The developed earth fault distance measuring unit (DMU) algorithms touch on the subject of the effectiveness increase for distance relay operation. The impedance-measuring problem is considered as the optimization problem. It is proposed the control bus voltage balance equations to use as the objective function of optimization. The balance is determined as difference between the measured bus voltage and the bus voltage, which is calculated by monitoring currents and network parameters. The specific DMU algorithms, which are based on Newton optimization methods, are presented. It is analyzed by CAPE program of Latvenergo network model. The earth faults conditions at 330kV HVTL for single and tapped line configuration were performed. It is shown, that the developed DMU algorithms are more effective then classic.