Page 1 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Application of Power Circuit Breakers for Switching Capacitive and Light Inductive

CurrentsIEEE Circuit Breaker Tutorial

Dr. John H. Brunke, P.E.Fellow

Page 2 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Nature of Capacitive and Small Inductive Currents

Small in magnitudeSome technologies use current to assist in interruption

Current and voltage 90 degrees out of phaseCircuit breakers frequently called upon to deal with switching these

currentsSwitching can result in extreme magnitudes of currents and extreme

rates of change of voltage

This presentation is based on C37.012 and C37.015, the application guides for switching these currents. It is impossible to cover all the material in these in detail, and there are other important issues with switching these currents that are not covered in the application guides. This presentation is intended to provide an overview of all the issues associated with switching these currents.

Page 3 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Shunt Capacitor Bank SwitchingContinuous Current

Margins for capacitor toleranceMargins for harmonic currentMargin of 35% typical

Interrupting shunt capacitor bank current

Page 4 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

What is a Restrike?

Page 5 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Restrike, Back to Back with CLR’s

Page 6 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Energizing Shunt Capacitor Banks

Single or isolated bank

Back to back

Page 7 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

500 kV Single Bank Energization

Page 8 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

500 kV Back to Back Energization

Page 9 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Consequences of Capacitor Inrush Transients

Dip to zero voltageInterference with devices that use zero crossing detectors

Back to back results in extremely high currentsDamage to primary and secondary equipmentSafety

Restrike (trapped charge)2 X the voltage, effects 2 X

Page 10 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Mitigation of Closing TransientsClosing Resistor or Reactor

Fixed Current Limiting Reactor

Controlled closing

Page 11 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

500 kV Back to Back Energization with CLR

Page 12 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Controlled Closing, Single Bank

Page 13 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Controlled Closing, Back to Back

Page 14 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Controlled Closing, Capacitor Banks, targeting

Page 15 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Switching Capacitor Through a Transformer

Page 16 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Faults Near Capacitor Banks

•Outrush, TRV effects, high source impedance voltage rises (or long lining), etc.

Page 17 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Line Fault, 500 kV system, with 430 Mvar of Connected Capacitors

Page 18 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Circuit Breaker StandardsRestrike probability: C0, no rating, C1, ~ 1 restrike in 50 operations, C2, ~ 1 restrike in 300 operations

Page 19 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Circuit Breaker Standards

Page 20 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Switching Overhead Transmission Lines - Interruption

Page 21 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Switching Overhead Transmission Lines

Page 22 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Charging Current and Recovery Voltage

Page 23 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Recovery Voltage on Unfaulted Phases

Neutral shift, coupling of transients

Page 24 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

De-energization of a Line with Connected Transformer

Page 25 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Energization of Transmission Lines, Switching Surges

Page 26 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Switching Surge Overvoltages

Page 27 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Switching Surge MitigationOnly needed above 245 kV (rarely at 245 kV)

Closing resistorsLine connected surge arrestersControlled closingTrapped charge reduction (line connected PT’s – caution)Single pole reclosing (limited due to secondary arc)Controlled closingStaggered pole closing

Page 28 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Traveling Waves Present on Most Line Phenomena

Closing into a fault, 500 kV field test data.

Page 29 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Shunt Reactor Switching

1st Parallel 1 to 10 MHz

2nd parallel 50 to 1000 kHZ

Load oscillation 1 to 5 kHz

Page 30 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

225 Mvar Shunt Reactor Interruption

500 kV bus and reactor voltages, field test data

Page 31 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Time Expansion of Previous Slide

Page 32 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Re-ignition and Current Chopping

Page 33 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Time Expansion of Previous Slide

Page 34 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Reactor Current Interruption Failure

•Interruption still a difficult duty for circuit breakers

•Differences in the parameters make a standard test nearly impossible

Page 35 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Shunt Reactor Current Interruption w/o Controlled Opening

Page 36 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Shunt Reactor Current Interruption with Controlled Opening

Page 37 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Energizing Shunt ReactorsInrush currents smaller than for power transformers (to be discussed

next), and not generally considered a problem

Can cause sympathetic inrush in nearby power transformers

Problems have only been observed in certain configurations

Page 38 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Switching Transformer Magnetizing Currents

Page 39 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Transformer Core Characteristic

Page 40 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Magnetizing Current Interruption

Magnetizing current interruption also showing core flux

Residual core flux remains (typical pattern)

Page 41 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Energizing a Transformer

Page 42 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Inrush Current

Page 43 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Controlled Closing Applied to Transformers

Page 44 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Three Phase Transformers

Page 45 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Prospective and Dynamic Flux

5 8 .05 4 .05 0 .04 6 .04 2 .0

T im e m s

F lu x , re s id u a l 0 % , -7 0 % , 7 0 %0 .8 0

0 .0

-0 .8 0

F lu x kV s

ACB

Page 46 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Core Flux - No residual

Page 47 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Core flux with residual flux

Time 6 ms/div

Core flux, EMTP Study 800

0.0

-800Vs

Page 48 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Verification - Laboratory Tests Delayed Closing Strategy

T im e 6 m s /d iv

.8 0 0 0

0 .0

- .8 0 0 0V s

Page 49 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Test on Laboratory Transformer

Page 50 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

Controlled Closing on 500 kV Transformer

Page 51 Capacitor and Reactor Switching, J. H. Brunke, July 2008 Presented at IEEE Circuit Breaker Tutorial

SummaryCapacitive and light reactive currents are frequently seen and may be

the most difficult duties for a circuit breakerSwitching surge/transient problems are typically associated with

switching shunt capacitor banks, shunt reactors, transformers, cables, and lines (capacitive and light reactive currents).

Due to the complexity, correct application for these duties can be among the most difficult application issuesToday solutions are available which were not in the past (modern circuit

breaker technologies, controlled switching, MOSA’s, etc.)

Questions?