Model of implicit pole electric machine based on mathematical formulation of magnetic field in air gap

When modeling transient processes in electric power systems, the issue of designing reliable models of electrical machines is of great interest. The most difficult task is to design the models of synchronous and asynchronous machines. The purpose of the project is to develop mathematical models of synchronous and asynchronous machines based on a generalized model of an implicit-pole machine that considers the change of rotor speed, geometric shapes, and the type of rotor and stator windings. Methods of mathematical modeling of electromagnetic fields in the air gap based on Maxwell equations and methods of the theory of electrical circuits are applied. A system of nonlinear differential equations is considered as a mathematical model of a generalized implicit-pole machine. The key assumption made is the high magnetic permeability of the stator and rotor cores. Technical data of real electric machines have been used for verification. Mathematical models of an implicit pole synchronous machine and an asynchronous machine with a phase rotor have been developed. These models can be used to analyze transient processes in the aggregate without dividing them into electromagnetic and electromechanical ones. The novelty of the models is the fact of non-sinusoidal distribution of the magnetic field in the air gap, various types of multiphase AC windings and rejecting the principle of constant rotation frequency at the time step of the simulation. The proposed mathematical models can be used to solve design problems, to analyze the modes of electric power systems, the operation of relay protection and automation of electric power facilities, and emergency automation. In the future, the equations that consider the influence of the damper circuits and the peculiarities of the windings will be added to the developed mathematical models. The purpose of further research is to develop models of salient-pole synchronous machines and asynchronous machines with a squirrel-cage rotor.

KEY FACTORS AFFECTING THE DISCONNECTION OF EXPERIMENTAL AND MODEL CURVES IN MODELING P–N-TRANSITION ON PULSE BROADBAND SIGNALS

The article discusses the key factors influencing the discrepancy between the experimental and model curves when simulating a p – n junction on pulsed broadband signals. The reason for the discrepancy lies in the quasi-static representation of the forward and backward reconstruction of the p – n junction in the standard SPICE model. The quasi-static approximation does not take into account the transient processes in the p – n junction, which are associated with the transit time of minority charge carriers and the series resistance of losses.

RADIATION EFFECTS IN INTEGRATED CHIPS WHEN EXPOSED TO IONIZING RADIATION

In the onboard equipment, components of electronics, which have increased sensitivity to the effects of ionizing radiation are widely used. The transient processes in electronic products are particularly dangerous, associated with an absorbed dose of radiation, leading to functional or irre-versible failures in the operation of onboard systems.

Research of transition processes in the operation of reclamation pumping stations

This paper presents the results of field studies carried out on existing pressure systems with pumping stations. The considered field experiments were carried out on a closed irrigation system, which includes a pumping station with a water intake, a closed irrigation pipeline network and sprinklers. On this system, field studies of transient processes were carried out with the simultaneous shutdown of all pumping units simulating emergency power outages of the motors, and with shutdown of one of the units simulating the automatic operation of the station. The presented results make it possible to carry out practical calculations of transient processes for pumping stations with different water supplies, heads, capacities, diameters and lengths of pressure pipelines and shockproof devices.

Simulation study of 6–10 kV cable lines for transient processes calculation during earth faults

As a rule, researchers do not consider the dependence of the inductance of cable lines on frequency in their scientific papers devoted to the calculation of transient processes during single phase-to-ground fault in 6–10 cable networks. In some cases, it can lead to significant errors in evaluation of current and voltage transient components parameters. Therefore, it is an urgent task to estimate defined errors and the scope of application of frequency-independent equivalent circuits and models of 6–10 kV cable lines during calculation and simulation of transient processes in case of single phase-to-ground fault. The authors applied PSCAD / EMTDC software to study the effect of the frequency dependence of the inductances of 6–10 kV cable lines on the calculation accuracy of transient processes during single phase-to-ground fault. It allows to simulate electric power systems models with the usage of both frequency-dependent and frequency-independent cable line models with round conductors only. To check the adequacy of the frequency-dependent three phase cable model developed in PSCAD software, the authors have used a frequency-dependent model of 6–10 kV three-phase cable with sector-shaped conductors designed in COMSOL Multiphysics software. The authors have developed an approach to develop of 610 kV cable lines models with frequency-dependent and frequency-independent parameters. The authors have obtained error estimation in transient current and voltage parameters during single phase-to-ground fault in cable networks models that do not consider the frequency dependence on inductance (for discharge components the error is 1520 %, for charging components the error is equal to 510 %). It is shown that models with cable line parameters defined according to spreading speed of electromagnetic wave, can be used for approximate calculation of transient current and voltage to solve most of tasks of investigation of transient processes during single phase-to-ground faults. Application of the developed recommendations to determine three phase medium voltage cable lines parameters will increase the calculation accuracy of transient processes during single phase-to-ground faults in 6–10 kV cable networks. Only application of frequency-dependent models of cable lines allows us to provide required accuracy to develop methods of distant earth fault localization in 6–10 kV networks.