In this paper, a fuzzy expert off-line system has been developed for fault diagnosis in the distribution network based on the structural and functional operation of the relay and circuit breakers. Functional operations (correct operation, false operation and failure to operate) of the relays and circuit breakers are described by fuzzy logic. Input data for the proposed fuzzy expert fault diagnosis system (FDS) are status and time stamps of the alarms, associated with relays and circuit breakers. The diagnostic system from a huge number of alarms sets, logically organizes and quantifies the diagnosis. FDS can diagnose correct operation, false operation and failure to operate of the relays and circuit breakers. Also, it can identify and quantify fault location based on the Hamacher’s operator of a fuzzy union. The additional contribution of this paper is in modeling unknown information using linear fuzzy membership function. Statuses of certain components may be unknown due to telemetry failures or are simply unavailable to the operator and proposed FDS can make diagnosis in such a situation. Developed fuzzy expert FDS is tested on the two examples of faults in real life distribution network

In electric power systems, grid elements are often subjected to very complex and demanding disturbances or dangerous operating conditions. Determining initial fault or cause of those states is a difficult task. When fault occurs, often it is an imperative to disconnect affected grid element from the grid. This paper contains an overview of possibilities for using fuzzy logic in an assessment of primary faults in the transmission grid. The tool for this task is SCADA system, which is based on information of currents, voltages, events of protection devices and status of circuit breakers in the grid. The function model described with the membership function and fuzzy logic systems will be presented in the paper. For input data, diagnostics system uses information of protection devices tripping, states of circuit breakers and measurements of currents and voltages before and after faults.K e y w o r d s: fuzzy logic, primary faults, transmission grid Nomenclature |∆I| -absolute value of current change sensitivity I t -current after the event

Subject reviewEnergy Audit of Electrical Installations is an integral part of the overall energy audit of complex technical systems, and infrared thermography is one of the non-destructive testing (NDT) methods for that type of analysis of power distribution subsystems. During the energy audit of the power subsystem by means of a thermal camera, it is necessary to carry out some additional measurements of electrical quantities which are often not performed easily. The paper provides an overview of the standards in the field of thermography and safety criteria of electrical installations based on a thermal image and measured electrical parameters. As a practical example, an analysis of an electric power distribution subsystem of large complex industrial consumers is presented.The procedure of the audit and decision making for future maintenance is described in detail. Recommendations of corrective actions in the maintenance procedure based on the absolute temperature criterion and the delta-T criterion under consideration of the measured load are given as well. Keywords: electrical power installations; fault rating; thermography Infracrvena termografija u energetskom pregledu električnih instalacijaPregledni članak Energetski pregled elektroenergetskih sustava sastavni je dio energetskog pregleda složenih tehničkih sustava, a infracrvena termografija jedna je od nezaobilaznih nedestruktivnih metoda ovakve vrste analize elektroenergetskih podsustava. Prilikom energetskog pregleda elektroenergetskog sustava termokamerom potrebno je provesti dodatna mjerenja električnih veličina što se često ne može izvesti na jednostavan način. Rad daje pregled standarda na području termovizije i kriterija ispravnosti elektroenergetskih instalacija na osnovu termograma uzimajući u obzir izmjerene električne veličine. Na praktičnom primjeru velikog složenog industrijskog potrošača prikazan je detaljan postupak analize i donošenja suda o ispravnosti instalacija kao i preporuka korektivnih radnji u postupku održavanja.

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