Thytronic NV021, Руководство пользователя

Страница: 26 / 146

26
NV021 - Manual - 08 - 2012
CHARACTERISTICS
Calculated
By means vector addition of direct measures the following are calculated (RMS value of fundamen-
tal components):
Positive and negative sequence voltage: U
1
, U
2
[1]
Ten minutes RMS voltage
From the values of phase voltages U
L1
, U
L2
, U
L3
(versions with electronic sensors) or U
12
, U
23
, U
31
(versions with inductive VTs), the RMS voltage is calculated by aggregating 10 minutes of:
The RMS voltages are acquired every 0.2 seconds;
Separately for each phase, the acquired values are aggregated to 10 minutes (600 s) performing
the square root of the arithmetic mean of the last 600/0, 2 = 3000 values squared. The aggregation
of 10 minutes is updated every 3 s.
In response to a step change of the input voltage U (with voltage initially already stabilized), the volt-
age
U
m
has a transitional trend with square-law as shown in the following fi gure.
Nota 1 Calcolate sulle tre tensioni concatenate
•
•
•
U 2 . a i
U
L1
U
1
U
2
= ( U
L1
+ e
-j120°
U
L 2
+ e
+j120°
U
L 3
)/3
U
1
= ( U
L1
+ e
+j120°
U
L 2
+ e
-j120°
U
L 3
)/3
U
L3
U
L2
e
-j120°
= -
√3
j
1
2
2
- e
+j120°
= -
√3
j
1
2
2
+
( U
n
)
U
2
( U
n
)
U 2 . a i
U
L1
U
1
U
2
= ( U
L1
+ e
-j120°
U
L 2
+ e
+j120°
U
L 3
)/3
U
1
= ( U
L1
+ e
+j120°
U
L 2
+ e
-j120°
U
L 3
)/3
U
L3
U
L2
e
-j120°
= -
√3
j
1
2
2
- e
+j120°
= -
√3
j
1
2
2
+
( U
n
)
U
2
( U
n
)
U
m
=
3000
i=1
¥
3000
1
( U i )
2 U
m
=
3000
i=1
¥
3000
1
( U i )
2
Ten minutes RMS voltage (59Uavg)
200 100 100 200 300 400 500 600
U
Um
0.1
0.3
0.5
0.7
0.9
1.1
1.3
Ten minutes RMS voltage (59Uavg)
200 100 100 200 300 400 500 600
U
Um
0.1
0.3
0.5
0.7
0.9
1.1
1.3