PRESENTATION OVERVIEW
What is controlled switching
Why using controlled switching
Controlled switching benefits
How the SynchroTeq POW works
Capacitor bank, Reactor and power transformer applications
SynchroTeq in its operating environment
CB requirements for controlled switching
Review and questions
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CONTROLLED SWITCHING
“Controlled switching” is one of several terminologies
applied to the principle of coordinating the instant of
opening or closing of a circuit with a specific target point on
an associated voltage or current waveform.
It is an additional capability added to the standard circuit
breaker to operate at synchronized precise electrical
moment on source voltage or current waveform
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RANDOM SWITCHING
WHAT CAN GO WRONG WHEN SWITCHING IS RANDOM ?
Depending on the reactive load being switched, different undesirable
consequences can occur. Such as
Re-strikes, Re-ignitions- during opening operation
High inrush currents –during closing operation
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RANDOM SWITCHING
Documented studies show existence of such issues while
switching
 Shunt Reactors
 Unloaded Power Transformers
 Unloaded Transmission Lines
 Shunt Capacitor Banks
 Static VAR Compensation
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RANDOM SWITCHING
Consequential negative effects resulting from random Switching
Power quality degradation
• Short over voltages to industrial customers
• HF disturbances (transients)
Remote disturbances (e.g. line faults)
Reduced power equipment life
• Electrical stress
• Mechanical stress
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RANDOM OPENING
Random Opening
Voltage
Current
CB Operating time
(Tmo)
Random open command
CB Main contacts
separation
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Controlled Opening
Voltage
Current
Arcing time (Tarc)
Current zero crossing
(Phase A)
Random open command
to
Mechanical opening
(Tmo3)
Zero crossing wait time(Maximum Tco)
Calculated delay(Ty)
Controlled open copmmand
CB Main contacts
separtaion
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Command time (Tro)
Controlled Closing
Current
Voltage
Phase delay angle Tkf (90º)
Tf
Voltage zero crossing
(Phase A)
Random close command
Mechanical closing
(Tmf3)
Zero crossing wait time (maximum of Tcf)
Calculated delay (Tx)
Controlled close command
CB main contacts
closure
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Command time (Trf)
Planned pre-arc (Tdel)
BASIC REQUIREMENTS OF CONTROLLED SWITCHING
o
o
Breaker shall be independent pole operated type with separate
operating mechanism for operation of each pole
Three opening and closing coils shall be provided with
independent supply of control voltage
The Compensation of variation in operating timing with reference to
Control voltage
Temperature
Operating mechanism pressure
o A good co-relation between the main contact timings and auxiliary
contact timings shall be established
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OPERATING ENVIRONMENT
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SYNCHROTEQ PLUS WEB INTERFACE
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SYNCHROTEQ PLUS RECORDING FUNCTION
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SYNCHROTEQ PLUS CONFIGURATOR
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SWITCHING OF SHUNT REACTORS
Random switching shunt reactors involve re-ignitions and
asymmetrical currents which can lead to
Damage to the reactor itself
(due to voltage transients or inrush current stresses on closing),
Damage to the circuit breaker
(typically caused by re-ignitions),
System reliability issues
(due to spurious protection operations)
Power quality problems
(due to prolonged harmonic effects due to sympathetic interactions with local
Power Transformers
Asymmetrical currents which in turn mechanically stress the reactor and
generate long time constant, high amplitude, zero sequence currents
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SWITCHING OF SHUNT REACTORS
To mitigate these effects there are two basic strategies followed
for controlled switching of reactors
• Closure at voltage peak to minimise system capacitance effect
• Opening in the re-ignition free window at a point to minimise
the impact of re-ignitions.
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SHUNT REACTOR OPENEING: RE-IGNITION
Current
flowing
by arc:
energy
dissipated in
the CB!
Dielectric strength/
CB contacts gap
not high enough at
current zero crossing
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SHUNT REACTOR CONTROLLED OPENEING
Conduction by
arc
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SHUNT REACTOR CONTROLLED OPENEING
Dielectric strength/
CB contacts gap
must be high enough
at current zero
crossing
Arc time should be
around 135°
Phase A current zero crossing
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Target
relative to
phase A
SHUNT REACTOR CONTROLLED OPENING
No current flowing
allowed beyong this
vertical bar
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REACTOR CLOSING : RANDOM
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SHUNT REATOR CLOSING :CONTROLLED
Controlled conduction
by arc
Dielectric strength/
CB contacts gap
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ENERGISATION OF POWER T/F
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ENERZISATION OF POWER T/F
Transformers are normally energized by closing the
circuit breaker contacts arbitrarily.
This introduces an asymmetrical magnetic flux
driving the transformer into saturation and as a
result, high transient magnetizing inrush currents
are produced in the transformer
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TRANSFORMER SWITCHING
Uncontrolled inrush currents during closing of
unloaded Transformer may lead to
 Deterioration of the insulation and mechanical
support structure of windings
 Reduction in system power quality
 Operation failure of transformer due to differential
protection activation
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POWER T/F RE-ENERGISATION WITH CS
Two methods of closing with SynchroTeq+
1. Closing the HV C/B at maximum voltage
2. Closing the HV C/B using the delayed control strategy, taking
into account the residual flux of the power transformer
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SWITCHING OF POWER T/F
Normally energized transformer
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SWITCHING OF POWER T/F
Power transformer de-energization
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SWITCHING OF UNLOADED POWER T/F
Residual flux
Excessive inrush current!
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FIRST CLOSING
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OPENING AND RESIDUAL FLUX CALCULATION
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CONROLLED SWITCHING WITH RESIDUAL FLUX MESMT.
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POWER TRANSFORMER SWITCHING BY CS
Uncontrolled switching
With Voltage peak closing
With Residual flux closing
4 PU
2 PU
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PURPOSE OF CAPACITOR BANKS
• Inductive load compensation (motors)
• Power factor correction ( cos φ )
• Voltage regulation
Imaginary
component
Apparent power
(S)
Reactive power (Q)
[generation]
Reactive power (Q)
[consumption]
Active power
(P)
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Real
component
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INRUSH CURRENTS IN CAPACITOR BANK ENERGISATION
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CAPACITOR DISCHARGE CURVE
While closing the CB the voltage on the capacitor is calculated with
a patented algorithm and the CB will be made to close exactly at
the same instant of the waveform corresponding to the discharge
curve.
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BENEFITS CONTROLLED SWITCHING
Controls the exact moment the circuit breaker is operated:
Reduces inrush currents
Eliminates the high voltage switching transients
Eliminates pre-insertion resistors:
Reduce the circuit breaker maintenance costs
Improve the circuit breaker reliability
Provides extended circuit breaker monitoring:
Detection of C/B degradation of performance
Detection of mechanical/electrical problems
The circuit breaker becomes a smart device!
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FIELD PROVEN technology developed with Hydro-Quebec
C/B Manufacturer AGNOSTIC solution
Applicable to either BRAND NEW or EXISTING circuit breakers
Controlled switching system & CB MONITORING
One system for all C/Bs + one common interface = LESS TRAINING
Modbus, IEC 61850 & DNP3 compatible
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