Functional description
15
VMD460-NA_D00001_05_M_XXEN/01.2020
6. t
(ON) SHORT INT.
A short interruption occurs when the reconnection conditions are fulfilled within a
short period of time (t
SHORT INT.
) after disconnection.
In case of a short interruption, automatic reconnection takes place with a shortened de-
lay time (t
(ON) SHORT INT.
).
3.3.3.2 Reconnection after df/dt detection (ROCOF)
Menu: 3. Settings -> 4. df/dt ->:
6. t
(ON)
If the VMD460-NA has been disconnected due to a df/dt detection, it reconnects after
the separate delay time for connection t
(ON)
has elapsed. If t
(ON)
is set to "off", reconnec-
tion takes place after the delay time for connection t
(ON)NORMAL
has elapsed.
3.3.3.3 Reconnection after vector shift detection
Menu: 3. Settings-> 5. Vect.shift. ->:
4. t
(ON)
If the VMD460-NA has been disconnected due to a df/dt detection, it reconnects after
the separate delay time for connection t
(ON)
has elapsed. If t
(ON)
is set to "off", reconnec-
tion takes place after the delay time for connection t
(ON)NORMAL
has elapsed.
3.4 Protective and monitoring functions
3.4.1 Voltage protection functions U<, U<<, U>> and U>
The following voltage protection functions are implemented in the VMD460-NA:
• Rise-in-voltage protection: U>> and U>
• Voltage drop protection: U<<, U<
Depending on the coupling, all available phase voltages and line-to-line voltages (U
L1-
N
, U
L2-N
, U
L3-N
, U
L1-L2
, U
L2-L3
and U
L3-L1
) are evaluated separately by the voltage protec-
tion functions (OR operation).
3.4.1.1 Rise-in-voltage protection, U>> and U>
Menu: 3. Settings-> 2. Voltage ->:
1. U>> and 2. t
(OFF)
3. U> and 4. t
(OFF)
In the case of rise-in-voltage protection, the measured value is compared to the re-
sponse value (U>> and U>). If the measured value exceeds the response value for the
duration of the corresponding response delay, the protective function is tripped. If the
measured value falls below the response value, the protective function is reset.
The measured value is equal to the instantaneous value.
The implementation of the rise-in-voltage protection U> depends on the set applica-
tion standard.
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