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This When the power generated by the distributed power generation system matches with the consumed power of the local loads, and the load phase angle is equal to the angle of the current disturbance, even if the islanding occurs, the voltage frequency at the point of the common coupling (PCC) always keeps in non-detecting zone (NDZ). A detection method based on the alternate current disturbance (ACD)...
Penetration of distributed generation (DG) into the distribution network has changed the nature of conventional power distribution system, which was radial in nature. Power flow is now bidirectional and thus the increased penetration of DGs imposes a challenge on the conventional protection scheme which is only meant for passive distribution network. This paper deals with the protection of active...
The existing power grid is experiencing sustaining energy shortage. Distributed generation (DG) including wind energy, solar energy can be a solution for the energy shortage in the existing power grid. Distributed generation is the generation of power using small sized generators that produces electric power at low voltage levels and is connected to the distribution network directly near the load...
The problems of selectivity and coordination of protection devices is one of the concerns related to the effects of the insertion of distributed sources. Those problems directly affect the safety of equipment and personnel and continuity of service. Analysis should be done to determine if the protective devices installed on the network are properly coordinated after inserting distributed sources....
This paper presents a comparison study of two major distributed generation islanding detection methods including rate of change of frequency (ROCOF) and over/under frequency (OUF) techniques which could be used for Provincial Electricity Authority (PEA) distribution systems. The analysis is based on the detection time in different scenarios and false operations. Two practical distribution systems...
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...
Now more and more distributed generations will be connected to distributed power system. It's found that different distributed generation has its own operation characteristic such as fluctuation and uncertainty. When micro-grid is to be island the voltage and frequency will change, so different control modes have been used on different distributed generation. Different kinds of distributed generation...
Microgrids have been proposed in order to handle the impacts of Distributed Generators (DGs) and make conventional grids suitable for large scale deployments of distributed generation. However, the introduction of microgrids brings some challenges. Protection of a microgrid and its entities is one of them. Due to the existence of generators at all levels of the distribution system and two distinct...
A trend away from large conventional electrical power generation stations such as hydro, coal-fired, and nuclear toward smaller Distributed Generation (DG) has both benefits and complications. While DG can capitalize on renewable energy and can reduce transmission losses by being closer to local loads, the intermittent availability of some power sources coupled with the current lack of a “smart grid”...
Conventional power distribution system is radial in nature, characterized by a single source feeding a network of downstream feeders. Protection scheme for distribution system, primarily consisting of fuses and reclosures and, in some cases, relays, has traditionally been designed assuming the system to be radial. In last year extra attention applied in use of distributed generator units in distribution...
This article presents an analysis of the behavior of the electrical frequency in Caracas during four major events of the year 2008. The frequency was computed from the voltage signals of the fault recorders. The events of April 29 and September 01 were faults in transmission lines of the National Grid, and the event of October 19 was the erratic trip of two main lines at 765kV (Guri-Malena). In these...
Wind turbines are rapidly increasing and some times are disconnected from the grid intentionally or inadvertently and continue to supply local loads. If it was decided to reconnect to the grid, some problems may happen. This paper deals with the reconnection of islanded wind turbines to the grid and proposes a new method to reduce the high current effects of reconnection. The new method is simple...
This paper describes the possible evolution of Italian distribution system in facing the growing penetration of Dispersed Generation (DG), in the perspective of smart grids. As for the Italian system, after discussing the Hosting Capacity of MV distribution networks, it is recognized that some challenges are to be faced due to the increasing amount of DG. Even though current technology provides satisfactory...
Experience with connecting farm biogas generation to rural distribution feeders in Ontario has revealed several challenges with electrical protection. The biogas projects are small (<;500kW), synchronous, farm-based, and looking for an affordable protection solution involving the use of only low-voltage equipments. The utility feeders are generally at the 8.3kV and 12.5kV voltage levels, can involve...
The impact of distributed generation (DG) in a distribution network depends on the design of the protection system and the coordination between the different protective devices. This paper presents the main features of a library of protective devices implemented in an EMTP-type tool for power quality studies in distribution networks with distributed generation. The document discusses the present protection...
this paper discusses the reliability benefits (reduction in SAIFI and SAIDI) that could be achieved through the implementation of single-phase tripping in four-wire multigrounded medium-voltage distribution feeders. Several issues and concerns regarding the potential problems caused by single-phase tripping are discussed, and the potential reliability benefits due to the implementation of this protection...
Selection of the DG interconnection protective relay is based on several criteria such as power system characteristics, the dynamic response of the generator, the system grounding, the DG transformer connection, etc., as well as the protection policy of the utility and coordination requirements. The interconnection protection IED design can be summarized as follows: Disconnection of DG plants when...
Islanding detection is an important issue for distributed generation operating with main network. To solve the problem of reliability and sensitivity of conventional vector shift method, this paper presents a composite islanding detection method utilizing both angle change and frequency variation derived from distributed generator terminal voltage. The method consists of main criterion and auxiliary...
With the increasing capacity of power system, fault currents (CBs) may exceed the interrupting capacity ratings of circuit breakers. Fault current limiters (FCLs) can be applied to maintain circuit breakers within their interrupt ratings. The degree of fault current limiting on system performance is analyzed in radial and meshed system structures. Heavy limitation modes and light limitation modes...
Distributed generation (DG) is gaining popularity in the United States and across the world. The Florida Public Service Commission recently passed rules encouraging the use of renewable resources. Integrating DG with the utility network poses challenges for anti-islanding schemes. These schemes detect islanding conditions and trip the DG. Fig. 1 shows a typical network configuration for DG installations...
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