DIFFERENTIAL PROTECTION METHOD OF ELECTRICAL INSTALLATION Russian patent published in 2015 - IPC H02H3/28 

FIELD: electricity.

SUBSTANCE: differential current is shaped phase-by-phase. Based on the obtained instantaneous values of secondary currents, excitation currents and recovered primary currents of current transformers are determined; with that, direction of currents towards a protected object is assumed as positive directions of currents. The obtained signals of secondary, recovered primary currents and excitation currents of current transformers (CT) of protection arms are reduced to one relative unit considering transformation coefficients of current transformers and other levelling coefficients. After that, differential current is shaped, which is proportional to a sum of recovered primary currents of the corresponding connections of the protected object. A brake current proportional to excitation currents of current transformers is calculated. Then, the obtained values of brake and differential currents for the period of industrial frequency are integrated, and the obtained integral differential current is compared to a setpoint and to integral brake current. In case the value of integral differential current exceeds the value of the sum of integral brake current and the actuation setpoint, a command for deactivation of an electrical installation is shaped.

EFFECT: increasing sensitivity and quick action of a protection and its functioning stability.

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