Hørbyebreen surged in the 19th or early 20th century, as suggested by geomorphological evidences and looped medial moraines. In this study, we investigate its wide−spread geometry changes and geodetic mass balance with 1960 contour lines, 1990 and 2009 digital elevation models, in order to define the present−day state of the glacier. We also study its thermal structure from ground−penetrating radar data. Little is known about the glacier behaviour in the first part of the 20th century, but from its surge maximum until 1960 it has been retreating and losing its area. In the period 1960–1990, fast frontal thinning (2–3 m a −1 ) and a slow mass build−up in the higher zones (~0.15 m a −1 ) have been noted, resulting in generally negative mass balance (−0.40 ± 0.07 m w. eq. a −1 ). In the last studied period 1990–2009, the glacier showed an acceleration of mass loss (−0.64 m ± 0.07 w. eq. a −1 ) and no build−up was observed anymore. We conclude that Hørbyebreen system under present climate will not surge anymore and relate this behaviour to a considerable increase in summer temperature on Svalbard after 1990. Radar soundings indicate that the studied glacial system is polythermal, with temperate ice below 100–130 m depth. It has therefore not (or not yet) switched to cold−bedded, as has been suggested in previous works for some small Svalbard surge−type glaciers in a negative mass balance mode.

The paper presents results of investigation of microstructure and micro-hardness for material of ZnO varistors applied to 110 kV surge arrester and surge arrester counter. The research combined two pairs of varistors, each consisted of one varistor subjected before to operation, while the other one was brand new unit and constituted a reference. All varistors were made of the same material by the reputable manufacture. The tests revealed a different degree of the material degradation for varistors subjected before to operation. This also refers to different degradation mechanism observed for the material of these varistors, if typical effects of degradation of aged ZnO varistors were considered as a reference. Physical state of spinel in the microstructure had a significant impact on the material degradation, however a considerable loosening of the microstructure associated with bismuth oxide was observed too. It was surprising, since the precipitates of the bismuth oxide phase most often showed very good binding to the ZnO matrix and high resistance to associated electrical, thermal and mechanical effects. The degradation effects in the ZnO matrix proved to be limited only.

The paper presents a concept of an active filter with energy storage. This solution can be used for the compensation of momentary one phase high power loads with discontinued power consumption (e.g. spot welding machines). Apart from the typical filtering capabilities, the system’s task is also the continuity of the input power from the feeder line and limiting its fluctuation. The proposed by the author’s solution can produce measurable economic benefits by reducing the rated power necessary to energize periodically operating loads and improving the indicators of electrical energy quality. The developed method of active power surges compensation enables a flexible approach to requirements concerning the rated power of the point to which the periodically operating loads with high peak current value are connected. The tests were conducted on a simulation model specially developed in Matlab & Simulink environment, proving high effectiveness of the presented solution.

The paper presents the test results for the microstructure of ZnO varistors comprising high voltage gapless surge arresters. The tests were performed on varistors produced in different periods and by various manufacturers. The research was inspired by different characteristics of changes in values of current flowing through surge arresters as a function of changes in values of system voltage in a 220 kV substation, and the temperature in a multi-year cycle. Furthermore, the effects of varistor microstructure degradation following a failure of an unsealed surge arrester were investigated. The results provided the grounds for assessment of ZnO varistor microstructure parameters in terms of their durability and resistance to degradation processes.

This paper presents details of 37 storm surges that occurred on the Polish southern Baltic Sea coast in the autumn/winter 2021–2022 season. They emerged during the passage of a larger number of low-pressure systems than usual from the SW-W direction over the Baltic Sea. Based on an assessment of meteorological and hydrological conditions during the storms, the relationship between the wind parameters, the sea level increase, and its maximum elevation was ascertained. The relationship between the sea level and the run-up elevation was ascertained. The elevation of the sea level and run-up on the onshore were compared with the beach height. Sections with a lower beach were affected by dune erosion already at a lower sea level. The dependence of dune erosion on the sea level elevation was presented. The value of the dune base retreat depended on the beach elevation and the sea level expressed by the onshore flow called run-up. The most significant erosion occurred during the storm Nadine with a sea level of 1.0–1.28 m AMSL. The average erosion varied between 1.0 and 4.5 m. The maximum erosion values reached 8–13 m.

The paper presents investigations of microstructure of varistors of damaged surge arrester counters. A similar ZnO varistor, not subjected before to operation, was a point of reference in this research. The results of investigations of the ZnO varistors show an untypical phase composition of their material, which was characterized by unsatisfying homogeneity and cohesion. The degradation processes of varistor material in the subsequent stages were recognized and described. A harmful impact of humidity inside the untight surge arrester counter on its operation and its ZnO varistors was proved. Some conclusions being the result of the operation checking of surge arrester counters were presented too.

This paper investigated the problems and impacts of transient flow in pipeline systems due to pump power failure. The impact of different protection devices was presented to assure surge protection for the pipeline system. A model via Bent-ley HAMMER V8.0 Edition was employed to analyse and simulate hydraulic transients in the pipeline system, and protec-tion alternatives were studied.

Surge protection included using only an air vessel, using an air vessel and two surge tanks, and employing five air ves-sels and vacuum breaker. The obtained results for pressures, heads, and cavitation along the pipeline system were graph-ically presented for various operating conditions. Using five air vessels with vacuum breaker valve as surge protection proved to be more effective and economical against pump power failure.

Changing the flow density did not have a significant impact on the pressures.

For protection with an air vessel; it was concluded that the value 40% of the original diameter for inlet pipe diameter of air vessel, and the value of 2/3 of original pipe diameter were critical values for the transient pressures. Cast iron pipes proved to be the best pipe material for all studied volumes of the air vessel.

For protection with an air vessel and two surge tanks; as the inlet pipe diameters increased the maximum pressures in-creased and the minimum pressures decreased.

Regression analyses were performed obtaining equations to predict the pressures according to the inlet pipe diameter, the area of surge tank, and the pipe diameter.

This paper presents the results of testing samples of shield-centering elements from medium-voltage surge arresters. The elements were made of TSE glass textolite. The elements have been dismantled from different operated surge arresters, which were subjected to discharge currents (short-circuit currents) of different intensity and duration. The discharge currents led to degradation of the tested elements with various degrees of advancement. The degradation was investigated using microscopic methods and energy-dispersive X-ray spectroscopy (EDS). Changes in the content of elements of the surface of textolite materials – as the degradation progresses – were documented.
It was found that high discharge current flows resulted in melting of the organic binder, epoxy resin, especially its surface layer. Partial charring and even burning of the resin was noticeable. Furthermore, it was found that with increasing degradation on the surface of the TSE laminate, the carbon and oxygen content, which are part of the organic resin, decreases. Simultaneously the amount of silicon, calcium and aluminium, which are present in the glass fibres, increases. The charring effect of the resin and the formation of conductive paths result in a decrease in the performance of surge arresters and their subsequent failure.

Tensile strength of aluminum castings has been improved by employing surge and filter in a conventional non-pressurizing gating system. For this purpose, three non-pressurizing bottom-gating systems were designed where the first design was a simple design with no filter and no surge, in the second design filter and in the third one surge was added to the end of runner. Tensile strength, Weibull module, scanning electron microscopy, chemical analysis, and melt pattern during the mold filling were thoroughly analyzed to compare these three designs. It was observed that employing filter and surge in the gating system reduces flow kinetic energy and consequently avoid surface turbulence and air entrainment, which leads to castings with fewer defects and higher reliabilities. Finally, it found that appropriate use of surge in the running system can be as effective as employing a filter in reducing melt front velocity.