Petr Toman

Bio: Petr Toman is an academic researcher from Brno University of Technology. The author has contributed to research in topics: Fault (power engineering) & Ground. The author has an hindex of 8, co-authored 60 publications receiving 266 citations.

Interharmonic - Flicker Curves of Lamps and Compatibility Lever for Interharmonic Voltages

Abstract: The aim of the paper is to describe procedures for systematical determination of immunity of lamps to supply voltage variations caused by interharmonics. The curve of lamp immunity is presented as an interharmonic magnitude versus interharmonic frequency curve and is called interharmonic-flicker curve. The interharmonic-flicker curves of lamps are determined by utilizing a modified concept for measurement of a lamp gain factor in frequency domain and by utilizing the published limits on voltage flicker. Another described method for establishing the interharmonic-flicker curves of lamps is the method based on measuring the luminous flux flicker curve which is defined by utilizing the published limits on voltage flicker as well. Further a complex measured data file of interharmonic-flicker curves in various combinations of discharge lamps (fluorescent lamps and high intensity discharge lamps) and ballasts are pointed. Measured and compared combinations include various types of discharge lamps, various wattages, modes of operation of the ballast and its specific designs and dimensioning of circuit elements etc. Finally, determined interharmonic-flicker curves of chosen lamps are used for proposal approach how to revise the compatibility level for interharmonic voltages relating to flicker.

Earth fault location based on evaluation of voltage sag at secondary side of medium voltage/low voltage transformers

Abstract: The main reasons for installation of power quality meters in distribution transformer substations are power quality monitoring and global evolution of electrical network towards the ‘smart grid’. In case that all measurements from the meters are properly synchronised and centralised, new possibilities of control or evaluation of the network are enabled. This contribution proposes the possibility for an earth fault localisation with the aid of synchronised data recorded on the low-voltage side of the medium voltage/low voltage transformers in compensated neutral distribution networks which are equipped with auxiliary resistor for short-time increasing of the active part of the fault current. The described method uses voltage sags evoked by connecting of the auxiliary resistor for locating the faulty section. The proposed method is tested with the help of numerical model which presents a part of the distribution network.

Performance Testing and Methodology for Evaluation of Power Line Communication

Abstract: The paper describes a unified methodology which takes into account the advantages and disadvantages of different Power Line Communication (PLC) technologies suitable for Smart Metering deployment. The methodology should provide a detailed evaluation of PLC technologies based on a clear definition of the different parameters and their measurement. Based on this methodology, we should be able to provide a comparison of the selected technologies and the methodology should also provide data for the design of a telecommunication infrastructure for Smart Metering/Smart Grids. In this paper and based on this methodology, we also present the performance tests carried out in laboratory environment on low voltage and in on-field conditions on medium voltage.DOI: http://dx.doi.org/10.5755/j01.eie.24.3.20983

Possible Solutions to Problems of Voltage Asymmetry and Localization of Failures in MV Compensated Networks

Abstract: The compensated networks are affected by the phase capacity asymmetry of wiring, which causes the unbalancing of the phase voltages in the tuned condition of the arc-suppression coil. In the especially unfavourable cases this effect reduces the possibility of network operation with the tuned arc-suppression coil. The operation with the arc-suppression coil out of tune is accompanied by higher values of the fault currents during the ground faults and the natural frequency of the course of recovery voltage in the network after switching off or interrupting the ground fault. These disadvantages can only be removed by efficient elimination of the phase asymmetry. The new methods of eliminating the phase capacity asymmetry allow for controlling the phase asymmetry size (its reduction as well as its possible increase), they keep it within a specified tolerance band (Uo value in the tuned condition of the arc-suppression coil is typically maintained at levels from 1% to 4% of the network voltage phase value). The new methods of elimination of the phase capacity asymmetry have favourable effects on the network operation during the ground fault and do not reduce the protecting elements sensitivity to high-ohm ground faults. By improving the accuracy of the arc-suppression coil tuning the safety of the compensated networks operation can be enhanced. The other properties of the whole system of phase capacity asymmetry elimination designed to increase the compensated networks operation safety, to improve the reliability of ground- fault protections and to locate the fault areas, can be fully utilized

