Vladimir Lebedev

Bio: Vladimir Lebedev is an academic researcher from Ivanovo State Power University. The author has contributed to research in topics: Transformer & Current transformer. The author has an hindex of 4, co-authored 19 publications receiving 43 citations.

Physical simulation of heat exchange between 6(10) kV voltage instrument transformer and its environment with natural convection and insolation

Abstract: This study examines the results of thermal tests on a 6(10) kV digital combined current and voltage transformer conducted in an environmental chamber. This measuring instrument consists of current and voltage transformers, featuring a resistive divider, and is used for commercial and technical electric power accounting. Ambient temperatures and levels of insolation on the transformer surface were set for the environmental chamber, with simulation of voltage transformer functioning in normal and emergency modes. We determined the time needed for the thermodynamic system to move to steady heat exchange mode, and also the final temperatures in the lower resistors and on the surface of the voltage transformer insulation cover. The results of our study have been used in developing algorithms for self-diagnostics of the thermal state of a digital combined transformer.

Study of possibility of digital voltage transformers usage in fault location determination

Abstract: Innovative development of electric power systems is aimed at creating active-adaptive networks. Control of active-adaptive networks is based on usage of primary data measured at voltage and current transformers. In particular, the voltage transformers can be a source of information for devices determining fault location. The problem of fault location (FL) has always been and remains relevant because its solution may improve reliability of power supply. Overhead and cable high voltage power lines are most often-damageable elements of the electric power system. Power line cut-off is always accompanied by power undersupply or reduction of its reliability and quality. The paper investigates possibility of using transient voltage parameters obtained by digital voltage transformers for the FL on the cable lines.

Study and modeling of zero sequence current sensors in the transient modes in Matlab

Abstract: Solving the problems associated with the improvement of single-phase earth fault (SPEF) protection devices and SPEF location determination devices on the lines is of practical interest to study the operation of cable current transformers and other sensors in the transients states. The paper discusses the principles of constructing models of current sensors in the environment Matlab.

Modeling of measuring current and voltage transformers in dynamic modes

Abstract: Most of the works devoted to the study of measuring current and voltage transformers are focused on defining the characteristics of transformers in steady-state conditions to determine whether the transformers satisfy the metrological requirements. Such studies are often carried out using a chain of equivalent circuits or on the basis of field calculation methods. Field calculations methods definitely allow more precisely measuring the leakage field and the distribution of magnetic flux in the magnetic circuit. The study of transformers in dynamic modes is also of much interest. Nonlinearity of the core magnetization of measuring transformers leads to the need to create mathematical models that contain not only a model of the transformer itself, but also the model of circuits connected to it. In particular, of practical interest is the study of the stability of the voltage transformer to ferroresonance phenomena, when the transformer resonates with elements of the primary network connected to it. Thus, it is necessary to develop a mathematical tool allowing to create field models of instrument transformers connected to the primary and secondary circuits allow modeling not only steady modes, but transients ones as well. Problem solving in this formulation became possible after emerging of powerful computers and development of software packages capable to integrate for solving the problems.

Thermal and aerodynamic tests of a digital combined current and voltage transformer

Abstract: This study examines the results of thermal and aerodynamic tests of a digital combined current and voltage transformer conducted in an environmental chamber. This measuring instruments consist of current and voltage transformers, featuring a resistive divider, and are used for commercial and technical electric power accounting. Different ambient temperatures, airflow rates and levels of insolation were set for the environmental chamber, with simulation of transformer functioning in emergency modes. It was established that heat release at transformer outer surface with natural convection depends to a larger extent on the difference between the temperature at the transformer surface and ambient temperature, while with forced convection this heat release depends more on air mass speed, with greater heat release on the surface of an upward facing rib than on the surface of a downward facing rib. The results of our study have been used in developing algorithms for diagnostics of the thermal state of digital combined transformers.

Using of non-traditional current and voltage sensors for the fault location

Abstract: The article describes the possibilities of using the non-traditional current and voltage sensors to solve the problem of fault location in terms of digital transformers developed at the Ivanovo State Power Engineering University (ISPEU). Frequency and metrological characteristics of current and voltage sensors are given.

Modeling Capacitive Low-Power Voltage Transformer Behavior over Temperature and Frequency.

Abstract: The use of capacitive dividers (CDs) in medium-voltage (MV) networks started as simple voltage detectors and as rough voltage measurement instruments for protective purposes. Now, with the spread of intelligent electronic devices and renewable energy sources at the distribution level, capacitive dividers are designed and installed to perform accurate voltage measurements. Such a requirement is mandatory when the power quality has to be assessed. Therefore, CDs are currently being used either for power frequency or for high-frequency (supraharmonic- or partial-discharge-level) measurements. In this paper, typical off-the-shelf CDs are studied and modeled to understand how they behave in a wide range of frequencies and when the temperature varies. To this purpose, specific setups and tests have been developed and performed. From the results, it is clear that with proper modeling of CDs, it is possible to exploit them for measuring phenomena in a wide range of frequencies, including the effects due to temperature variations and self-resonances.

Calibration Procedure to Test the Effects of Multiple Influence Quantities on Low-Power Voltage Transformers.

Abstract: The article presents a study on low-power voltage transformers (LPVTs). Considering their increasing spread among Smart Grids, it is fundamental to assess their accuracy behavior in as realistic conditions as possible. Therefore, this article presents a detailed calibration procedure to test LPVTs’ accuracy when various external influence quantities are simultaneously acting on them. In the calibration procedure, the considered quantities are frequency, air temperature, and external electric field. Afterwards, the designed procedure is applied on three different off-the-shelf LPVTs using a measurement setup developed in a laboratory environment. The presented results (i) confirm the easy applicability of the designed calibration procedure; (ii) highlight the various effects of the influence quantities on the accuracy of different types of LPVTs; (iii) confirm the need to include more realistic tests, like the type-tests presented, into the standards to appreciate a wider set of possible in-field behaviors.

Study of possibility of digital voltage transformers usage in fault location determination

Abstract: Innovative development of electric power systems is aimed at creating active-adaptive networks. Control of active-adaptive networks is based on usage of primary data measured at voltage and current transformers. In particular, the voltage transformers can be a source of information for devices determining fault location. The problem of fault location (FL) has always been and remains relevant because its solution may improve reliability of power supply. Overhead and cable high voltage power lines are most often-damageable elements of the electric power system. Power line cut-off is always accompanied by power undersupply or reduction of its reliability and quality. The paper investigates possibility of using transient voltage parameters obtained by digital voltage transformers for the FL on the cable lines.