Study On Fault Analysis And Protection Strategy Of Regional Power Grid With Large Scale Motor Group

In recent years,with the rapid promotion of the national economy and the rapid development of national industry,the proportion of electric motor load in the power system is increasing.In some regional power grids,except for some large industrial users with large capacity motors on the lines,some small industries and enterprises on some lines use a large number of small capacity motors,which constitute a large scale motor group.The grounding fault occurs in the power system,the stator voltage drop to zero,but due to inertia of the rotor of the motor is still in the rotation,according to Faraday's law of electromagnetic induction,the induction electromotive force in the stator side corresponding,the induced electromotive force caused by motor transport group feedback current to the transmission line,and thus have an impact even damage to the transformer and other power transmission equipment.Compared with a large capacity motor,the feedback current of a single small capacity motor is very small,and it will not cause a significant impact on the power grid.However,because of the large number of such small capacity motors,the influence of feedback current on the power system can not be ignored.This paper starts with the current motor feedback mechanism,put forward a new motor group clustering method,and the application of the clustering method,the aggregation of motor group,the motor short-circuit feedback current is established based on the application of PSCAD/EMTDC,and realizes the simulation,to verify the validity of the equivalent method.Then the influence mechanism of the feedback current of the motor group is analyzed for a power grid fault with large scale motor group in a certain area of North China.Using the motor group polymerization equivalent method to achieve the simulation of the fault,and put forward the improvement scheme of relay protection for motor fault group feedback current caused by the new protection scheme design work,thus improving the reliability of power supply of the power system,to meet the demand for high quality of electric energy user.