ABB Relion 670 Series Applications Manual page 287

1MRK 505 370-UUS Rev. K
Line
protection
Operate time
Circuit
breaker
Auto-reclosing
function
ANSI04000146 V1 EN-US
Figure 132: Single-shot automatic reclosing at a permanent fault
Single-pole tripping and single-phase automatic reclosing is a way of limiting the effect of a single-phase
line fault on power system operation. Especially at higher voltage levels, the majority of faults are of
single-phase type (around 90%). To maintain system stability in power systems with limited meshing or
parallel routing single-phase auto reclosing is of particular value. During the single-phase dead time the
system is still capable of transmitting load on the two healthy phases and the system is still synchronized.
It requires that each circuit breaker pole can be operated individually, which is usually the case for higher
transmission voltages.
A somewhat longer dead time may be required for single-phase reclosing compared to high-speed three-
phase reclosing. This is due to the influence on the fault arc from the voltage and the current in the non-
faulted phases.
To maximize the availability of the power system it is possible to choose single-phase tripping and
automatic reclosing during single-phase faults and three-phase tripping and automatic reclosing during
multi-phase faults. Three-phase automatic reclosing can be performed with or without the use of
synchrocheck.
During the single-phase dead time there is an equivalent "series"-fault in the system resulting in a flow of
zero sequence current. It is therefore necessary to coordinate the residual current protections (ground
fault protection) with the single-phase tripping and the auto reclosing function. Attention shall also be paid
to "pole discrepancy" that arises when circuit breakers are provided with single-phase operating devices.
These breakers need pole discrepancy protection. They must also be coordinated with the single-phase
auto recloser and blocked during the dead time when a normal discrepancy occurs. Alternatively, they
should use a trip time longer than the set single-phase dead time.
Busbar protection REB670
Application manual
Closed
Open
Break time
Fault duration
Set AR open time
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Operate
time
Closing time
Fault duration
AR open time for breaker
Reset time
Break time
en04000146_ansi.vsd
Section 12
Control
281