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 ?A 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