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2006-04-20 PTSX Gunnar Stranne
SantiagoSeptiembre 5, 2006
Transformer protection IED RET 670
Gunnar Stranne
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2006-04-20 PTSX Gunnar Stranne
Transformer protection IED RET670
� Introduction – features and applications
� Differential protection functions
� Restricted Earth Fault protection function
� High Impedance Differential protection function
� Some additional functions and application examples
� Preconfigured ready-made packages
� Summary and conclusions
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2006-04-20 PTSX Gunnar Stranne
Benefits of RET670 – outstanding features� Half cycle operating time – a new performance standard!
� One or two differential functions
� Differential function compensated automatically for tapchanger position for improved sensitivity
� An additional sensitive and fast differential functionbased on negative sequence current - ~1% sensitivity
� High impedance or low impedance restricted earth-fault differential protection for each winding
� Possibility to use multi - CT arrangements for increaseddifferential protection stability
� Tap changer control
� Breaker control , measuring, monitoring and recording
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Applications
� Power transformers, including autotransformers, reactors and generator transformer blocks
� Two or three vector group (or winding) transformers
� Single- or multi circuit breaker arrangements� Up to six stabilized 3-phase
current inputs
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Three-winding Transformer
� Three-winding variant up to 6 restraint three-phase CT inputs
� Ensures enhanced through-fault stability for multi-breaker arrangements
� Tap changer control
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Auto Transformer
� Phased segregated biased differential protection for � Autotransformers in 1½ CB
applications
� Serial and common windings
� Up to 4 three-phase CT inputs
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Phase Shifting Transformer
Transformer key data� 1400 MVA
� 400/ 400 kV
� +-25°
� 1200 tons
� 32 MUSD contract
Project aspects� Cooperation between End
User, Relay Manufacturer & PST Manufacturer is of outmost importance
� Cooperation required in the very early design stage of the project
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2006-04-20 PTSX Gunnar Stranne
Shunt Reactor Protection And Control
� Protection� Phase segregated biased
differential protection
� High-impedance differential protection
� Over/under-voltage protection
� Switching control for lines and busses
RET 670 is optimized for eachapplication with maximum reliability
and short operating time
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2006-04-20 PTSX Gunnar Stranne
Step-up Transformer In Power Stations
� Overall differential protection of a generator – transformer unit
� Differential protection for the step-up transformer and/or the auxiliary transformer
� Back-up protection functionality
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Complementary Protection Functions
� Full scheme distance
� Overcurrent – 19 inverse
� Thermal overload
� Breaker failure
� Voltage functions with high reset ratio
RET 670 fits all power system elements that require unit and additional protection functionality
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Differential Protection
� Two-winding or three-winding functions
� Two-winding variant up to 4 three-phase CT inputs� Enhanced through-fault stability for multi-breaker arrangements
� Three-winding variant up to 6 three-phase CT inputs � Enhanced through-fault stability for multi-breaker arrangements
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2006-04-20 PTSX Gunnar Stranne
Transformer Protection Terminal
Differential Protection of 2- winding Power Transformers
2- winding power transformer
2- winding power transformer with unconnected delta tertiary winding
2- winding power transformer with 2 circuit breakers on primary side
2- winding power transformer with 2 circuit breakers on secondary side
�- winding power transformer with 2 circuit breakers on both sides
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Transformer Protection Terminal
Differential Protection of 3- winding Power Transformers
3- winding power transformer with 2 circuit breakers on (any) one side,(e.g. 2 parallel power lines on one side)
3- winding power transformer with 2 circuit breakers on 2 out of 3 sides,(e.g. a meshed power network) Note! Also 3-out of 3 with 2 breakers is possible.
3- winding power transformer with all 3 windings connected
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Differential Protection
� A differential current does not always mean there is a fault in the transformer� Inrush current in power transformers
� Saturation of current transformers
� Overexcitation
� Tap changer position
� etc.
