DSP-OHMNI Instruction Manual I-GARD
15
If more Feeder Modules need to be set-up then select Y and ENTER to repeat, or if not select N and ENTER
to exit the Feeder Module Set-up and enter the PULSE Set-up. The Pulse set-up screen allows the pulsing
mode for fault location to be changed for different frequencies and mode of operation. The screen of Figure
6.9 is shown.
6.4 Pulsing
SETUP PULSE? Y/N
Figure 6.9 Pulse Set-up Request
PULSE
INVRT?
OFF
FREQ 0 LOCK? OFF
Figure 6.10 Pulse Mode Set-up
Select Y to enter the Pulse Set-up Screen which looks like Figure 6.10 which will show the existing set-up
of the PULSE module. The pulsing information is stored in the DSP-DSM, which must be installed during
setup. Press
t
to toggle the setting ON or OFF as required.
6.4.1 Invert / NDR MAL
The output from the DSP-DPS module is connected to a solid state relay. Normally (non Inverted operation)
the output from the ‘+’ and ‘-‘ terminals of the DSP-DPS module is zero prior to any pulsing operation,
and the relay is OFF. If Inverted mode is selected, then this voltage is 12V dc. And the relay is, therefore,
energized continuously. The choice of NORMAL or INVERTED operation depends on how the Grounding
Resistor current is connected. If the Grounding resistor consists of two series or two parallel resistors (one
main resistor and one pulse resistor) with the pulse resistor to be switched in and out by a solid state relay
then the following two options exist.
a) Pulse Up current
Pulsing upwards means to increase current from IGmax 5A to IGmax 10A, for example. In this case the
pulse resistor is normally OFF and the INVRT OFF would be selected. Pulsing would then change the
current to a higher level from 5A to 10A alternating when a 100% fault exists.
b) Pulse Down current
Pulsing downwards means to reduce the current from IGmax 5A to IGmax 2.5A, for example. In this case
the pulse resistor will be Normally ON and thus the INVRT ON mode would have to be selected. This
will mean that the solid state relay will be ON when the system is normal (no fault) and will open when
pulsing is started thus reducing current.
See Diagram 6.11 for examples of both series and parallel connected resistor arrangements.
NOTE:
the INVRTed mode is the mode used with the standard OHMNI-PM resistors as supplied by I-GARD.
