Technische Diagnostik — Strategie für eine moderne Instandhaltung

The quality of electrical equipment is secured for a long time by maintenance. On that occasion the maintenance uses different strategies. The importance and costs of the equipment are decisive for the optimal strategy. The maintenance contains technical diagnostics, service and reconditioning. On that occasion the technical diagnostics is the science of the identification of the condition of technical systems.     

Fixation of porous calcium phosphate with expanded bone marrow cells using an autologous plasma clot

Multipotent human mesenchymal stromal cells (hMSCs) are currently the most promising cell type for regenerative medicine and tissue engineering. For clinical applications with special focus on fracture repair a method to deliver in vitro‐expanded bone marrow cells to the fracture site is presented. Autologous blood plasma clotting was used to fix expanded cells and synthetic tricalcium phosphate particles. A jelly‐like but solid composite matrix was obtained which could easily be handled by the surgeon. The majority of embedded cells remained viable after the plasma gelation process, as was determined by fluorescence microscopy. Experimental cell culture over a period of 15 days showed proliferating mesenchymal stromal cells within the plasma clot.     

Monitoring und Diagnostik in der Hochspannungstechnik

To use electrical resources economically, it is useful to know the available remaining service life of used resources. With the use of technical diagnostic systems significant variables can be recorded. On the basis of these variables (temperatures, optical, electrical and mechanical variables etc.), conclusions concerning the future behaviour of the technical resources will be made. Based on the received data information, modifications in the operation behaviour can be diagnosed; tendencies can be detected and suitable counter measures can be set. The so-called “partial discharge measuring technique” can be regarded as a subsection and an important diagnostic equipment. For the detection of partial discharges different methods can be used.     

WATER-TREEING — Ein Alterungsphänomen in kunststoffisolierten Mittelspannungskabeln

Today, water-treeing is one of the most important ageing phenomena of plastic-insulated cables. Generally, the simultaneous reactions between electrical field and water cause small tree structures. These water-tree-structures resemble to a bush, start at imperfection points in polyolefin-insulations and expand in the direction of the applied electrical field. This process can be regarded as irreversible, causes a damage of the cable dielectrica as well as a decrease of the breakdown stress level. Water-treeing is a very complex process and the growth or acceleration of water-trees depends on many different parameters.     

Technical diagnostics for power apparatus

The purpose of technical diagnostics and preventive maintenance for power apparatus should be recognized in protecting equipment against failures and malfunctions. Due to an earlier detection of incipient faults in power apparatus economic benefits can be gained. This is important to reduce operating costs.     

Persönliches

Ohne Zusammenfassung     

Experiences with the Weather Parameter Method for the use in overhead line monitoring systems

Summary  Overhead lines are essential components of high voltage power systems worldwide. The performance of this network element is important for a save and reliable transmission of electrical energy. The load capability of a line is related basically to the line design itself and takes centre stage of the economic operation whereas the sag behaviour and the technical condition of the conductor and their components are more related to the line and network safety. Based on this situation overhead line monitoring systems are actually under discussion in many committees worldwide. This auxiliary equipment for overhead power lines helps to evaluate the actual transfer capability and/or to increase the system reliability. Therefore, a number of systems using different measuring methods and monitoring techniques are available on the market. More or less all methods are based on physical data and process information to achieve a suitable output to control the line stress. One of these methods is called the Weather Parameter Method, which uses local metrological weather data and system load information to estimate the conductor temperature. In a research project running over years an overhead line monitoring system was set up in cooperation with the Austrian transmission utility APG. After these years of experience a number of information and data based on the principle of the Weather Parameter Method is available and gives the scientific basement for this contribution. Three observation stations are collecting data all over the year; two stations are at a 220 kV overhead line and one station at the open air test field of the IHS in Graz in use. This contribution focuses on the coherences of the different parameters collected for the evaluation of the conductor temperature and it is not the main goal to discuss the improved performance by using a thermal management system, as mentioned in many other papers. By the knowledge of the punch-through of significant parameters in combination with the appearance probability a more accurate scheduling of the utilisation of the line under observation will be possible. A well prepared processing of many significant parameters for an overhead line monitoring system and a scientific approach based on some years of practical experience is presented in this contribution.     

Lifetime management of power transformers

Power transformers belong to the most important and most cost-intensive equipment of electrical power transmission and distribution. If an error in a transformer occurs, this causes not only an interruption of the electrical power supply of far areas but also large economic losses beyond that. Thus, the operation of transformers must guarantee a continuous and error free power supply over decades. Occurring errors and thus self-announcing possible failures of transformers should be detected in time, in order to initiate suitable measures for error correction. A continuous entry of the isolation status can prevent large errors, extend service life of the system and optimize maintenance. Thus, apart from higher system availability an avoidance of unplanned disconnections and expensive repairs are achieved. The emphasis of this contribution is to present methods which permit a substantially more exact and more reliable predicate about the current status of the isolation system of liquid-isolated power transformers.     

Femoral neck fracture in the elderly--differential procedure

Recent investigations and new devices allow specific regimens in the management of dislocated femoral neck fractures. Very old, immobile patients with a bad prognosis should be treated with a femoral head prosthesis. Patients with either arthritis, osteopenia, dysplasia or rheumatoid arthritis should receive a total hip prosthesis. The remaining population (age > 65 years) with dislocated femoral neck fractures and intact acetabulum should be managed with a bipolar hemialloarthroplasty. The protrusion rate is not significant.