High voltage automatic protection circuit

The indicator is a high-voltage power grid automatic control protection circuit . In the circuit, VT1 forms an oscillator; VT2 forms a frequency-selective high-amp circuit;
VT3 and VT4 form a switching circuit; c9 is the protection capacitor of VT4. When no one approaches the protection circle, the switching circuit is turned on, and the relay
KA operates, and its normally open contact Point KA is connected, and the power supply of the high-voltage grid is connected to the high-voltage line. When people and animals approach the protective circle, the distributed capacitance Ci value changes, the oscillation frequency also changes, the frequency-selected high-amplification output is very small, the switching tubes VT3 and VT4 are cut off, the relay KA is released, and the high-voltage power supply is cut off
through the contact KA.
This protects humans and animals from the risk of electric shock caused by high voltage. The installation of high-voltage power grids is mainly used to eliminate
pests in rural areas. When using high-voltage power grids to eliminate pests in rural areas, firstly, a protective area must be set up to prohibit the entry of people and livestock, and secondly,
protective measures must be taken. Ensure safety: When installing automatic control protection devices for high-voltage power grids , security circles should be erected outside the high-voltage power grid to protect people
and livestock from entering dangerous areas.