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EATON ELECTRICAL
55
Predictive Diagnostics
6 Appendix 2. Synchronization and Phase Reference Shift
One should clearly distinguish between synchronization and phase reference shift. While the first is a vital
part of taking PD reading, the second is used for correct phase-resolved data representation in InsulGard
software and part analysis associated with this phase-resolved data.
Loss of synchronization stops InsulGard operation! InsulGard displays this error as “- -SYnC- -”.
Incorrect phase reference shift does not affect data acquisition by IG, integral quantities calculations and
alarm operation. Even more, establishing correct phase reference shift later will allow for correct phase-
resolved data analysis of the data acquired earlier.
Correct phase reference shift should be set regardless to the selected synchronization option.
6.1 Synchronization
InsulGard allows for external and internal synchronization from 115/230VAC power supply. The second is
most reliable option and it is default for InsulGard. InsulGard stops operation only if power is off.
External synchronization is used only when it is really necessary, if power supply voltage is not
synchronous with the voltage on the monitored object. This happens in VFD applications or isolated
systems such as 25Hz systems.
Be cautious if power an InsulGard from UPS, unless UPS has constant phase shift to the voltage
in the monitored object in stand by mode. If not, you get an “asynchronous” situation.
Two jumpers that are shown in the figure 6.1 in the internal synchronization position provide for a choice
of synchronization. The jumpers are located inside InsulGard enclosure to the right from the power supply
transformer. Both jumpers should be moved to the right for an external synchronization.
Figure 6.1
6.1.1 Pre-Revision 1
External synchro-signal should be connected to the IG sensor interface board. There are two external
synchronization options that are configured by jumpers in the sensor interface board:
•
Using an external signal (most preferred is potential transformer). This signal should be
connected to the “Ref” #8 terminal and the ground wire should be connected to the terminal #6.
The signal should not exceed 3.5 VAC and, if exceeds, should be externally conditioned by, for
example, resistive divider. Note that “Ref” has 1 MOhm internal impedance and 47nF capacitance
to the ground.
•
Using coupling capacitor connected to PD channel #1. Coupling capacitor signal contains both
high frequency partial discharge and power frequency components. Power frequency component