Analysis of the power quality and the impact of photovoltaic power plant operation on low-voltage distribution network

Abstract: In general, the power quality analysis is a very complex issue and it requires a long-term measurement in real distribution networks. Moreover, the voltage has to be within specific voltage tolerance for the low-voltage distribution network. In this paper the measurement of the low-voltage network after the connection of a small photovoltaic power plant is evaluated. Therefore, the influence on the changes of the voltage, flicker and total harmonic distortion by connected power plant under different operating states is described in the paper. The main task of the article is to present the results of the voltage quality measurements carried out in low-voltage distribution network.

Introduction to Signal Processing

Abstract: The previous chapter introduced the concept of a random process and explored in depth the temporal (i.e., time-related) properties of such processes. Many of the specific random processes introduced in Chap. 7 are used in modern engineering to model noise or other unpredictable phenomena in signal communications. In this chapter, we investigate the frequency-related properties of random processes, with a particular emphasis on power and filtering.

Application of Grey Correlation Analysis in Evolutionary Programming for Distribution System Feeder Reconfiguration

Abstract: Feeder reconfiguration is a common technique that is used by distribution system operators during normal or emergency operational planning. By changing the status of switches on the distribution systems, the feeders can be reconfigured. During a feeder reconfiguration, more than one objective is considered by the distribution system operators. Due to the complexity of the reconfiguration problems, the system operators are looking for assistance from computer program that can provide adequate switching plans to reconfigure the feeders such that the desired goal can be achieved. Thus, the feeder reconfiguration is a type of discrete multi-objective optimization problems. Evolutionary programming (EP) technique is a method that can be applied to identify an optimal switching plan for feeder reconfiguration. A fitness function is required in EP for chromosome selection during reproduction process. The fitness function needs to integrate the objectives to provide a measure for each chromosome. Normalizing the objectives is a typical method for multi-objective optimizations such that these objectives are comparable. In this paper, Gray CoRrelation Analysis (GCRA) method is proposed. The proposed method is used to integrate the objectives and provide a relative measure to a particular switching plan associated with a chromosome without any prior knowledge of the system under reconfiguration. Two different distribution systems are used in this paper to demonstrate how the proposed GCRA is applied during the selection process of EP. Several simulations show that the EP can identify the solution more accurately when GCRA is applied than other methods.

An Accurate Noniterative Fault-Location Technique for Low-Voltage DC Microgrid

Abstract: The least erroneous knowledge on fault location in distribution systems helps the restoration process, expedites maintenance, and reduces power outage duration. A fault-location method using the probe power unit (PPU) in dc microgrid assumes that the natural frequency of the system is equal to the damped resonant frequency of probe current. This assumption leads to prominent error in fault-location calculation. To estimate the location of fault in the low-voltage dc microgrid system, a noniterative fault-location technique using PPU is proposed in this paper. Considering damping frequency and attenuation of the probe current, which is a function of fault distance and damping coefficient, the fault location is obtained. The technique is tested for high-resistance fault as well as radial and looped topologies and is found to be more accurate.

Location of Single Phase to Ground Faults in Distribution Networks Based on Synchronous Transients Energy Analysis

Abstract: As a result of small fault current, high level of noise and a large penetration of distributed generators (DG), in the neutral non-effectively grounded medium-voltage (MV) distribution networks, it is quite difficult to locate the faulted line section for single phase to ground faults. In this paper, using a technique based on synchronized measurements in distribution networks, a fault location method based on the analysis of the energy of the transient zero-sequence current in the selected frequency band (SFB) is proposed. The equivalent impedance of the distribution network with lateral branches is studied with an equivalent network, and the phase-frequency characteristics of the equivalent impedance are analyzed. The SFB, within which the transient energy of the faulty line section is larger than that of the healthy line sections is determined. A combined fault-section location criterion is proposed and the implementation scheme is illustrated with the distribution level phasor measurement units. Numerical simulations of the IEEE 34 node system and the field experiments of a 10kV distribution network validate the feasibility and effectiveness of the proposed method.