Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Flavio B. COSTA"

Distance Protection Analysis Applied for Distribution System with Distributed Generation DOI:10.15199/48.2018.03.03

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Traditionally, the distribution systems are designed to bring the electricity from substations to loads, in a one direc- tion power flow. For this reason, the protection system was designed with the assumption that the distribution system is single source and radial [1]. Fuses and instantaneous over- current relays are used for radial systems with one direction flow [2]. These devices are coordinated in a way that ensures correct identification and isolation of the faulted section. [3]. With the increase of the electricity consumption, more power plants and transmission lines are needed. However, the restriction to construct new power plants and transmission lines is high, since these projects have high costs and they have the society opposition. These issues are mitigated with the usage of distributed generation (DG). The DG, which are small generating units installed next to the centers of consumption, has gained strength due to the deregulation of the energy market, distribution system operation benefits, and due to environmental issues [4-6]. New technologies applied to DG increase the diversity of energy sources, reducing de- pendence on fossil fuels [7]. With the penetration of DG in the distribution system, a new paradigm of protection arises, specially in protection coordination [8-11] due to the power flow being on both sides, turning the distribution system in a meshed power system. The protection used in meshed power systems (transmission lines) is usually the distance and differential protection [12]. Distance protection is the main protection in transmission lines due to several factors such as easy coordination, directionality, and only depends on line impedance [13]. This type of protection is present in several manufacturers relays used in the protection of transmission lines [14-16] and it is a consolidated technology [17]. Despite distance protection being a mature technology used in transmission line pro[...]

Assessment of Power Frequency Estimation Methods in Distributed Generation in Islanding Condition DOI:10.15199/48.2018.05.01

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The power system frequency has an important role in order to perform monitoring and controlling the power quality in electrical distribution systems with distributed generation (DG). However, in electrical systems with high penetration of DG changes occurs such as the unintentional islanding of DG for example. Islanding situations can occur with the disconnection of DG during the normal operation, then, the frequency, changes suffer from the high load disconnection of the system that can affect the safety and reliability of the islanded area. For this reason, many algorithms are presented for fundamental frequency estimation applied in electric power systems, such as: zero-crossing method [1, 3], adjustment of points to a pure sinusoidal waveform (APPSW) [1], hybrid method [4, 5], discrete Fourier transform method (DFT) [2, 6], Prony-Fourier-based algorithm [7, 8], and other methodologies such as: Kalman filtering [10], least mean square (LMS) [11]. To solve the problem of islanding detection, schemes are used to detect an islanding operation of DG. Different methods for islanding detection have been reported in recent years [14, 15]. Islanding detection techniques are usually divided into: (a) local detection methods when the detection is based on the DG side, and (b) remote detection methods when the detection is based on the network side. Local detection methods can be passive methods or active methods [16]. The passive methods monitor voltages and currents waveforms. Voltage, frequency, harmonic and phase measurements are taken separately or simultaneously to determine an islanding situation. Frequency-based schemes [15, 16] as frequency relay [14-16], rate of change of frequency (ROCOF) relay [17, 18] were studied to islanding detection. However, in the aforementioned papers, the transient state is not taken in account in the frequency estimation. The transient state affects the frequency estimation quality. In tran[...]

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