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Protection Discrimination and Timing
On the ADVC Controller
With a flexVUE Operator Interface
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Schneider Electric 2 < AUTHOR >
The purpose of this presentation is to show howprotection discrimination is achieved with the ADVCController.
The following topics will be covered:
Discrimination by time.
Discrimination by current.
Discrimination by time and current.
Standard and non standard curves available on the ADVC.
How protection curves can be modified to assist inachieving coordination and discrimination.
Discrimination Overview
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Schneider Electric 3 < AUTHOR >
Principle of Discrimination
Correct discrimination ensuresthat the faulty part of a power
system only is isolated as quicklyas possible, leaving all of thefault-free parts energised.
Fault F1 may be detected by
protection devices A, B, C and D.
Time to Trip for D should beshorter than C which is shorterthan B etc.
This ensures that only the circuitnecessary to clear the fault isdisconnected by either primary orback-up protection.
A
B
C
D
F1
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Schneider Electric 4 < AUTHOR >
Discrimination Interval
The difference in operation time
T between two successive
protection devices is thediscrimination interval.
It takes into account
-Breaking timeTc
of the
downstream circuit breaker, which
includes the breaker response time
and the arcing time.
-Time delay tolerances dT
-Upstream protection unit overshoot
time tr.
-A safety margin m.
T should therefore satisfy the
relation:
-T Tc + tr +2dT + m
Example:
-Tc = 50 ms
-dT = 30 ms
-Tr = 30 ms
TB TA
dTB dTATcB m trA
30ms 30ms 30ms50ms 60ms
Discrimination Interval T
200 ms
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Schneider Electric 5 < AUTHOR >
Time to Trip
The time delay between Pickup
and Trip is determined by the
protection settings applied.
The Time to Trip is dependant on
whether the active trip is set to:
-Definite Time
-Instantaneous Only
-Inverse Time
Possible Active Trips
-Trip 1
-Trip 2
-Trip 3
-Trip4
-Single Shot
-Work Tag
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Schneider Electric 6 < AUTHOR >
Trip Settings on the flexVUE Operator Interface
PROTECTION MENU
Protection Global
Protection Trip Settings
Protection Control
Directional Elements
ENGINEERING MENU
Protection menu
Configuration menu
Power quality
Telemetry menu
Automation menu
Measurements menu
PROT TRIP SETTINGS
Trip 1, 2, 3, 4
(Reclose time, Protection &
reset curve for P, E, SEF,
NPS)
Single Shot
(SS reset time, Protection
& reset curve for P, E, SEF,
NPS)
Work Tag
(Protection & reset curve
for P, E, SEF, NPS)
Under Over Frequency
(Under, Over, Normal
Close, Low V inhibit,
Bushing)
Under Over Voltage
(Under, Over, Config)
Loss of Phase
(On/Off/Alarm, Voltage,
Timeout)
7/28/2019 02 ADVC_206B_FV Protection Coordination and Timing
7/39Schneider Electric 7 < AUTHOR >
Types of Discrimination
Various means can be used by
the ADVC controller to implement
discrimination between devices.
Time-based discrimination
-Definite Time
Current-based discrimination
-Instantaneous Only
Discrimination based on time and
current-Inverse Curves
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Time-Based Discrimination
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Time-Based Discrimination
Time-based discriminationconsists of assigning different
time delays to the overcurrentprotection units distributedthrough the power system.
The closer the relay is to thesource, the longer the time delay.
Advantages:
-Provides back-up
-It is simple
Drawbacks
-The longest fault clearance timeoccurs for faults closest to thesource where the fault level ishighest.
A
B
C
D
F1
DT = 0.2s
DT = 0.5s
DT = 0.8s
DT = 1.1s
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Trip 1 Phase Protection Definite Time
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Schneider Electric 11 < AUTHOR >
1.0 s Definite Time Curve
> 200A
1.0s 4.00
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Schneider Electric 12 < AUTHOR >
1.0 s Definite Time Curve with x4 Instantaneous
>800A
1.0s
200-800A
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Schneider Electric 13 < AUTHOR >
Current-Based Discrimination
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Schneider Electric 14 < AUTHOR >
Current-Based Discrimination
Current-based discrimination
works on the principle that the
further the fault is from the source,the lower the fault current will be.
The threshold is set to a value
lower than the minimum short-
circuit current caused by a fault inthe protected section and higher
than the maximum current caused
by a fault in the next section.
Each protection device should
only pickup for faults located in
the section of feeder immediately
downstream.
