Transformer Protection

TRANSFORMER PROTECTION

Introduction

• A Power Transformer is a vital link in a power transmission system and impact of a transformer fault is more serious

than a transmission line outage.

• Following are important.• High quality transformer.• Operating the transformer within specified limits of temperature and voltage.

• Proper checking and maintaining OLTC.• Providing suitable protective relays and monitoring devices.

Insulation Breakdown

Main causes of this are• Aging of insulation due to over temperature during long time.• Contaminated oil.• Corona discharges in the insulation.• Transient overvoltages due to thunderstorms or switching in the network. • Current forces on the windings due to external faults with high current.

Aging of Insulation

• Aging of insulation is a function of time and temperature.

• Part of the winding operated at highest temperature undergoes greatest deterioration.

• Improved cooling of transformer helps avoid accelerated aging of the insulation.

Overheating due to overexcitation

Oil contamination and leakage

• Quality of oil should be checked to ensure dielectric strength at site.

• Silica get breather helps avoid moisture.

• Oil level monitored to avoid breakdown of insulation.

• The overexcited transformer flux is forced through metal tank and other unlaminated parts of the transformer and result in heating up.

• Curve shows IEEE general guide for permissible short time over excitation.

• To get correct representation V/Hz relay should be connected to PT measuring voltage of an untapped transformer winding.

Fundamental of differential protection

Basic consideration

Type of transformer

Vector

Requirement of CT

Type of differential

Fundamental of differential protectionBasic

considerationTYPE of transformer

Generator transformer

Sub station transformer

Furnace transformer

Rectifier transformer


Basic consideration

Vector

Phase shift


Basic consideration

CT

Ratio

Class

Polarity

Connection

Fundamental of differential protectionTypes of differential

High impedance differential::Here a high impedance is added to relay circuit to prevent relay operation due to CT saturation under through fault conditions.This is very sensitive and fast operating for internal faults.Biased differential :Here the operation depends upon differential current exceeding the bias current.The bias characteristics is variable so that it is applicable to a wide variation in transformer design and configuration. This bias slope is set to stabilizeThe protection for small differential currents,which flow due to tap changer variation and CT tolerance under through fault conditions.

Harmonic restraint

Harmonics present in transformer charging in rush current

Reduced Cooling

• Forced cooling systems should be supervised to get alarm.

• Oil temperature should be watched and appropriate action taken if transformer gets overheated.

Under Impedance Relay

• Overcurrent relays are not suitable for system transformer connecting two networks or in networks with a large difference between maximum and minimum short-circuit fault MVA.

• Under impedance relay used should be having same reach for two and three phase faults.

•

Harmonic Restraint Overcurrent Relay• Overcurrent relay with second harmonic restraint can be used which will be stable for magnetizing inrush.

Ground Fault Protection

• Low impedance residual overcurrent relays or harmonic restraint overcurrent relays can be connected according to connection A.

• Should be delayed to give chance for other protections in the network to operate.

• They act as slow back up for transformer differential relays.

High Impedance Restricted Earth fault Relay

• Provides sensitive high speed restraint protection.

• Vk > 2 Us.

• CT’s should be dedicated and having identical turns ratio.

• The combination of relays on the same CT core should be avoided.

• Due to impedance of REF relay differential relay may not get enough current for operation for a phase-ground fault.

• Non-linear resistors should be connected in parallel with high impedance relay. This reduces the high peak voltage which can be developed during an internal fault.

• The interconnected secondary circuit of the CT should be grounded at only one point.

Overexcitation Protection

• Overexcited transformers become overheated and damaged.

• V/Hz overexcitation relay is required for transformers which may be operated at too high voltage or low frequency.

• Especially GT can be overexcited during acceleration and deceleration of turbine.

• Ratio should not exceed 1.1 times the ratio of rated voltage and frequency of the transformer.

Monitors

Gas Detector Relay• During fault, arching occurs releasing gas.

• Gas collected in alarm device gives alarm.

• Can detect a slowly developing fault before it becomes more serious.

• Trip devices responds to the high flow of oil which occurs during the sudden occurrence of a serious fault.

• Monitors are very important devices which detect faults and abnormal service conditions which may develop into fault.

Temperature Monitoring

• Transformer can stand short time overload upto 1.5 times the rated.

• Overcurrent relays cannot be used for overload monitoring as they have to be set above the set short time overload.

• Oil temperature and winding temperature therefore provide better monitoring.

