Electronic switch release circuit

The electronic switch tripper circuit first amplifies the leakage signal detected by the zero-sequence current transformer through a shielding amplifier, and then sends the amplified signal
to the relay through the switch circuit and causes it to operate to send out a leakage signal, as shown in Figure 14 -38 shown. Normally, both transistors VT1 and VT2 are cut
off; when leakage occurs, the L2 and C2 resonant circuits give a 50Hz signal voltage to the VT1 emitter during the positive half cycle. VT1 is turned on. VT2 is also
turned on during the negative half cycle. Both VT1 and VTZ are cut off. In this way, the VT2 collector has a pulse current with a frequency of 50Hz. This current,
after being filtered by G, causes KM to act and send out a leakage signal . This circuit has extremely high sensitivity and the operating current is less than 15mA. It should be noted here that this type of
tripper is not a standard circuit, it is just to illustrate the working principle.