ret 670 ied santiago - file/ret+670+ied_santiago.pdf · ret 670 gunnar stranne. 2 ... transformer...

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2006-04-20 PTSX Gunnar Stranne

SantiagoSeptiembre 5, 2006

Transformer protection IED RET 670

Gunnar Stranne

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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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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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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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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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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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� 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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� 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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� 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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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!


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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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� 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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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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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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� 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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Directionalcheck

3I0 < 3% of Ibase

IN > 50% of Idset

TRIP

START

≥1

≥1

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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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� 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


� Rate-of-change of frequency� Generation shedding

� Load shedding


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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


breaker, current and voltage inputs


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 ®

ret 670 ied santiago - file/ret+670+ied_santiago.pdf · ret 670 gunnar stranne. 2 ... transformer...

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