Na1

Insulation Systems

Breaker Capacitances -Parallel to interrupters or between phase and earth (on the line side): Delayed oscillation voltage (Δt =Z • Cu) -parallel parallel to chamber of a multi multi-chamber chamber switch: uneven voltage distribution (Versteuerung) U U1 U2 U1 CS U2 CS CS U1 CE CS CS U U CE CE CE CE CS U2 CE CE CE

Live Tank

Dead Tank

Metal Enclosed

(Säulenschalter)

(Kesselschalter)

(völlig gekapselt)

CS U2 U2 = = U U1 +U 2 2C s + C E

Voltage distribution is better with increasing CS/CE Increasing of Cs through additional capacitors grading g g capacitors p (Steuerkondensatoren)) Electric Power Systems

Typical values: Cs CE (substation) CE (SF6) Cgrading cap.

= = = =

5-20 pF 5-10 pF 50-400 pF 100-2000 pF

Electric Power Systems

Uneven Voltage Distribution

Uneven Voltage Distribution Breaker with four interrupters in series De-gradationfactor σ (Versteuerungsfaktor) for n interrupters in series

ΔU

σ =

m

−

ΔU n

ΔU n Equivalent circuit diagram (Ersatzschaltbild) of the open breaker

Voltage over m-th m th Interrupter = ΔUm

ΔU

Electric Power Systems

m

=

ΔU (1 + σ ) n

Ua

ΔU1

ΔU2

ΔU3

ΔU4

C1

C2

C3

C4 Ub

Voltage across the breaker: ΔU = Ua + Ub ΔU = ΔU1 + ΔU2 + ΔU3 + ΔU4

Electric Power Systems

Dead Tank Circuit Breaker

Oil Circuit Breakers Application: Extinction medium:

Advantages:

Disadvantages:

medium and high voltage oil ⇒ H2 (70%), acetylene (20%), methane (10%) Low noise emissions, robust, low manufacturing requirements, high thermal extinction capability (no short-line fault problem)

Fire hazard, limited interruption capacity ( 170kV/30kA), (ca. kV/ kA) aging i effects ff t off oil il

Principle: self self-blast, blast, for small, often forced flows Design variations: 1) Minimum Oil Breaker (Ölarmer Schalter) 2) Dead Tank Circuit Breaker (Kesselschalter) Electric Power Systems

Oil Breaker (1901)

Electric Power Systems

The Minimum Oil Breaker: Principle

Stack of insulation plates

Electric Power Systems

Electric Power Systems

Dead Tank Oil Circuit Breaker

Oil Circuit Breaker Explosion

FILM

Electric Power Systems

Minimum Oil Breaker

Electric Power Systems

Cross Section of a Minimum Oil Extinction Chamber

Electric Power Systems

Electric Power Systems

AEG ‘‘Freistrahlschalter“ (obsolete, from 1950s)

The Air Blast Circuit Breaker Application: 3 – 765kV, up to 80kA (generator circuit breakers up to 250kA) Extinction medium: air (N2) pressurized valves Principle: air at 35 bar

expansion volume to atmosphere Valve system with axial arc blowout through supersonic flow

Thermal time constant: several 10 – several 100 μs Advantages: cheap extinction medium insensitive to low temperatures (-50°C) pressure chamber with very high pressures (regulatory requirements) Disadvantes: h h noise emissions high high chopping currents (chopping number up to 100 • 104) Maximum power per interrupter: ca. 140kV • 40kA (benchmark) Critical distance of a short-line short line fault: 2 – 3 km Electric Power Systems

Air-blast Circuit Breaker (Druckluftschalter) 500kV (until 1970s)

Electric Power Systems

Electric Power Systems

Air-blast Circuit Breaker 550kV (until 1980s)

Electric Power Systems

Development of Interruption Capacity of Pressurized Air and SF6 Circuit Breakers

Phase diagram of SF6

GVA/ break SF6: -high dielectric strength (88kV/cm bar) (88kV/cm.bar) -good arc quenching properties -non-poisonous, non poisonous odor free, free inert

20 15

SF6

10

5

1950

Air blast 1960

1970

1980

1990

2000

Electric Power Systems

Live tank SF6 Puffer Circuit Breaker 300kV (Blaskolbenschalter)

Electric Power Systems

Electric Power Systems

SF6 Puffer Circuit Breaker 550kV with Closing 55 g Resistor (Einschaltwiderstand)

Electric Power Systems

auxiliary contacts

Buildup of SF6 Puffer Circuit Breaker

(Hilfskontakt)

Resistor (Widerstand)

main interrupter (Hauptschaltkammer)

grading capacitors (Steuerkondensator)

insulation to earth (Erdisolation)

Spring-hydraulic spring drive (Feder-Hydraulischer (Feder Hydraulischer Antrieb)

SF6 Puffer Circuit Breaker 550kV kV Electric Power Systems

SF6 Puffer Circuit Breaker: Opening

Electric Power Systems

Electric Power Systems

SF6 Puffer Circuit Breaker: Closing

Electric Power Systems

SF6 Dead Tank Circuit Breaker 245kV

SF6 Circuit Breaker 500kV

Electric Power Systems

550 kV SF6 Dead Tank Circuit Breaker

Electric Power Systems

Electric Power Systems

SF6 Dead Tank Circuit Breaker 145 kV

Electric Power Systems

1000kV GIS Puffer Circuit Breaker

Electric Power Systems

Electric Power Systems

SF6 Generator Circuit Breaker (Generatorschalter)

Medium Voltage SF6 Breaker 24kV

;

Electric Power Systems

Electric Power Systems

SF6 Self Blast Circuit Breaker (Selbstblasschalter): Opening

Electric Power Systems

SF6 Self Blast Circuit Breaker: Closing

Electric Power Systems

SF6 Self Blast Circuit Breaker: Interruption of Small Currents

Electric Power Systems

SF6 Double Motion Self Blast Circuit Breaker

Electric Power Systems

Flow Conditions in a SF6 Puffer Circuit Breaker

Temperature Profile in a Switchgear

Electric Power Systems

Gas Density during No-load Switching of a SF6 Puffer Circuit Breakers

Electric Power Systems

Switchgear Design: Vacuum Tube (Vakuumröhre)

elements:

condenser screen breaker contacts

movable contact

bellows (Faltenbalg) Electric Power Systems

Fixed contact vacuum

insulation Electric Power Systems