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L90 Line Differential Relay
Digital Energy
Multilin
Agenda
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Introduction
1) Reliability: has two aspects:
Dependability: the degree of certainty that the relay will operate
correctly.
Security: the relay will not operate incorrectly
2) Speed: Very high power during fault conditions: delays translate intoincreased damage: faster protection tends to compromise relay system
security and selectivity.
3) Sensitivity: The minimum operating quantities allows the relay to detect
an abnormal condition. High-impedance ground faults,voltage unbalance
and high source- to- line impedance ratio affect the sensitivity
4) Selectivity : or coordination: ability of the relay system to minimize
outages as a result of a fault by operating as fast as possible within their
primary zone.
5) Simplicity and ergonomics: simple to apply and to obtain maximum
protection for the minimum cost in one box
Terms: Coordination, Unit Protection/None Unit Protection, Primary/Back up
Transmission Line Protection Considerations
High voltage transmission lines have extremely high level of fault current and
low impedance characteristics. Over current protection can not be as fast as it’s
needed.
Solutions:
• Current Differential:
• Unit Protection
Measure the current phasors at both ends of the line. If you have a line fault
there will be a difference in the current magnitude at each end and/or a changein current phase angle with respect to applied voltage.
• Distance or (Impedance):
• None Unit Protection
Impedance known as Distance: The distance relay operates by using bothvoltage and current to determine if a fault is in a relay’s zone of protection. At
time of fault Current increases and voltage decreases which translates into a
change in impedance.
Introduction
Transmission Line Protection Considerations
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L90 Current Differential Relay:
• Protection:
– Segregated Line current differential (87L)
– 87L Trip logic
– Phase/Neutral/Ground TOCs
– Phase/Neutral/Ground IOCs
– Negative sequence TOC
– Negative sequence IOC
– Phase directional OCs
– Neutral and negative sequence directional OC – Phase under- and overvoltage
– 3-zone distance back-up with power swing detect,load encroachment, POTT and line pickup
Features
L90 Current Differential Relay:
• Control:
– Breaker Failure (phase/neutral amps)
– Synchrocheck & Autoreclosure
– Direct messaging (8 extra inter-relay DTT bits exchanged)
• UR Metering:
– Fault Locator
– Oscillography
– Event Recorder
– Data Logger
– Phasors / true RMS / active, reactive and apparent power, powerfactor
• 87L Metering:
– actual differential current
– local and remote phasors
– communication channel status
Features
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L90 Current Differential Relay:
Features
831706AS.CDR
L90 Line Differential Relay
52
Monitoring CLOSE TRIP
Data From/To Remote End(via Dedicated Communications) MeteringFlexElement
TM Transducer Inputs
50DD 51N(2)50N(2)67P(2)87L 21P 68 7850BF(2)51_2(2)51P(2)50_2(2)
79
50P(2) 21G67N/G
27P(2)
27X
59N
59X
59P
25(2)
3V_0
51G(2)50G(2)
L90 Current Differential Relay:
Line Current Differential
• Improved operation of the line current di fferential (87L)element:
– Dynamic Restraint increasing security without jeopardizingsensitivity
– Line Charging Current Compensation to increase sensitivity
– Self-synchronization
– Channel Asymmetry Compensation to compensate forasymmetrical channel delay on multiplexed channels
– CT Saturation Detection
– Zero sequence current removal for applications on lines witha tapped transformers with a primary wye neutral grounded.
– Relay ID for secure applications on higher ordercommunication systems.
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L90 Current Differential Relay:
Line Current Differential
L90 can be appliedon bo th 2-terminaland 3-terminalapllications:hardware andfirmware are thesame.
Direct point-to-point Fiber
(up to 100Km)
ORVia SONET system telecom multiplexer
(GE’s FSC)
FSC
(SONET)
FSC
(SONET)
(64Kbps)
(155Mbps)
- G.703
- RS422
- G.703
- RS422
L90 Current Differential Relay:
Installation
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FIBER - LED & ELED
TRANSMITTERS
The above figure shows the 2-Terminal
configuration for the 7A, 7B, & 7C fiber-
only modules.
LASER FIBER MODULES
WARNING: When using a 1300/1550 nm
LASER Interface, attenuators may be
necessary to ensure that you do not exceed
Maximum Optical Input Power (-14 dBm) to
the receiver.
DIRECT FIBER
L90 Current Differential Relay:
Installation
DIRECT FIBER
L90 Current Differential Relay:
Installation
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DIRECT FIBER OPTICAL POWER BUDGET
L90 Current Differential Relay:
Installation
Typical pin interconnection between two G.703 interfaces back-to-
back.
G.703 CO-DIRECTIONAL INTERFACE
L90 Current Differential Relay:
Installation
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G.703 INTERFACE
G.703 module dip switches..