• Static thermal relays with characteristic matching can also be used.

• Other devices used include• Pressure relay for OLTC• Oil level monitor• Silica gel dehydrating breather.

Fault Currents

• The reactance decreases rapidly for fault close to neutral.

• Primary fault current for ground fault between 0-40% from neutral is below 1.5In and therefore O/C relay will not be able to detect this.

• Primary current is approximately proportional to square of the short circuited fraction of the winding.

Turn-to-turn Faults

• Turn to turn faults between a few turns is difficult to detect by current measuring relays. Fault current is of the order of rated current when 2 to 4% of the turns are short circuited.

• The current in the short circuited loop is high (50-100 times In) and causes local damage and release of gas.

• Therefore rate of rise of pressure relay may detect this fault.

Protective Relays Used

Protective relays limit the damage in case of fault and monitorsto prevent the fault. Therefore fast and reliable protective relaysshould be used.

Normal protections used are

For transformers larger than 5 MVA Transformers smaller than 5 MVA

• Gas detector relay (Buchholz) - Gas detector relay (Buchholz)

• Overload protection (thermal relays - Overload protection or temperature monitoring relays) - Overcurrent protection

• Overcurrent protection - Ground fault protection

• Ground fault protection

• Differential protection

• Pressure relay for tap-changer compartment

• Oil level monitor

Differential Relay

• The protective zone of a Differential relay includes faults in transformer, faults on Buses or cables between the CT and transformer. Therefore it has a large protective zone than a gas detector relay.

• A transformer differential relay must be able to cope with the following conditions.

1. Magnetizing inrush current:

This is developed when voltage is returning to normal after a line fault and depends on

- The size of the power transformer - The source impedance - The magnetic properties of the core material - The remanence of the core - The moment when the transformer is switched in

The magnitude can be 5-10 times the rated current when switchingis done on outer winding of the transformer and 10-20 times ratedcurrent when done on the inner winding.

• Damping of inrush current depends on total resistance of source network and lasts for few seconds.

• Inrush can also develop in an energized transformer when a parallel transformer is switched. (The damping of the combined inrush current will then be less than normal and inrush may last for several minutes)

• 2nd harmonic restraint prevents unwanted operation of the relay due to inrush is prevented.

Inrush current test

2. Normal service:• Differential current flows due to excitation current of transformer, ratio errors in CT and predominantly due to position of tap changer.

• A setting 15% higher than mismatch is usual.

3. Internal Faults:• Operating time of typical differential relay(ABB RADSB relay ) for a

fault current of 5 times the rated current is 27ms.

• Unrestrained operation circuit to speed up the operation for a high fault current 8ms at 10 times the set operating current.

Recommended Setting for Unrestrained Operation:

PowerTransformerConnection (1)

Rated Power Recommended setting*In when energizing from

HV Side LV Side<10 MVA 20 10

Yy 10-100 MVA 13 13

Yy >100 MVA 8 8

Yd - 13 13

Dy <100 MVA 13 20

Dy >100 MVA 8 13

Setting of 20*In required when large through fault currents cansaturate the CTs and causes a large differential current for 1 & 1/2

CB arrangement.

4. External Faults:

• For faults outside the protective zone of the relay a relatively large

differential current can occur due to position of the tap changer and

differences between the CTs.

• The differential relay should not operate for this differential current.

• The differential relays are provided with a through-fault restraint

circuit which makes the relay operate for a certain % differential

current related to the current through the transformer.

Restraint characteristic

Use of Auxiliary CTs:

• Aux. CTs of Y are required even for YY transformer to prevent any operation of relay for external ground fault.

• For Y Power transformer, aux. CTs are required for balancing of currents and for correction of phase angles.

• Aux CTs are recommended on all sides of the transformer so that same time is taken for saturation for all the inputs.

• Connection of aux. CTs will depend on the connection of the Power transformer.

Differential Protection for Auto-transformers:

• Delta winding may or may not be connected to the network. If not connected CTs are not required.

•The differential relay will protect the main winding as well as the delta winding.

•High impedance relay can be used by applying CTs in the neutral point of the main winding.

• The relays protect the main winding but not the delta connected wdg. • All CTs should have the same ratio and auxiliary CTs can not be used. Saturation voltage of all the CTs should be at least twice the selected operating voltage.

Overexcitation:

• For an overvoltage of 20%, the excitation current can increase above the pick-up level of differential relay.

