Functional description
16
VMD460-NA_D00001_05_M_XXEN/01.2020
Please observe that:
In the following application standards, the U> measured value corresponds to a 10-
minute mean value, which is calculated by averaging 3-second measuring intervals
over 10 minutes. The mean value is determined as follows:
•
CEI 0-21
The measured value is a root-mean-square value acc. to IEC EN 61000-4-30.
•
VDE-AR-N 4105 and DIN V VDE V 0126-1-1
The measured value is an arithmetical average
3.4.1.2
Voltage drop protection, U>> and U>
Menu: 3. Settings-> 2. Voltage ->:
7. U< and 8. t
(OFF)
9. U<< and 10. t
(OFF)
In the case of voltage drop protection, the measured value is compared to the response
value (U< or U<<). If the measured value falls below the response value for the duration
of the corresponding response delay (t
(OFF)
), the protective function is tripped.
If the measured value exceeds the response value, the protective function is reset.
The measured value is equal to the instantaneous value.
3.4.2
Frequency protection functions f<, f<<, f>> and f>
The following frequency protection functions are implemented in the VMD460-NA:
•
Frequency increase protection f>, f>>
•
Frequency decrease protection f<, f<<
3.4.2.1
Frequency decrease protection f<, f<<
Menu: 3. Settings-> 3. Frequency ->:
7. f< and 8. t
(OFF)
9. f<< and 10. t
(OFF)
In the case of frequency decrease protection, the measured value is compared to the re-
sponse value (f< or f<<). If the measured value falls below the response value for the du-
ration of the corresponding response delay (t
(OFF)
), the protective function is tripped.
If the measured value falls below the response value, the protective function is reset.
3.4.2.2
Frequency increase protection f>, f>>
Menu: 3. Settings-> 3. Frequency ->:
1. f>> and 2. t
(OFF)
3. f> and 4. t
(OFF)
In the case of frequency increase protection, the measured value is compared to the re-
sponse value (f>> or f>). If the measured value exceeds the response value for the du-
ration of the corresponding response delay (t
(OFF)
), the protective function is tripped.
If the measured value falls below the response value, the protective function is reset.