L90 Current Differential Relay:
Installation
G.703 INTERFACE
Connection to higher order system
G.703 Timing Selection
L90 Current Differential Relay:
Installation
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G.703 INTERFACE
Minimum Remote Loopback Test mode data processing
L90 Current Differential Relay:
Installation
G.703 INTERFACE
Dual Loopback Test mode data processing
L90 Current Differential Relay:
Installation
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Back to Back: Correct
Internal Timing mode
(S1=Off, S5=On, S6=Off)
Back to Back : Will work but not ideal.
G.703 INTERFACE
Loop Timing mode
(S1=Off, S5=Off, S6=Off)
Internal Timing mode
(S1=Off, S5=On, S6=Off)
Loop Timing mode (factory
default for connections to
higher order system
(S1=On, S5=Off, S6=Off)
L90 Current Differential Relay:
Installation
Point to Point using Modems (for example RAD modem):
• Octet Timing
Disabled
• Loop Timing
mode
• Octet Timing
Disabled
•Internal
Loop Timing
mode
Loop Timing
mode
Rad Modem Rad Modem
Only one clock per system
generated by right L90.
G.703 INTERFACE
L90 Current Differential Relay:
Installation
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Connection via multiplexers (higher order system):
The multiplexer provides the clock for all relays: again, one clock per
system:
Multiplexer Multiplexer • Octet Timingenabled
• Loop Timing
mode
• Octet Timing
enabled
• Loop Timing
mode
G.703 INTERFACE
L90 Current Differential Relay:
Installation
Typical pin interconnection between two RS422 interfaces
RS.422 INTERFACE
L90 Current Differential Relay:
Installation
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WARNING: When using a 1300 nm LASER Interface, attenuators may be
necessary to ensure that you do not exceed Maximum Optical Input Power
(-14 dBm) to the receiver.
RS422 & FIBER INTERFACE CONFIGURATION
MIXED INTERFACES
L90 Current Differential Relay:
Installation
The IEEE C37.94 Standard defines a point to point opt ical link for
synchronous data between a multiplexer and a teleprotection
device. Designed to interface with IEEE C37.94 compliant digital multiplexer
and/or an IEEE C37.94 compliant interface converter for use wi thL90.
IEEE fiber C37.94 INTERFACE
L90 Current Differential Relay:
Installation
Connected directly to
MUX
Connected to MUX
via converter
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For the Internal Timing Mode, the system clock is generatedinternally; therefore, the timing switch selection should be Internal
Timing for Relay 1 and Loop Timed for Relay 2. There must be only
one timing source configured. For the Looped Timing Mode, the system clock is derived from the
received line signal; therefore, the timing selection should be inLoop Timing Mode for connections to h igher order systems.
IEEE fiber C37.94 INTERFACE
L90 Current Differential Relay:
Installation
G7X
G7R
Transmitted
data blocked
Local Loopback Test Mode
Local relay
COMMS CHANNEL TESTING
L90 Current Differential Relay:
Installation
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G7X
G7R
Received data
echoed back.Remote Loopback Test
Local relay
COMMS CHANNEL TESTING
G7X
G7R
Remote
relay
L90 Current Differential Relay:
Installation
COMMS CHANNEL ON-LINE DIAGNOSTICS
Current comms status is available
in Actual Values.History of comms di sturbances is l ogged
into event recorder .
L90 Current Differential Relay:
Installation
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COMMS CHANNEL ON-LINE DIAGNOSTICS
L90 Current Differential Relay:
Installation
MAJOR COMMS ALARMS
1. 87L DIFF CH1/2 FAIL
2. 87L DIFF PFLL FAIL
3. 87L DIFF CH1/2 ID FAIL
87L DIFF BLOCKED
MINOR COMMS ALARMS
1. 87L DIFF CH1/2 CRCFAIL
2. 87L DIFF CH1/2 LOSTPKT
3. 87L DIFF TIME CHANGED
4. 87L DIFF ASYM DETECTED
5. 87L DIFF 1/2 ASYM MAX
6. 87L DIFF GPS1/2 FAIL
COMMS CHANNEL ON-LINE DIAGNOSTICS
CHANNEL ID FAIL
1. Each packet carries relay
ID number per channel
2. Each received packet is
compared with ID
programmed L90 PowerSystem menu.
3. “0” means NO Channel ID
check is required (for
direct fibers).