� Means of coping with these situations must be included in the design
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Differential Protection
� Ability is included to handle two tap changers, i.e. one tap changer per winding on any two windings
� Functionality � Three-section settable restrain characteristic
� High set unrestrained operation
Idiff
Ibias
Idmin
1.25 pu
1.0 pu
operate
restrain
Unrestrained operationIdunre
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Transformer Inrush Current Stabilization
Transformer inrush currents contain a percentage of second harmonic current. This is used for discrimination but second harmonic blocking normally causes delayed operation in case of CT saturation. It is also possible to monitor the shape of the differential current signal. The low-current gap measurement indicates inrush.
� Second harmonic stabilisation
� Wave form stabilisation
� wave block
CT saturation cause a second harmonic component in the secondary current
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Transformer Inrush Current Stabilisation
Delayed trip of the restraineddifferentialfunction due to the traditionaluse of secondharmonic blocking(Set level 15 %)
Internal fault followed by CT saturation
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Overvoltage Stabilization
The fifth harmonic component appears as a characteristic quantity in the transformer
magnetizing current during overvoltage.
0 �� �� �� �� ��� ��� ��� ���
-3
-2
-1
1
2
3
Magnetizing current at system overvoltage
iL1
iL2
iL3
The fifth harmonic componentis used for stabilization
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Differential Protection
� Two- and three winding applications
� Stabilization of up to 6 inputs
� Inrush current stabilization
� Second harmonic
� Waveform
� Phase segregated
� Selectable ”Cross-blocking”
� 5th harmonic stabilization at overvoltage
� Sensitivity influenced by tap changer position (selectable)
� Selectable subtraction of zero sequence currents
DIFP- application
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Differential Protection
restrained
unrestrained
Blocking condition:2nd harmonic, 5th harmonicwaveblock, cross block
TRIP
START
&
≥1
Neg Seq Int / Ext Fault Discriminator
internal
sensitive&
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Testing RET670 for maximum performanceFault detection in 7 ms!
Differential Protection
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Negative sequence current differential function
� Internal / external fault discriminator� Based on the measurement of negative sequence current
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Negative sequence current differential function
� Before comparison, all negative sequence currents are compensated for turns ratio and vector group phase displacement
� External fault: 180°relative phase displacement
� Internal fault: 0°relative phase displacement
IminNegSeq2% - 20%Default 4%
NegSeqROA30°– 120°Default 60°
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Negative sequence current differential function
0.5 kA
30
210
60
240
90
270
120
300
150
330
180 0
HV side contribution to the total negative sequence differential current in kADirectional limit (within the region delimited by ± 60 degrees is internal fault)
1.0 kA
1.5 kA
definitely an internalfault
Internal fault declared 7 ms afterinternal fault occurred
trip commandin 12 ms
excursion from 0 degreesdue to CT saturation
externalfault region
35 ms
Directional Comparison Criterion: Internal fault as seen from the HV side
� An internal fault with heavy CT saturation
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Negative Sequence Differential Protection
20 A
30
210
60
240
90
270
120
300
150
330
180 0
Contribution to total neg. seq. diff. current from HV side (in A)Directional limit (within ± negSeqROA degrees is internal fault)
30 A
40 A
50 A
8 10
Internal faultdeclared 12 ms after fault
steady-stateposition for this internal fault 19
External fault region
If one or the other of currents is too low, then no measurement is done
Directional Comparison Criterion: Internal fault as seen from the HV side
(negSeqROA = ± 60 deg)
