GE C60 Instruction Manual page 355

5 SETTINGS 5.7 CONTROL ELEMENTS
c) SPECIAL APPLICATION OF THE SYNCHROCHECK ELEMENT
The synchrocheck element is intended for applications where the potential sources are located on either side of the breaker
to be closed. It can also be used in cases where a power transformer is located between the two potential sources by com-
pensating for the power transformer phase shift with the auxiliary VT connection to the C60 and the auxiliary VT connection
setting, as shown in the following example for the 230/13.8 kV Yn/D-1 transformer.
5
Figure 5–96: SYNCHROCHECK APPLIED ACROSS A TRANSFORMER
In this example, the phase voltage VT input is programmed as "Delta" with a ratio of 14400 V / 120 V = 120 and with a sec-
ondary voltage setting of 13800 V / 120 = 115 volts. The auxiliary VT connection is selected to be VAB since this vector is in
phase with VA on the transformer 13.8 kV side. The auxiliary secondary voltage setting is 230000 V / (√3/2000) = 66.4 volts
and the auxiliary VT ratio is calculated as 2000 * √3 * 13.8 kV / 230 kV = 208. Note that auxiliary VT ratio is chosen to match
primary voltage on the 13.8 kV side, because synchrocheck is comparing voltages in primary volts. Therefore metered val-
ues for the auxiliary VT now reflect and are referenced to the AB voltage of the 13.8 kV side of the transformer.
GE Multilin C60 Breaker Protection System 5-219