L90 Current Differential Relay:
Installation
Protection against:
1. Inadvertent loopback
2. Inadvertent connection to awrong L90 relay.
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Percent Current Differential
L90 Current Differential Function
IA @Timestamp2
IB @Timestamp2
IC@Timestamp2
ChargingCurrent
DATA FROMLOCALEND
ACTUALVALUES
SETTING
CURRENTDIFFPICKUP:
CURRENTDIFFRESTRAINT1:
CURRENTDIFFRESTRAINT2:
CURRENTDIFFBREAKPT:
SETTING
SETTING
SETTING
SETTING
SETTING
SETTING
SETTING
SETTINGS
Channel 1OK=1
Channel 2OK=1
IA @Timestamp2
IA @Timestamp2
IB @Timestamp2
IB @Timestamp2
IC @Timestamp2
IC @Timestamp2
DTTPHASEA
DTTPHASEA
DTTPHASEB
DTTPHASEB
DTTPHASEC
DTTPHASEC
CURRENTDIFFDTT:
CURRENTDIFFKEYDTT:
L90POWER SYSTEMXC0& XC1:
CURRENTDIFFSOURCE:
CURRENTDIFFTAP1:
CURRENTDIFFTAP2:
L90POWERSYSTEMNUM.OFTERMINALS:
L90POWERSYSTEMNUM.OFCHANNELS:
RUN
RUN
RUN
To RemoteRela yschannel 1& 2
827056A9.CDR
VCG
IC
VBG
IB
Enabled=1
Off
DATA FROMREMOTE1
DATA FROMREMOTE2
RUN
FLEXLOGICOPERANDS
87LDIFFOPA
87LDIFFOPB
87LDIFFOPC
87LDIFFRECVDDTTA
87LDIFFRECVDDTTB
87LDIFFRECVDDTTC
87LDIFF CH2CRCFAIL
87LDIFFKEYDTT
87LDIFFCH1 CRCFAIL
87LDIFF CH2LOSTPKT
87LDIFF CH1LOSTPKT
87LDIFFCH2FAIL
87LDIFFCH1FAIL
87LDIFFPFLLFAIL
87LDIFFOP
ORAND
ORAND
OR
OR
OR
OR
OR
OR
OR
OR
OR
AND
AND
AND
AND
AND
AND
AND
OR
VAG
IA
ComputeChargingCurrent
“3 ” =1
“2” =1
ComputePhasors& Variance(Local)
ComputePhasors& Variance(Remote1)
ComputePhasors& Variance(Remote2)
IC
IC
IC
IA
IA
IA
IB
IB
IB
IA Operate
IARestraint>1
2
2
IB Operate>1
IBRestraint
2
2
ICOperate>1
ICRestraint
2
2
FLEXLOGICOPERAND
STUB BUSOP
ToRemoteRelayschannel 1& 2
RUN
ProcessPhasorsComputations
IC
IA
IB
AND
ND
AND
87LDIFFCH1IDFAIL
87LDIFFCH2IDFAIL
87LBLOCKED
AND
Channel 1IDFail
Channel 2IDFail
AND
AND
AND
AND
AND
AND
ANDOR
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Restraint Current
O p e r a t e C u r r e n t
K1
K2
L90 Current Differential Relay:
Traditional Restraint Method
• Traditional method is STATIC
• Compromise between Sensitivity and Security
L90 Current Differential Relay:
Dynamic Restraint
• Dynamic restraint uses an estimate of a
measurement error to dynamically increase the
restraint
• On-line estimation of an error is possible owing to
digital measuring techniques
• In digital relaying to measure means to calculate or
to estimate a given signal feature such as magnitude
from the raw samples of the signal waveform
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L90 Current Differential Relay:
Digital Phasor MeasurementSliding Data Window
waveform magnitude
windo
w
timetime
present
time
32 samples for
Transmission
of one phaselet
32 samples for
Transmission of
next phaselet
L90 Current Differential Relay:
Phasor Goodness of Fit
window
time
• A sum of squared differences between the actual
waveform and an ideal sinusoid over last window is a
measure of a “goodness of fit” (a measurement error)
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L90 Current Differential Relay:
Phasor Goodness of Fit
• The goodness of fit is an accuracy index for the digital
measurement
• The goodness of fit reflects inaccuracy due to:
– transients
– CT saturation
– inrush currents and other signal distortions
– electrical noise
• The goodness of fit is used by the L90 to alter the
traditional restraint signal (dynamic restraint)
L90 Current Differential Relay:
Operate-Restraint Regions
ILOC – local current
IREM – remote end current
Imaginary (ILOC /IREM)
Real (ILOC /IREM)
OPERATE
OPERATE
OPERATE
OPERATE
RESTRAINT
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L90 Current Differential Relay:
Dynamic RestraintDynamic restraint signal =
Traditional restraint signal + Error factor Imaginary (ILOC /IREM)
Real (ILOC /IREM)
OPERATE
REST.
