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
Fundamental of differential protection
Basic consideration
Vector
Phase shift
Fundamental of differential protection
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
Comparison of technologies
conventional numerical
• 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
Comparison of technologies
conventional numerical
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
Remote I/OTripOutputs
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
Remote I/OTripOutputs
Sign.Outputs
Bin.Inputs
Remote I/OTripOutputs
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 with Inverse time delay (24)
Overexcitation (24)Overexcitation (24)
Instantaneous Overvoltage (27/59)
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:
• Single or three-phase measurement
• 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
• Single or three-phase measurement
• 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:
• Delay: Time between the function picking up and tripping
• I-Setting: Pick-up current setting
• f-min: Minimum frequency for which measurement is required
• 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
Inverse time Over Current (51)
Features:
• Operating characteristic according to British standard 142
• Single or three-phase measurement
• 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
• MaxMin: Over or Under current
• t-min: Definite minimum tripping time
• NrOfPhases: Defines the number of phases measured
• CurrentInp: Analog current input channel
• IB-setting: Base current for taking account of differences of rated current
• BlockInp: Input for blocking the function
• Trip signal: Tripping signal
• Start signal: Pick-up signal
Definite time Over & Under voltage (27/59)
Features:
• Single or three-phase measurement
• 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:
• Delay: Time between the function picking up and tripping
• V-Setting: Voltage setting for tripping
• MaxMin: Over or Under voltage selection
• NrOfPhases: Number of phases included in the measurement
• VoltageInp: Analog input channel
• BlockInp: Input for blocking the function
• Trip signal: Tripping signal
• Start signal: Pick-up signal
Instantaneous Overvoltage (27/59)
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:
• Delay: Time between the function picking up and tripping
• 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
• BlockInp: Input for blocking the function
• Trip signal: Tripping signal
• Start signal: Pick-up signal
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
• BlockInp: Input for blocking the function
• Trip signal: Tripping signal
• Start signal: Pick-up signal
Overexcitation with Inverse time delay (24)
Features:
• Evaluation of the voltage/frequency ratio
• Single phase measurement
• Inverse time delay according to U/f ratio
• Determination of frequency from the complex voltage vector
• According to IEEE guide C37.91-1985
• Insensitive to DC components & harmonics
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
• Insensitive to DC components & harmonics
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:
• Single phase measurement
• 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