ABB A43 User Manual page 89

Measurement Methods
2-element metering in a 4-wire system
2-element metering can also be used in a 4-wire system if the current in the neutral
connection is zero. Applying this method in a system having a non-zero neutral
current will decrease the accuracy, but can sometimes be justified if the current is
small compared to the line currents or if high accuracy is not required.
It is also possible to use this method for measuring one current only. This method
will only give correct result in a balanced system. Note that the current flows
backwards through phase 1 and 3 and that the phase voltages not are connected to
the normal inputs when the current transformer is connected to phase 1 and 3.
2CMC48001M0201
Revision: C
U3-U2
U3
I3
32 = -30
12 = 30
I2
U2
89
U1-U2


U1
I1
A43/A44
User Manual