Hitachi Relion 670 Series Applications Manual page 218

Section 12
Control
Automatic reclosing is usually started by the line protection and in particular by instantaneous tripping
of such protection. The auto recloser can be inhibited (blocked) when certain protection functions
detecting permanent faults (e.g. thermal overload protection). Back-up protection zones indicating
faults outside the own line are typically connected to inhibit the auto recloser.
Automatic reclosing should not be attempted when closing a CB and energizing a line onto a fault
(SOTF), except when multiple-shots are used where shots 2 etc. will be started at SOTF. Auto
reclosing is often combined with a release condition from synchrocheck and dead line or dead
busbar check.
Protection systems are usually sub-divided and provided with two redundant protection IEDs. In such
systems it is common to provide auto reclosing in only one of the sub-systems as the requirement is
for fault clearance and a failure to reclose because of the auto recloser being out of service is not
considered a major disturbance. If two auto reclosers are provided on the same breaker, the
application must be carefully checked and normally one must be the master and be connected to
inhibit the other auto recloser if it has started. This inhibit can, for example, be done from an auto
recloser by using operation in progress signal.
A permanent fault will cause the line protection to trip again when it recloses in an attempt to
energize the line.
The auto reclosing function allows a number of parameters to be adjusted.
Examples:
• number of auto reclosing shots
• auto reclosing dead times for each shot
12.2.3.1 Auto reclosing operation Off and On
Operation of the automatic recloser can be set to Off and On by a setting parameter or by external
control. The setting parameter Operation = Off, or On sets the function to Off or On. With the settings
Operation = On and ExternalCtrl = On , the control is made by input signal pulses to the inputs On
and Off, for example, from a control system or by a control switch.
When the auto recloser is set On, the SETON output is set, and the auto recloser becomes operative
if other conditions such as circuit breaker is closed and circuit breaker is ready are also fulfilled, the
READY output is activated (high). Then the auto recloser is ready to accept a start.
12.2.3.2 Start auto reclosing and conditions for start of a reclosing cycle
The usual way to start an auto reclosing cycle, or sequence, is to start it at selective tripping by line
protection by applying a signal to the START input. Starting signals can be either, general trip signals
or, only the conditions for differential, distance protection zone 1 and distance protection aided trip. In
some cases also directional earth fault protection aided trip can be connected to start an auto reclose
attempt. If general trip is used to start the auto recloser it is important to block it from other functions
that should not start an auto reclosing sequence.
In cases where one wants to differentiate auto reclosing dead time, for different power system
configuration or at tripping by different protection stages, one can also use the STARTHS input (start
high-speed reclosing). When initiating STARTHS , the auto reclosing dead time for high-speed shot
1, t1_HS is used and the closing is done without checking the synchrocheck condition.
A number of conditions need to be fulfilled for the start to be accepted and a new auto reclosing cycle
to be started. They are linked to dedicated inputs. The inputs are:
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