Relay protection and automation of the three-winding transformer of the «Zavodska» substation based on the RET-670 digital terminal
Students Name: Maikut Vitalii Ruslanovych
Qualification Level: magister
Speciality: Electric Power Generation and Distribution Management Systems
Institute: Institute of Power Engineering and Control Systems
Mode of Study: full
Academic Year: 2022-2023 н.р.
Language of Defence: ukrainian
Abstract: The high level of the modern energy system is manifested in the newest complexes of electrical equipment, which are united by a single generation mode and are able to supply energy consumers without interruption. An integral part in the uninterrupted operation of the network is represented by relay protection and automation. The concept of relay protection and automation involves compliance with the following requirements: speed, sensitivity, selectivity, reliability. Also important factors are the cheapness of products and compatibility when used with other devices [1]. Automation devices are improved every year and new digital protection devices appear. This makes it possible to replace several devices with different functions with one. This work was dedicated to the development of relay protection and automation, built on digital principles [2, 3]. The object of the study is the electric substation "Zavodska" with voltage classes of 110/35/10 kV. The subject of the research is the relay protection and automation of the three-winding transformer of the "Zavodska" substation. The purpose of the work is the development of relay protection and automation of the three-winding transformer of the "Zavodska" substation based on the RET-670 digital terminal of the ABB company. The master’s thesis provides information on the location of the "Zavodska" substation and the part of the electrical network of PrJSC "Lvivoblenergo" with the substation under study [4]. The main diagram of electrical connections of the substation and technical characteristics of the main electrical equipment of the substation after the reconstruction are given. The paper considered the main types of transformer damage and special modes of operation of networks of the studied voltage classes. The features of differential, current and gas protection of the transformer are also considered [1, 5, 6]. Also, information is given about the features of relay protection and automation made on a digital basis, the advantages of digital devices, their accuracy and speed of operation are indicated. The general characteristics and main functions of the ABB REF-670 digital terminal, which is used for protection and automation of all types of transformers and shunt reactors, are given. Typical REF-670 configurations and functions implemented in them are considered. The typical configuration of the "A05" terminal was selected, the set of functions of which allows to implement all the necessary protections and automation of the three-winding transformer with a capacity of 16 MVA of the "Zavodska" 110/35/10 kV substation. Also, the basic control and management functions of the digital terminal were given, and the circuit breaker failure backup device was separately considered as part of the device’s automation [7]. With the help of the "DAKAR" software complex, the calculation of short-circuit currents (SCC) on the high-voltage (HV), medium-voltage (LV) and low-voltage (LV) sides of the transformer was performed for the maximum and minimum modes of short-circuit currents. The results of the calculations were used during the design of transformer protection and automation. The parameters of the protection of the transformer of the "Zavodska" substation were calculated, namely: differential protection, maximum current protection (MCP) with starting by voltage from overcurrent of external short-circuits, protection against overloads [3, 6]. The calculated relay protection of the three-winding transformer based on the REF-670 digital terminal provides protection against all types of damage. The necessary sensitivity conditions are provided in protections. The operating parameters were calculated and the sensitivity test of the circuit breaker failure backup device was performed. The use of a circuit breaker failure redundancy device provides near and far redundancy of damage shutdown in the event of a main circuit breaker failure. For the configuration of the digital terminal, appropriate tables with parameters and settings of protection and automation activations were created.