2003-04 florida workshop.ppt conditions for successful interruption: current contact parting 1)after...

2003-04 FLORIDA WORKSHOP.PPT

CONDITIONS FOR SUCCESSFUL INTERRUPTION:

CurrentContact parting

1) After contact parting there must be current zeros present

Current

2) The circuit-breaker must pass the thermal interrupting mode


Contact partingCurrent

Recoveryvoltage

3) The circuit-breaker must pass the dielectric interrupting mode

Tarc

Interruption

2) The circuit-breaker must pass the thermal interrupting mode


Contact partingCurrent

Recoveryvoltage


THERMAL INTERRUPTION

Post arccurrent

Rising voltage after clearing thermal interruption

Electric conductivity at successful thermal interruption

Current

Voltage

time

time

Current at failed thermal interruption

Arc voltage after failed thermal interruption

Electric conductivity after failed thermal interruption


DIELECTRIC INTERRUPTION

Current

Voltage

time

time

Current at failed dielectric interruption

Insufficient voltage withstand capability for successful interruption.

Dielectric failure


Insufficient voltage withstand capability for successful interruption.

Dielectric failure



Voltage withstand capability for successful interruption


CONDITIONS FOR INTERRUPTION

C urren t

R ecovery vo ltag e

C on tac t pa rtin g

In te rrup tio n

T arc

Conditions for successful interruption:1) After contact parting there must be current zeros present2) The circuit-breaker must pass the thermal interrupting mode3) The circuit-breaker must pass the dielectric interrupting mode

Conclusion: The interrupting performance is strongly related to the arcing time


Additional performanceby controlled interruption ???

LIMITATIONS FOR SUCCESSFUL INTERRUPTION

Random interruptionVoltage

Current

Dielectriclimit

Thermallimit

??

??

?

?


Possible upgrading area bymeans of controlled switching



CurrentNo thermal interrupting stress


INCREASED DIELECTRIC PERFORMANCE

Approach:

Controlled reactor switching has become an accepted methodfor making circuit-breakers reignition free


SOLVING AN INHERENT PROBLEM

Recoveryvoltagephase R

Recoveryvoltagephase Y

Recoveryvoltagephase B

Voltagewithstand capabilityRRDS


DE-ENERGISING A GROUNDED REACTOR BANK

Controlled contact partings



Reignition

Supply side voltage

Load side voltage

Voltage across CB

Current

Contact travel

Trip coil current

4 ms



Supply side voltage

Load side voltage

Voltage across CB

Current

Contact travel

Trip coil current

9 ms


RRDS Rate of Rise of Dielectric Strength at opening

Tarcmin

Typical: TARCMIN 4 ms

(Shorter arcing times will result in re-ignition)

Window allowingReignition-free operation

SAFE contact parting area

USource

Current

RRDS at min. arcing time

Uacross CB

Voltage withstand characteristic of the

circuit-breaker contact gap at opening,

RRDS

REACTOR CURRENT INTERRUPTION

Uacross CBUacross CBUacross CB

Contact separationInstant 1

Contact separationInstant 2


DE-ENERGISING OF CAPACITIVE LOAD

+ +

_ _

~

I

US UC

US = UC

I

time

+ UB -

Interruption

UC

USBus voltage

Load side voltage


T/2 = 10 msat 50 Hz

Capacitive current case

Recovery voltages

Inductive current case

200 s

COMPARISON OF RECOVERY VOLTAGESInductive and capacitive case

Voltage across contacts

Time

0


Recovery voltages

COMPARISON OF RECOVERY VOLTAGES


Time

0

Typical RRDS starting several ms prior to current zero resulting in proper interruption

Inductive current case

200 s

Inductive case

Typical RRDS starting at minimum arcing time (0 ms)

T/2 = 10 msat 50 Hz

Capacitive current case

Inductive and capacitive case




T/2 = 8,33 msat 60 Hz

T/2 = 10 msat 50 Hz Time

0


RECOVERY VOLTAGE VERSUS TYPICAL RRDS,capacitive case

Typical RRDS starting some ms before current zero

T/2 = 7,58 msat 66 Hz

Upgrading potential at 60 Hz


Test circuit for determination of RRDS (“Cold characteristic”)

TB

U_LS

WB-Q14 WB-Q10 X3

S1 CH1

Uch +

-

shunt1

Cd

S1- G U_SS

W2

Rs ext

AB

S1-LF

Rf ext

shunt2

Synthetic test circuit Test cell

0 kV


Test circuit for determination of RRDS (“Cold characteristic”)

TB

U_LS

WB-Q14 WB-Q10 X3

S1 CH1

Uch +

-

shunt1

Cd

S1- G U_SS

W2

Rs ext

AB

S1-LF

Rf ext

shunt2

Synthetic test circuit Test cell

0 kV 0 kV


Test record from “Cold characteristic test”

Supply side voltage

Load side voltage

Voltage across CB (160 Hz)

Current

Contact travel

Contact parting

Limit of voltage withstandvs. time or distance


Test record from “Cold characteristic test”

Limit of voltage withstandvs. time or distance


Plot of RRDS vs. time for a certain condition

0

0,5

1

1,5

2

2,5

3

3,5

0,0 5,0 10,0 15,0 20,0 25,0

"Arcing tim e" (m s)

Volta

ge (p

.u.)