� An internal small transformer interturn fault was cleared by Buckholz relay and existing differential protection failed to detect fault
� Test of RET 670 with recorded signals proved successful
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Negative sequence current function - summary�Fast operating times – half cycle
�Start from ordinary differential protection required, but blocking conditions are bypassed
�Sensitive negative sequence protection
�Gives sensitive turn-to-turn fault protection
�The trip request must be confirmed several times in succession before the final trip request is placed – this security feature causes an increase in the operating time
�The operating time is about 30ms for very low-level turn-to-turn faults
�This sensitive negative sequence protection is blocked for high fault current conditions
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Restricted Earth Fault Protection
bias current in per unit
0 1 2 3 4 5 6
diff currentin pu
Step : 1 % transformer rated current
minimum base sensitivity 50 % default base sensitivity 30 %
maximum base sensitivity 5 %
1.25 pu
Operate characteristic
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Restricted Earth Fault Protection
ROA
MTA
3I0
ROA
reference isneutral current
operate for internal fault
internal fault
restrain for external fault
-IN
3I0
zone of protection
IN
IL1
IL2
IL3
IFAULT IN 3I0
zone of protection
IN
IL1
IL2
IL3
IFAULT IN
3I0ROA
MTA
ROA
reference isneutral current
external fault
-INoperate for internal fault
restrain for external fault
Internal fault External fault
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Differential Protection
� Switch-on-to-fault
�Built-in logic to improve operating speed for switch-on-to-fault condition
� Possible to record the differential currents and/or bias current by the disturbance recorder channels 31-40
�Differential currents
� Instantaneous or RMS
�Bias current
�RMS
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Restricted Earth Fault Protection
Directionalcheck
3I0 < 3% of Ibase
IN > 50% of Idset
TRIP
START
≥1
≥1
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Restricted Earth Fault Protection
I1I3PRI1I3PRI2I3SEC1I3SEC2
I1I2I3 I3P
I1I2I3
I3P REFx
I I1N
I1I2I3
I3P
� Up to 4 three-phase CT inputs makes it possible to handle autotransformers in 1½ CB applications
� Enhanced function for autotransformer applications
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Restricted Earth Fault Protection
� Switch-on-to-fault
�Built-in logic to improve operating speed for switch-on-to-fault condition
� Possible to record differential currents and/or bias current by the disturbance recorder
�Differential currents
� Instantaneous or RMS
�Bias current
�RMS
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High Impedance Differential Protection
� Three instances → 1 or 3 high impedance differential
� External stabilizing resistors & metrosils are used
Typical applications
� High impedance REF – Restricted Earth Fault protection
� Tee - feeder differential protection
� Bus differential
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Overexcitation Protection
� V/Hz measurement
� Positive sequence or single phase-to-phase voltage
� Transformer magnetic core cooling time constant setting
� IEEE inverse time and User defined trip curves available
� Alarm level as percentage of trip level
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Thermal Overload protection function
86/94I->O
Ith49-1
86/94I->O
Ith49-1
•Two thermal overload functions•Tripping of load will give cooling chance to restore normal temperatures.•Settable thermal time constants for short circuits and low overloads•Measures RMS current•Lockout reset level (in % of heat content trip value)
�Alarm levels 1 and 2 (each in % of heat content trip value)
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TOF/TUF/RVF(df/dt) – Frequency Protection
� Over-frequency and under-frequency
� Six steps OF & UF – settable frequency and time delay
� Measures Ph-Ph or Positive sequence voltage
� Under-voltage blocking
� Df/dt with positive or negative derivative setting
� High accuracy
� Short operating time
� Accuracy 2 mHz for three phase
� Accuracy 10 mHz for single phase
Voltage dependent tripping time possible!
