Current transformer secondary open circuit alarm circuit

Open circuit of the secondary load of the current transformer will generate high voltage, endangering equipment and personal safety. It will also cause the relay protector to not
work properly and the instrument to have no indication. For this purpose, a self-made secondary open circuit automatic alarm can be made, and its circuit is shown in Figure 3-109.
    Tests show that when the current transformer TA is operating normally, its
secondary side voltage is very low, about 1 to 3V. By adjusting the potentiometer
RP, the relay KA can be activated according to the required voltage.
Generally, it is appropriate to set it at 30 to 40V.