Application Notes
P44x/EN AP/E33
MiCOM P441/P442 & P444
Page 127/220
4.5.2
Benefits of Autoreclosure
An analysis of faults on any overhead line network has shown that 80-90% are transient in
nature. Lightning is the most common cause, other possibilities being clashing conductors
and wind blown debris. Such faults can be cleared by the immediate tripping of one or more
circuit breakers to isolate the fault, followed by a reclose cycle for the circuit breakers. As
the faults are generally self clearing ‘non-damage’ faults, a healthy restoration of supply will
result.
The remaining 10 - 20% of faults are either semi-permanent or permanent. A semi-
permanent fault could be caused by a small tree branch falling on the line. The cause of the
fault may not be removed by the immediate tripping of the circuit, but could be burnt
away/thrown clear after several further reclose attempts or “shots”. Thus several time
delayed shots may be required in forest areas.
Permanent faults could be broken conductors, transformer faults or cable faults which must
be located and repaired before the supply can be restored.
In the majority of fault incidents, if the faulty line is immediately tripped out, and time is
allowed for the fault arc to de-ionise, reclosure of the circuit breakers will result in the line
being successfully re-energised, with obvious benefits. The main advantages to be derived
from using autoreclose can be summarised as follows:
•
Minimises interruptions in supply to the consumer;
•
A high speed trip and reclose cycle clears the fault without threatening system
stability.
When considering feeders which are partly overhead line and partly underground cable, any
decision to install auto-reclosing would be influenced by any data known on the frequency of
transient faults. When a significant proportion of the faults are permanent, the advantages of
auto-reclosing are small, particularly since reclosing on to a faulty cable is likely to aggravate
the damage.
At subtransmission and transmission voltages, utilities often employ single pole tripping for
earth faults, leaving circuit breaker poles on the two unfaulted phases closed. High speed
single phase autoreclosure then follows. The advantages and disadvantages of such single
pole trip/reclose cycles are:
•
Synchronising power flows on the unfaulted phases, using the line to maintain
synchronism between remote regions of a relatively weakly interconnected system.
•
However, the capacitive current induced from the healthy phases can increase the
time taken to de-ionise fault arcs.
Summary of Contents for MiCOM P441
Page 1: ...MiCOM P441 P442 P444 Numerical Distance Protection VC2 x Technical Guide P44x EN T E44...
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Page 4: ...P44x EN T E44 Technical Guide Page 2 2 MiCOM P441 P442 P444 BLANK PAGE...
Page 5: ...Pxxxx EN SS C11 SAFETY SECTION...
Page 6: ......
Page 8: ...Pxxxx EN SS C11 Page 2 10 Safety Section BLANK PAGE...
Page 17: ...Update Documentation P44x EN AD E44 MiCOM P441 P442 P444 UPDATE DOCUMENTATION VERSION C2 X...
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Page 22: ...P44x EN AD E44 Update Documentation Page 4 82 MiCOM P441 P442 P444 BLANK PAGE...
Page 23: ...Update Documentation P44x EN AD E44 MiCOM P441 P442 P444 Page 5 82 P44X EN IT E33 INTRODUCTION...
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Page 96: ...P44x EN AD E44 Update Documentation Page 78 82 MiCOM P441 P442 P444 BLANK PAGE...
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Page 100: ...P44x EN AD E44 Update Documentation Page 82 82 MiCOM P441 P442 P444 BLANK PAGE...
Page 101: ...Introduction P44x EN IT E33 MiCOM P441 P442 P444 INTRODUCTION...
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Page 104: ...P44x EN IT E33 Introduction Page 2 24 MiCOM P441 P442 P444 BLANK PAGE...
Page 127: ...Relay Description P44x EN HW E33 MiCOM P441 P442 P444 RELAY DESCRIPTION...
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Page 132: ...P44x EN HW E33 Relay Description Page 4 44 MiCOM P441 P442 P444 BLANK PAGE...
Page 152: ...P44x EN HW E33 Relay Description Page 24 44 MiCOM P441 P442 P444 Example isolated AC fault...
Page 153: ...Relay Description P44x EN HW E33 MiCOM P441 P442 P444 Page 25 44...
Page 173: ...Application Notes P44x EN AP E33 MiCOM P441 P442 P444 APPLICATION NOTES...
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Page 180: ...P44x EN AP E33 Application Notes Page 6 220 MiCOM P441 P442 P444 BLANK PAGE...
Page 357: ...Application Notes P44x EN AP E33 MiCOM P441 P442 P444 Page 183 220...
Page 364: ...P44x EN AP E33 Application Notes Page 190 220 MiCOM P441 P442 P444 BLANK PAGE...
Page 394: ...P44x EN AP E33 Application Notes Page 220 220 MiCOM P441 P442 P444 BLANK PAGE...
Page 395: ...Technical Data P44x EN TD E33 MiCOM P441 P442 P444 TECHNICAL DATA...
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Page 400: ...P44x EN TD E33 Technical Data Page 4 30 MiCOM P441 P442 P444 BLANK PAGE...
Page 427: ...Installation P44x EN IN E33 MiCOM P441 P442 P444 INSTALLATION...
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Page 430: ...P44x EN IN E33 Installation Page 2 10 MiCOM P441 P442 P444 BLANK PAGE...
Page 438: ...P44x EN IN E33 Installation Page 10 10 MiCOM P441 P442 P444 BLANK PAGE...
Page 439: ...Commissioning P44x EN CM E33 MiCOM P441 P442 P444 COMMISSIONING...
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Page 494: ...P44x EN CM E33 Commissioning Page 54 54 MiCOM P441 P442 P444 BLANK PAGE...
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Page 498: ...P44x EN RS E33 Commissioning Test Record Sheets Page 2 10 MiCOM P441 P442 P444 BLANK PAGE...
Page 507: ...Connection Diagrams P44x EN CO E33 MiCOM P441 P442 P444 CONNECTION DIAGRAMS...
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Page 510: ...P44x EN CO E33 Connection Diagrams Page 2 12 MiCOM P441 P442 P444 BLANK PAGE...
Page 520: ...P44x EN CO E33 Connection Diagrams Page 12 12 MiCOM P441 P442 P444 BLANK PAGE...
Page 521: ...Courrier Data Base P44x EN GC E44 MiCOM P441 P442 P444 CONFIGURATION MAPPING...
Page 610: ...Courier Data Base P44x EN GC E44 MiCOM P441 P442 P444 DEFAULT PROGRAMMABLE SCHEME LOGIC PSL...
Page 615: ...Menu Content Tables P44x EN HI E44 MiCOM P441 P442 P444 MENU CONTENT TABLES...
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Page 634: ...P44x EN VC E44 Hardware Software Version Page 8 8 MiCOM P441 P442 P444 BLANK PAGE...
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