Thytronic NA20, Manual, Page: 29 / 208

FUNCTION CHARACTERISTICS
29 NA20 - Manual - 04 - 2022
Samples are processed by means DFT (Discrete Fourier Transform) algorithm and the phase and
amplitude of fundamental are computed:
• Phase currents I
L1
, I
L2
, I
L3
• Residual current I
E
Calculated
By means vector addition of direct measures the following are calculated (RMS value of fundamen-
tal components):
• Thermal image ∆ θ
Sequence
• Fundamental RMS positive sequence current: I
1
• Fundamental RMS negative sequence current: I
2
On demand
• Fixed demand ( I
L1FIX
, I
L2FIX
, I
L3FIX
, ± P
FIX
, ± Q
FIX
)
Inside an adjustable time interval t
FIX
, an average magnitude is calculated for phase currents I
L1
, I
L2
,
I
L3
, active power ± P and reactive power ± Q of measures taken every second. The average values are
stored at the end of the same time interval.
IL1.ai
( I
n
)
ACQUISITION
i
L1
, i
L2
, i
L3
DFT
CT
≈
I
L1
, I
L2
, I
L3
IE.ai
( I
En
)
ACQUISITION
i
E
DFT
CT
≈
I
E
Theta.ai
I
L1
I
2
I
2
= ( I
L1
+ e
-j120°
I
L 2
+ e
+j120°
I
L 3
)
I
1
= ( I
L1
+ e
+j120°
I
L 2
+ e
-j120°
I
L 3
)
I
L3
I
L2
I
1
I
th
= √( I
1
2
+ K
2
2
∙ I
2
2
)
∆
θ
(∆ θ
B
)
2
d∆ θ
dt
I
B
I
th
∆ θ
T+ T+
( )
+ =
I1-I2.ai
I
L1
I
2
I
2
= ( I
L1
+ e
-j120°
I
L 2
+ e
+j120°
I
L 3
) / 3
I
1
= ( I
L1
+ e
+j120°
I
L 2
+ e
-j120°
I
L 3
) / 3
I
L3
I
L2
( I
n
)
I
1
( I
n
)
e
-j120°
= -
√3
j
1
2
2
- e
+j120°
= -
√3
j
1
2
2
+
Fix-Demand.ai
1s
I
L1FIX
, I
L 2FIX
, I
L 3FIX
t
FIX
( I
n
)
I
L2
I
L1
I
L3
I
L xFIX
I
L xn
t
FIX
∙ 60
t
FIX
∙ 60
n=1
∑
1
t
FIX
t
FIX
t
FIX