Digital Elements - GE C60 Instruction Manual

CONTROL ELEMENTS
5.8.7.2 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 where a power transformer is located between the two potential sources by
compensating 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
In this example, the phase voltage VT input is programmed as "Delta" with a ratio of 14400 V / 120 V = 120 and with a
secondary 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 values for the auxiliary VT now reflect and are referenced to the AB voltage of the 13.8 kV side of the transformer.

5.8.8 Digital elements

SETTINGS  CONTROL ELEMENTS  DIGITAL ELEMENTS  DIGITAL ELEMENT 1(48)
 DIGITAL ELEMENT 1

5-270
Figure 5-146: Synchrocheck applied across a transformer
DIGITAL ELEMENT 1

FUNCTION: Disabled
DIG ELEM 1 NAME:

Dig Element 1
DIG ELEM 1 INPUT:

Off
DIG ELEM 1 PICKUP

DELAY: 0.000 s
DIG ELEM 1 RESET

DELAY: 0.000 s
DIGITAL ELEMENT 1

PICKUP LED: Enabled
Range: Disabled, Enabled
Range: up to 16 alphanumeric characters
Range: FlexLogic operand
Range: 0.000 to 999999.999 s in steps of 0.001
Range: 0.000 to 999999.999 s in steps of 0.001
Range: Disabled, Enabled
C60 BREAKER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS