- Auto-reclosers are used to temporarily disconnect faulted lines to allow arcs to extinguish for transient faults. They attempt reclosure 1-3 times before locking out permanently for sustained faults.
- They help maintain stability on extra high voltage systems and are governed by international standards.
- Recloser selection depends on voltage rating, continuous current rating, interrupting rating, and minimum tripping current to ensure proper sensitivity.
2. Commercial ACRs are governed by the ANSI/IEEE C37.60, IEC 62271-111 and
IEC 62271-200 standards.
3. • 80-90% of the line faults are short lived (transient) and can be removed faster if the
disturbed phase is disconnected from the system momentarily so that the arc is
extinguished.
• If the fault is not cleared at first attempt then a double or triple attempt of isolation
and reclosure can be made. If the fault still persists then breaker is permanantly
opened.
• Auto-reclosing helps to maintain stability & synchronism in EHV systems.
Automatic Circuit Recloser (ACR)
• If recloser is unsuccessful the auto-reclose relay locks out the circuit breaker. Some
schemes provide a lockout relay with a flag, with provision of a contact for remote
alarm. The circuit breaker can then only be closed by hand.
• This action can be arranged to reset the auto-reclose relay element automatically.
CB lock-out
7. • The initial reclosure can be high speed (0.2 -0.5sec) or delayed for 3 - 5 seconds. This allows for
de-ionization time for fault arc.
• Typical schedule might be instantaneous, followed by 30sec, or 35sec, followed by 15sec. If the
circuit still continues to trip, the fault is declared as permanent and the recloser is locked out.
• Reclosers use three phase and single phase oil or vacuum circuit breakers for overhead
distribution lines.
• With underground network, faults tend to be more often permanent and reclosers are not
recommended.
• In case of large synchronous motors, distributed generators or induction motor loads, it is
recommended that sufficient time is allowed for under-frequency relays to trip these sources of
back emf out-of-the-circuit.
8. Application
Application Methodology Requirements
Renewable
Connection
Modern Recloser Controllers use ANSI 25
Synchrocheck, 59N Neutral Voltage
Displacement, Synchrophasors, ANSI
25A Auto-Synchronizer and other voltage
protection
Voltage Sensing on
both sides of Recloser
Substation
Circuit
Breakers
Using Reclosers installed in a Substation where
peak fault currents do not exceed the maximum
rated interrupting capacity, usually only Rural
Substations.
Typically maximum bus fault
currents below 16kA
9. Application
Application Methodology Requirements
Single
Wire Earth
Return
Network
Protection
A Single Phase Recloser unit
can be deployed. SWER network design topology
is discouraged in modern electrical engineering
due to safety reasons, but due to cost savings it is
sometimes deployed. Single Phase Recloser can
be used to improve safety on these lines
Single Phase Recloser
Single
Phase
Laterals
Permanent faults are typically 3 phase lockout,
despite the ability to lock single phases, as the
risk of circulating currents is
high.
Single Triple Recloser or Single
Phase Recloser System
10. Application
Application Methodology Requirements
Mid-
Feeder
Protection
Conventional recloser deployment Conventional
recloser
Fire
risk
mitigation
Not required as SEF protection pickup at 500mA
removes 80% risk of fire start.
Recloser with SGF/SEF
capability at 500mA.
Smart grid
distribution
network
automation
Centralized or distributed Remote communication
through SCADA or otherwise
configurable
from controller
11. Recloser control panel
1. Local human-machine interface
2. Indicator lights
3. Front panel push-buttons
4. Hot line tagging feature
5. Front mounted RS-232 port
6. Separate open and close
7. push-buttons
12. Recloser selection
Reclosers have to be selected by considering the following factors.
• Voltage Rating
• Continuous current Rating : This is the maximum load current the recloser has
to carry.
• Maximum Symmetrical Interrupting Rating: The maximum symmetrical fault
current should not exceed this rating.
• Minimum Tripping current : This is the minimum fault current that a recloser
will clear. It is equal to two times the continuous current rating. Usually
tolerance is ±10%. This decides the sensitivity of the recloser.
14. EXAMPLE
Consider a three phase distribution
system with a single
phase tap as shown. Maximum load on
this single phase tap is 40A and that on
three phase line is 200A. Fault currents at
F1 ,F2 , F3 and F4 are also shown in the
Table . Select the ratings of reclosers at A
and B.
15. EXAMPLE
Recloser at B
Max. load current on this tap= 40A
Recloser max. current rating= 40x1.5= 60A (25-50% larger is taken considering load growth)
Max. single phase fault current at F3= 1750A
So, recloser marked in green is selected from table
Min. tripping current= continuous current rating x2m10%= 100x2m10%= 220A
Min. fault current in that line at F4= 250A
Thus 220A recloser will be able to protect entire line
Line voltage= 11kV hence recloser rated maximum voltage should be= 15.5 kV rms
16. EXAMPLE
Recloser at A
Max. load current on the three phase line= 200A
Recloser max. current rating= 200x1.25= 250A (25-50% larger is taken considering load growth)
Max. single phase fault current at F1= 3500A
So, recloser marked in red is selected from table
Min. tripping current= continuous current rating x2m10%= 280x2m10%= 616A
Min. fault current in that line at F2= 280A
Thus 280A recloser will NOT be able to protect entire line
Hence, in order to increase sensitivity ground relay can be added here.