Error factor is high
Error factor is low
L90 Current Differential Relay:
Charge Current Compensation
• The L90 calculates the instantaneous values of the
line charging current using the instantaneous values
of the terminal voltage and shunt parameters of the
line
• The calculated charging current is subtracted from
the actually measured terminal current
• The compensation reduces the spurious differential
current and allows for more sensitive settings
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L90 Current Differential Relay:
Charge Current Compensation
• The compensating algorithm:
– is accurate over wide range of frequencies
– works with shunt reactors installed on the line
– works in steady state and during transients
– works with both wye- and delta-connected VTs
(for delta VTs the accuracy of compensation is
limited)
L90 Current Differential Relay:
Effect of Compensation
0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-200
-150
-100
-50
0
50
100
150
200
0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-200
-150
-100
-50
0
50
100
150
200
Voltage, V
time, sec
Local and remote voltages
Time ofenergization
Time of out of zone fault
~
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0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
L90 Current Differential Relay:
Effect of Compensation
Current, A
time, sec
Traditional and compensated differential
currents (waveforms)
Time of
energization
Theoretical compensated
current
Actual none compensated
current
0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.180
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.180
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
L90 Current Differential Relay:
Effect of Compensation
Current, A
time, sec
Traditional and compensated differential
currents (magnitudes)
Actual none compensated
current after filtering and
Fourier algorithm
Actual compensated current
after filtering and fourier
algorithm
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L90 Current Differential Relay:
Self-Synchronization
t0
t1
t2
t3
tf
tr
Forward
travel
time
Return
travel
time
Relay
turn-around
time
RELAY 1 RELAY 2
2
1203 t t t t
t t r f
2
1203 t t t t
t t r f
“ping-pong”
L90 Current Differential Relay:
Ping-Pong (example)
Communication path
Initial clocks mismatch=1.4ms or 30°
8.33 ms
8.33 ms
8.33 ms
Store T1i-2=5.1
8.33 ms
t1 t2
Slow down
Relay 1
0
5.1
0
2.3
8.33
8.33 Send T2i-2=2.3
Send T1i-2=5.1
Capture T1i-2=5.1
8.33 ms
Send start bit
Store T1i-3=0Send start bit
Store T2i-3=0
13.4310.53
Send T1i-1=16.66
Capture T2i-2=2.3
16.66
21.76
16.66
18.96
Send T2i-1=16.66
Store T2i-1=16.66
Capture T1i=21.76
Store T2i-2=2.3
Store T1i-1=8.33
Capture T2i=18.96
T2i-3=0
T1i-2=5.1
T1i-1=16.66
T2i=18.96
a2=5.1-0=5.1
b2=18.96-16.66=2.3
2=(5.1-2.3)/2=
= +1.4ms (behind)
T1i-3=0
T2i-2=2.3
T2i-1=16.66
T1i=21.76
a1=2.3-0=2.3
b1=21.76-16.66=5.1
1=(2.3-5.1)/2=
= -1.4ms (ahead)
Speed up
Relay 2
30°0°
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L90 Current Differential Relay:
Ping-Pong (example continued)
8.52 ms
8.14 ms
8.14 ms
Store T1i-2=38.28
8.52 ms
t1 t2
Slow down
Relay 1
33.32
38.28
33.32
35.62
41.5541.55
Send T2i-2=35.62Send T1i-2=38.28
Capture T1i-2=38.28
8.52 ms
Store T1i-3=33.32
Store T2i-3=33.32
Send T1i-1=50.00
Capture T2i-2=35.62
50.00
54.03
49.93
53.16
Send T2i-1=49.93
Store T2i-1=49.93Capture T1i=54.03
Store T2i-2=35.62
Store T1i-1=50.00
Capture T2i=53.16
T2i-3=33.32
T1i-2=38.28
T1i-1=50.00
T2i=53.16
a2=38.28-33.32=4.96
b2=53.16-50.00=3.16
2=(4.96-3.16)/2=
= +0.9ms (behind)
T1i-3=33.32
T2i-2=35.62
T2i-1=49.93
T1i=54.03
a1=35.62-33.32=2.3
b1=54.03-49.93=4.1
1=(2.3-4.1)/2=
= -0.9ms (ahead)
Speed up
Relay 2
30°19.5°0°
8.14 ms
L90 Current Differential Relay:
Digital “Flywheel”
clock 1 clock 2
“Virtual Shaft”
• If communications is lost, sample clocks continue
to “free wheel”
• Long term accuracy is only a function of the base
crystal stability
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L90 Current Differential Relay:
Zero-sequence Current RemovalThe L90 protection system could be applied to lines with tapped
transformer(s) even if the latter has its windings connected in a grounded
wye on the line side and the transformer(s) currents are not measured by
the L90 protection system..
