The purpose of the work is to increase the protection efficiency of 0.4 kV power lines with branch lines from single-phase short circuits by means of using the multi-contact switching system MSS-2-3. It can be not possible to provide the necessary sensitivity of protecting 0.4 kV power lines against one-phase short circuits when the power line length is too high and when the wire cross section does not provide the necessary value of the phase-zero loop resistance. Power line sectionalizing helps to solve this problem. It allows dividing power lines into sections, each is protected by its protective device. The settings of the protective devices installed at the beginning of a power transmission line and at the sectioning units (SU) are different. It provides the necessary selectivity of their work. At the same time, many power transmission lines (PTL) have long branch lines. The choice of the installation site of SU in such lines is difficult since a short circuit or other damage can occur both on a trunk line section and on a branch line. When installing SU both before a branch line and behind it, there might be the cases of unjustified power supply outages. Therefore, it is necessary to develop devices allowing for sectionalizing such power lines at the installation site of SU while ensuring the possibility of disconnecting both a trunk line section and a branch line directly. Such a device is a multi-contact switching system having two independent contact groups and three outputs (MSS-2-3). Installing the MSS-2-3 at a branch line point increases the security of the power transmission line against short circuits including single-phase ones and also increases power supply reliability to consumers since only a damaged section is disconnected in case of damage to the power transmission line. The feature of choosing the settings for the operation of switching devices installed in the MKS-2-3 to protect the switched power line sections is the need to take into account the parameters of a trunk line section and a branch line
The paper gives a method of accounting the dynamics of technological connections when forming a list of objects for the reconstruction and construction of electrical networks. The specified method allows maintaining a database of technological connections taking into account the information received from the monitoring systems for electric network operating modes. It makes it possible to assess the dynamics of technological connections by settlements and regions. Based on this, it allows determining the availability of a power reserve for new technological connections and pre-compile a list of objects for reconstruction and construction of electrical network taking into account the dynamics of technological connections.
The assessment of the technical and operational characteristics of overhead transmission lines of voltage classes 35-110 kV in the Oryol Region has been carried out in accordance with the methodology presented in the order of the Ministry of Energy of the Russian Federation dated July 26, 2017 No. 676; their service life was determined according to STO 56947007-29.240.01.053-2010. The analysis of the length of overhead lines and the types of conductors used has taken place using support-by-support schemes. In the construction of 35 kV lines, steel-aluminum wire (sectional area - 70 mm) is mainly used, the length of which is 1,358,456 km, and 110 kV overhead lines are made using an AS-120 conductor (1,094 km). Overhead transmission lines are characterized by high indicators of technical condition, since 40 % of lines of voltage class 35 kV and 53 % of lines of voltage class 110 kV are in very good technical condition with a wear rate of no more than 15 %. The study has found that 71 % of overhead lines with a voltage of 35 kV and 85 % of lines with a voltage of 110 kV have been in operation for more than 35 years; at the same time, due to the implementation of a timely strategy for maintenance and repair, the lines are characterized by high indicators of technical condition.
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