METHOD OF HIGH-SPEED OVERCURRENT PROTECTION OF ELECTRICAL CIRCUITS (VERSIONS) Russian patent published in 2009 - IPC H02H3/08 

FIELD: electricity.

SUBSTANCE: present invention can be used for protecting three-phase electrical circuits. According to the method, instantaneous current values are measured and converted from analogue to digital. The root-mean-square value of the symmetrical current component l_ph in each phase is determined, after which the l_ph value determined by integration is compared with a preset current value I_sd. Under the condition that l_ph≥l_sd, a signal is chosen for generating a fixed delay time t_sd. Further, after equal time intervals Δt, the change in current of the electrical circuit Δi_j is measured in each period of measuring current. The sum of the squares of the instantaneous values of change in currents for all three phases, S(Δi² _j) is determined and the value of the symmetrical component of the change in current Δl_ph, is calculated. This value is added to the current value in the previous period of measuring current l_p. The sum l_ph=l_p+Δl_ph is compared with the preset current value I_sd and under the condition that I_ph≥I_sd, a control signal is generated for launching the "integral" protection channel. In this channel, there is calculation of the value of the integral of the square of instantaneous values of the change in current in each phase Q_ph=ΣΔi² _jΔt, which is compared with the preset value Q_sd and at time t_q, corresponding to Q_ph=Q_sd, a signal is generated for switching off the protection device.

EFFECT: more reliable and faster protection.

4 cl, 6 dwg