Bender VMD460-NA - Islanding Detection Df;Dt (ROCOF), Vector Shift Detection

Functional description
17
VMD460-NA_D00001_05_M_XXEN/01.2020
3.4.3 Islanding detection df/dt (ROCOF), vector shift detection
The VMD460-NA uses a passive method for islanding detection. The following methods
are available:
• Three-phase voltage monitoring, refer to voltage protection functions
• Rate of Change of Frequency (ROCOF) df/dt
• Vector shift detection
3.4.3.1 Islanding detection
Rate of Change of Frequency (ROCOF) df/dt
Menu: 3. Settings -> 4. df/dt ->:
1. Function
2. Response value
3. Hysteresis
4. Meas. window
5. t
(OFF)
6. t
(ON)
In the case of the ROCOF method, the df/dt measured value (Rate Of Change Of Fre-
quency) is compared to the response value. If the measured value exceeds the response
value for the duration of the corresponding response delay (t
(OFF)
), the protective func-
tion is tripped.
If the df/dt measured value falls below the response value by the hysteresis, the protec-
tive function is reset.
The df/dt detection can be enabled or disabled via the "
Function " parameter.
The interval for averaging of the df/dt measured values is set via the "
Meas. window " pa-
rameter.
The parameter "
t(ON) " can be used to set a separate reconnection delay after a df/dt
disconnection, see also ... .
3.4.3.2 Vector shift detection
Menu: 3. Settings-> 5. Vect.shift ->:
1. Function
2. Response value
3. t
(START-UP)
4. t
(ON)
Particularities of VDE-AR-N 4105:2018-11
(4105_2; profiles 1 and 2)
If it has been detected that dynamic network support is required, is-
landing detection is disabled for 8 seconds, suppressing unwanted dis-
connection from the network.