Celal Kocatepe

Harmonic Effects of Power System Loads: An Experimental Study

Especially with the developing semi-conductor technology, harmonics have become one of the most popular issues in power system. In this study, the measurements for the harmonic effects of the loads in power system were carried out and also contribution of these loads to harmonic distortion was exhibited. Moreover, the effect of harmonics existing in power sys‐ tem on the performance of some equipment was analyzed experimentally. The obtained re‐ sults were discussed and suggestions were given.

A new multi-objective optimization technique for generation dispatch

The economic and secure operation of power systems has significant importance. Due to technical limitations, the best economical operation point is not always the desired operating point for the system stability. In this study, first, the most economical operating point is obtained by solving the non-linear, network-constrained economic dispatch problem using genetic algorithm. Then, the system voltage stability is taken into account to compare the different possible operating points using V-Q sensitivity analysis. Finally, these two criteria are combined using the learning automata technique to achieve a multi-objective optimization solution, which corresponds to a desired operating point considering both economical operation and stability region. This is of particular interest in regions with significant concerns of voltage stability. The methodology was implemented in MATLAB and applied on a 6-bus test system. The same technique of learning automata may be applied in the future to similar problems that need multi-objective consideration.

Electric field measurement and analysis around a line model at different voltage levels

The aim of this work is the experimental study of the electric field distribution around a line model in high voltage laboratory. Thereby study and knowledge of the electric field around a line at different voltage levels can be purposive for safety, settlements and design procedures of power lines. The measurements were carried out by using HOLADAY/HI-3604 electromagnetic field survey meter. Additionally, to compare the results obtained from the measurements, Finite Element Method Magnetics (FEMM) packaged program is used. The results show that the electric field intensity around a distribution line is changing with the distance in any direction. The electric field under and also near the distribution line is influenced with the increasing voltage levels.

Breakdown voltage analysis of insulating oils under different conditions

The dielectric performance of insulating oils used in high voltage equipment is very important for the power system continuity and reliability. In this study, breakdown voltage measurements of mineral insulating oil were carried at different temperatures and water quantity rates were researched. Additionally, the effect of water content inside the oil sample, approximately 2.5 percent, on the breakdown voltage was analyzed for particular temperatures. In the experimental study, the breakdown voltage behavior of mineral oil which is widely used in power transformers was acquired according to the ASTM D877 standard for different service conditions and the obtained results were presented.

The influence of voltage and frequency variations on insulation quality of a high voltage cable

Insulation quality issue has had a significant place in high voltage systems for long years. Especially for high voltage cables, which is one of the most crucial elements in power systems, the measurements of dissipation factor or tan delta has a great importance on the insulation life time. Besides, when the power system parameters such as frequency and voltage level are not steady, tan delta measurement values will also be changed. Therefore, tan delta and dielectric loss measurement should be realized in case of unsteady power system conditions to get more exact results. In this study, tan delta measurement of a 20,1/34,5 kV, single core high voltage cable is carried out. By changing the frequency and voltage level, dissipation factor, capacitance (Cs), insulation resistance (Rs) and dielectric losses (Pk) measurement values are obtained.

Measurement of the dielectric performance of an instrument transformer at different voltage and frequencies

In this study, the capacity, tan delta and dielectric loss of an IVT are measured for different voltage levels and frequency values. The measurement process is realized for the isolation between the primary and secondary windings of a 10kV/0,1 kV nominal rated IVT. As a measurement device, CPC100/CP TD1, which is frequently preferred especially in field applications, is used. Results indicated that, the dissipation factor changes according to the voltage levels. When voltage level gets closer to nominal value or exceeds it, it is seen that tan delta value increases rapidly. Moreover, it is found that the rising frequency has a negative effect on the dielectric loss of the material as a result of the measurements at different frequency values between 50 Hz - 400 Hz.

Analysis of harmonics influences on load switching transients in simple power system

This paper presents the transient analysis of a simple power system. Measurements are taken from a simple system that takes place at Turkish National Power System. Matlab Simpower Toolbox is used for the analysis. Dynamic analysis of the system studied for switching operations. Effects of load acception and reduction are studied as switching operations. Constant impedance load model is used for the simulations. At the case study, added loads have different harmonic components for analyzing effects of harmonics to the system. Harmonic components of the load current are modeled by using current injection method.

Continuous Control of a Synchronous Generator's Active and Reactive Power Connected to Network by Using Fuzzy Neural Networks Algorithms

The fuzzy logic controller based on the fuzzy set theory provides a useful tool for converting the linguistic control rules from the expert knowledge into automatic control rules [1]. By using fuzzy automatic rules from the heuristic or mathematical strategies, complex processes can be controlled effectively in many situations. But the most important and difficult point is how to obtain the proper control rules for a given system. In addition to that Artificial Neural Networks (ANN) is successfully used in many areas such as fault detection, control and signal processing in our daily technology. Artificial Neural Networks have nonlinear structure and this is an effective feature that it approaches to the results of learning phase. Then, it gives results in test phase in short time (the degree about 10−3 second). It is a very preferable according to the other approaching methods.

Power Factor Correction in Power Systems Having Load Asymmetry by Using Fuzzy Logic Controller

As known, the studies on power factor correction have been carried out for many years. But in these studies, generally, phase powers received from supply are assumed to be balanced. In the paper, power systems having unbalanced load are considered.