METREL MI 2885, Manual

Page: 183 / 241

MI 2893 / MI 2892 / MI 2885 Measurement methods
183
Combined phase active power:
 
 
  
N
j
j
p
j
p
N
j
j
p p
I U
N
p
N
P
1 1
1 1
[W], p: 1,2,3
(7)
Combined apparent and nonactive power, and power factor are calculated according to the following
equations:
Combined phase apparent power:
p p p
I U S
 
[VA], p: 1,2,3
(8)
Combined phase nonactive power:
2 2
) (
p p p p
P S Q Sign N
  
[var], p: 1,2,3
(9)
Phase power factor:
p
p
p
S
P
PF

, p: 1,2,3
(10)
Total combined power measurements
Standard compliance: IEEE STD 1459-2010
Total combined (funda nonfundamental) active, nonactive and apparent power and total power
factor are calculated according to the following equation:
Total active power: 3 2 1 P P P P
tot
  
[W], (11)
Total nonactive power: 3 2 1 N N N N
tot
  
[var],
(12)
Total apparent power (effective):
Ie Ue Se
tot
  
3 [VA],
(13)
Total power factor (effective):
tot
tot
tot
Se
P
PFe

. (14)
In this formula U
e
and I
e
are calculated differently for three phase four wire (4W) and three phase three
wire (3W) systems.
Effective voltage Ue and current Ie in 4W systems:
3
2 2
3
2
2
2
1 N
I I I I
Ie
  

18
) ( 3
2
31
2
23
2
12
2
3
2
2
2
1
U U U U U U
Ue
     

(15)
Effective voltage U
e
and current I
e
in 3W systems:
3
2
3
2
2
2
1
I I I
Ie
 

9
2
31
2
23
2
12
U U U
Ue
 

(16)