L90-1 L90-2
I_0
L90 Current Differential Relay:
CT Saturation Detection
Current differential protection is inherently dependent on adequate CT
performance at all terminals of the protected line especially during
external faults. CT saturation, particularly if happens at one terminal of
the line only, introduces a spurious differential current that may cause the
differential protection to misoperate.
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L90 Current Differential Relay:
Breaker-and-a-half The L90 has
advantages on
systems with breaker-
and-a-half or ring bus
configurations. In these
applications, each of
the two three-phase
sets of individual
phase currents (one
associated with eachbreaker) can be used
as an input to a
breaker failure
element.
L90 Current Differential Relay:
Breaker-and-a-half
Benefits:
• For restraint forming, maximum of 2 (or more currents is
used). Conventional sum might not provide enough
restraint.
• CTs matching is done
internally, different CT
ratios possible
• Current are available
individually for BF,
metering etc
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L90 Current Differential Relay:
Breaker-and-a-half
Distributed bus
differential
Up to 4 CTs can be
processed
individually and
summed up with
L90. For application
where buses are
located remotely,this is beneficial as
CT leads don’t allow
applying bus
differential.
L90 Current Differential Relay:
Channel asymmetry
• On SONET/SDH system, transmit and receive channel
delays can be different. Normally, Tx_delay=Rx_delay.
• If one path is broken, it can be re-routed to another
physical fiber, resulting in Tx_delayRx_delay.
RELAY 1
ADM-2 ADM-3
ADM-4
RELAY 2
ADM-1
Tx Rx
TxRx
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L90 Current Differential Relay:
Channel asymmetry• Difference in transmit-receive paths is causing
incorrect synchronization between relays as ping-pong is operating based on assumption that transmit-receive delays are the equal.
• That results in apparent differential current,proportional to the value of the channel asymmetry.
• If currents and channel asymmetry are high enough,relay misoperates.
IDIFFIA IB
Half of the channel
asymmetry in
electrical degrees
L90 Current Differential Relay:
Channel asymmetry
• L90 can cope with channel asymmetry as high as upto 10 ms using GPS signal.
• No additional input is required-GPS clock isconnected to the regular IRIG-B UR input, providingaccurate clock to both events time-stamping andchannel asymmetry compensation algorithm.
RELAY 1
ADM-2 ADM-3
ADM-4
RELAY 2
ADM-1Tx Rx
TxRx
GPS clock GPS clock
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L90 Current Differential Relay:
Channel asymmetry
| Ch1Assymetry | > MAX
REALTIM ECLOCK:IRIG-B SIGNALTYPE
None =0
O R 87LGPSStatus Fail
To Remote RelaysChannels 1and 2
DATA FROM REMOTE
TERMINAL 1
87LCh 1Status (OK=1)
L90POWERSYSTEM:CHNLASYM COMP:
Off = 0
O R
GPS COMPENSATION
Use CalculatedCorrection, Establish andUpdate Memory
Use MemorizedCorrection
RUN
FLEXLOGICOPERAND
87LDIFF GPS FAIL
87LDIFFGPS1FAIL
A N D
SETTINGS
L90POWER SYSTEM:MAX CHNLASYMMETRY:
L90POWER SYSTEM:ROUND TRIPTI MECHANGE:
RUN
|Ch1T-Time New -Ch1T-TIMEOld| > CHANGE
FLEXLOGICOPERAND
87LDIFF1MAX ASYM
FLEXLOGICOPERAND
87LDIFF1TIME CHNG
| Ch2Assymetry | > MAX
RUN
FLEXLOGICOPERAND
87LDIFF2MAX ASYM
FLEXLOGICOPERAND
87LDIFF2TIME CHNG
A N D
Ch1Assymtery
Ch1Round Trip Time
SETTINGS
L90POWERSYSTEM:BLOCK GPS TIMEREF:
Off = 0
FLEXLOGICOPERAND
IRIG-B FAILURE
87LGPS 1Status (OK=1)
FLEXLOGICOPERAND
A N D
O R
|Ch2T-Time New -Ch2T-TIM EOld| > CHANGE
ACTUALVALUES
87LDIFFGPS2FAIL
Ch2Assymtery
FLEXLOGICOPERAND
ACTUALVALUES
DATA FROM REMOTE
TERMINAL 1
A N D
O R
DATA FROM REMOTE
TERMINAL 1
A N D
O R
DATA FROM REMOTE
TERMINAL 2
87LCh 2Status (OK=1)
87LGPS2Status (OK=1) A N D
O R
RUN
ACTUALVALUES
RUN
Ch2Round Trip Time
ACTUALVALUES
GPS function
L90 Current Differential Relay:
Channel asymmetry
• Important consideration is fallback mode if GPS signal is
lost: for example, relay can be programmed to continue
to provide sensitive differential function using memorized
value of last measured channel asymmetry until step
change in the communications path is detected.
