B. Hillstrom

Bio: B. Hillstrom is an academic researcher from Wrocław University of Technology. The author has contributed to research in topics: Fuzzy logic & Digital protective relay. The author has an hindex of 4, co-authored 5 publications receiving 178 citations.

A self-organizing fuzzy logic based protective relay-an application to power transformer protection

Abstract: In the paper the fuzzy logic based multi-criteria protective relay for a three-phase power transformer is presented. Twelve criteria used to stabilize the relay are introduced and integrated by means of multi-objective decision-making methods. The introduced protection scheme contains several internal functions and coefficients which are subject to off-line pre-installation self-setting. Three unique procedures are delivered for self-adjusting the relay, and thus, making it self-organized. The results of testing show significant gains in both sensitivity and selectivity of the self-organized relay compared with traditional approaches.

Dynamic compensation of capacitive voltage transformers

Abstract: This paper presents the digital algorithm for on-line dynamic compensation of the secondary voltage of a capacitive voltage transformer (CVT). The adopted CVT model together with the assumed simplifications is given first. Next, the compensating algorithm based on digital inversion of the CVT transfer function is derived. Frequency domain analysis and quantitative evaluation of the compensation follow. The ATP-EMTP simulations are included that show the improvement of the measurement of protective criteria quantities as a result of dynamic compensation of a CVT.

Fuzzy logic controller for on-load transformer tap changer

Abstract: This paper presents a new fuzzy logic controller (FLC) for on-load tap change control for distribution transformers. The model of a transformer with its tap changing mechanism is given first. Next, the FLC is presented in detail. The proposed algorithm is optimized from the numerical point of view and proved to be implementable on contemporary programmable logic controllers (PLCs). Simulation results are included that compare the proposed control algorithm with the classical inverse-time controller and prove the efficiency of the new solution.

A multi-criteria fuzzy logic transformer protection

Abstract: The paper describes a multi-criteria self-organized fuzzy logic based protective relay for three-phase power transformers. The employed protection criteria and the overall relay organization are presented as well as the novel algorithms for off-line pre-installation self-setting of the relay. These algorithms are based on statistical information obtained by mass-simulation using ATP-EMTP package and enable a kind of learning phase similar to that known from artificial neural network applications to power system protection. The example and results of testing demonstrate high stability and sensitivity of the presented relay which operates with average tripping time below half a cycle. Robustness of the relay has been also confirmed.

Une protection de transformateur basee sur la logique fuzzy

Abstract: ans les protections de transformateur de puissance, le principe de la protection différentielle présente certaines limitations car la détection par courant différentiel ne permet pas d’opérer une distinction claire et nette entre les défauts internes et les autres conditions d’exploitation. Un appel de courant à l’enclenchement, une surexcitation stationnaire dans un enroulement, un défaut externe avec saturation des transformateurs de courant (T. I.) et/ou une mauvaise adaptation des transformateurs de courant aux caractéristiques du transformateur de puissance à protéger constituent les principaux phénomènes qui perturbent la mesure différentielle et qui peuvent, par conséquent, conduire à un comportement erroné du dispositif de protection. Afin de remédier à ces problèmes, un certain nombre de critères de protection plus ou moins fiables ont été mis en oeuvre: ces critères influencent favorablement la caractéristique de déclenchement stabilisée à l’aide des harmoniques 2 et 5 [1,2]. Les critères ainsi retenus au cours des dernières décennies sont, entre autres, le principe différentiel, l’identification directe de la forme d’onde, les algorithmes de protection basés sur les équations électromagnétiques du transformateur de puissance à protéger ainsi que le comportement adaptatif. Il faut mentionner aussi que les techniques de mesure ont été améliorées dans les protections grâce à l’introduction des méthodes de Fourier, des techniques de filtrage de Kalman et grâce à une meilleure observation des états de fonctionnement. Les travaux de recherche entrepris conduisent tout naturellement au développement d’une protection basée sur plusieurs critères. Un des résultats obtenus dans ces travaux concerne le développement d’une plate-forme s’appuyant sur une logique Fuzzy et faisant appel à des concepts proches de ceux de l’intelligence artificielle (IA) [3–5]. Les possibilités d’optimalisation d’un dispositif de protection doté de caractéristiques d’intelligence artificielle (IA) sont très prometteuses. Un certain nombre de coefficients internes, de fonctions et de seuils [3,4] peuvent être adaptés au but recherché, à savoir l’amélioration de la qualité de la protection. Cependant, il n’existe pas encore des recommandations ou des retours d’expérience qui permettent de régler les paramètres internes mentionnés. Des recherches ont été entreprises afin de surmonter ce problème. Ce rapport décrit une protection de transformateur avec logique Fuzzy (FLR) basée sur 12 critères ainsi que sur des algorithmes inédits afin d’obtenir un réglage automatique de la protection «en différé» avant la mise en service.

Combined fuzzy-logic wavelet-based fault classification technique for power system relaying

Abstract: This paper presents a new approach to real-time fault classification in power transmission systems using fuzzy-logic-based multicriteria approach Only the three line currents are utilized to detect fault types such as LG, LL, and LLG, and then to define the faulty line An online wavelet-based preprocessor stage is used with data window of ten samples (based on 45-kHz sampling rate and 50-Hz power frequency) The multicriteria algorithm is developed based on fuzzy sets for the decision-making part of the scheme Computer simulation has been conducted using EMTP programs Results are shown and they indicate that this approach can be used as an effective tool for high-speed digital relaying, as the correct detection is achieved in less than half a cycle and that computational burden is much simpler than the recently postulated fault classification techniques

Fuzzy logic-based relaying for large power transformer protection

Abstract: Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. The frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. Then, traditional approaches will likely be maloperated in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.

Control of a ULTC Considering the Dispatch Schedule of Capacitors in a Distribution System

Abstract: This paper proposes a coordinated control method for an under-load tap changer (ULTC) with switching capacitors in distribution systems to reduce the operation numbers of both devices. The proposed method consists of two stages. In the first stage, the dispatch schedule of capacitors is determined using a genetic algorithm with forecasted loads to reduce the power loss and to improve the voltage profile during a day. In the second stage, each capacitor operates according to this dispatch schedule and the ULTC is controlled in real time with the modified reference voltages considering the dispatch schedule of the capacitors. Simulation results show that the proposed method performs better than a conventional control method

A novel wavelet-based algorithm for discrimination of internal faults from magnetizing inrush currents in power transformers

Abstract: In this paper, a new algorithm based on processing differential current is proposed for digital differential protection of power transformers by considering different behaviors of the differential currents under fault and inrush current conditions. In this method, a criterion function is defined in terms of difference of amplitude of wavelet coefficients over a specific frequency band. The criterion function is then used for three phases, and internal faults are precisely discriminated from inrush current less than a quarter a cycle after the disturbance; this is one advantage of the method. Another advantage of the proposed method is that the fault detection algorithm does not depend on the selection of thresholds. The merit of this method is demonstrated by simulation of different faults and switching conditions on a power transformer using PSCAD/EMTDC software. Also the proposed algorithm is tested offline using data collected from a prototype laboratory three-phase power transformer. The test results show that the new algorithm is very quick and accurate

Bibliography on the fuzzy set theory applications in power systems (1994-2001)

Abstract: In recent years, fuzzy set theory applications have received increasing attention in various areas of power systems such as operation, planning, and control. A number of research articles appeared which indicate applicability of fuzzy systems to power systems for wider operating conditions under uncertainties. While most of these systems are still under investigation, however, there already exist several practical applications of fuzzy systems. This paper presents a comprehensive set of references on fuzzy set theory applications in power systems.