An improved differential equation method for earth fault location in non-effectively earthed system

An improved differential equation method for earth fault location in non-effectively earthed system is proposed. Karrenbauer transformation is used to construct the compound mode network of single phase earth fault. Based on the mode network, the fault equation including mode voltage, mode current, line parameters and earthed resistance is derived .The fault distance can be gotten by solving the equation with the least square estimation. In the calculation characteristics of different line models are compared and model is proved to be the best in accuracy and simplicity. ATP simulation and laboratory test proved that the proposed fault location method is feasible and has satisfactory accuracy. Because of using transient signal, the method is more sensitive and only need half cycle data, which can accelerate fault location speed and be more applicable.