The most common type of short circuit in a three-phase system is a single-phase-to-ground short circuit, accounting for 70 to 90% of electrical faults. In this paper simulation of the protective device from single-phase-to-ground short circuit with automatic change of current setting in electrical networks of 6-10 kV voltage on the basis of Coloured Petri Net is considered. The complexity of elaborated technical systems makes the problem of their modelling actual at the stage of development with the purpose of obtaining estimations of prospective and achievable characteristics. Now the modelling theory of the dynamic discrete systems, based on the formalism of Coloured Petri Nets has a wide application. Petri Net, describing the device operation, was designed and analysed using CPN Tools Programm. The resulting Petri net is correct, as it is live, reversible and safe. Thereby designed device can provide the selective protection from single-phase-to-ground short circuit.

In this paper, on the basis of simulation modeling, an algorithm for studying the current resonance that occurs in the power supply system with a chaotic change of the load power and variation of reactive power compensation degree, in the presence of consumers with a nonlinear current-voltage characteristic is proposed. It is shown that overloading of capacitor banks can occur in a wide frequency range, close to the resonant frequency. The proposed algorithm determines all possible frequencies at which an increase of currents in capacitor banks can occur above the permissible values in parallel resonance. The purpose of the proposed work: to show in what operating modes of the enterprise power supply system an overload of capacitors by currents of higher harmonics can occur when the load power changes and the degree of reactive power compensation varies.

"This scientific article examines the measurement method for determining the location of damage in a 6(10) kV cable line in a network with an isolated neutral. The method involves the use of location devices when measuring distances to the site of defecation in cable networks from two sides. This is necessary to identify complex types of short circuits and more accurately determine the distance to the accident site. The results of theoretical studies have been confirmed by experiments conducted using the R5–13/1 inhomogeneity meter together with the tracer measuring receiver–IP–8. In addition to the main experiments to determine the location of complex damage, experiments were conducted to study the parameters of the pulse measurement method. The influence of the instrumental characteristic of the shortening factor on the accuracy in determining the distance to the damage site is studied.. The method of two–way measurements of finding the distance to the place of damage in cable networks with a voltage of 6 (10) kV can be used to increase the continuity and reliability of power supply systems, as well as increase the level of electrical safety during their operation. Keywords: cable break, reflectometry, non–uniformity meter, electric grid, isolated neutral, grounding, damage location, simulation, isolation, reliability, power quality, emergency mode. "

We consider the issues of modeling power lines using a self-adjusting mathematical model which allows analyzing the lines operating modes while tracking instantaneous values of parameters. The obtained model can be used to build high-speed protection against phase-to-phase faults in power lines with a voltage of 10-35 kV, which have a small length.

No abstract