Tamás Iváncsy

Investigation of dielectric properties of cable insulation by the extended voltage response method

The voltage response method is based on the measurement of the decay and return voltages on a charged and shorted dielectric. From the initial slopes of these voltages, two material properties, namely the specific conductivity and the polarization conductivity can be determined. By changing the shorting time of the charged insulation the polarization processes can be examined separately and the whole polarization spectrum can be investigated more precisely. This paper introduces how the voltage response measurement technique is extended by the variation of discharging times. Measurements on oil-paper and polymeric insulated cables were carried out and the results have been compared. By this measurement method the differences of polarization processes of different insulating materials can be investigated more precisely.

Advanced Risk Analysis for the Application of ESP-s to Clean Flammable Gas-pollutant Mixtures

There are several processes, in which risk of fire or explosion in electrostatic precipitator must be analyzed, like at certain types of biomass fired boilers, fine particle removal in pharmaceutical processes, etc. Appropriate, reliable risk analysis of such systems is vital to ensure safe operation. Application of fault tree analysis for risk calculation is a well known method, but in some cases it is difficult to identify all of the significant events and it is more difficult to determine the initial probability values for the basic events of the fault tree. When the determination of the probabilities contains uncertain information, it is necessary to evaluate the reliability of the result or to decrease uncertainty of initial probability values. This paper represents an advanced method based on fuzzy logic, that is capable to estimate the effect of uncertainty, and determine reliable input parameters for the fault tree analysis in such cases, when risk of fire or explosion in the electrostatic precipitator must be taken into consideration. The paper represents the process of the creation of fault tree, the determination of fuzzy membership functions for the input probabilities, the calculation process and the evaluation of the final result of the analysis.

Analysis of the Energy Consumption of Building Automation Systems

Nowadays, the efficient energy usage is more and more important, and reducing the energy usage of buildings lowers the overall environmental effect of energy systems. The building automation systems provide a possible solution to create smart energy distribution in buildings by controlling lighting, heating, cooling and other energy-consuming systems. One possible solution for reducing energy consumption is the use of building automation systems for energy management, and these automation systems can help to optimize the efficiency of heating, air conditioning and the electric energy consumption. In most cases, the overall consumed energy reduction with a building automation system is considered, but without the exact knowledge of the electric energy consumption of the automation system, the overall energy efficiency cannot be evaluated. The aim of our study is to analyze the electric energy consumption of a building management system. The energy consumption of a building automation system is measured in a small office-like environment. The system uses a separate power supply for the sensors and actors on the bus, so the energy consumption of the power supply gives the overall electric consumption of the building management system in different conditions. Based on the result of the analysis, the ratio of the used energy by the system and the energy consumption reduction has been estimated, and an optimal design of these systems is suggested.

A nanogrid concept for supplying ICT devices to improve the energy efficiency of small offices

Nowadays, the energy consumption of information and communication technology (ICT) devices became more and more dominant factor of electricity consumption of the offices, therefore supplying these devices from renewable sources can help to improve the energy efficiency and makes the offices greener. On the other hand, the mobile devices (laptop computers, tablets smartphones) have become more popular in the offices thanks for their versatile usability. In addition, for longer operation time the battery capacity of these devices has increased therefore the usage of their battery capacity for energy storage can foster the integration of the renewable sources into the electricity system of offices. One solution for greener office can be to connect these devices into one nanogrid with integrated renewable sources. By this solution the consumption, storage and generation of electricity by small scale renewable sources can be optimized.

Testing of high voltage cable lines by damped ac technique — A case study

In this paper, a case-study is presented, which emphasizes the role of local degradation detection besides the general condition assessment of the high voltage cable line insulation. The applied damped AC method provides several diagnostic parameters e.g. PD inception and extinction voltages, PD map and loss factor therefore it is an effective tool in cable diagnosis. The partial discharge tests detected the weak points of the investigated cable line, which were mounted with porcelain terminations. After the replacement of the terminations the cable line has become PD free. This case study emphasizes that from the point of view of reliability, the weakest points of the HV cable lines are the cable accessories. The time of the failure of these components cannot be predicted exactly, the only way to prevent the failure is the regular diagnostic testing of critical cable lines.

Evaluation of nerve stimulation of electromagnetic field by lightning current pulses

The lightning current generates a time varying magnetic field near down conductors, when lightning strikes the connected Franklin-rod. The down conductors are mounted on the wall of buildings, where residential places can be situated. It is well known that the rapidly changing magnetic fields could generate dangerous eddy currents in the human body. If the duration and the gradient of the magnetic field were high enough, the peripheral nerves are excited. In this study, the authors introduce an improved model of the interaction of electromagnetic fields of lighting current near a down conductor with the human body. The new interaction model has two parts: estimation of the magnetic fields surrounding the down conductor by a new numerical model and evaluation of health effects of rapid changing magnetic fields on the human body based on different nerve and neuron excitation models.

Modelling of Complex Physical Processes in Electrostatic Precipitators

Electrostatic precipitator (ESP) models have improved significantly in the past years. The dramatic development of the capacity of computers made it possible to increase the complexity of ESP models. Recently the different interactions between the gas, the electric field with ion space charge and the charged particles to be precipitated can be described more accurately by the newly developed complex approach. However even some of the newest computer models are limited; they are not able to follow the interactions of the complicated physical phenomena properly. For example pulse energisation of short time impulses cannot be described correctly with models assuming continuous corona current. There is another important problem, namely the examined duration of operation. Some of the models determine the trajectories of dust particles assuming that they are unchanged during the operation of an ESP. The validity of this assumption is very limited in such cases, where the development of certain phenomena is time dependent (e.g. back corona formation). In this paper the authors focus on the long term models, analysing such situations in which it is vital to investigate a longer period of operation of ESP-s. Using the newly developed model the effect of back corona, rapping, etc. can be analysed with higher reliability than it has been performed in previous ESP models.

Modeling of Back Corona in Pulse Energized “Multizone” Precipitators

Most of the electrostatic precipitators have at least two zones in which different supply parameters, rapping programs can be used. Lot of ESP models are handling the electrostatic precipitator as one block whit the same energization. However, separated operation of zones is useful to improve collection efficiency. In this paper authors represent an improved numerical ESP model that is capable to handle multiple zones with different properties. The represented modeling process is focused on different energization modes and the formation of back corona.

Improved modelling of impulse mode ESP energization

Regulations to reduce air pollution give more and more strict limits for the emission. Electrostatic precipitators (ESP-s) operating with traditional DC supply voltage are often not able to fulfil the requirements, therefore lot of them needs upgrading. The DC power supply is substituted by pulse energization to obtain energy saving and better efficiency of precipitation. To provide safe, reliable and efficient operation of the upgraded ESP, several problems have to be solved. One of them is the prediction of time of safe operation of the cables and insulations. Authors applied different diagnostic methods for this purpose. Another important problem is the prediction of precipitation performance. For this purpose authors developed a numerical model of modular structure. Separate modules calculate the velocity field of the gas, the charging of particles, the back corona and dust reentrainment. By the help of the model a detailed analysis of different supply modes can be made, to obtain the best possible operation of a given electrostatic precipitator applying a certain supply mode.