FIELD: electricity.
SUBSTANCE: amplitude of signal current introduced to BC phases of 0.4 kV line to be compared in prototype and in the proposed method is the same and is equal to Im=17A. Result is achieved by the fact that in the proposed method the signal current is supplied to three-phase power transmission line to low-voltage windings of transformer 10/0.4 kV of phases B and C through series resonance circuit formed with the first capacitor, low-voltage winding of transformer 10/0.4 kV of phase C, low-voltage winding of transformer 10/0.4 kV of phase B, the second capacitor, inductance coil. At that, owing to stored electromagnetic energy W in inductance coil, in resonance coil at time interval 0.18T0≤t≤T0, at opened switch the current of free vibrations i2(t) is formed at frequency ω0=ωfree, which is equal to i2(t)=Im cos ω0t·e-δt; at that, series resonance circuit is tuned to current frequency of signal f0, where: 
where - current amplitude i2(t), at the moment of time of switch opening, which is equal to t=0.18T0, L - inductance of air inductance coil, Im = 
, C=C1=C2, where CΣ - resonance value of capacity of resonance circuit, 
- constant component of rectified double-wave three-phase voltage 0.4 kV of frequency 50 Hz, R - resistance of resistor; at that, inductances of transformer windings of 10/0.4 kV of phases A, B, C are disregarded because of their low values in comparison to inductance of inductance coil; also, active resistances of transformer windings 10/0.4 kV are disregarded because of their low values in comparison to resistance of resistor R, 
C1 and C2 are capacities of the first and the second capacitors respectively, ω0=ωfree =2π f0 - angular frequency of current of free vibrations in series resonance circuit. 
- period of current frequency T0 of signal, eδt - attenuation coefficient of signal current at time interval 0.18T0≤t≤T0 at open switch.
EFFECT: reducing the consumed power from network 0,4 kV by 2,8 times.
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