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Microgrids have been proposed in an effort to handle the impact of distributed generators (DGs) and make conventional grids suitable for large scale deployments of DGs. However, the introduction of microgrids brings some challenges such as the protection of a microgrid and its entities. Due to the existence of generators at all levels of the distribution system, the fault currents vary substantially...
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...
In this paper, a new Prony's method for frequency estimation is investigated to calculate df/dt. for the rate of change of frequency (ROCOF) protection technique. This algorithm provides accurate and fast frequency calculation for fault detection. System with noise and non-linear load are added during simulation to provide a system similar to real. During non-islanding situation (load adding or adding),...
The growing sophistication and complexity of power system control apparatus and systems plus the addition of new topological features such as distributed generation at the distribution level requires new test environments which can evaluate and optimise these systems prior to deployment in the real system. One such environment is described in this paper along with examples of its use in evaluating...
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...
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...
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...
Experience with connecting farm biogas generation to rural distribution feeders has revealed that a particular costly barrier can be protection against unplanned islanding. When the size of the generation is small compared to the load on the feeder, the cost of anti-islanding protection is very small. However, once a certain size threshold is reached, alternative protection methods are required, and...
The present work deals with the research of novel technical solutions to improve service continuity in MV distribution networks in presence of dispersed generation (DG). In particular, the paper focuses on the development of new criteria to manage both network protections and DG interface protections in a coordinated way, also in view of allowing portions of MV distribution networks to operate as...
In this paper the development of protection schemes for multi-phase and phase-to-ground faults in autonomous micro-grids is dealt with, accounting for the fact that a distribution ldquoislandrdquo can be intentionally intended to operate for a long time duration (e.g. during maintenance in the main upstream network or due to economic advantages for the micro-grid electrical customers). The definition...
Distribution power system islanding will involve significant grid reconfiguration, especially if maximum flexibility of operation is to be achieved. Protection selectivity will be a challenge because of the associated changes in fault conditions, and is further complicated by distributed generator fault characteristics. This paper proposes a three-stage communication assisted protection selectivity...
This paper deals with the protection system in distribution networks with distributed generation. It describes the dynamic influences of synchronous generators on the direction determination of protection relays during network disturbances. Therefore the dynamic behaviour of the measured electrical quantities during network disturbances is derived. A relay-model is implemented to study the behaviour...
Renewable energy driven distributed generators (DGs) are mostly connected to radial distribution network with overhead feeders. It is estimated that 80% of network faults are temporary single phase to ground faults and therefore automatic restoration is required. A combination of automatic re-closer devices, circuit breaker, sectionalizer and fuse is applied to clear the temporary fault and isolate...
Anti-islanding protection schemes currently enforce the DGs to disconnect immediately for grid faults through loss of grid (LOG) protection system. This greatly reduces the benefits of DG deployment. For preventing disconnection of DGs during LOG, several islanding protection schemes are being developed. Their main objectives are to detect LOG and disconnect the DGs from the utility. This allows the...
Interconnect protection allows DG to operate in parallel with the utility power system and is the single most important technical issue in most DG projects. Typically, protection requirements to connect distributed generators to the utility grid had been established by each utility. These guidelines generally cover smaller distributed generators (10 MW or less), which are usually connected to the...
Distributed generators (DGs) that are rated between several kVA and 250 kVA in size are increasingly being connected at the 400 V electrical distribution level. Therefore, new requirements for the traditional network protection schemes and the co-ordination between network protection and intertie protection are needed. Actual problems have been experienced relating to DG transient behaviour, thereby,...
This paper presents a new transient based scheme to detect single phase to ground faults (or grounded faults in general) in distribution systems with high penetration of distributed generation. This algorithm combines the fault direction based approach and the distance estimation based approach in order to determine the faulted section. The wavelet coefficients of the transient fault currents measured...
Due to the increasing levels of distributed generation in the distribution network, the correct operation of loss-of mains protection is of utmost importance. Utilities have voiced their concern relating to the false operation of ROCOF relays, which are one of the most commonly employed loss-of-mains detection method. Whilst 'standard settings' are used, the performances of commercially available...
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