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ABB i-bus
EIB
2
Measurement
of energy
2.1
Basic measurement
techniques
EIB Delta-Meter
Electricity Meters
Various measurement methods are used in the EIB Delta-Meters depending
on the type of meter. The following equations are vector equations.
Measurement method with one measuring element
This method only produces the correct result if the phase load is symmetrical.
L1
L2
I
L3
U
N
Measurement method with two measuring elements
This method is used in polyphase voltage networks without a neutral
conductor (three-wire network) with symmetrical or asymmetrical loading.
I
L1
U
L2
U
I
L3
This method (with 2 measuring elements) is not suitable for carrying out
accurate measurements in networks with inductive or capacitive loads with a
low cos ϕ. In this case, the method that uses 3 measuring elements should
be selected.
Measurement method with three measuring elements
This method is used in polyphase voltage networks with a neutral conductor
(four-wire network). It can however also be used in networks without a
neutral conductor, provided that an artificial neutral point is created.
I
L1
I
L2
I
L3
U
U
U
N
P = 3 · I
· U
L3
L3
This method is not suitable for carrying out
Load
accurate measurements in polyphase
voltage networks as 100% symmetrical
loading seldom occurs.
P = U
· I
+ U
L1
L1
ΣI = I
+ I
+ I
L1
L2
Load
P = U
· I
- U
L1
L1
P = I
(U
) + I
L1
L1 - L2
P = U
· I
+ U
L1
L1
This method is very accurate, even in the
Load
case of asymmetrical loads and low cos ϕ.
· I
+ U
· I
L2
L2
L3
L3
= 0
L3
(I
+ I
) + U
· I
L2
L1
L3
L3
L3
(U
)
L3
L3 - L2
· I
+ U
· I
L2
L2
L3
L3
7
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