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Rio de JaneiroApril 23-25, 2006

2006-04-20 PTSX Gunnar Stranne

Transformerprotection IEDRET 670

Gunnar Stranne

Rio de JaneiroApril 23-25, 2006

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Transformer protection IED RET670

Introduction features and applications

Differential protection functions

Restricted Earth Fault protectionfunction

High Impedance Differential protection

functionSome additional functions andapplication examples

Preconfigured ready-made packagesSummary 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 windingPossibility 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, includingautotransformers, reactors andgenerator transformer blocks

Two or three vector group (orwinding) transformers

Single- or multi circuit breakerarrangements

Up to six stabilized 3-phasecurrent inputs

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Three-winding Transformer

Three-winding variant up to6 restraint three-phase CTinputs

Ensures enhanced through-fault stability for multi-breaker arrangements

Tap changer control

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Auto Transformer

Phased segregatedbiased differentialprotection for

Autotransformers in 1 CBapplications

Serial and common

windingsUp to 4 three-phase CTinputs

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Phase Shifting Transformer

Transformer key data1400 MVA

400/ 400 kV

+-25

1200 tons

32 MUSD contract

Project aspectsCooperation between EndUser, Relay Manufacturer &PST Manufacturer is ofoutmost importance

Cooperation required in thevery early design stage of theproject

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Shunt Reactor Protection And Control

ProtectionPhase segregated biased

differential protectionHigh-impedancedifferential protection

Over/under-voltage

protectionSwitching control for linesand 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 differentialprotection of a generator

transformer unit

Differential protection forthe step-up transformerand/or the auxiliarytransformer

Back-up protectionfunctionality

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Complementary Protection Functions

Full scheme distance

Overcurrent 19 inverse

Thermal overloadBreaker failure

Voltage functions withhigh reset ratio

RET 670 fits all power system elements thatrequire 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 inputsEnhanced through-fault stability for multi-breaker arrangements

Three-winding variant up to 6 three-phase CT inputsEnhanced 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 withunconnected delta tertiary winding

2- winding power transformer with2 circuit breakers on primary side

2- winding power transformer with2 circuit breakers on secondary side

- winding power transformer with2 circuit breakers on both sides

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Transformer Protection Terminal

Differential Protection of 3- winding Power Transformers

3- winding power transformer with2 circuit breakers on (any) one side,

(e.g. 2 parallel power lines on one side)

3- winding power transformer with2 circuit breakers on 2 out of 3 sides,(e.g. a meshed power network)Note! Also 3-out of 3 with 2 breakers ispossible.

3- winding power transformer

with all 3 windings connected

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A differential current does not always mean there is afault in the transformer

Inrush current in power transformers

Saturation of current transformers

Overexcitation

Tap changer position

etc.

Means of coping with these situations must beincluded in the design

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Ability is included to handle two tap changers, i.e. onetap changer per winding on any two windings

FunctionalityThree-section settable restrain characteristic

High set unrestrained operation

Idiff

Ibias

Idmin

1.25 pu

1.0 puoperate

restrain

Unrestrained operationIdunre

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Transformer Inrush Current Stabilization

Transformer inrush currents contain a percentage of secondharmonic current. This is used for discrimination but secondharmonic blocking normally causes delayed operation in case ofCT saturation. It is also possible to monitor the shape of thedifferential current signal. The low-current gap measurementindicates inrush.

Second harmonic stabilisation

Wave form stabilisation

wave block

CT saturation cause a secondharmonic component in thesecondary current

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Transformer Inrush Current Stabilisation

Delayed trip ofthe restrained

differentialfunction due tothe traditionaluse of second

harmonic blocking(Set level 15 %)

Internal fault followed by CT saturation

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Overvoltage Stabilization

The fifth harmonic component appearsas a characteristic quantity in the transformer

magnetizing current during overvoltage.

0

-3

-2

-1

1

2

3

Magnetizing current atsystem overvoltage

iL1

iL2iL3

The fifthharmoniccomponent

is used forstabilization

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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 changerposition (selectable)

Selectable subtraction of zero sequencecurrents

DIFP- application

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restrained

unrestrained

Blocking condition:2nd harmonic, 5 th harmonicwaveblock, cross block

TRIP

START

&

1

Neg Seq Int /Ext FaultDiscriminator

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 discriminatorBased on the measurement of negative sequence current

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Before comparison, all negative sequence currents arecompensated for turns ratio and vector group phase displacement

External fault: 180relative phase displacement

Internal fault: 0relative phase displacement

IminNegSeq2% - 20%Default 4%

NegSeqROA

30 120Default 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 kA

Directional limit (within the region delimited by 60 degrees is internal fault)

1.0 kA

1.5 kA

definitelyan internalfault

Internalfault

declared7 ms afterinternalfaultoccurred

trip commandin 12 ms

excursion

from 0 degreesdue toCT saturation

externalfaultregion

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 current function - summary

Fast operating times half cycleStart from ordinary differential protectionrequired, but blocking conditions are bypassed