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L90 Current Differential Relay:
Channel asymmetry
Asymmetry-disabled
(about 3 ms of
asymmetry present)
Diff. Current
high
Asymmetry-enabled
(about 3 ms of
asymmetry present)Diff. Current
low
L90 Current Differential Relay:
Channel asymmetry
It’s beneficial to monitor
differential current to
raise an alarm if it
becomes relatively high.
This can happen due toasymmetry is present,
problems in CT
secondary. Flexelements
are used for that.
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L90 Current Differential Relay:
Synchronization
+
( 2 – 1)/2
time stamps
SystemFrequency
ComputeFrequencyDeviation
Ping-PongPhase
Deviation
Phase FrequencyLoop Filter
f
+
+
+
_
RELAY 1 RELAY 2
f1f – f1
GPSClock
GPSPhaseDeviation
1
( 2 – 1)/2
+
f
+
+
+
_
f2 f – f2
2
time stamps
ComputeFrequencyDeviation
Phase FrequencyLoop Filter
Ping-PongPhase
Deviation
GPSPhaseDeviation
GPSClock
( 2 – 1)/2
( 2 – 1)/2
Overall Relays synchronizationdiagram
L90 Current Differential Relay:
Synchronization
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L90 Current Differential Relay:
Frequency Tracking1. It is important for current differential to track the
frequency to fit exactly 64 samples within one powercycle and to provide synchronized sampling at eachL90 relay.
2. L90 starts tracking the frequency if current at anyterminal is above 0.125 pu
3. L90 tracks the frequency from positive- sequencecurrent from all terminals.
4. If positive-sequence current is below 0.125 pu, allrelays track to nominal frequency, 50 Hz or 60 Hz.
5. Tracking frequency is displayed in ActualValues\Metering menu.
L90 Current Differential Relay:
Benefits
• Increased Sensitivity w ithout sacrif icing Security:
– Fast operation (11.5 cycles)
– Lower restraint settings / higher sensitivity
– Charging current compensation
– Unique precise synchronization with frequency tracking
– Channel Asymmetry Compensation
– CT saturation detection
– Dynamic restraint ensures security during noise, harmonics,CT saturation or transient conditions
– Reduced CT requirements
– Direct messaging
– Increased redundancy due to master-master configuration
– Reliable CRC-32 communication packet protection againstnoise
– Breaker-and-a half applications
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Lab: setting up 87L
Direct point-to-point Fiber
Test Set 1 Test Set 2
L90 Current Differential Relay:
Lab 1: Setting up 87L
(64Kbps)
Tx Rx
Rx Tx
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L90 Power System menu.
L90 Current Differential Relay:
Lab 1: Setting up 87L
L90 system ischosen
Charging currentenabled/disabled
Channel IDenabled/disabled
Channel IDenabled/disabled
87L Current Differential menu.
87L enabled
Source chosen
Pickup
CT Tap
L90 Current Differential Relay:
Lab 1: Setting up 87L
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L90 Current Differential Relay:
Lab 1: Setting up 87L
87L Current Differential menu.
Slope 1
Slope 2
DTT
External DTT
L90 can accommodate CT ratios mismatch
up to 5 times even if CTs secondary
nominal current is different.
1000/1 2000/5
L90 Current Differential Relay:
Lab 1: Setting up 87L
(64Kbps)
Tx Rx
Rx Tx
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Pickup
Breakpoint
(200% of I nominal)
Restraint 1
Restraint 2
Current Differential major
settings
L90 Current Differential Relay:
Lab 1: Setting up 87L
This portion of logic will not
reset for a continuous
disturbance.
