Studying internal overvoltages in the 10 kV urban cable distribution network

The article presents the results of long-term experimental studies conducted in 10 kV cable networks of two power facilities in Chelyabinsk. It employs well-known and previously tested methodological approaches to organize oscillographic recording of transient processes. A total of 79 oscillograms were obtained over 526 days, including both switching and temporary overvoltages. The article presents typical oscillograms for transition of a single-phase-to-ground fault to a short circuit; asymmetrical switching on of the disconnector contacts; switching in the network. Under conditions of natural operation of a cable distribution network, the study obtained the dependence of the cumulative probability overvoltage and its statistical metrics and moments. It was found that the overvoltage of probability with a multiplicity of K > 2.2 p.u. is less than 5 %. The average annual number of overvoltages NK.year exceeding 1.7 p.u. for power facilities is 36.96 and 42.46 pcs per year. The obtained data may be useful for conducting research on establishing the relationship between the insulation residual strength and the overvoltages affecting it.