Installation manual

UNIPOWER
Installation manual PQ Secure
25
4.4.7 4.4.7 HV 3-phase measurement with 3CT’s and 3PT’s (Line-to-neutral voltages)
Figure 15
The above wiring diagram is used for three-phase measurement in electricity networks with 3 CT´s
and 3 PT’s, when you want to store the line-to-neutral voltage instead of the line-to-line voltage. The
voltage channels (+) of the unit are connected to PT’s positive polarity (normally 110 V AC
secondary), meanwhile the negative polarity of voltage channels (-) from the unit and transformer are
connected to protective ground. Current channels are connected to 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. The connection for this type of measurement is as follows:
Channel: Measured object: Channel: Measured object:
U1+ = L1 PT+ I1+ = L1 CT+
U1- = (Grounded) I1- = L1 CT- (Grounded)
U2+ = L2 PT+ I2+ = L2 CT+
U2- = (Grounded) I2- = L2 CT- (Grounded)
U3+ = L3 PT+ I3+ = L3 CT+
U3- = (Grounded) I3- = L3 CT- (Grounded)
Note: When this method is used, the voltages are measured to ground. Therefore, configure
the unit for 4-Wire system (In PQ Online: 4-Wire). This method is used when focus is
on disturbance analysis in medium voltage networks. In power quality standards, like
EN 50160, measurements are based on line-to-line voltages.
1A
1A
1A