Operation

The FGD-2 continuously monitors the machine field circuit for ground faults.

Ground faults are detected through the measurement of leakage current to

ground which is determined by measuring the voltage drop across a shunt

resistor within the ground detector source. The Basler device connected to

the FGD-2 receives a voltage signal from the ground detection source that

is proportional to the level of field leakage current. The excitation

capabilities and analog input ranges of different Basler products will limit

the maximum compatible field voltage for accurate field ground resistance

measurements. Refer to Table 2 for more details.

AIOM-2

In a DECS-2100 system, the AIOM-2/AIOM digitizes the signal and transmits

it via fiber optic cables to the ECM-2. In an ECS2100 system, the digitized

signal is received by the ECM/SIM. The value of leakage current appears as

an input to the BESTCOMS™Pro FLDGND logic block. Within the FLDGND

logic block, a value of resistance to ground is calculated from the voltage

applied and the level of leakage current measured. Typically, this calculated

resistance value is transmitted to a display panel via the PMOUT logic block.

In the event of a low field ground resistance value, the FLDGND logic block

issues a Low Field Ground Resistance alarm. During detection of low field

ground resistance, an alarm issued by the DIGROUT logic block can be used

to energize a relay within the system’s Digital I/O Module (DIOM-2 or DIOM).

This annunciation may be used to provide a dry relay contact for a remote

alarm.