Digital protection of the «Lviv 2» substation autotransformer with a capacity of 125 MVA. Configuring the protection terminal
Students Name: Shcherbei Anton Valeriiovych
Qualification Level: magister
Speciality: Electrical Energetics, Electrical Engineering and Electromechanics
Institute: Institute of Power Engineering and Control Systems
Mode of Study: full
Academic Year: 2023-2024 н.р.
Language of Defence: ukrainian
Abstract: The electric power system consists of a complex of electrical equipment, which is united by a single technological process of generation, transmission and consumption of electric energy and is located on a large territory. To ensure uninterrupted supply of high-quality electrical energy to the consumer, there is an urgent need to use means of relay protection and automation (RZA). The use of RZA allows you to significantly reduce the number of accidents and economic losses from them in the power system, increases the reliability of work and ensures a longer service life of expensive equipment. This, in turn, imposes certain requirements for the construction of control systems, automation, protection of elements that make up electric power systems - generators, transformers, power transmission lines, etc. Implementation of these requirements using control, automation, and protection systems built on a traditional electromechanical base is practically impossible. Electromechanical devices were replaced by a new generation of devices whose work is based on digital devices. In a short period of time, these devices have undergone rapid development - from simple single-function elements implemented on microcontrollers to complex digital terminals based on powerful microprocessors.Relay protection and automation (RZA) are important elements of the electric power system, which ensure its reliable operation, protection of electrical equipment from emergency damage and abnormal modes [1-3]. Nowadays, digital devices of RZA are becoming more and more popular. The use of modern microprocessor-based protection devices allows to increase the speed of operation of relay protection, reduce the duration of an accident, combine a number of functions in one terminal, and implement complex protection algorithms [4, 5]. The research object is an autotransformer of the ATDCTN-125000/220/110/6-U1 type, located at the Lviv-2 substation. The subject of the study is the relay protection of the autotransformer against technological and electrical damage. The purpose of the research: development of relay protection of the autotransformer type 125000/220/110/6-U1 based on the RET 670 digital terminal. In the master’s thesis, a fragment of the normal circuit diagram of the 220/110/6 kV electrical network of PrJSC "Lvivoblenergo" with the substation "Lviv-2" is given, the main diagram with the placement of current transformers and the technical characteristics of the protected equipment are given. An analysis of the main circuit of electrical connections of the Lviv-2 substation was carried out, the connection of the substation from all voltage sides was indicated. The work analyzes technological and electrical damage on transformers and autotransformers. The calculation of the short-circuit currents of the electrical network at characteristic points in the modes of maximum and minimum currents was carried out using the V-VI-50P2 software complex.The purpose, principles of construction and operation of autotransformer relay protection are considered in the work [1, 3]. The general characteristics and main functions of the digital terminal RET 670 of the company ABB are given. The considered functions of relay protection, automation, control and management, which are implemented in this terminal [7]. The calculation of the operation parameters of the relay protection of the autotransformer, namely differential protection, maximum current protection and overload protection, was performed. The braking characteristic of differential protection is calculated [1, 3]. The sensitivity of the calculated protections was checked. When calculating the differential protection of the transformer, the parameterization of the data of the analog inputs of the terminal and the autotransformer was carried out, the provision of digital alignment in the arms of the differential protection was checked, the requirements for the current transformers of the protection arms were checked, the parameters of the operation of the differential protection were calculated. Calculated autotransformer relay protections with a capacity of 125 MVA based on the RET 670 digital terminal provide the necessary sensitivity. The principle scheme of relay protection, control and signaling of the autotransformer is developed, the corresponding drawings are given.