The DGF100 is a microprocessor based ground fault relay for use on solidly grounded or resistance grounded systems. This innovative digital electronic relay measures
ground fault current using a built-in 46 mm zero sequence Current Sensor (CS), or an external Current Sensor. External Current Sensors with different cable windows,
round or square, and various current ratios are available
(Go to Sensors)
. The external
current sensors must be connected to terminals T1 & T2. The system will react to alternating current (ac) only and will reject direct current (dc) signals. Accuracy will be
maintained over a frequency range of 45 to 450 Hz, making it suitable for variable frequency drive applications. The DGF100 is a Class A device as defined in the IEC 60755 standard;
it is therefore fully characterised for operation with sinusoidal ac and pulsating dc currents.
The DGF100 houses an isolated universal power supply from 24-240 V ac or dc and is equipped with form 'Z' (4-wire) isolated N.O and N.C. contacts. The Ground Fault Current
Trip level (30mA-9A, 14 steps), Trip Delay Time (20ms-5s, 8 steps) and the Relay Operating Mode (F/S, non-F/S, pulsed auto reset and pulsed Non-FS) are set on a front accessible
dipswitch array. A single press of the RESET button, or an external, voltage free, momentary pushbutton connected to terminals R1 and R2, resets the relay after a trip.
A functional test of the DGF100 is started by either double clicking the cover mounted or external button, or by invoking a test on the DGF100 Display.
A green RUN LED flashes (1s on 1s off) to indicate that sufficient control voltage is applied to terminals L+ and N-. A red TRIP LED indicates that the DGF100 has sensed a Ground Fault and that the output contacts have operated.
7 point and 3 point pull-apart terminal blocks simplifies connection of field wiring. A captive screw secures the 7 point block to the relay, safe from the effects of shock
A communications port provides access for a remote display. The remote DGF100 Display shows the actual ground fault current during normal running of the systems. After a trip
the ground fault current just prior to the trip is displayed. If the DGF100 Display was connected to the DGF100 at the moment of a trip and the DGF100's Control Voltage is
turned off, pressing the VERIFY button will show a red LED indicating a ground fault. If no fault was present the green LED will light. For all features, see the Instruction
Manual for the DGF100 Display.
To ensure that the DGF100 will function in all circumstances, encapsulating in polyurethane (PUR) makes sure it is not vulnerable to mechanical shock, vibration nor weather.
The maximum system operating voltage for the DGF100 is 660 V, when passing the system power conductors through the built-in CS. However, by using any GFS external CS and
insulating the busbars, or by using any suitably rated, commercially available, interposing CT and passing the secondary lead through the built-in CS, the relay can be used
on any system voltage.