Relevance Devices for determining the location of fault on power lines assume a known type of short circuit and faulty phases. However, their algorithms, as a rule, can not distinguish the faulty phase. Therefore, the determination of faulty phases during short circuits on power lines is performed by separate devices – faulty phase selectors. The transient resistance at the point of closure has a strong influence on the work of selectors. The influence of transient resistance is especially strong at single phase-to-ground faults. Therefore, the study of the effect of transient resistance on the work of selectors at single phase-to-ground faults is an urgent task. Aim of research The aim of the article is to investigate and develop features of a faulty phase at single phase-to-ground faults via transient resistance in networks with an isolated neutral. Research method To study the features of a faulty phase, the article uses vector diagrams and graphs of changes in phase voltages when the transient resistance changes at fault location. When closing through a transient resistance, it is assumed that the vertices of the linear voltage triangle on the vector diagram and the neutral potential move around the circles with increasing transient resistance, and the ground potential remains unchanged. To study the change in the magnitude of phase voltages during short circuits through the transient resistance, a new variable was introduced — the angle by which the neutral voltage vector, taken with the reverse sign, lags behind the voltage vector of the faulty phase in the pre-emergency mode. The introduction of such a variable simplifies the equations for stresses and makes the analysis of the effect of transient resistance more general and visual. Results It is shown that, depending on the magnitude of the transient resistance, the lowest of the phase voltages in single phase-to-ground faults can be either the voltage of the faulty phase or the voltage of the unfaulted phase lagging in relation to the faulty one. At the same time, the lowest value of the phase voltage can be a sign of a faulty phase only in the range of transient resistances from zero to the boundary value. The features of a faulty phase during short circuits through the transient resistance are formulated. It is shown that the features of a faulty phase using angular relations between stresses are valid for any value of the transient resistance. While the features based on the determination of the phase with the lowest phase voltage act only in a limited range of transient resistance values. Keywords: single phase-to-ground fault, network with isolated neutral, faulty phase, transient resistance