Tuning Problem In The Calculation Of Of The Power Plant Protection

With the new protection equipments unceasing applying to power system, the original guide of calculating settings of relay protection for large generator and transformer can't be directly acted on the settings of these new equipments.About the problem, this paper focuses on the setting of main equipment protection, especially on the influence of the coefficient of balance to the setting of the differential current threshold in differential protection for transformers.My researches are mainly on the pringciple and setting methods of electric power equipment protection, including Generator Protection, Transformer Protection, Protection of Generator-Transformer Unit and Motor Protection.About Generator Protection, we introduce longitudinal differential protection principle using percentage restraint, Single element transverse differential protection for turn-to-turn faults, Longitudinal zero sequence voltage (3Uo) protection for stator turn-to-turn faults, Split phase transverse differential protection for turn-to-turn faults and so on.My researches on Transformer Protection setting focuse on the influence of the coefficient of balance to the setting of the differential current threshold in differential protection for the differential protection for transformers.Instead of the balance windings for the traditional relays protection, digital transformer relay protection chooses the coefficient of balance. For the setting of the coefficient of balance, different choices of the reference windings will directly affect the setting of the differential current threshold. This paper reviews the current four basic ways for choosing the reference windings and comes up with the relation of setting of the differential current threshold and the reference windings. The purpose is to come up with the more reasonable setting of the differential current threshold for the different relays protection equipments.