METHOD FOR CARRYING OUT SELECTIVITY OF PROTECTION AGAINST ONE-PHASE EARTH CONNECTIONS IN ISOLATED-NEUTRAL SYSTEMS

摘要

FIELD: electricity. ^ SUBSTANCE: application: in electric engineering in particular in relay protection devices. Essence of invention: zero-sequence current integration is performed in unit (1) and difference of voltage signals in zero-sequence and at unit (1) output is formed in unit (2). Modulus of signal at unit (2) output is formed in unit (3). Sum of voltage signals of zero-sequence and unit (1) output is formed in unit (4). Modulus of signal at unit (4) output is formed in unit (5). Subtraction of signals from unit (3) and unit (5) is performed in unit (6). Signal from unit (6) output is applied to input of unit (7) which represents aperiodic link of the first order. Signal from unit (7) output is compared with set value and when it is exceeded cutoff signal is generated. ^ EFFECT: providing selectivity in case of one-phase earth connection in isolated-neutral systems. ^ 1 dwg