Disturbance Detector-logic
diagram
L90 Current Differential Relay:
Lab 1: Setting up 50DD
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Disturbance Detector-element’s menu
L90 Current Differential Relay:
Lab 1: Setting up 50DD
L90 Current Differential Relay:
Lab 1 Comms Channel Check
Channel Status menu- Actual
Values\Statis\Channel Tests
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L90 Current Differential Relay:
Lab 1: Faults Simulation
Direct point-to-point Fiber
Test Set
(64Kbps)
Tx Rx
Rx Tx
87L should
operate at the
current…
Direct point-to-point Fiber
Test Set
(64Kbps)
Tx Rx
Rx Tx
87L should
NOT operate
L90 Current Differential Relay:
Lab 1: 87L Characteristics Check
Direct point-to-point Fiber
Test Set 1 Test Set 2
(64Kbps)
Tx Rx
Rx Tx
Operate /
Restraint
Characteristics
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L90 Current Differential Relay:
Lab 1: 87L Characteristics Check
User 87L settings
Operate currentRestraint current
Injected currents
Relays response
87LTRIPOP
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
87LTRIPOPA
87LTRIPOPB
87LTRIPOPC
87LTRIP FUNCTION:
AND
AND
AND
AND
SETTING
SETTING SETTING
SETTING
SETTING
SETTING
IA IA >PICKUP
IB IB >PICKUP
IC IC> PICKUP
Enable=1
50DDSV
1-Pole=0
3-Pole=1
87L TRIP SOURCE: 87L TRIP SEAL-IN PICKUP:
87LTRIPSEAL-IN:
87LTRIPSUPV:
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
87LDIFFOPA
87LRECVDDTT A
87LRECVDDTT B
87LRECVDDTT C
87LDIFFOPB
87LDIFFOPC
87LTRIPMODE:
Enable=1
Disable=0
OR
OR
OR
OR
AND
AND
AND
AND
SETTING
Off=0
87LTRIPFORCE3- :
FLEXLOGICOPERAND
OPEN POLEOP
OR
OR
OR
OR
OR0
50
OR
OR
OR
OR
AND
AND
AND
L90 Current Differential Relay:
87L Trip element
87L Trip Logic
87L and DTTare OR-ed
Mode is hosen:
1P or 3P
Supervisingelement 50DD
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87LTRIPOP
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
87LTRIPOPA
87LTRIPOPB
87LTRIPOPC
87LTRIP FUNCTION:
AND
AND
AND
AND
SETTING
SETTING SETTING
SETTING
SETTING
SETTING
IA IA >PICKUP
IB IB >PICKUP
IC IC> PICKUP
Enable=1
50DDSV
1-Pole=0
3-Pole=1
87L TRIP SOURCE: 87L TRIP SEAL-IN PICKUP:
87LTRIPSEAL-IN:
87LTRIPSUPV:
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
87LDIFFOPA
87LRECVDDTT A
87LRECVDDTT B
87LRECVDDTT C
87LDIFFOPB
87LDIFFOPC
87LTRIPMODE:
Enable=1
Disable=0
OR
OR
OR
OR
AND
AND
AND
AND
SETTING
Off=0
87LTRIPFORCE3- :
FLEXLOGICOPERAND
OPEN POLEOP
OR
OR
OR
OR
OR0
50
OR
OR
OR
OR
AND
AND
AND
L90 Current Differential Relay:
87L Trip element
87L Trip Logic
Logic to detectmulti-phaseevolving and
sequential faults
Seal-in outputs if
desirable
Open Poleforces 3P trip
if anotherfault occursduring open
poleconditions
Outputs perphase or 3-phase
Grouped elements
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L90 Current Differential Relay:
Grouped elements
L90 Current Differential Relay:
Grouped: Stub bus
Line disconnect
switch 52b contact
IOC trigger
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Breaker Breaker
LineStub Bus
zone
+ IOC
L90 Current Differential Relay:
Grouped: Stub bus
L90 Current Differential Relay:
Grouped: Distance
L90 phase and ground distance is the same as D60 elements.
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L90 backup distance is complimented by line pickup, power swing
detection, POTT and load encroachment.
L90 Current Differential Relay:
Grouped: Distance
L90 Current Differential Relay:
Grouped: Breaker Failure
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L90 Current Differential Relay:
Grouped: Breaker Failure
3- Pole Breaker Failure
3- Pole Breaker Failure
L90 Current Differential Relay:
Grouped: Breaker Failure
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3- Pole Breaker Failure
L90 Current Differential Relay:
Grouped: Breaker Failure
3- Pole Breaker Failure
L90 Current Differential Relay:
Grouped: Breaker Failure
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1- Pole Breaker Failure
L90 Current Differential Relay:
Grouped: Breaker Failure
1- Pole Breaker Failure
L90 Current Differential Relay:
Grouped: Breaker Failure
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L90 Current Differential Relay:
Grouped: Open Pole Detector
Control elements
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L90 Current Differential Relay:
Control Elements
Control elements
available in L90
Synchrocheck
Logic
L90 Current Differential Relay:
Control: Synchrocheck
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L90 Current Differential Relay:
Control: Synchrocheck
3-phase
line VT
1-phase
bus VT
Time that the twovoltages remain withinthe admissible angledifference
AutoReclose sequence
L90 Current Differential Relay:
Control: AutoReclose
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AutoReclose
logic
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERAND
AR3-P/2RIP
SETTING
SETTING
AND
OR
OR
OR
OR
OR
OR AND
OR
AND
AND
AND
AND
AND
OR
OR
ARINCOMPLETESEQ.