• An overexcited condition is not a transformer fault and hence the differential relay should not operate.

• If differential relay operates valuable time will be wasted on the investigation of the transformer.

• 5th harmonic restraint will prevent the tripping for Overexcitation as overexcited condition results in pronounced 5th harmonic

component.

Time Overcurrent Relays:

• Used on all feeding circuits of a transformer to provide back-up to differential relay and relays on the load side of transformer.

• An instantaneous highset overcurrent element is normally used to give fast fault clearance to severe faults.

• Time Overcurrent relay is set to 150% of the rated current and time delay must be set long enough to avoid tripping due to magnetizing inrush.

• The instantaneous element should be set to about 25% above the maximum through fault current and above the maximum inrush current. With this setting instantaneous tripping is obtained only for severe faults on the feeding side of the transformer.

Relay operates delayed for faults on the remaining parts of the windings and for faults on the load side of the transformer.

TRANSFORMER PROTECTION TERMINALS

electromechanical single function static single function digital single function digital multifunction relays numerical multifunction relays numerical multifunction systems

Historical evolution

• protection functions realised with different HW

• Quantity and types of protection func. fixed and limited

• HW-extensions difficult

• No. of CT's and PT's higher

• Requirements to primary transformers higher

• fixed HW prot.functions realised with SW

• Complete library of func. available

• Adaptation by SW

• No.of CT's and PT's lower

• Requirement to primary transformers lower

Comparison of technologies

conventional numerical

• Settings and operation locally

• no documentation ( only hand-made)

• Only binary information

• Periodical tests necessary

• Various spare parts

• Settings and operation locally or remote

• Self-documentation of all settings and events etc.

• Numerical information, meas..values, events, etc.

• Selfsupervision and test functions reduces maintenance.

• Five different types only



• integration to control systems difficult

• only protection

• only protection

• fixed solution

• integration to control systems possible

• integrated protection and control possible

• monitoring with available information possible

• extension and new developments possible --> open architecture



Transformer TerminalGenerator Terminal Control Terminal Line Terminal

Generation Transmission Distribution Load

GM

R

BayUnits

E

C

Line protection

Transformerprotection

Generator protection

Control

Automation

Human-machine-communication

RemoteInput/Output Unit

StationAutomation

System

LONSPAIEC 870-5-103IEC 1375

IEC 1375

SoftwareLibrary

Complete library with functions for bay control, monitoring, protection of generators, transformers.

Software and hardware proven and well introduced.

Extremely powerful and cost efficient solutions for MV and HV applications.

Selective Protection of:

• Two or Three winding Transformer

• Auto Transformers

• Generator-Transformer unit

Detection of Faults:

• All phase faults

• Earth faults at solidly or Low impedance grounded systems

• Inter-turn faults

• No interposing CT's

• Standard wiring diagram

• Inputs for external functions (Buchholz, temperature sensors) available• Programmable indication of tripping and signaling

• Indication of measuring values

• Continuous self-monitoring

• Modular SW protection functions

• 4 serial interfaces: - one front for local communication (PC) - one rear for remote communication - two others (spare)

1) Analog input unit up to 6 transformer

3) CPU with serial port

4) Binary input/output unit

5) Communication PCMCIA

6) Mother Board

7) Power Supply

7 4 4 4 4 3 12

6 2) Digital/Optical unit

5

1 2 3

Compact Design

Open communicationstrategy

Flexible input and output configuration

R

BayUnits

7 4 4 4 4 3 1

5

6

Interbay bus

Up to 1024 binary I/Os

RIO580

Process bus

8

1

3

4

5

6

7

8

Analog input module, up to 9 input transformers for AC voltage and current

CPU

Binary I/O modules (max. 56 binary inputs, max. 32 binary outputs)

Communication interface for the interbay bus (PC-Card)

Connection module

Supply module

Communication interface for the process bus (MVB PC-Card)

R

BayUnits

Hardware concept

Hardware concept

MMC

PC-

CA

R

D

a

b

c

d

DCAC

DC+5V

+15V

-15V

+24V

PowerSupply

A/D DSPCPU

486DX

SerialController

RS232

FLASHEPROM

Tranceiver

RAM

SW-Key

PC-Card

LONe.g. LON

SPA / IEC870-5-103 (VDEW6)

