Installation manual

UNIPOWER
Installation manual PQ Secure
22
4.4.4 HV 3-phase measurement with 2CT’s and 3PT’s (Line-to-line voltages)
Figure 12
The above wiring diagram is used for three-phase measurement in electricity networks with 2 CT’s
and 3 PT’s. The voltage channels of the unit are connected to the PT’s (normally 110 V AC
secondary), for supplying line-to-line voltages, and current channels are connected to the CT´s
(normally 1 - 5 A AC secondary). Always protect the voltage inputs with a 1A fuse in each
conductor (red conductor) on the secondary side of the PT. Two current channels are measured and
the third is calculated by the measuring instrument. The connection for this type of measurement is
as follows:
Channel: Measured object: Channel Measured object:
U1+ = L1 PT+ I1+ = L1 CT+
U1- = L2 PT+ I1- = L1 CT- (Grounded)
U2+ = L2 PT+ I3+ = L3 CT+
U2- = L3 PT+ I3- = L3 CT- (Grounded)
U3+ = L3 PT+
U3- = L1 PT+
Note: If this method is used, the recorder will automatically calculate the current I2. This
configuration is normally used in medium voltage networks.
1A