For quantifying unbalance responsibility of the unbalance source of the system and user side in common joint point system of the system in the three-phase and four-wire system

the negative sequence voltage responsibility index for the system side

user side and each user is defined. The equivalent negative sequence model of three-phase four-wire system is studied and the evaluating method of each equivalent parameters of the model is defined

and then the responsibility division of equivalent voltage source of the system side

and negative sequence voltage of the transmission line and each load of the user side. The negative sequence voltage responsibility calculation for the equivalent power supply

transmission line and load in the simulation example is performed at such four cases as symmetrical of equivalent power supply

transmission line and equivalent voltage source

asymmetrical of transmission line

equivalent voltage source

symmetrical of equivalent voltage source and asymmetrical of transmission line

and correctness and feasibility of the proposed method is verified by the result.