METHOD OF PHASE-TO-PHASE DISTANCE PROTECTION FOR PREVENTING MAL-OPERATION DURING OVERLOAD

摘要

A method of phase-to-phase distance protection for preventing mal-operation during overload is provided. For a relay of 3 stages phase-to-phase distance, limiting condition is added as: formula (1)：k₅(U_φφcosφ_φφ)puk₆, wherein: U_φφ is a module value of bus phase-to-phase voltage at protection installation position, U_φφ is an angle between phase-to-phase voltage at protection installation position and line phase-to-phase current at protection installation position, k₅ is a maximum calculation error tuning when considering faults, the value range is -0.25~-0.1, and k₆ is a minimum U_φφcosφ_φφ per-unitvalue tuning under less than faults overload condition, the value range is 0.4~0.6. When the formula (1) is satisfied, the relay is on, else the relay is off. The present invention can ensure the relay of 3 stages phase-to-phase distance to implement motion performance of distance protection under overload and overload re-fault, and can avoid the distance protection mal-operation caused by overload.