A
B
C
D
F1
IsC=490A
IsB=780A
IsA=960A
IscAmin = 1000A
IscBmin = 800A
IscCmin = 500A
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Schneider Electric 15 < AUTHOR >
Current-Based Discrimination with Transformers
For sections of lines separated by
a transformer, it can be of benefit
to use this system since it issimple, cost effective and fast
(instantaneous).
IsA < IscAmin
IsA=960A
F1
IscAmin=1250A
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Schneider Electric 16 < AUTHOR >
Current-Based Discrimination with Transformers
Protection devices should be set
such that:
IscBmax < IsA < IscAmin
Time delays TA and TB are
independent and TA may be
shorter than TB
Drawbacks:
-The upstream protection device (A)
does not provide back-up for the
downstream device.
-In practice it is difficult to define the
settings for two cascading
protection devices and still ensure
discrimination unless there are
transformers between sections.
IsB=600A
IscBmax 760A
F1
IscAmin=1250A
IsA=960A
TA=0.6s
TB=0.9s
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Schneider Electric 17 < AUTHOR >
Current-Based Discrimination with Transformers
IsB=600A
IscBmax 760A
F1
IscBmax < IsA < IscAmin
IscAmin=1250A
IsA=960At
I
AB
IsB IscB
maxIsA IscA
min
TA
TB
TB=0.9s
TA=0.6s
To ensure discrimination:
1.25 IscBmax < IsA < 0.8 IscAmin
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Schneider Electric 18 < AUTHOR >
Trip 1 Phase Protection Instantaneous Only
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Schneider Electric 19 < AUTHOR >
Instantaneous Only Curve
0.3
200A
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Schneider Electric 20 < AUTHOR >
Instantaneous Only Curve with Minimum Time
0.3
> 200A
0.30s
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Schneider Electric 21 < AUTHOR >
Discrimination by Time and Current
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Schneider Electric 22 < AUTHOR >
Discrimination by Time and Current
A combination of both time andcurrent discrimination can be
used to achieve totaldiscrimination with built-inredundancy or back-up.
In the example below device Buses Definite Time and device Auses Definite Time with anInstantaneous multiplier.
A
B
t
I
T
B A
A DT
A Inst
B DT
IsB IsA IscB IinstA IscA
Feeder 1
Feeder 2
A is thePrimary
protection
device for
Feeder 1
Back-up for
feeder 2
B is the
Primary
protection
device for
Feeder 2
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Schneider Electric 23 < AUTHOR >
IDMT Inverse Time Curves
With this characteristic, the time ofoperation is inversely proportional
to the fault current level and theactual characteristic is a functionof both time and currentsettings.
ADVC Inverse Curves
-IEC255Standard Inverse
Very Inverse
Extremely Inverse
-IEEE
Standard Moderately Inverse
Standard Very Inverse
Standard Extremely Inverse
-TCC
42 Non-standard curves
I
t
1 1
0
1
0
0
1
0
0
0
0.01
0.1
1.0
10.0
IEC255 I C
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Schneider Electric 24 < AUTHOR >
IEC255 Inverse Curves
IEC60255 Standard Curves
Standard Inverse Time
Time to Trip = 0.14 / ( Im0.02 1)
Very Inverse Time
Time to Trip = 13.5 / ( Im 1)
Extremely Inverse Time
Time to Trip = 80.0 / (Im2 1)
IEC255 Inverse Curves
IEEE I C
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Schneider Electric 25 < AUTHOR >
IEEE Inverse Curves
IEEE Standard Inverse Curves
Moderately Inverse Time
Time to Trip = (0.0515( Im0.02
1)) + 0.114
Very Inverse TimeTime to Trip = (19.61 / (Im2 1))
+ 0.491
Extremely Inverse Time
Time to Trip = (28.2 / (Im2 1))
+ 0.1217
IEEE Inverse Curves
TCC N St d d I C
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Schneider Electric 26 < AUTHOR >
TCC Non-Standard Inverse Curves
The group of 42 TCC non-standard curves are generally
plotted curves that do not complyto a formulae.
