I'm not sure about your actual application but we use similar system for voltage indication in medium voltage switchgear.
The voltage indicator is adapted to cooperate with reactive or resistance insulator having output currents from 20 up to 500 μA at nominal voltage of power network. Visual elements which indicate voltage appearance in individual phases are three LED visible in front of indicator unit. Depending on type of used insulator (value of its output current) and nominal voltage of power network there is need to match and adjust the threshold current value Iw of internal indicator showing voltage presence according with requirements of standard PN-EN
61958:2002 “The sets of prefabricated high voltage switchgears. Voltage presence indicators”. That standard regarding threshold value of indicating voltage presence of set consisted of reactive (resistance) insulators and voltage indicator requires that in three-phase systems an indicating connected with signal “voltage presence”:
- should appear if the real value of phase voltage is between 45% nominal voltage and nominal voltage,
- should not appear if the real value of phase voltage is less than 10% of nominal voltage.
Changing the current threshold value Iw of indicator (internal indicator showing voltage presence) can be done by rearrange the jumpers on the printed-circuit board (pcb). Access to those jumpers is available after opening the rear panel of indicator and there’s no need to take the board out of enclosure.