oc relay seting
TRANSCRIPT
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Power System Protection
S.A.Soman
Department of Electrical EngineeringIIT Bombay
Fundamentals of Overcurrent Protection
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2 Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3
Pick up Current SettingGuidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2 Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3
Pick up Current SettingGuidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Limitations of a Fuse
It is difficult to control the time to trip.This makes primary backup relay coordination difficult.
Once fuse melts, it has to be replaced for
reenergization of the equipment.
Thus it is difficult to have remote operation.
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2 Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3
Pick up Current SettingGuidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Algorithm for Overcurrent Relay
Set reference or threshold for discriminating
overcurrent Iref.Measure device current I.
Compute the ratio abs( IIref) which is known as the Plug
Setting Multiplier.
Trip the device, if PSM is above the threshold. Thethreshold is always greater than 1.
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2 Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3 Pick up Current Setting
Guidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent RelayTime Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Time Multiplier Setting
Overcurrent relays normally play the dual roles of
primary and backup protection.
Backup action requires a wait state.By providing the additional setting feature of TMS, this
can be achieved.
TMS is defined as the ratio TTm
, where T is the desired
relay operating time for a given PSM and Tm is the
corresponding operating time at TMS=1.
Relay operating time can be varied by varying the TMS
setting.
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Classification of Overcurrent Relay
Instantaneous relay
Its action is very fast.It has only pick up setting.It does not have any TMS setting.This relay is not suitable for backup protection.
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Power System
Protection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Classification of Overcurrent Relay
Instantaneous relay
Its action is very fast.It has only pick up setting.It does not have any TMS setting.This relay is not suitable for backup protection.
Time delayed definite time relay
It can be adjusted to issue trip decision after a specified
delay.This delay is independant of PSM value.It has both time setting and pick up setting.It is used for short length feeders.
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Power System
ProtectionS.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Overcurrent Protection Using Definite Time Relay
R1 trips without any intentional time delay.
R2 has to coordinate with R1 and its operation is
delayed by CTI.
R3 has to back up R2 and it is again time delayed.
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Power System
ProtectionS.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2 Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3 Pick up Current Setting
Guidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power System
ProtectionS.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Lack of Coordination Between Fuse and DT relay
DT relay R1 has to back
up fuse.
After point X relay acts
faster than fuse.
This lack of coordination
is due to different
characteristics of fuse
and relay.This lead to the
development of inverse
characteristics for
overcurrent relay.
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Power System
ProtectionS.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Classification of Overcurrent Relay
Inverse definite minimum time relayIt is inverse in the initial part and tends to approach adefinite minimum operating time characteristics as thecurrent becomes high.This is the most widely used characteristics.
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Power System
ProtectionS.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE Standard
Equations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2
Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3 Pick up Current Setting
Guidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power System
ProtectionS.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
IEC Standard Equations for Inverse Characteristics
Standard Inverse Characteristics
t = TMS0.14
(I/Is)0.02 1
Very Inverse Characteristics
t = TMS13.5
(I/Is) 1
Extremely Inverse Characteristics
t = TMS80
(I/Is)2 1
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2
Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3 Pick up Current Setting
Guidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
http://find/ -
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
IEEE Stanard Equations for Inverse Characteristics
Moderately inverse: t= TD7
0.0515
(I/Is)0.021
+ 0.114
Very inverse: t=TD
7
19.61(I/Is)21+ 0.491
Extremely Inverse: t= TD7
28.2
(I/Is)21
+ 0.1217
US CO8 Inverse: t=TD
7 5.95
(I/Is)2
1+ 0.18
US CO2 Inverse: t= TD7
0.02394
(I/Is)0.021
+ 0.01694
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
IEEE Standard Curves
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2
Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3 Pick up Current Setting
Guidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Faults are classified into two:
Phase fault which do not involve ground.
Earth fault which involve ground.
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Guidelines for Setting Pickup Current for Phase Fault
Relays
Pickup current should be above the maximum load
current.Pickup current should be below minimum fault current.
Pickup current should also be below the minimum fault
current of the feeder that it has to back up.
The back up relay also should provide time for primaryrelay to operate. This time interval is known as
coordination time interval.
F d l f O P i
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2
Classification of Overcurrent RelayLack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3 Pick up Current Setting
Guidelines
Primary and Back up Relays
Setting and Coordination
4 Summary
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Algorithm for Identifying Primary and Backup Relays
Identify leaf nodes and
root nodes.
Find the parents of theactive child nodes.
The corresponding
relays should back up
the leaf node relays.
Update active child
nodes to corresponding
parent node.
F d t l f O t P t ti
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
F d t l f O t P t ti
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Fundamentals of Overcurrent Protection
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time Multiplier
Setting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Fundamentals of Overcurrent Protection
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time MultiplierSetting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
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Fundamentals of Overcurrent Protection
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time MultiplierSetting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
1 Principles of Overcurrent ProtectionLimitations of a Fuse
Algorithm for Overcurrent Relay
Time Multiplier Setting
2 Classification of Overcurrent Relay
Lack of Coordination Problem
IEC Standard Equations
IEEE Standard Equations
3 Pick up Current Setting
GuidelinesPrimary and Back up Relays
Setting and Coordination
4 Summary
Fundamentals of Overcurrent Protection
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Power SystemProtection
S.A.Soman
Principles ofOvercurrentProtection
Limitations of a Fuse
Algorithm for
Overcurrent Relay
Time MultiplierSetting
Classificationof OvercurrentRelay
Lack of Coordination
Problem
IEC Standard
Equations
IEEE StandardEquations
Pick upCurrentSetting
Guidelines
Primary and Back up
Relays
Setting and
Coordination
Summary
Fundamentals of Overcurrent Protection
Algorithm for Setting and Coordination of Overcurrent
Relays in a Radial System
Initialize the coordination tree.
Are there any leaf nodes except the root? If yes, go to
step 3, else go to step 7.
Identify the leaf node in coordination tree.
If the PSM of these relays are not set so far, set their
PSM.
Identify the parents of leaf nodes in step 3. Compute
their PSM and TMS for backup protection andcoordination.
Delete the leaf nodes. Update the coordination tree and
go back to step 2.
Coordination activity is complete.
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