-TCC136
-TCC101
-TCC131
-TCC121
-TCC161
-TCC200
Selection of TCC Inverse Curves
S l ti I C
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Schneider Electric 27 < AUTHOR >
Selecting an Inverse Curve
IEC255 St d d I C
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Schneider Electric 28 < AUTHOR >
IEC255 Standard Inverse Curve
400A x2
10.03s
2000A x10
2.97s
2.00
IEC255 St d d I C TM 2
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Schneider Electric 29 < AUTHOR >
IEC255 Standard Inverse Curve TM x2
2.00
400A x2
20.06s
0.20
2000A x10
5.94s
IEC255 St d d I C TM 0 2
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Schneider Electric 30 < AUTHOR >
IEC255 Standard Inverse Curve TM x0.2
2.00
400A x2
2.006s
0.20
2000A x10
0.59s
IEC255 St d d I C TM 0 2
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Schneider Electric 31 < AUTHOR >
IEC255 Standard Inverse Curve TM x0.2
2.00
400A x2
2.006s
0.20
2000A x10
0.59s
0.80
IEC255 Standard Inverse Curve Min Time = 0 8s
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Schneider Electric 32 < AUTHOR >
IEC255 Standard Inverse Curve Min Time = 0.8s
2.00
400A x2
2.006s
0.20
2000A x10
0.80s
0.80
0.20
IEC255 Standard Inverse Curve Add Time = 0 2s
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Schneider Electric 33 < AUTHOR >
IEC255 Standard Inverse Curve Add Time = 0.2s
2.00
400A x2
2.206s
0.20
2000A x10
0.80s
0.80
0.20
IEC255 Standard Inverse Tripping Times
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Schneider Electric 34 < AUTHOR >
IEC255 Standard Inverse Tripping Times
BCDE
40A
IEC255SI
200A
IEC255SI
A
F1
400A
F2
2500A
Current Trip
ACR Setting Multiple Time
Fault F1 400A B X 10 2.97s
E X 2 10.03s
Fault F2 2000A E X 12.5 2.7s
Effect of Applying Time Multiplier = 0 2
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Schneider Electric 35 < AUTHOR >
Effect of Applying Time Multiplier = 0.2
BCDE
40A
IEC255SI
200A
IEC255SI
A
F1
400A
F2
2500A
Current Trip Time
ACR Setting Multiple Time Multiplier
0.2
Fault F1 400A B X 10 2.97s 0.594s
E X 2 10.03s 2.006s
Fault F2 2000A E X 12.5 2.7s 0.54s
Effect of Applying Minimum Time = 2 0s
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Schneider Electric 36 < AUTHOR >
Effect of Applying Minimum Time = 2.0s
BCDE
40A
IEC255SI
200A
IEC255SI
A
F1
400A
F2
2500A
Current Trip Time Minimum
ACR Setting Multiple Time Multiplier Time
0.2 2.0s
Fault F1 400A B X 10 2.97s 0.594s 2.0s
E X 2 10.03s 2.006s 2.006s
Fault F2 2000A E X 12.5 2.7s 0.54s 2.0s
Effect of Applying Additional Time = 1 0s
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Schneider Electric 37 < AUTHOR >
Effect of Applying Additional Time = 1.0s
BCDE
40A
IEC255SI
200A
IEC255SI
A
F1
400A
F2
2500A
Current Trip Time Minimum Additional
ACR Setting Multiple Time Multiplier Time Time
0.2 2.0s 1.0s
Fault F1 400A B X 10 2.97s 0.594s 2.0s 2.0s
E X 2 10.03s 2.006s 2.006s 3.006s
Fault F2 2000A E X 12.5 2.7s 0.54s 2.0s 2.0s
Applying an Instantaneous Modifier
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Schneider Electric 38 < AUTHOR >
Applying an Instantaneous Modifier
BCDE
40A
IEC255SI
200A
IEC255SI
A
F2
3000A
Current
ACR Setting
Multiple
Trip
Time
Instantaneous
Multiplier
Additional
Time
Minimum
Time
X 14 1.0s 2.0s
Fault F2 3000A E X 15 2.52s
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Protection Discrimination - Review
The main objectives of Protection Coordination are:
When a fault is detected, only the smallest part of the network necessary to
isolate that fault should be disconnected.This means that for a given fault the primary protection device should operate
in the shortest possible time to clear the fault.
If the primary protection device fails to clear the fault in the expected time, aback-up device should clear the fault in a longer but still acceptable time.
Three types of discrimination can be used by the ADVC controller:
1. Discrimination by Time Definite time2. Discrimination by Current Instantaneous Only
3. Discrimination by both Time and Current Inverse Curves
Definite Time curves can be modified by:
Instantaneous
Instantaneous Only curves can be modified by:Minimum Time
Inverse Curves can be modified by:
Time Multiplier, Instantaneous, Additional Time and Minimum Time.