ABB Relion 670 Series Applications Manual page 277

1MRK 511 358-UUS A
Line
protection
Operate time
Circuit
breaker
Auto-reclosing
function
ANSI04000146 V1 EN-US
Figure 110: 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 phase breaker operates
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-tripped phases.
To maximize the availability of the power system it is possible to choose single pole tripping and
automatic reclosing during single-phase faults and three pole tripping and automatic reclosing
during multi-phase faults. Three-phase automatic reclosing can be performed with or without the
use of a synchronism check, and an energizing check, such as dead line or dead busbar check.
During the single-pole open 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 pole tripping and the auto-reclosing
function. Attention shall also be paid to "pole discrepancy" that arises when circuit breakers are
provided with single pole operating devices. These breakers need pole discrepancy protection.
They must also be coordinated with the single pole 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.
Application manual
Closed
Open
Break time
Fault duration
Set AR open time
Operate
time
Closing time
Fault duration
AR open time for breaker
Reset time
Break time
en04000146_ansi.vsd
Section 13
Control
271