LED'sSCSSMS

SerialController

RS232

DPM

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

PC-Card

Process bus

IEC1375

TripOutputs

Sign.Outputs

Bin.Inputs

Remote I/OTripOutputs

Sign.Outputs

Bin.Inputs


Sign.Outputs

Bin.Inputs

Remote I/O

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts (MVB)

a

b

c

d

DCAC

DC+5V

+15V

-15V

+24V

PowerSupply

A/D DSP

CPU486DX

SerialController

RS232

FLASHEPROM

Tranceiver

RAM

SW-Key

LONe.g. LON

SPA / IEC870-5-103 (VDEW6)

LED'sSCSSMS

SerialController

RS232

DPM

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

Process bus

IEC1375

TripOutputs

Sign.Outputs

Bin.Inputs


Sign.Outputs

Bin.Inputs


Sign.Outputs

Bin.Inputs

Remote I/O

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

A/D DSP

RX Tx

DPM

(MVB)

Hardware concept

PC-

CA

R

D

PC-Card

PC-Card

MMC

etc.

Trip

MUX

1 DiffGen on

2 Current on

3 BinInp 2 off

COMI>U<Z<

etc.

MMI

Analog todigital

conversion

Numericalsignal

processing

Binary signal

processingB/O

A/I

B/I

Signal data flow

A/DS

H

DSP

COMSCS/SMS

Typical tripping time

MUXA/I B/O

Binaryoutput

isolation

Algorithm and Logicprocessor

DigitalfilterAmplifier

Low passfilterShunt

Analoginput

isolation

47230

0 ms 0 ms 3 ms 5 ms 12 ms 21 ms 25 ms

Z<I >I

etc

FUPLA

etc

9

A/DS

H

I>51

I87G

U>59

Z<21

U64S

0>

I>>50

I87T

U<27

X<40

CTRL

I>U<51-27

F<>81

Ucos78

Logic

U60

I49

TH

U/f24

P<-32

TimerCounter

I46

2

I>51

I87G

U>59

Z<21

U64S

0>

I>>50

I87T

U<27

X<40

CTRL

I>U<51-27

F<>81

Ucos78

Logic

U60

I49

TH

U/f24

P<-32

TimerCounter

I46

2

I>51

I87G

U>59

Z<21

U64S

0>

I>>50

I87T

U<27

X<40

CTRL

I>U<51-27

F<>81

Ucos78

Logic

U60

I49

TH

U/f24

P<-32

TimerCounter

I46

2

Software Library

Metering (UlfPQ)Metering (UlfPQ)

Frequency (81)Frequency (81)

Overexcitation with Inverse time delay (24)


Overexcitation (24)Overexcitation (24)

Instantaneous Overvoltage (27/59)


Definite time Over and Under Voltage (27/59)

Definite time Over and Under Voltage (27/59)

Inverse time Overcurrent (51)Inverse time Overcurrent (51)

Instantaneous Overcurrent (50)Instantaneous Overcurrent (50)

Definite time Over and Under Current (51DT)

Definite time Over and Under Current (51DT)

Thermal overload (49)Thermal overload (49)

Restricted Earth Fault (64)Restricted Earth Fault (64)

Function Library

Transformer-differential2 or 3 Winding (87T)

Transformer-differential2 or 3 Winding (87T)

4 parameter sets4 parameter sets

Counter, TimerCounter, Timer

Logic's (OR, AND, RS-FF)Logic's (OR, AND, RS-FF)

Remote Inputs and OutputsRemote Inputs and Outputs

Additional I/O unitsAdditional I/O units

Operating values I, U, P, Q, fOperating values I, U, P, Q, f

Event recordingEvent recording

Disturbance recorderDisturbance recorder

Self supervisionSelf supervision

Remote communicationRemote communication

Human Machine InterfaceHuman Machine Interface

MONITORING ANDAUXILIARY FUNCTIONS

MONITORING ANDAUXILIARY FUNCTIONS

Local Display unitLocal Display unit

Function Library

RE21604

I >I >5151

I > >I > >5050

I I

6060

I I

87 L87 LI I THTH

4949

U > U > 5959

U <U <2727

Z <Z <2121

UcosUcos7878

P < -P < -3232

LogicsLogics TimerTimer

I >I >5151

P<-P<-3232

U <U <2727

Z<Z<2121

3 I03 I0

67N67NUcosUcos7878

e.g. Z < (Distance) need 50 %

CPU CapacityProtection

Library

U U

6060

Fupla

FUP1FUP1FUP1FUP1FUP1FUP1FUP4FUP4

FUP1FUP1FUP1FUP1

ARAR2121

3 I03 I0

67N67N

I I

87 L87 L

SCSC2525

BinaryBinarySignalSignalTrans.Trans.