TIMER:
ARLO
ARINCOMPLETESEQ
ARFORCE3PTRIP
ARZONE1EXTENT
RESET(tosheet 2)
827089AD.CDR
AR3-PDEADTIME2:
0
0
OR
OR
SETTING
SETTING
Off =0
AND
OR
OR
AREXTENDDEADTIME
1:
CLOSE(topage 2)
ARDEADTIME1
EXTENSION:
0
(Topage2, Reset ARTRANSFERTIMER)
To:ARFORCE3PTRIP
(Evolvingfault)
ARINITIATE
Evolvingfault
BKRFAILTORECLS(fromsheet 2)
ARDISABLED
FLEXLOGICOPERAND
FLEXLOGICOPERAND
FLEXLOGICOPERANDS
AR1-PRIP
AR3-P/1RIP
ARENABLED
ARDISABLED
SETTING
SETTING
LO
OR
OR
OR
AND
OR
AND
AND
OR
OR
OR
AND
AND
AR3-PDEADTIME1:
AR1-PDEADTIME:
0
0
SETTING
0
ARBLKTIMEUPON MAN
CLS:
FLEXLOGICOPERAND
ARRIP
0.5cycle
FLEXLOGICOPERAND
FLEXLOGICOPERAND
SETTING
ARSHOTCOUNT>0
PHASESELECTMULTI-P
D60Relay OnlyFromPhaseSelector
ARPAUSE
SETTING
SETTING
SETTING
SETTING
SETTING
BKRONEPOLEOPEN:
BKR3POLE OPEN:
ARRESET:
ARMULTI-PFAULT:
ARM0DE:
Off =0
Off =0
Off =0
Off =0
Off =0
1& 3Pole
1Pole
3Pole- A
3Pole-B
OR
OR
SHOTCOUNT=MAX
CLOSEBKR1ORBKR2
RESET
BKRONEPOLE OPEN
BKR3POLE OPEN
F r o m s h e e t 3
D 6 0 R e l a y O n l y F r o m T r i p O u t p u t
D60RelayOnly
F r o m S h e e t 2
FLEXLOGICOPERAND
FLEXLOGICOPERAND
SETTING
TRIP1-POLE
LINEPICKUP OP
TRIPARINIT3-POLE
AR3PTDINIT:
SETTING
SETTING
SETTING
SETTING
Enable=1
Disable=0
ARFUNCTION:
ARBLOCK:
ARBKRMANCLOSE:
BKRMA NUALCLOSE:
AR1PINIT:
Off =0
Off =0
Off =0
SETTING
AR3PINIT:
Off =0
Off=0
OR
(Fromsheet3)
FLEXLOGICOPERAND
5ms
0
ANDOR
L90 Current Differential Relay:
Control: AutoReclose
AutoReclose
logic
BKRCLOSED(frompage3)
RESET
Tosheet 3
LO
LO
LO
LO
AND
AND
827090A9.CDR
2ms
2ms
OR
OR
OR
OR
S
ROR
Latch
AND
AND
AND
AND
OR
OR
OR
AND
AND
AND
AND
AND
AND
OR
AND
AND
L90 Current Differential Relay:
Control: AutoReclose
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AutoReclose
logic
L90 Current Differential Relay:
Control: AutoReclose
This piece of the AR is
reading status of
breaker(s) and feeds
main AR logic to
proceed action further
accordingly number of
breakers, mode chosen
and sequence chosen.
Breaker Function AutoReclosure Function
LEDs
L90 Current Differential Relay:
Control: AutoReclose
Breakers are set inSystem Setup\
Breakers
AR is set per user ’srequirements (reads
breakers status
automatically) LEDs are needed to
know AR ststus
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CT Fail Detector is designed to detect
failures in CT secondary circui try
L90 Current Differential Relay:
Control: CT Fail Detector
L90 Current Differential Relay:
Control: VT Fuse Fail
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POTT scheme requires 1-bit
comms channel, for example
PLC.
L90 Current Differential Relay:
Control: POTT
L90 1
Line 2
Line 1
C60 3
L90 1-2 LAN
L90 2
B3
B2
B1
B4
Substation 1
Ethernet
Substation
2
B5
Ethernet
L90 Current Differential Relay:
Direct Inputs and Outputs
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L90 Current Differential Relay:
Direct Inputs and Outputs
This is activein 3-terminal
only
Defaultmeans state
whenchannel is
brokenDirect
Outputs areassigned with
Flexlogicoperands
L90 Current Differential Relay:
Direct Inputs and Outputs
Channel statuscontrols either
Direct Input is readfrom the received
data or set todefault
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Local Relay Remote Relay
L90 Current Differential Relay:
Direct Inputs and Outputs
Direct Input 1-1 (BFat remote S/S) isassigned to a trip
gate.
Example
Breaker Fail isassigned to Direct
Output 1-1
Monitoring & Metering
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L90 Current Differential Relay:
Metering: 87L
L90 Current Differential Relay:
Oscillography: 87L analogs
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Thank you.