Virginia Ivanov

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The power transformers are essential equipment in all transport and distribution grids. Minor faults or defects of this equipment can lead to ravaging effects. The most part of the monitoring and diagnosis systems are developed around expert systems. The expert systems regroup the methods based on analytical models and the ones based on knowledge on the(More)
The paper deals with the vector control and predictive control of the induction motor. For the vector control, the rotor flux oriented one is pointed out, with highlight on the voltage source inverter type. The influence of the most important parameter variations (e.g. stator resistance) is discussed. A simple (and practical) method for avoiding these(More)
This paper describes a Matlab program designed to compute the switching over voltages which appear when no-load high voltage lines are energized. The mathematical models of the high voltage distribution lines are presented also. The Matlab program is applied for the case of the high voltage distribution lines from the 220kV network of the ST Craiova, for(More)
In this paper, a Matlab application based on the graphical user interface (GUI) environment for sizing of technological equipment of a certain production system, designed for the current instrument transformer manufacturing, hereinafter referred to product, is presented. The designed product according to the customer requirements is part from the range of(More)
The assurance of the reliability for the transformation substations is one of primary goals of the manufacturers and distributors of electricity. Therefore, a proper monitoring and maintenance program is required. The circuit breaker is a complex device, subject to the thermal and mechanical stresses during the normal or fault currents switching. The(More)
The computation program of the transient recovery voltages that appears across the terminals of a circuit breaker, after the low inductive current has been interrupted at the disconnecting no load high voltage transformers, using the routines set developed in Matlab is presented. The computation algorithm is based on the peculiarities of operation of the(More)
The paper applies the diagnosis method based on the analytic model by investigating the output waveforms of the currents, torque and speed specific to a PMSM driving system. Several faults are simulated: open phase, entire phase short circuit in two situations (with and without current measurement, short circuit before and after current sensor respectively)(More)
The controlled switching can be applied to any type of commutations. Now there are dedicated controllers which are used more often for the switching of the transport and distribution lines, of the small inductive loads, of the capacitors batteries, or the energizing the no load power transformers. The paper presents a microcontroller (8051 family) based(More)
Recently, worldwide, the controlled switch became a technical solution for reducing the switching stress. After 90es, the number of equipment which uses the controlled switch fast increased, mainly due to the achieved performances. The controlled switching can be applied to any type of commutations. Now there are dedicated controllers which are used more(More)