Distribution networks operated with isolated neutral point the capacitive earth-fault current flows through the point of fault in the case of a single-phase-to-earth fault. The magnitude of the current depends on the used type of line and the scope of network. There are many reasons for determining values of the capacitive earth-fault current. One of the most important reasons is the distribution networks operation safety. During a single phase earth fault, it is necessary to adhere to the allowed values of the touch voltage. This article has been written based on own knowledge and long-time experience acquired by the processing of measurements in the distribution network. The described method has been verified in real operation and based on the results a special-purpose automatic system for the measurement of the capacitive earth-fault current in a network with isolated neutral point has been developed.