limit. The lockout is released after the recovery time has elapsed. The recovery time can
be defined with the
Frq Op recovery time
setting .
If the circuit breaker is manually closed during the recovery time, the reclaim time is
activated after the recovery timer has elapsed.
9.2.5
Counters
The AR function contains six counters. Their values are stored in a semi-retain memory.
The counters are increased at the rising edge of the reclosing command. The counters
count the following situations.
•
COUNTER
: counts every reclosing command activation
•
CNT_SHOT1
: counts reclosing commands that are executed from shot 1
•
CNT_SHOT2
: counts reclosing commands that are executed from shot 2
•
CNT_SHOT3
: counts reclosing commands that are executed from shot 3
•
CNT_SHOT4
: counts reclosing commands that are executed from shot 4
•
CNT_SHOT5
: counts reclosing commands that are executed from shot 5
The counters are disabled through communication with the
DsaCnt
parameter. When the
counters are disabled, the values are not updated.
The counters are reset through communication with the
RsCnt
parameter.
9.2.6
Application
Modern electric power systems can deliver energy to users very reliably. However,
different kind of faults can occur. Protection relays play an important role in detecting
failures or abnormalities in the system. They detect faults and give commands for
corresponding circuit breakers to isolate the defective element before excessive damage
or a possible power system collapse occurs. A fast isolation also limits the disturbances
caused for the healthy parts of the power system.
The faults can be transient, semi-transient or permanent. For example, a permanent fault
in power cables means that there is a physical damage in the fault location that must first
be located and repaired before the network voltage can be restored.
In overhead lines, the insulating material between phase conductors is air. The majority of
the faults are flash-over arcing faults caused by lightning, for example. Only a short
interruption is needed for extinguishing the arc. These faults are transient by nature.
A semi-transient fault can be caused for example by a bird or a tree branch falling on the
overhead line. The fault disappears on its own if the fault current burns the branch or the
wind blows it away.
Section 9
1MRS240050-IB C
Control functions
476
REF615R
Technical Manual
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