UNIPOWER
UP-2210R/P Hardware installation and configuration manual
26
4.4.9
HV 3-phase measurement with 2 CT’s and 2 PT’s (Line-to-line voltages)
Figure 18
The above wiring diagram is used for three-phase measurement in public distribution networks with
2 CT´s and 2 PT’s. The voltage channels of the unit are connected to PT’s for measuring line-to-line.
The current channels are connected to CT´s. Two channels are measured while the third current and
voltage values are calculated from the measured channels.
Always
protect the voltage inputs with a
suitable fuse in each conductor on the secondary side of the PT. The connection for this type of
measurement is as follows:
Channel:
Measured object:
Channel:
Measured object:
U1
=
L1-L2 PT+
I1+
=
L1 CT+
U2
=
L2-L3 PT-
I1-
=
L1 CT-
Ref =
L1-L2 PT-, L2-L3 PT+
I3+
=
L3 CT+
I3-
=
L3 CT-
Note: If this method is used, the meter will automatically calculate the third line-to-line
voltage (
UL3 - L1
) and the current I2. This configuration is normally used in medium
voltage networks
.
Note: In this configuration the constants for U1-U3 must be the same. Also the constants for
I1-I3 must be the same. This is because the missing U2/I2 is calculated by the instrument.
