Alarm Indication - ABB RED615 Technical Manual

Section 9
Control functions
9.5.14
750
Fast lowering control causes successive LOWER_OWN pulses to be activated. The
time between consecutive pulse starts is the pulse length plus 1.5 seconds.
• There is no tap changer operating delay (otherwise six seconds) taken into
account in this cycle (meaning that some command pulses are ineffective due
to tap changer operation, as described in the
• Timer mode set by Delay characteristic has no effect here (always the DT timer-
type operation). Because the minimum pulse length (the LTC pulse time
setting) is 0.5 seconds, the shortest interval between successive pulses can be
two seconds.
In the automatic follower mode, the fast lowering is not triggered. In this way, the
awkward dispersion of position values in different units can be avoided. The
master always decides on the fast lowering on behalf of the follower units.
Moreover, master and follower should measure an equal voltage level and have
similar setting values for the overvoltage blocking limit.

Alarm indication

Tap Changer Monitoring
OLATCC supervises the operation of the tap changer and alarms if the alarm
condition is detected. An alarm activation means that the ALARM output is
activated and the alarm reason can be read from the monitored data
ALARM_REAS. Alarms are in use by default but they can be set not to be in use
by setting Alarms enabled to "False". Three different alarm conditions and their
combinations can be detected by OLATCC.
Command error
OLATCC supervises the tap changer position information of the own transformer
when a control pulse is given. If the correct position change (direction depends on
the comparison of the settings Raise block tap and Lower block tap) is not seen by
OLATCC in Cmd error delay time after the pulse start, the alarm is issued.
If the position information is not connected, no alarm is generated. The alarm is
reset when the correct change in position value is detected after a given pulse or if
a new command pulse is given.
The monitored data ALARM_REAS is set during an alarm. This means that if the
alarm reason is active, ALARM_REAS has the value "Cmd error".
TCO signal fails
If the tap changer operating signal TCO stays active for more than 15 seconds after
the output pulse deactivation, OLATCC concludes this as an abnormal condition
and assumes that the tap changer is stuck. The alarm is reset when the TCO input
signal deactivates. The monitored data ALARM_REAS is set during the alarm.
This means that only if alarm reason is active, ALARM_REAS has the value "TCO
error".
1YHT530004D05 D
Pulse control chapter)
Technical Manual
615 series