Zlatan Stojković

Development of a portable fiber-optic current sensor for power systems monitoring

The paper presents a portable fiber-optic current sensor (FOCS), based on the Faraday effect, with a magnetic concentrator. Both the optical sensing head and electronic processing block are illustrated. A detailed experimental study to confirm the performance of the device is also reported. According to the measured values of ac rms current up to 1 kA, a calibration procedure was performed. The paper provides an analysis of the results obtained for various conductor displacements within the concentrator. The well-known temperature dependence of the Faraday current sensor and its influence on the measurement accuracy are tested by means of a special double-layer thermal insulated chamber. The calibrated and characterized FOCS is applied for harmonic analysis of the current. The results clearly illustrate the nature of the sensing process and demonstrate odd-order harmonics presence, as predicted by the mathematical model. The paper indicates that the developed device is suitable for the power systems monitoring.

Practical application of fiber-optic current sensor in power system harmonic measurement

This paper presents a portable fiber-optic current sensor (FOCS), modified for current harmonic measurement in high-voltage electric power systems. The details of the sensing head redesign are illustrated. Also, both electronic processing block and harmonic analysis algorithm have been illustrated. The practical application of the so-redesigned device has been successfully verified experimentally at a thermal power plant. The measurements have been made for the operation of a 6-kV induction motor with different load conditions and the thyristor excitation of a 15-kV alternating current generator. The experimentally determined current waveforms, the corresponding relative harmonic content computed by discrete Fourier transform, and total harmonic current distortion for various measuring points have been displayed. Important requirements for accurate harmonic measurements have been discussed. The results clearly verified the applicability of the FOCS for monitoring electric power quality as suggested in this paper

AutoCAD-based concept for estimating lightning protection zone of transmission lines and structures

The paper presents lightning protection zone visualisation for transmission lines and structures. Different methods used for protection zone evaluation are discussed. A software tool realised by applying AutoCAD and programming languages AutoLISP and Visual Basic is demonstrated. Some of the software tool possibilities are illustrated for concrete calculation examples.

The high-voltage substation configuration influence on the estimated lightning performance

ContentsThe substation configuration has a great influence on the lightning overvoltages caused by backflashes at the lines connected in front of the substations. In most of the analyses the critical substation configuration is assumed with only one connected line. In the paper the influence of the substation configuration the line performance is analyzed. The mean time between power transformer insulation failures is computed taking into account the monthly distribution of the lightning activities and also the monthly probability distribution of certain substation configurations. The method is illustrated by a 400 kV substation example.ÜbersichtDie Schaltungen von Hochspannungsanlagen beinflussen erheblich die Höhe und Form der Überspannungen, die von rückwärtigen Überschlägen auf den zugeschalteten Freileitungen verursacht werden. In konventionellen Überspannungsberechnungen wird die Schaltung mit nur einer Freileitung betrachtet. Der vorliegende Aufsatz analysiert den Einfluß von verschiedenen Schaltungen auf die Überspannungen. Das mittlere Zeit-intervall zwischen Isolationsfehlern von Transformatoren wird berechnet unter Berücksichtigung der monatlichen Verteilung und auch der Verteilungsfunktion der monatlichen Wahrscheinlichkeit von Blitzeinschlägen von verschiedenen Anlageschaltungen. Die Berechnungsmethode wird am Beispiel einer 400 kV-Schaltanlage eingehend dargestellt.

Software Tool for Evaluation of Electrical Energy Produced by Photovoltaic Systems

This paper presents a software tool for evaluation of electrical energy generated by photovoltaic (PV) systems. The software was developed using the MATLAB software package and contains the elements of an expert system. The software is designed for engineers who are involved in photovoltaic system design and for students (undergraduates and Masters) of electrical engineering who, using the software, adopt theoretical assumptions and solve practical engineering problems. The structure, organization and software capabilities are illustrated within the example of the design of an actual photovoltaic system.

Fuzzy logic and artificial neural network-based thermography approach for monitoring of high-voltage equipment

This paper presents two methods for condition monitoring of high-voltage equipment based on the thermography approach. The overheating temperature of the hot spot has been obtained using the performed thermography procedure. MATLAB® technical computing software has been used to design the fuzzy controller and artificial neural network. The age of the element, the voltage level, the overheating temperature and the temperature of the previous overheating have been used as the reference inputs for the designed controller and artificial neural network. The developed software tool has been applied for the evaluation of the urgency of intervention in the function of the input data, designed rule base and the methods of defuzzification. Real measurements were used as input data in both methods so that the results were confirmed. The results might serve as a good orientation in the high-voltage equipment condition monitoring. The educational aspects of the application of this software tool are very important for both undergraduate and masters students studying Monitoring and Diagnostics of High Voltage Substations. During the past two academic years, the software application has received favorable comments from students.

Computer-Aided Modeling and Simulation

The purpose of this chapter is to familiarize the reader with the following: The definition of the concept of computer-aided modeling and simulation; A review of the method for model development; The principles of carrying out computer-aided simulation and its limitations; A review of an example for initialization of computer-aided modeling and simulation.

Application of Software Tools in Power Engineering Calculations

MATLAB® technical computing software is a software tool for solving mathematical problems, analyzing data and visualization. This tool integrates numerical analysis, matrix calculation, data processing and graphical display. It is characterized by its ability to solve all mathematical problems. The advantage of this software tool is in its simple expression of mathematical problems and solutions as they are written in mathematics, by which traditional programming is avoided [1-4].

Software Tool for Estimating the 3D Lightning Protection Zone of High Voltage Substations

This work presents the application of an expanded version of a software tool, formed using powerful AutoCAD software and the programming language Visual Basic, which enables the estimation and visualisation of a 3D lightning protection zone for a high voltage substation (HVS). Various models, methods and protective devices used for protected zone evaluation are discussed. Special attention is dedicated to ground wires as an efficient protective device in forming lighting protection for an HVS. A sensitivity analysis is conducted for a presented 220/110/10 kV HVS protected zone construction depending on the type and dimensions of the protective devices, impulse current magnitude and the various methods. The educational aspects of the application of this software tool are very important for both undergraduate and PhD students studying High Voltage Technique and Computer-Aided Design/Engineering (CAD/CAE) in Power Systems. During the past two academic years, the software application has received favourable comments from students.

Development of a Fibre Optic Impulse Current Sensor for High Voltage Equipment Tests

This paper presents the procedure for design and testing of the Fibre Optic Impulse Current Sensor (FOICS) based on the Faraday effect. A laboratory prototype based on the Bi12GeO20 Faraday crystal is realised. Experimentally determined 8/20 μs standard impulse current waveforms for different magnitudes obtained by applying FOICS and a conventional shunt sensing system are discussed. The results indicate that FOICS is suitable for the accurate and safe masurement of impulse current. This paper can aid engineers and PhD students in learning the comprehensive application of an attractive fibre optic technique for measurements in high voltage power systems. During the past three academic years, the FOICS development project has received favourable comments from students.