FUNCTION CHARACTERISTICS
261
NVA100X-D - Manual - 02 - 2016
Frequency tracking
Within the frequency range 20...63 Hz (
f
n
= 50 Hz or 60 Hz) a frequency tracking algorithm adjusts the
currents sampling frequency, so as to keep the number of samples in any given period constant.
With 64 samples for periods the sampling rate is adjusted from 1.28 kHz with f = 20 Hz to 4.032 kHz with
f= 63 Hz.
For a frequency step change the tracking response time is 0.1 Hz/s.
The frequency measure is based on the largest phase voltage; if the largest signal between the input
phase voltages are lower than 1.5%
E
n
the frequency measurement is performed on the current
signals
I
L1L
,
I
L2L
,
I
L3L
.
If the larger phase input current is lower than 25%
I
n
and the larger phase input voltage is lower
than 1.5%
E
n
the sampling frequency is fi xed to
f
n
(50 or 60 Hz).
If the measured frequency is outside the locking range
,
the sampling frequency is fi xed to the lower
or upper value (20 - 63 Hz).
All protective elements are always operative; accuracy is guaranteed inside the locked frequency
band.
—
•
•
0.25
I
n
- 1.5%
E
n
IF.ai
Frequency tracking
f
(Hz)
50 Hz o 60 Hz
Locked frequency
Sampling frequency
Max I
L1...L3
> 0.25
I
n
Max U
L1...L3
> 0.015
E
n
≥
f
(Hz)
0 Hz
Rated frequency
f
n
= 50 Hz or 60 Hz
Rated frequency
f
n
= 50 Hz or 60 Hz
Displayed value
f
measured
20 Hz
16 Hz
90 Hz
20
16
90
63
63 Hz
0.25
I
n
- 1.5%
E
n
Max I
L1L...L3L
Max U
L1...L3
I
L1L
I
L2L
I
L3L
U
L1
U
L2
U
L3
Max I
L1L...L3L
Max U
L1...L3
