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A new method for detection occurrences of CT saturation is presented in this paper. The presented algorithm applies only first order derivatives of signals which is possible it has been designed in a new innovative methodology in which phase current signals are considered as coordinates of a 3D vector. The proposed algorithm is compared with standard one applying secondary current signal combined...
A large-scale implementation of distributed generation (DG) for households involves each house generating its energy from photovoltaic (PV) cells. This approach is particularly suitable in rural electrification projects where demand is relatively low and yet grid connection is costly. A meshed microgrid is an attractive solution for energy generation and sharing in domestic electrification projects...
This paper presents a combined method for discrimination between inrush current and internal fault current of power transformers. The mentioned method is based on wavelet analysis of power system frequency which is estimated by Prony method. The Prony method is utilized to estimate power system frequency with three consecutive samples rapidly and also Daubechies wavelet family uses the estimated frequency...
Fuse-saving practices have coordination limitations at higher current levels — it is common for the upline device to trip and the fuse to operate at the same time. The result is frequent momentary outages for many customers and blown fuses, even for temporary faults. These challenges have led some utilities to abandon the practice of fuse-saving and instead migrate to a fuse-blowing philosophy. The...
This paper presents the results of the analysis of a vast fault records database. The fault records were obtained during numerous experiments performed from 2005 to 2011 in real resonant-earthed distribution networks. The purpose of these experiments was to provide data either for verifying distribution network safety during earth faults or for testing methods of earth fault location or elimination...
Distribution system operator (DSO) sometimes needs to operate the large network which means operating of the network with big capacitive current (in Czech Republic more than 800A). This operation puts the emphasis not only on the setting of the earth fault relays but on the safety of the point of fault too. The paper describes the theoretical analysis, simulation and tests in real compensated distribution...
The paper describes a Transient Bias technique designed to overcome the effects of Current Transformer (CT) saturation, which might severely affect the behaviour of a protection system. This Transient Biasing, as the name implies, is only active during transient conditions in the power system, and it decays quickly once the transients disappear. A complementary algorithm for fast detection of external...
A common practice for improving electric service reliability is to provide an alternate source of supply. On the distribution system, two feeders — each with one or more mid-line overcurrent protective devices — can be tied together through a normally-open tie point to restore service to unfaulted sections of line. Conventional looped distribution systems rely on overcurrent coordination to ensure...
This paper presents a novel approach designed for centralize substation level protection to determine the faulty feeder in a distribution network In opposite to phase-to-earth faults in the transmission networks (HV), which neutral points are solidly earthed, fault-loops in a fault-to-earth case in MV distribution networks have big impedance. Additionally during the earth-fault the transient component...
High impedance fault (HIF) exposes great hazard for personal safety and property security. High impedance fault (HIF) in MV distribution with restricted fault current cannot be detected and cleared by conventional over current relays. In this paper, an integrated scheme utilizing different features of HIF is presented. Various documented field data has been investigated and summarized to get the most...
In this paper, the application of static series compensator as a fault current limiter is proposed to preserve the integrity of the overcurrent relays' settings in a microgrid for both modes of operations, i.e., utility-grid connected and autonomous (islanded). Static series compensator could be multiple low-power single-phase inverters that attach to the overhead conductor and dynamically control...
In this paper, the capability of the numerical relays within the microgrid is sophisticatedly used to adapt the settings of the relays to the status of the microgrid. Different settings for the overcurrent relays are calculated off-line and saved in the relays. Whenever the microgrid is disconnected from the grid, the settings are automatically changed to the associated group of settings. This would...
Protection of an inverter dominated microgrid is always a great challenge, as inverters are well known for their insufficient contribution to the fault current, undermining the accuracy and viability of traditional overcurrent protection schemes. Based on the wide review of solutions developed in the past, this paper proposes a novel protection strategy, with the main protection method based on the...
Due to its current limitation, Inverter-interfaced Distributed Generation (IIDG) is supposed to have little impact on protection system of distribution networks. However, in case of high power IIDG, the situation could be changed. This paper aims to show situations in which IIDG could provoke false tripping to overcurrent protections along distribution feeders. Proposed solution is to provide directional...
Transformer differential protection schemes normally use multi slope characteristics to provide stability during CT saturation with 2nd harmonic restraint or blocking for inrush conditions. This paper presents new algorithms that have been developed to improve the performance of the differential protection. Extensive testing has been used to demonstrate that the transient bias algorithm can reduce...
In the last two decades there has been a continuous increase in the amount of Distributed Generation (DG) connected to the power network. This has resulted in a number of technical challenges for network protection including: sympathetic tripping of DG interface protection; blinding of feeder over-current (OC) protection; and deterioration of feeder OC protection grading. While the available literature...
This paper proposes a Multi-agent System (MAS) approach to coordinate overcurrent relays, aiming to protect distribution systems with distributed generators. The connection of distributed generation (DG) units causes a reduction in the efficacy of protection systems coordination and, in some cases, an increase of operating times. Coordination studies aim to guarantee the protection selectivity in...
This paper presents an accurate fault location algorithm for double-circuit transmission lines with series capacitor compensation at both ends. It has been considered that a fault locator utilizes a communication channel of differential protective relays through it phasors of currents at both line ends are exchanged. Besides the phasors of two-end currents, three-phase voltage measured at a local...
Integrating Distributed Generation (DG) in distribution systems will have an impact on the fault current magnitudes. This could have an impact on the coordination of the protective devices. In this paper, the optimal DG locations are determined in order to minimize the overall relay operating times for a meshed distribution system. The problem is formulated as a Non-Linear Programming (NLP) problem...
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