ABB REL670 2.2 IEC, Applications Manual

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“dead time” differ then, the line will be energized until the breakers at both ends
have opened.
Open
Closed
Operate time
Line
protection
Circuit
breaker
Break time
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Fault duration Circuit breaker open time Fault duration
R
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In
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fa
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Break time Closing time
Operate time
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Set AR dead time Reclaim time
Auto-reclosing
function
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IEC04000146-3-en.vsd
IEC04000146 V3 EN-US
Figure 305: Single-shot automatic reclosing at a permanent fault
Single-phase 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
Section 15
1MRK 506 369-UEN B
Control
614 Line distance protection REL670 2.2 IEC
Application manual