Sensitive negative sequence protectionGives sensitive turn-to-turn fault protection

The trip request must be confirmed severaltimes in succession before the final trip requestis placed this security feature causes anincrease 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 % transformerrated 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 forinternal fault

internal fault

restrain forexternal 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 forinternal fault

restrain forexternal 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 conditionPossible to record the differential currents and/or biascurrent by the disturbance recorder channels 31-40

Differential currentsInstantaneous or RMS

Bias current

RMS

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Directionalcheck

3I0 < 3% of I baseIN > 50% of Idset

TRIP

START

1

1

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I1I3PRI1I3PRI2I3SEC1I3SEC2

I1I2

I3I3P

I1I2I3

I3P REFx

I I1N

I1I2I3

I3P

Up to 4 three-phase CT inputs makes it possible tohandle autotransformers in 1 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 conditionPossible to record differential currents and/or biascurrent by the disturbance recorder

Differential currentsInstantaneous 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 protectionBus 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 functionsTripping of load will give coolingchance to restore normaltemperatures.Settable thermal time constants forshort circuits and low overloadsMeasures RMS current

Lockout reset level (in % of heat contenttrip value)

Alarm levels 1 and 2 (each in % ofheat 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 voltageUnder-voltage blocking

Df/dt with positive or negative derivative setting

High accuracyShort 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 frequencyLoad shedding systems

Remedial action schemes

Over frequencyGeneration shedding


Rate-of-change of frequencyGeneration 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 (1 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 (1 CB or double CB on any, or all, sides of

the transformer)

RET670 B40 Three winding transformer, multi circuit

breaker (1 CB or double CB on any, or all, sides of

the transformer)

Six Pre-configured RET 670 - Ready To Use

T Wi di T f Si l Ci i B k

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Two Winding Transformer Single Circuit Breaker

SC/VC25/27

3I>50/51-1

51N-2I

60FF

UN59N

3U>59

3UBF50BF

ContrInterl

3Id/I>87T

86/94I->O

Ind>87N-1

Ind>87N-2

21Z50/51-2

I51N-1

86/94I->O

UN59N

3U>59

3U24

3I>BF50BF

60FF

O1

O2

O4

O3

52PDPD

f81O/81U

O5

DR

DR

RET 670-A30

T Wi di T f M lti Ci it B k

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Two Winding Transformer Multi Circuit Breaker

SC/VC

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3I>50/51-1

51N-2I

60FF

UN59N

3U>59

3U87T

86/94I->O

Ind>87N-1

Ind>87N-2

21

Z

50/51-2

I51N-1

86/94I->O

UN59N

3U>59

3UBF50BF

3I>BF50BF

U/f>24

3I>BF50BF

60FF

52PD

PD

f81O/81U

O6

O1

O2

O4

O3

O5

SC/VC25/27

O72*

2*

2* O8

DR

DR

3I>BF50BF

RET 670-B30

Three Winding Transformer Single Circuit Breaker

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Three Winding Transformer Single Circuit Breaker

SC/VC25/27

3I>50/51-1

51N-2I

60FF

UN59N

3U>59

3UBF50BF

ContrInterl

3Id/I>87T

86/94I->O

Ind>87N-1

Ind>87N-2

21Z50/51-2

I51N-1

86/94I->O

UN59N

3U>59

3U50/51-3

INd>87N-3

86/94I->O

I51N-3

3I>BF

50BF

U/f>24

SC/VC25/27

FF60

60FF

O6

O1

O2

O4

O3

O5

52PDPD

f81O/81U

O7

DR

DR

3I>BF50BF

RET 670-A20

Three Winding Transformer Multi Circuit Breaker

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Three Winding Transformer Multi Circuit Breaker

SC/VC25/27

3I>50/51-1

51N-2I

60FF

UN59N

3U>59

3UBF50BF

ContrInterl

3Id/I>87T

86/94I->O

3I>BF50BF

Ind>87N-1

Ind>87N-2

21Z50/51-2

I51N-1

86/94I->O

UN59N

3U>59

3U50/51-3

INd>87N-3

86/94I->O

I51N-3

3I>BF50BF

U/f>24

3I>BF50BF

SC/VC25/27

60FF

60FF

O6

O1

O2

O4

O3

O5

52PDPD

f81O/81U

O7

O8DR

DR

RET670 B40

B fi f RET670

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Benefits of RET670

Functional flexibilityConfiguration flexibilityHigh performance

User friendlyPre-defined packagesIED 670 series member means;

Less spare parts neededSimplified engineering and maintenanceCommon look and feel and common toolsExtensive Self-supervision

Remote communication flexibilityEasy integration in Substation AutomationSystemsEvery step you take

- ABB has the solution

B fit f RET670 t t di f t

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Benefits of RET670 outstanding features

Fast, sensitive and secure differentialfunction tap-changer compensated

Fast and sensitive negative sequencedifferential function -> half cycle operation

Multi-CT inputs increases security andfunctionality

High or low impedance restricted earth-fault winding differential funcionsExtensive 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

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