Dist.Dist.Rec.Rec.

U >> U >> 5959

Software concept

Hardware-key

eg. SM300

HMI functionality

• LED-displays

• Measurand display

• Event list

• Operating instructions

• Disturbance recorded information

• Self supervision

• Acknowledgement functions

• Optical connector for external HMI

LED indicationsAvailabilityStartOperation

Measurand displayAnalog channels (amplitude, angle, frequency)Functional measurands (e.g. differential current)Binary signals (I/O signals, tripping)

Event list (tripping values only, e.g. distance to fault)Operating instructions

HMI functionality

Disturbance recorder informationNumber of recorded events and date

DiagnosticsOperating status of the unitOperating status of the interbay busOperating status of the process bus

Acknowledgement functionsResetting the LED'sResetting the latching outputsEvent erasingWarm start

HMI functionality

Transformer Differential Protection (87T)

Features:• Non-linear, current dependent operating characteristic.• High stability during through faults and in the presence of CT saturation.• Short tripping times.• Three phase measurement.• Inrush current restraint.

• using the second harmonic.• detection of the highest phase current.• detection of the load current to determine whether the transformer is energized or not.

• Compensation of phase group.• Compensation of CT ratio.• DC current component filter and harmonic filter.

Differential protection of two or three winding power transformers& generator/transformer units.

Analogue Inputs:

Current ( 2 or 3 sets of 3 inputs)

Binary inputs:

Blocking

Binary Outputs:

Tripping R phase trip S phase trip T phase trip

Measurements:

R phase summation current S phase summation current T phase summation current R phase restraining current S phase restraining current T phase restraining current

Inputs & Outputs

AI 1,2,3 AI 7,8,9

AD

DIFF AD

Transformer Differentialfor 2-windings

Transformer Differentialfor 3-windings

AI 1,2,3

AI 7,8,9

AD

DIFF

AD

AD

AI 4,5,6

Operation

Operation for I’1

< b

IN

or

I’2

< b

IN

Restraint

b 21 3

1

2

3

gv

IH

IN

I

IN

Operating Characteristic:

Protected unitI 1

I 2

I 3

I = | I 1 + I 2 + I 3 |Operating (diff.) current

I H = I’1 * I’2 * Cos for Cos 0

= 0 for Cos < 0

Restrain current

Where I’1 = greatest of I 1 , I 2 , I 3

I’2 = I 1 + I 2 + I 3 - I’1

= ( I’1 - I’2 )

Fault outside protected zoneLow short circuit current

1

2

3

4

1 2 3 4 5 IH

I

v=50%

I1 I2

IH = I1 = I2 = ILoad < (1.5...3)*Irated

g

I < (1.5...3) * Irated

cos = 1

IH I1 I2 cos

Load

Fault outside protected zoneHigh short circuit current

1

2

3

4

1 2 3 4 5 IH

I

v=50%

I1 I2

IH = I1 = I2 g

I > (1.5....3) * Irated

cos = 1

v= infinite

IH I1 I2 cos

b

Isc

Fault inside protected zone

1

2

3

4

1 2 3 4 5 IH

II1 I2

IH = 0g

cos < 0

Thermal Overload Protection (49)

Features:

• 1st order thermal model

• Alarm and tripping stages

• Adjustable initial temperature

• Single or three-phase measurement

• Maximum value detection for three-phase measurement

• Temperature rise calculated 40 times for each thermal time constant setting

Thermal overload protection with accuratethermal image of the protected unit

49

Analogue Inputs:

Current

Binary inputs:

Blocking

Binary Outputs:

Alarm Tripping

Measurements:

Temperature rise Power dissipation Current

Inputs & Outputs

Definite time Over & Under Current (51DT)

Features:


• 2nd harmonic restraint for high inrush currents

• Insensitive to DC component• Maximum respectively minimum value detection in the three-phase mode

• May also be used as REF protection with additional hardware

General purpose current function forPhase fault protection and Back-up protn.

