This document discusses auto-reclosing, which aims to minimize power interruptions by automatically reconnecting faulty lines after faults. It describes the benefits of auto-reclosing such as reduced outages and manpower. It also discusses different types of faults and various auto-reclosing schemes for transient, permanent, and EHV transmission line faults. Factors considered for high speed auto-reclosing include protection characteristics, de-ionization time, circuit breaker performance, and reclaim time. Single phase auto-reclosing is also covered. The document concludes by describing features of auto-reclosing schemes and examples of auto-isolation in single switch and 4 switch mesh corner substations.

1. Auto - Reclosing

2. Benefits Of Auto - Reclosing
• Minimizing the interruption of supply
• Maintenance of system stability and Synchronism
• Minimum Outage and least expenditure of manpower
• Ability to run substation unattended

3. Type Of Faults
• Transient Fault
• Semi Permanent fault
• Permanent Fault

4. Auto reclose Scheme for Transient Fault

5. Auto reclose Scheme for Permanent Fault

6. Auto reclose on EHV Transmission
Line

7. FACTORS CONSIDERED IN HIGH SPEED
AUTO RECLOSING ON
EHV SYSTEMS
• Protection Characteristics
• De- Ionization of Fault Arc
• Circuit Breaker Characteristics
• Reclaim Time
• Number of Shots

8. De- Ionization of Fault Arc
• In single Pole switching De- Ionization time required is more

9. SINGLE PHASE AUTO – RECLOSING
• Maintenance of System Integrity
• Reduced switching overvoltage due to reclosing
• Reduced shock to generators.
Sudden changes in mechanical output are less
DISADVANTAGE
• Longer De – ionization time

10. Delayed Auto-Reclose Application
1. Densely interconnected systems.

Where the Loss of a single line is unlikely to
cause loss of synchronism between two ends
2. Dead Time is allowed to be long enough for any
power swings due to fault and tripping allowed
to decay before reclosing

a) Less shock to system than with high speed
A/R
b) Problems of arc de – ionization times, and
circuit breaker operating charactersitics are
eliminated

11. Delayed Auto- Reclosing
Protection
High speed not critical for system stability
desirable to limit fault damage
improves probability of successful A/R
Dead Time
Allow for power swings and rotor oscillations to die down.
Different settings for opposite feeder ends.
Typically 5 to 60 secs.

12. Scheme Operation
• Live bus/ Dead Line Charging
• Other end closing under synchronism check relay
• Live Bus/ Live line charging

13. Synchronism check relay
• Phase Angle Difference
20 – 45 if exceed it waits to lie within the range
• Voltage
under voltage/differential voltage
• Rate of change of Frequency
frequency difference check either by direct
measurement or by using timer in conjunction

14. Operating feature of Auto reclosing schemes
• Initiation
• Dead Timer
• Anti Pumping Devices
• Reclaim timer
• CB Lockout
• Manual Closing
• Multi Shot Scheme

15. Auto-isolation - Single Switch
Substation
• Transient Fault - Line 1
– 120/G1/Remote Open
103 120 203
– 120/Remote Reclose
Line 1
Line 2
– T1 Energised
113 213
– G1 Close After Time Delay
• Persistent Line Fault
T1 T2
– 120/Remote Opens Again
– 103 Opens Automatically
G1 G2
– 120 Closes Followed By G1
– T1/T2 Fed From Line 2
• Transformer Fault
– 120/G1/Remote Trip
– 113 Auto Opens
– G1 Lock Out
– 120/Remote Reclose

16. 4 Switch Mesh Corner
 Transient Line Fault
 120/420/G1 Trip
G1 LV CB
 120 Dead Line Charge
 420 Check Sync
Line 1 103
113
420  G1 Check Sync If Req.
 Persistent Line Fault
 120 Re-trips
HV Mesh
 103 Auto Isolation
120
CB
 120/420/G1 Seq. Close
 Transformer Fault
 120/420/G1 Trip
 113 Auto Isolation
 120/420 Sequence Close
 G1 Locked Out

17. 4 Switch Mesh Corner
G1 LV CB
 Transient Mesh Corner Fault
113
Line 1 103 420  120/420/G1 Trip
 Reclose In Sequence
 Persistent Mesh Corner Fault
120
HV Mesh
CB  120 Re Trip
 All CB`s Lockout
 103 Auto Isolation

18. Auto - Reclose Blocking
• Receipt of transfer Trip
• Manual Trip
• Breaker failure
• Three phase Fault
• Faults On Buses
• Under frequency/ Under voltage
load shedding trips

19. Thank you