Bogumił Dudek
Medical implants and electromagnetic fields 50 Hz
Here we can find an attempt to answer whether persons having medical implants may stay close to accessible transmission facilities (under transmission lines and in the vicinity of substations) and whether the energy staff can safely work there. These are important questions as the "Regulation on health and safety" of the year 2019 allows – for the first time – persons who are not professionally related to the power industry to perform auxilliary works on power lines and in substations. At the same time on substations' transmission facilities pictograms were posted informing about the presence of the non-ionizing radiation and prohibition of entry for persons with active medical implants.These restrictions do not relate to overhead power lines but the above mentioned "Regulation ..." does not exclude such possibility. In the summary it is concluded that the 50 Hz electromagnetic field cannot cause disruptions in functioning of active implants (e.g. pacemakers, cardioverter-defibrillators, cochlear implants, insulin pumps) and that it does not cause any thermal effects in the environs of passive implants (e.g. hip or knee joint endoprosthesis, endoprosthesis for reconstruction of facial bones, orthopaedic screws and plates or vascular stents).
Keywords: medical implants, 50 Hz electromagnetic field, transmission facilities under overhead lines and in the vicinity of substations
Andrzej Błaszczyk, Mariusz Nawrocki, Andrzej Werner, Dariusz Woźniak, Maciej Olędzki
Problems with modification of flow compressors control system in Bełchatów power plant
Przedsiębiorstwo Badawczo-Wdrożeniowe HYDRO-POMP Łódź has performed a task for the Bełchatów power plant consisting in modification of four (from seven) ČKD 6RMY56 compressors working in the compressed air network. The scope of modification covered the flow and control systems and its aim was adaptation of flow parameters to actual requirements of the compressed air network. Modification of the control system was caused by necessity of making changes in control valves' drives and improvement of compressors' control. Discussed is the selection of the control algorithm. Before the modification the compressors were, and they still are, controlled by individual controllers Simatic 7. On the basis of the presented here conditions of the compressors' parallel operation and records of runs from before the modification there had been made a preliminary selection of an algorithm which was then investigated and implemented. The most surprising observation was the relation concerning the influence of relief valve opening: weak to the prevention of a flow drop in a compressor and a strong one to reduction of air delivery to the network. It turned out that the cause was a rarely met placing of the relief valve i.e. not directly on the compressor outlet but behind the outlet cooler. An algorithm that makes it possible to overcome this obstacle, was elaborated and successfully implemented with no need to change the installation system. Conducting of the control in accordance with this algoritm enables preserving the traditional compressor anti-surge system, but in the pressure control, except realizing its tasks through the inlet valve, it also introduces in some situations an impact of this system onto the outlet valve.
Keywords: Przedsiębiorstwo Badawczo-Wdrożeniowe HYDRO-POMP Łódź, Bełchatów power plant, modification of ČKD 6RMY56 compressors working in the compressed air network, control algorithm selection
Antoni Salij
Influence of a power source change on the work of flue gas fans asynchronous motors
Discussed is the influence of a power source change on the work of two mechanically coupled asynchronous motors driving a flue gas fan in case when one of he motors is supplied from a rigid network and the other would switch to a dynamic source of supply. Described are effects of disturbances by presenting values of main electrical and mechanical parameters, calculated on the basis of data registered in a power unit control system. Figures show basic characteristics of fan motors work, having a close connection with the situation of changing the electrical energy source of supply during their operation. Description of this incident aims to turn attention to threats that can occur in the situation of disturbances in operation of such equipment and to present the necessary preventive measures.
Keywords: electrical energy quality, asynchronous motor, common shaft work
Krystian Leonard Chrzan
Cap-and-pin insulators
Presented is the development and construction of cap-and-pin insulators, their properties and basic types of porcelain insulators used in Poland in the 20th century. Explained are the reasons to cease the production and use porcelain disc insulators. Described is an examplary type of a glass cap-and-pin insulator used nowadays in new and modernized 400 kV power lines.
Keywords: cap-and-pin porcelain and glass insulators, production, application