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Frequency Protection - Applications
� Under frequency� Load shedding systems
� Remedial action schemes
� Over frequency� Generation shedding
� Remedial action schemes
� Rate-of-change of frequency� Generation shedding
� Load shedding
� Remedial action schemes
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� RET 670-A30 Two winding transformer, single circuit
breaker
� RET 670-B30 Two winding transformer, multi circuit
breaker (1½ CB or double CB on either, or both, sides
of the transformer)
� RET 670-A20 Three winding transformer, single circuit
breaker
� RET 670-A31 Three winding transformer, single circuit
breaker, current and voltage inputs
� RET 670-A40 Three winding transformer, single circuit
breaker (1½ CB or double CB on any, or all, sides of
the transformer)
� RET670 –B40 Three winding transformer, multi circuit
breaker (1½ CB or double CB on any, or all, sides of
the transformer)
Six Pre-configured RET 670 - Ready To Use
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Two Winding Transformer – Single Circuit Breaker
SC/VC25/27
3I>50/51-1
51N-2I
60FF
UN59N
3U>59
3U<27
3I>BF50BF
ContrInterl
3Id/I>87T
86/94I->O
Ind>87N-1
Ind>87N-2
21Z<
VCTR90
3I>50/51-2
I51N-1
86/94
I->O
UN59N
3U>59
3U<27
U/f>24
3I>BF50BF
60FF
O1
O2
O4
O3
52PDPD
f</>81O/81U
O5
DR
DR
RET 670-A30
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Two Winding Transformer – Multi Circuit Breaker
SC/VC
25/27
3I>50/51-1
51N-2I
60FF
UN59N
3U>59
3U<27 Contr
Interl
3Id/I>87T
86/94I->O
Ind>87N-1
Ind>87N-2
21Z<
3I>50/51-2
I51N-1
86/94I->O
UN59N
3U>59
3U<27
3I>BF50BF
3I>BF50BF
U/f>24
Σ
3I>BF50BF
60FF
52PDPD
f</>81O/81U
O6
O1
O2
O4
O3
O5
SC/VC25/27
O72*
2*
2* O8
DR
DR
3I>BF50BF
RET 670-B30
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Three Winding Transformer – Single Circuit Breaker
SC/VC25/27
3I>50/51-1
51N-2I
60FF
UN59N
3U>59
3U<27
3I>BF50BF
ContrInterl
3Id/I>87T
86/94I->O
Ind>87N-1
Ind>87N-2
21Z<
3I>50/51-2
I51N-1
86/94I->O
UN59N
3U>59
3U<27
3I>50/51-3
INd>87N-3
86/94I->O
I51N-3
3I>BF
50BF
U/f>24
SC/VC25/27FF60
60FF
O6
O1
O2
O4
O3
O5
52PDPD
f</>81O/81U
O7
DR
DR
3I>BF50BF
RET 670-A20
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Three Winding Transformer – Multi Circuit Breaker
SC/VC25/27
3I>50/51-1
51N-2I
60FF
UN59N
3U>59
3U<27
3I>BF50BF
ContrInterl
3Id/I>87T
86/94I->O
3I>BF50BF
Ind>87N-1
Ind>87N-2
21Z<
3I>50/51-2
I51N-1
86/94I->O
UN59N
3U>59
3U<27
3I>50/51-3
INd>87N-3
86/94I->O
I51N-3
3I>BF50BF
U/f>24
3I>BF50BF
SC/VC25/27
Σ
60FF
60FF
O6
O1
O2
O4
O3
O5
52PDPD
f</>81O/81U
O7
O8DR
DR
RET670 –B40
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Benefits of RET670
� Functional flexibility� Configuration flexibility� High performance � User friendly � Pre-defined packages� IED 670 series member means;
� Less spare parts needed� Simplified engineering and maintenance� Common look and feel and common tools� Extensive Self-supervision� Remote communication flexibility� Easy integration in Substation Automation
Systems Every step you take
- ABB has the solution
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Benefits of RET670 – outstanding features
� Fast, sensitive and secure differential function – tap-changer compensated
� Fast and sensitive negative sequencedifferential function -> half cycle operation
� Multi-CT inputs increases security and functionality
� High or low impedance restricted earth-fault winding differential funcions
� Extensive function library and options � Up to 12 general I -V functions; distance and extra differential functions
� High reset voltage functions
� Extendable analog and digital I/O
� Full control functionality
� Large HMI option
Potencia y productividad para un mundo mejor ®