GUID-6AA3C028-E7DD-4C87-A91C-4B8B1D43CBBA V2 EN
Figure 401: Inverse time characteristic for different values on T1 or T2 (The
smaller figure is a zoom-in of the larger one)
9.5.12 Pulse control
The tap changer generates an active operating signal when the tap-changing
process is active. This signal is to be connected to the TCO input. The signal is used
for alarming purposes. If the signal is active (=TRUE) for more than 15 seconds
after the control pulse has been deactivated, an alarm is generated (
Alarm
indication chapter). If the TCO input is not connected, no alarm is generated.
The control operation is disabled when the TCO input signal is active, unless no tap
changer stuck is detected (Alarm indication chapter). Thus, it is not possible for
the controller to send new pulses to the tap changer when it is already operating.
This is because the tap changers are typically immune to new pulses when they are
operating. Furthermore, because the pulses are omitted, the tap changer pulse
counter of the controller is not incremented either.
The commands are not tolerated during an active pulse. Therefore the command
pulse length (setting LTC pulse time) has to be carefully selected, although an
active TCO input is used internally to prevent new commands from reaching the tap
changer.
To be more certain that no new pulses are to be sent when the tap changer is in
operation, the tap changer operating signal can also be connected to the
1YHT530004D05 D Section 9
Control functions
615 series 745
Technical Manual
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