / bar

-> around +5-10 % better insulation performance

[1] R. Krishna and C. B. Panchal, “Condensation of a binary

vapour mixture in the presence of an inert gas,”

Chem. Eng. Sci., vol. 32, no. 7, pp. 741–745, 1977

[2] C. C. M. Luijten and M. E. H. van Dongen, “Nucleation at high

pressure. I. Theoretical considerations,”

J. Chem. Phys., vol. 111, no. 18, pp. 8524–8534, Nov. 1999

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D e c o m p o s i t i o n p r o d u c t s a f t e r e x t r e m e a r c i n g s t r e s s ( c i r c u i t b r e a k e r )G I S - B r e a k e r 2 4 5 k V / 5 0 k A a f t e r 8 x T 1 0 0 a , 3 . 1 M J a c c u m u l a t e d a r c i n g e n e r g y

C O N C L U S I O N 1

Gas analysis (EMPA, Switzerland)

C5-FK filling: 5.7 % at 7 bar , V = 380 Litres -> 6.8 Mol / 400 mbar

(partial pressure)

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AirP lus™ Consumpt ion Rate

F r o m n u m e r o u s d e v e l o p m e n tt e s t s

The measured decomposition products are not critical

Existing safety measures as known for SF6 are far on the safe

side when handling AirPlus

Decomposition rates of 0.14 mol/MJ (T10/T30) up to 0.5 mol/MJ

(T100a) have been measured

The «Aging» of the insulation gas by decomposition of the C5-

Fluorketones is not problematic for typical GIS breaker tank sizes

By correct dimensioning, the lifetime of the circuit breaker stays

determined by nozzle- and contact erosion

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Switch ing in A i rP lus

I n t r od u c t i on

G e n e r a l t o p i c sHigh-Voltage circuit breakers have to handle a large number of

switching gases safely (IEC 62271-100)

Today, the dominant technologies for SF6 - HV-interrupters are

self blast devices and for larger power the thermally supported

puffer breakers

All investigations have been performed with circuit breakers,

which originally were developed for SF6

Self blast interrupters as well as puffer unit with ratings up to 300

kV /50 kA were tested

No change of operating mechanism / linkage / contact speed

Only modifications were the new gas mixture, slightly increased

filling pressure and changes in the nozzle contour and flow cross

sections of the arc extinction system

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Switch ing performance 1/3

S m al l e r c u r r en t s - > c ap ac i t i v e / i n d u c t i v e / T 1 0 / T 3 0 / p h a s e op p os i t i o n

D e v e l o p m e n t t e s t s w i t h A i r P l u s ™Unmodified SF6 – Breaker: Problems at long arcing times (too

low no-load pressure), but already excellent interruption

performance for shorter arcing times

Modification of the flow cross section, adaptation to the changed

thermodynamic properties (density, sound velocity)

No modification of linkage and operating mechanism

Capacitive and inductive switching performance finally as good

as with SF6 (e.g. similar low chopping number)

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Switch ing per formance 2/3

S h or t l i n e f au l t s ( S L F, « t h er m al i n t e r r u p t i on » )

D e v e l o p m e n t t e s t s w i t h A i r P l u s ™With slightly modified nozzle contours around 80% of the thermal

interruption performance of the SF6-version can be achieved

Therefore the di/dt has to be down rated by 20%, if a short-line-

fault interruption capability is needed

«Decision time» for thermal interruption around 1 ms after

current zero, similar to SF6 -> SLF90 stays most critical case,

same as with SF6

Future improvements e.g. by providing higher blow pressure

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Switch ing per formance 3/3

H i g h s h or t c i r c u i t c u r r en t s T 6 0 – T 1 0 0 a / s

D e v e l o p m e n t t e s t s w i t h A i r P l u s ™General challenge for T100a - interruption: High temperature and

pressure, especially in self blast devices

With AirPlus the pressure build-up at long arcing times is lower

than with SF6, which is beneficial in this switching case

So far no problems by breakdowns to the tank due to hot exhaust

gases.

Nozzle contour and electric field in the arcing region, especially in

the so called diffusor area, has to be adapted

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Summary

C o n c l u s i o n a n d o u t l o o kCircuit Breakers with AirPlus™ reach the performance of the SF6-

version in most of the switching cases

For short-line-faults the maximum di/dt has to be downrated by

20% versus the SF6 – base version

Only minor modifications in the nozzle system in the breaker

Limitation today to indoor / warm climate installations

Technology is scalable for higher short circuit currents and

voltage ratings

Full compatibility for the unlikely case, that SF6 shall be used,

only exchange of the HV interrupter necessary in this case

Standard – products planned for 2020

Project-based installations possible on request