EIB Delta-Meter
Electricity Meters
9
ABB i-bus
®
EIB
Power consumption of the secondary measuring circuits:
If current
transformers are to be connected to an EIB Delta-Meter, it is necessary to
consider the power consumption of the entire secondary measuring circuits
when selecting the current transformers, so that accurate measured values
are achieved. The nominal power of the current transformer (S
sec
) must be
selected according to the power loss of the connected meter and the power
loss of the secondary measuring circuits.
The following applies:
S
sec
≥
S
cable
+ S
meter
S = Apparent power (VA)
The table of recommended values below represents the power consumption
of the cable (S
cable
) as a function of the cable length and cross section.
Secondary
Cross
Power consumption of cable
current
section
Cable lengths (outgoing and return cable)
A
mm
2
1 m
2 m
5 m
10 m
20 m
50 m
100 m
1 A
1.0
0.04
0.07
0.18
0.36
0.71
1.78
3.57
1 A
2.5
0.01
0.03
0.07
0.14
0.29
0.72
1.43
1 A
4.0
–
–
–
0.09
0.18
0.45
0.89
5 A
2.5
0.36
0.71
1.78
3.57
7.10
17.8
–
5 A
4.0
0.22
0.45
1.12
2.24
4.50
11.2
22.4
5 A
6.0
0.15
0.30
0.74
1.49
3.00
7.40
14.9
Energy summation:
If the energy of several loads is to be measured using
a single electricity meter connected to more than one current transformer per
phase, the individual lines that are assigned to the current transformer must
be operated in parallel. All current transformers used must have the same
transformer ratio. The total of all the currents may not exceed 6 A.
In the example shown (three-wire network), the meter measures the total
energy consumption of cable 1 and cable 2. The type of load (asymmetrical
or symmetrical) is not significant in this case.
The same application is possible in a four-wire network. Current transformers
must then be operated in L1, L2, L3. The current transformers must be
connected with the correct polarity (K1
⇒
L1, k1
⇒
l1).
L1 L2 L3
2 3
5
7 8 9
1
Cable 1
Cable 2
k
k
l
l
K
L
K
L
