GE N60 Instruction Manual page 65

CHAPTER 3: INSTALLATION WIRING
The auto-burnish circuitry has an internal fuse for safety purposes. During regular maintenance, check the auto-burnish
functionality using an oscilloscope.
3.3.6.3 Use of contact inputs with active impedance
In case of external devices that are susceptible to parasitic capacitance of long cable runs affected by switching surges
from external circuits, that can cause inadvertent activation of contact inputs with the external contact open, GE
recommends using the Digital I/O module with active impedance circuit.
Active impedance contact input can tolerate external capacitance of up to 0.2 µF, without entering the ON state for more
than 2 ms. The contact input debounce time can be set above 2 ms to prevent the transient ON state from being internally
used by the relay logic.
The figure shows the active impedance contact input V-I characteristic.
Figure 3-17: Active impedance contact input V-I characteristic
3
A contact input is in LOW state during non-operated system condition, and actively switches to HIGH state upon detection
of input voltage above the settable threshold. The contact input is in the ON (operated state) if the input voltage is to the
right of the threshold band (+/-10% tolerance), and the contact input is in the OFF (non-activated state) when input voltage
is to the left of the band.
N60 NETWORK STABILITY AND SYNCHROPHASOR MEASUREMENT SYSTEM – INSTRUCTION MANUAL 3-21