I < >51

Analogue Inputs:

Current

Binary inputs:

Blocking

Binary Outputs:

Pick-up Tripping

Measurements:

Current amplitude

Inputs & Outputs

Setting Parameters:

• Delay: Time between the function picking up and tripping

• I-Setting: Pick-up current setting

• MaxMin: Over or Under current

• NrOfPhases: 1ph or 3ph measurement

• CurrentInp: Analog current input channel

• BlockInp: Input for blocking the function

• Trip signal: Tripping signal

• Start signal: Pick-up signal

Instantaneous Over Current (50)

Features:

• Maximum or Minimum function (over & under current)

• Process instantaneous values and is therefore fast and largely independent of frequency


• Stores the peak value following pick-up

• Maximum value detection in the three-phase mode

• Adjustable lower frequency limit fmin

General current monitoring with instantaneous response

I < >50

Analogue Inputs:

Current

Binary inputs:

Blocking

Binary Outputs:

Pick-up Tripping

Measurements:

Current amplitude

(only available if function trips)

inputs & Outputs:

Setting Parameters:


• I-Setting: Pick-up current setting

• f-min: Minimum frequency for which measurement is required


• NrOfPhases: 1ph or 3ph measurement





Inverse time Over Current (51)

Features:

• Operating characteristic according to British standard 142


• Detection of the highest phase value in the three-phase mode

• Wider setting range than specified in B.S.142

Overcurrent function with time delay inverselyproportional to the current and definite minimumtripping time (IDMT)

I >51

Inputs & Outputs

Analogue Inputs:

Current

Binary inputs:

Blocking

Binary Outputs:

Pick-up Tripping

Measurements:

Current amplitude

Setting Parameters: • c-setting: Select operating char. According to BS142 or RXIDG char.

• k1-Setting: Time grading

• I-Start : Pick-up current at which the characteristic becomes active


• t-min: Definite minimum tripping time

• NrOfPhases: Defines the number of phases measured


• IB-setting: Base current for taking account of differences of rated current




Definite time Over & Under voltage (27/59)

Features:


• Maximum value, respectively minimum value, detection for three-phase measurement

• DC component filter

• Harmonic filter

Standard voltage applications (overvoltage &undervoltage function)

U < >59/27

Inputs & Outputs

Analogue Inputs:

Voltage

Binary inputs:

Blocking

Binary Outputs:

Pick-up Tripping

Measurements:

Voltage amplitude

Setting Parameters:


• V-Setting: Voltage setting for tripping

• MaxMin: Over or Under voltage selection

• NrOfPhases: Number of phases included in the measurement

• VoltageInp: Analog input channel





Features:

• Processes instantaneous values and is therefore fast and largely independent of frequency

• Stores the peak value following pick-up

• Single and three-phase measurement

• Maximum value detection in the three-phase mode

• Adjustable lower frequency limit fmin

General voltage monitoring with instantaneousresponse (over & undervoltage)

U > >59/27

Inputs & Outputs

Analogue Inputs:

Voltage

Binary inputs:

Blocking

Binary Outputs:

Pick-up Tripping

Measurements:

Voltage amplitude

(only available if function trips)

Setting Parameters:


• V-Setting: Pick-up voltage setting

• f-min: Minimum frequency for which measurement is required

• MaxMin: Over or Under voltage setting

• NrOfPhases: Defines whether 1ph or 3ph measurement

• VoltageInp: Analog voltage input channel




Overexcitation (24)

Features:

• Evaluation of the voltage/frequency ratio

• Single phase measurement

• Definite time delay

• Determination of frequency from the complex voltage vector

• Over or Underexcitation mode

• Insensitive to DC components & harmonics

Protection of generators and power transformers against excessive flux

U/ f24

Inputs & Outputs

Analogue Inputs:

Voltage

Binary inputs:

Blocking

Binary Outputs:

Pick-up Tripping

Measurements:

Voltage / frequency frequency

Setting Parameters:

• Delay: Time delay between the function picking up and tripping

• V/f- setting: Setting of the voltage/frequency ratio for tripping

• MaxMin: Over or Under fluxing setting

• VoltageInp: Analog voltage input channel





Features:

• Evaluation of the voltage/frequency ratio


• Inverse time delay according to U/f ratio

• Determination of frequency from the complex voltage vector

• According to IEEE guide C37.91-1985


Protection of generators and power transformersagainst excessive flux, especially in heavily loaded non-laminated metal parts, and the associated excessive heating of the unit.