W ithstand voltage

Breakdown voltage p.u.

RRDS CO LD CHARACTERISTICAG ED CB P=0.43 M Pa(abs) O pening speed = 1.09 x m /s


Plot of RRDS compared to a 50 Hz recovery voltage starting at minimum arcing time

0

0,5

1

1,5

2

2,5

3

3,5

0,0 5,0 10,0 15,0 20,0 25,0


Volta

ge (p

.u.) W ithstand voltage

Requirem ent for 50 Hz




Plot of RRDS compared to recovery voltages of 50 and 60 Hz and at minimum arcing times

0

0,5

1

1,5

2

2,5

3

3,5

0,0 5,0 10,0 15,0 20,0 25,0


Volta

ge (p

.u.)

W ithstand voltage






Plot of RRDS compared to recovery voltages of different frequencies and at minimum arcing times

0

0,5

1

1,5

2

2,5

3

3,5

0,0 5,0 10,0 15,0 20,0 25,0


Volta

ge (p

.u.)

W ithstand voltage







Plot of RRDS compared to recovery voltages of different frequencies and at minimum and prolonged arcing times

0

0,5

1

1,5

2

2,5

3

3,5

0,0 5,0 10,0 15,0 20,0 25,0

"Arcing time" (ms)

Volta

ge (p

.u.) Withstand voltage

Requirement for 60 Hz


Possible upgrading for 66 Hz



RRDS COLD CHARACTERISTICAGED CB P=0.43 MPa(abs) Opening speed = 1.09 x m/s


Plot of RRDS compared to recovery voltages of different frequencies and at minimum and prolonged arcing times

0

0,5

1

1,5

2

2,5

3

3,5

0,0 5,0 10,0 15,0 20,0 25,0

"A rc ing tim e" (m s)

Volta

ge (p

.u.)

W ithstand vo ltage

R equirem ent for 60 H z


Possib le upgrading for 66 H z


Breakdown vo ltage p.u.

R R D S C O LD C H A R A C TE R IS TICA G E D C B P =0.43 M P a(abs) O pening speed = 1.09 x m /s

About 15 % increased performance can be reached by pre-setting the arcing time by some ms.


Impact of missing arcing

How to compare “Cold characterisic” with cap. Switching performance?




“Cold characteristic” determined RRDS fits well to reactor switching performance




“Cold characteristic” determined RRDS fits well to reactor switching performance

“Full-scale” capacitive current switching tests show equal performance


IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS

Controlling the contact parting instant at interruption of capacitive loads can:

- compensate for a lower gas density.





- compensate for lower contact speed.






- improve the "safety" against restrikes by increasing the voltage withstand margin and taking care of scatter in the early stage.







- can make a circuit-breaker capable to operate in networks with higher frequencies if the performance at random switching is not good.








- compensate for ageing represented by contact burn-off.









If restrike-free perfomance at capacitive current switching is a limiting factor,controlled interruption is a useful tool for uprating.









If restrike-free perfomance at capacitive current switching is a limiting factor,controlled interruption is a useful tool for uprating.

Pre-set arcing time will not be longer than average: reduction of contact wear


IDEAL CASES FOR ADAPTING CONTROLLED OPENINGOF CAPACITIVE LOADS

FREQUENT OPERATIONS

REINSERTION OF LINE SERIES CAPACITORSvoltage steepness may be high due to power swing

SWITCHING OFF HARMONIC FILTER BANKSinitial slope of the recovery voltage is steeper and the peak is higher due to the harmonic content. When beeing used in combination with thyristor controlled equipment commutation transients may also be added to the recovery voltage across the circuit-breaker, thus increasing the risk.


APPLICATION WITH CONTROLLED DE-ENERGISING OF GROUNDED CAPACITOR BANK


Possible upgrading area bymeans of controlled switching



CurrentThermal interrupting stress


FUTURE? Controlled fault interruption?

Increased electrical life and improved performance compared to random fault interruption?

Reduced pressure build-upat current zero in worn CB

Pressure at current zero,new CB

Normal "arc extinguishing window” >1/2 cycle

Tarc

Blastpressure

Pressure required for interruption

Narrow window with increased interrupting

capability


WHAT CAN BE REACHED?

Increased electrical life compared to random interruption

Increased interrupting margins

Slightly increased performance


FUTURE? Controlled fault interruption?

Infoga tabellen

2003-04 florida workshop.ppt conditions for successful interruption: current contact parting 1)after...

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