User Manual

91
16.1.4.2. Three-phase system with virtual neutral
Three-phase distribution systems without neutral are considered as a whole (no phase-by-phase power calculation). The device
therefore displays only the total quantities.
The three-wattmeter method with virtual neutral is applied for the calculation of the total active power and of the total reactive power.
Total active power.
Total apparent power.
Note: This is the RMS total apparent power as defined in IEEE 1459-2010 for distribution systems without neutral.
Total reactive power (Non-active quantities broken down – Configuration > Methods of calculation > var)
Total distortion power (Non-active quantities broken down – Configuration > Methods of calculation > var)
Total non-active power (Non-active quantities not broken down – Configuration > Methods of calculation > var)
16.1.4.3. Three-phase system without neutral
Three-phase distribution systems without neutral are considered as a whole (no phase-by-phase power calculation). The device
therefore displays only the total quantities.
The two-wattmeter method (Aron method or two-element method) is applied for the calculation of the total active power and of
the total reactive power.
a) Reference in L1
Active power, Wattmeter 1
[ ] [ ] [ ][ ] [ ][ ]
∑
−
=
⋅⋅==
1
0
22
1
0W0P
NechSec
n
nAnU
NechSec
Active power, Wattmeter 2
[ ] [ ] [ ][ ] [ ][ ]
∑
−
=
⋅−⋅==
1
0
10
1
1W1P
NechSec
n
nAnU
NechSec
Reactive power, Wattmeter 1
[ ] [ ] [ ][ ]
∑
−
=
⋅−⋅==
1
0
1
2]
4
][2[
1
0VARF0Q
NechSec
n
nAF
NechPer
nUF
NechSec
Σ
2
i=0
1
NechSec
(
Σ
NechSec-1
n=0
V[i][n].A[i][n]
)
P[3]=W[3]=
S[3]=VA[3]=
1
√3
√
(Urms²[0]+Urms²[1]+Urms²[2])
(Arms²[0]+Arms²[1]+Arms²[2])
√
Σ
2
i=0
1
NechSec
(
Σ
NechSec-1
n=0
VF[i]
)
Q
1
[3]=VARF[3]=
. AF[i][n]
4
NechPer
n -
[
]
D[3]=VAD [3]=
√
(S[3]² - P[3]² - Q
1
[3]²
N[3]=VAR [3]=
√
(S[3]² - P[3]²
UF
AF