U/ f24

Inputs & Outputs

Analogue Inputs:

Voltage

Binary inputs:

Blocking

Binary Outputs:

Pick-up Tripping

Measurements:

Voltage / frequency frequency

Frequency (81)

Features:

• Measurement of one voltage

• Frequency calculation based on the complex voltage vector

• Undervoltage blocking


Under and Overfrequency,Load shedding

Inputs & Outputs

Analogue Inputs:

Voltage

Binary inputs:

Blocking

Binary Outputs:

Under voltage blocking Start Trip

Measurements:

Frequency Voltage

Metering (UIfPQ)

Features:


• Phase-to-ground or optionally phase-to-phase voltage measurement

• Suppression of DC components and harmonics in current & voltages

• Compensation of phase errors in main and input CT’s and VT’s

Measurement of voltage,current,real &apparent power and frequency.

Inputs & Outputs

Analogue Inputs:

Voltage Current

Binary inputs:

none

Binary Outputs:

none

Measurements:

Voltage (unit UN) Current (unit IN) Real power (unit PN (P)) Apparent power (unit PN (Q)) Frequency (unit Hz)

The right information for the right person at the right timeThe right information for the right person at the right time

SMSRemote Substation Monitoring System

On-demand information

SCSSubstation Control

SystemOn-line information

SMSLocal Substation Monitoring System

On-demand information TERMINAL

FAULT

On

Serial

ABB Strömberg SRIO 1000M

1

2

3

4

Local

12 3 4 5 6 7 8

Asea Brown Boveri

POWER

V1

OVP

LOCKACQR SATELLITE CONTROLLED CLOCK

GPS 166

NORMAL OPERATIONWED 11.12.1996MEZ 11.42.25SV 24 > SYN

MENUCLR

ACKNEXT INC

MEINBERG

Switch

Minute pulse

GPS-Clock

SPA-LOOP

SRIO

RE.316

Modem

Remote communication and time synchronisationRemote communication and time synchronisation

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

ABB Network Partner AG RET 316*4

C

E

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

ABB Network Partner AG RET 316*4

C

E

Remote communication and diagnosticsRemote communication and diagnostics

• Brings a terminal to the user - evaluations- disturbance clarifications- diagnostics

- change and control of relay setting- etc.

TERMINAL

Last specified number of events stored Event-No., Date, Time, Funct.-No...........Selectable informationFunction outputs (Start / Trip and special outputs)Binary inputs Trip-valuesStatus ON/ OFF per eventAbsolute and relative time (after GFC fulfillment)

Event recorderEvent recorder

9 analog channels

16 binary channels (function outputs, binary inputs)

12 function measurements (e.g Idelta, I2, Z )

Total record time 5s

Pre-Event 400ms,Event 3000ms, Post-Event 400ms

Selectable triggering (GFC, trip or functions and binary inputs)

Stop on full or overwrite mode

Disturbance recorderDisturbance recorder

Disturbance Recorder - Recording times

t pt pre t f

t lim

t pre Pre-fault time (0.04- 0.40 sec)

t f Fault time

t p1 Post-fault time (0.1 - 3.0 sec) t lim Time limit for total recording (0.5 - 4.0 sec)

A/D-Conversion

3ph-Voltagesand-Currents

External and internalPower supply

Signal Transfer

Error correction coding

Read/Write comparisonChecksum function

Tolerance check

Symmetry check

continuous conversionof 2 reference signals

MemoriesProgram Processing

Watchdog functions

PC-CARD

a

b

c

d

DCAC

DC+5V

+15V

-15V

+24V

PowerSupply

A/D DSP

CPU486

Serial Cont.

RS232

RS232

RS232

RS232

FLASHEPROM

Transceiver

RAM

SW-Key

TripOutputs

Sign.Outputs

Bin.Inputs

I / OPorts

PC-Card

Process bus

PC-Card

LONLON

SPA / IEC 870-5-103

LED's

MMC

SelfsupervisionSelfsupervision

IEC 1375

Serial Data Transfer

Hamming distance 4 to 6by frame format definition,

16 bit CRC or check sum+parity bit

Serial Cont.

Password protected Test protection functions send a numerical value to each function test characteristic setting and related

outputs Test signaling relays Test tripping relays Test LED's

Test function

AdvantagesAdvantages

• Self monitoring

• Long term stability

• Event recorder

• Self documentation

• Number of CT cores reduced

• User designed performance

• Selectable protection functions

• Facility for communication to SMS/SCS

REFERENCES

ABB manuals

Alsthom manuals

Easun Reyrolle manuals

Art & science of protective relaying by Russell Mason

Transformer Protection

Documents

Transcript of Transformer Protection