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Problems of measurements, diagnostics and exploitation in electric power systems are intensively explored in the last several years, especially in the context of so – called Intelligent Electric Power Systems (IEPS). Aforementioned problems are extremely important from a point of view of electric power system exploitation efficiency as well as of a reliability and operation correctness of the receivers installed in these systems. More and more common use of renewable and distributed energy sources together with an increase of a number and power of non – linear loads leads to the problems with the power balance in the systems under consideration. These problems are connected with changeable and difficult to predict and control distributed generation power sources and also with more and more higher distortion levels of voltages and currents in the analyzed systems.

A notable integration development of different elements of combined electrical power systems observed in the area of production and utilization technology of electric power as well as in the field of widely understood information technologies (with taking into account the issues of digital signal processing, communication, control and monitoring), leads to creation of a previously mentioned new class of systems, that is, intelligent electric power systems. Novelty of these systems is intelligent measurement structure with bidirectional change of information among the participants of the electrical energy market. Additionally, to amplify the advantages related to integration of numerous distributed electrical energy sources, often of a small amount of powers, and to limit the problems connected with reliability of electrical energy delivery to the key recipients, an implementation of local electric power subsystems, so – called microgrids, with possibility to auto – diagnosis and auto – reconfiguration is proposed. Experiences taken from the ship electric power systems operation are a relevant information source about future industrial microgrids, as the components of IEPS, and at the same time a development of a widely treated measurement infrastructure becomes a fundamental, key problem of a development of considered class of systems. A notion of measurement infrastructure in the meaning of the drafted subject matter
of IEPS should cover both measurement methods, including the measuring – control algorithms, and new system and hardware solutions, together with related software.
An appropriate measurement infrastructure is a necessary condition for efficient exploitation and effective diagnostics of electric power systems, both land and ship systems.

This issue of Scientific Journal of Gdynia Maritime University consists of thirteen research papers covering aforementioned drafted subject matter.

Presented articles can be divided into four groups, whereas the first four papers having both the cognitive and application aspects, concern the selected problems connected with measurements, diagnostics and exploitation of ship systems and three subsquent papers are related to innovative solutions of methods and systems in the area of smart grid, renewable energy sources and hybrid power supply systems.
Next, the three consecutive articles are addressed to new methods of analysis and design of electrical networks and electronic systems, and finally, the last four papers are devoted to investigations of exploitation properties and constructional parameters of inductive motors supplied by voltage with worsened quality.

The first article published in the current issue concerns an analysis of the cooperation of non – linear load with active filter and the main switchboard of marine power engineering laboratory. This paper is based on the experimental research results.

The second paper is devoted to comparative study on selected operation parameters of a combined cycle plant based on the data of producer and research results of the simulation model.

In the articles numbered as the thrid and the fourth some selected issues concerning the exploitation of ship electrical networks were discussed, whereas in the thrid paper a main focus is concentrated on the IT and TT networks type, and in the fourth one a description of selected hazardous issues during operating the power grid with the insulated neutral point is presented.

The fifth from the presented papers concerns the problems of monitoring low voltage (industrial smart grid) intelligent electric power networks, with emphasizing  the issues of erroneous indications of electrical energy counters.

In the sixth article an innovative approach to analysis of overhead high voltage power line capacity cooperating with wind farm power is shown.

The seventh article is dedicated to analysis of use energy profiles to choose elements and control algorithms in hybrid power supply systems, first of all for special applications.

The paper numbered as the eighth the ninth and the tenth are referred to selected methods of analysis and design of electrical and electronic networks. They concern the following issues, in turn: usefulness study of Rosenstein and Eckmann procedures for identification of chaotic time series (the eighth paper), the methods of analysis of chaotic behavior of measurement data of a complex energy system (ninth paper) and the design of electronic systems based on the GeckoCircuits environment (tenth paper).

The last part of the presented issue of Scientific Journal of Gdynia Maritime University is dedicated to analysis and research of exploitation properties and constructional parameters of inductive motors supplied by the voltage with worsened quality for different combinations of disturbances. These papers are oriented to investigation of the windings temperature of induction motor (the eleventh article),
to investigation of the load – carrying capacity of an induction cage machine
(the twelfth article) and to investigation of the influence of winding temperature on electromagnetic torque of induction motor under voltage containing subharmonics
(the thirteenth article).

Prof. dr hab. inż. Janusz Mindykowski