Laurentiu Alboteanu

Condition monitoring of transformer oil using thermal analysis and other techniques

Any transformer oil undergoes continuous degradation because of all electric, thermal, mechanical, and climatic stresses it suffers while operating in the transformer. Therefore, the oil has to be checked on regular basis in order to decide whether it is necessary to regenerate or replace it, avoiding thus a sudden failure of the transformer. This article presents results of in-the-laboratory-performed experiments on transformer mineral oil samples. Those samples came from a power transformer that works in the Romanian power network. There were three monitoring stages conducted over four-and-a-half years. We used two measuring techniques: (i) measurement of the state parameters of transformer oil (breakdown voltage, loss factor, water contents, acidity index, interfacial tension, number of particles larger than 5 microns, and gas contents) in order to describe the oil condition during the monitoring period and to anticipate any severe fault. This enables the user to take preventive action before a severe fault might eventually occur; (ii) thermal analysis (TA) and Fourier transform infrared spectroscopy (FTIR), in order to determine the stability of oil samples. By using TA and FTIR, and by evaluating each and every significant parameter, it has been proven that the tested oil is still adequate for further employment in the power transformer.

Energy efficiency of stand alone photovoltaic systems used in electrical drive for positioning ramps of anti hail missile

The paper gives one solution concerning the modality of power supply for anti-hail stations consumers. Because the anti-hail stations are situated in isolates areas, without electrical network access, the solution consist in the supply with electric energy from photovoltaic panels and accumulator batteries. There are also shown aspects regarding to energy efficiency of photovoltaic system, particularly to photovoltaic cells and photovoltaic modules. The simulation results of photovoltaic system used for anti hail stations were obtain with the HOMER program, version 2.1. This specialized software for renewable energy sources give the information about systems work and the energy production.

Active solar panel tracking system actuated by shape memory alloy springs

The unique properties (e.g. Shape memory effects) exhibited by shape memory alloys (SMAs) offer the possibility of producing Smart Sun Tracking Mechanisms (SSTMs) for photovoltaic panels. The paper presents an experimental model of an active solar panel tracking system, conceived by authors. This model uses SMA springs as actuators. The SMA springs work as linear actuators by contracting with great strength and speed when heated. The SMA springs attached to this structure can be activated to accurately change the position of the solar panel, following, this way, the motion of the sun throughout the day (appropriately tilted to directly face the sun during the day time). The active shape-change control of SMA spring, the possibilities for miniaturization, easy integration in system structure can effectively increase the efficiency of such SSTM.

Design of a Sun Tracking Automaton for Photovoltaic Panels with Low Concentration of Solar Radiation

It is known as photovoltaic (PV) panels have a low energy efficiency. A solution of increasing energy efficiency consists in use of sunlight concentrating elements equipped with automatic tracking systems. This paper presents aspects of designing an automaton for PV panels tracking system fitted with low sunlight concentrating elements.

Control of the electric drive of the anti-hail launching system

In the present, the Romanian anti-hail launchers are manually operated. This means that the positioning of the launcher on the two directions (azimuth and elevation) are adjusted based on the commands, by the human operator. The paper describes the implementation and experimental results of the electric drives of the two axes by using permanent magnets synchronous motors (PMSM) supplied by smart drives. The solution offers the possibility of automation and integration of the anti-hail launchers within intelligent systems.

Contributions to the development of the Romanian anti-hail system

The method used in Romania for combating hail is the sowing of the clouds method, with missiles launched from the ground. This paper presents contributions of the University of Craiova, Center for Innovation and Technology Transfer in the development Hail Suppression System.

Access system for vehicles powered by photovoltaic panels

To access the vehicles in different areas are frequently used automatic barriers. This paper presents such an access system, achieved a small scale that uses photovoltaic panels as main energy source.

Photovoltaic lighting for an educational room

The paper gives one solution concerning the modality of power supply for lighting in a laboratory for education students. Are presented aspects regarding to system design lighting and photovoltaic source. For sizing of lighting system utilization factor method was used. Design and simulation of lighting system was performed using Dialux dedicated program. Photovoltaic system was dimensioned based on a specific algorithm. Validation of the proposed solution for photovoltaic system was made using Homer dedicated numerical simulation program.