ABB Relion 611 Series, Technical Manual

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8.2.5 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 CntRs parameter.The same
functionality can also be found in the clear menu (DARREC1 counters).
8.2.6 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.
Transient and semi-transient faults can be cleared by momentarily de-energizing the
power line. Using the autoreclose function minimizes interruptions in the power
system service and brings the power back on-line quickly and effortlessly.
The basic idea of the autoreclose function is simple. In overhead lines, where the
possibility of self-clearing faults is high, the autoreclose function tries to restore the
power by reclosing the breaker. This is a method to get the power system back into
normal operation by removing the transient or semi-transient faults. Several trials, that
1MRS757454 D
Section 8
Control functions
611 series 421
Technical Manual