An islanding detection strategy for distribution network connected with hybrid DG resources

The exponential growth in electricity demand has driven the Distributed Generation (DG) technology a boost in the power system. The use of DG is beneficial to power utilities, DG owners', and end-users in terms of reliability, power quality, and economics. However, to fully utilize the benefits of DGs, some technical issues need to be addressed. Islanding condition is one of the most important issue in this context. Until now, several islanding detection techniques have been proposed for detecting the islanding condition. This paper presents a brief overview of existing islanding detection techniques with their relative merits and demerits. Apart from this, the paper presents an islanding detection strategy suitable for hybrid DG resources of mini-hydro and Bio-Mass. The proposed strategy uses average rate of change of reactive power and load shift strategy to detect islanding of the distribution network. The performance of proposed strategy is validated on various islanding and non-islanding events. The results of proposed strategy are compared with other existing techniques in terms of fast islanding detection, and non-detection zone. The simulation results show that the proposed strategy is effective in detecting islanding phenomenon possesses fast detection and negligible non-detection zone region compared to existing islanding detection techniques. (C) 2015 Elsevier Ltd. All rights reserved

The calculation of low voltage solution based on state space search method in ill-conditioned system

This paper implements the State Space Search Method (SSSM) in polar coordinate form to calculate low voltage solution and Maximum Loading Point of system in ill conditioned system. SSSM modifies the direction of state variable (buses voltage and phase) by using optimal multiplier in order to converge load flow equations in ill conditioned system. The privilege of SSSM emerges in the keeping dimension of load flow jacobian matrix constant. While another method such as continuation and homotopy methods change the framework of jacobian matrix based on predictor and corrector in term of increasing load demand. Indeed, the calculation process of SSSM is based on standard Newton Raphson load flow method. The validation of SSSM is shown by the testing IEEE test systems of 14 and 30 in well and maximum loading point as ill-conditioned systems

A comprehensive review of synchronization methods for grid-connected converters of renewable energy source

Recent interest in the integration of renewable energy sources (RES) into the power grid has raised concerns in synchronization of the various RES. Grid variables such as voltage, phase angle and frequency should be continuously monitored to guarantee correct operation and synchronization of power converters connected to the power grid. Numerous synchronization methods have been presented over the years to address issues such as unbalanced condition and frequency variation. This paper presents a review of past studies on synchronization methods for grid-connected converters together with their control and modeling techniques. Various estimation techniques for phase angle, frequency and harmonic are discussed and examined. Key challenges for a smart and efficient synchronization are briefly overviewed and possible future works are also recommended. A consolidated review is the particular focus of this paper, as is the provision of information on the best method for synchronizing grid-connected converters

Partial discharges within two spherical voids in an epoxy resin

A void in a dielectric insulation material may exist due to imperfection in the insulation manufacturing or long term stressing. Voids have been identified as one of the common sources of partial discharge (PD) activity within an insulation system, such as in cable insulation and power transformers. Therefore, it is important to study PD phenomenon within void cavities in insulation. In this work, a model of PD activity within two spherical voids in a homogeneous dielectric material has been developed using finite element analysis software to study the parameters affecting PD behaviour. The parameters that have been taken into account are the void surface conductivity, electron generation rate and the inception and extinction fields. Measurements of PD activity within two spherical voids in an epoxy resin under ac sinusoidal applied voltage have also been performed. The simulation results have been compared with the measurement data to validate the model and to identify the parameters affecting PD behaviour. Comparison between measurements of PD activity within single and two voids in a dielectric material have also been made to observe the difference of the results under both conditions

Experiment and modeling of void discharges within dielectric insulation material under impulse voltage

The presence of cavity in motor insulation fed by variable speed drive is one of the sources of partial discharge (PD) occurrence, especially under impulse voltage. This is a serious problem as PD can accelerate degradation of the motor insulation. Therefore, it is important to prevent void discharges from occurring in motor insulation under impulse voltage. In this work, the characteristics of void discharges within dielectric insulation material under impulse voltage were investigated through experiment and modeling. The test object consists of a rectangular void within a polyethylene material. The test object was stressed with different peak magnitude, front time and tail time of the applied impulse voltage. The experimental results were reproduced by simulation results from a void discharge model in insulation material. From the model that was developed, a better understanding on physical parameters that influence the characteristics of void discharges within dielectric material under impulse voltage can be attaine

Investigation of transient performance of capacitor voltage transformer

This paper reports the digital-time domain and frequency domain studies on a typical 132kV Capacitor Voltage Transformer (CVT) model. The transient studies are conducted using Alternative Transient Program (ATP-EMTP). Simulation results corresponding to the CVT transient response under both system fault and ferroresonance condition are reported in this paper. Transient studies are performed (1) to identify the CVT components that contribute to the transient response of CVT, (2) to determine system condition that affect the CVT transient response. A lightning simulation case study is also presented

Parameters affecting lightning backflash over pattern at 132kV double circuit transmission lines

In this paper, an analysis study on parameters which affecting the backflash over pattern cause by lightning is done. A 132kV double circuit transmission line is modeled using ElectroMagnetic Transient Program EMTP software for backflash over simulation. A vertically configured double circuit transmission line can be modeled into several parts: towers, insulators, phase conductors, ground wire and tower footing resistance. The backflash over pattern is simulating by model the lightning current that hit the ground wire at the aim tower. The parameters that include in this study are the values of front, peak and tail of lightning current, striking distance and lastly the tower ground system. The pattern can also be analysis by taking into account the position of the phase conductors on the double circuit transmission tower

Analysis of the performance of domestic lighting lamps

The power crisis problem is getting worse in the developing countries. Measures are being taken to overcome the power shortage problem by efficiently utilizing the available power. Replacement of high-power consumption lamps with energy efficient lamps is also among these steps. This paper presents a detailed comparative analysis between domestic lighting lamps (DLLs) use for producing artificial light. DLLs include incandescent lamp (IL), fluorescent lamp (FL) and compact fluorescent lamp (CFL). Light emitting diodes (LED) based lamp technology is relatively new in comparison with conventional incandescent and discharge lamps. However, the present study will also cover the LED lamps. Power quality based experiments have been conducted on DLLs in Power System Laboratory and power consumption based calculations are carried out using the lighting design software DIALux. The result shows that with the current technology, the use of FL and LED lamp is beneficial for utility as well as for consumer. However, with the current pace in the development of LED technology, it is possible LED lamps will lead the lighting market in the near future. The paper has also presented the uncertainties that exist in lighting market and proposed the guidelines that will help in making future energy policy

A review of ferroresonance in capacitive voltage transformer

Ferroresonance incidences in electrical power system have been commonly regarded as unexplained phenomenon, which is not critical for utility engineers. As a result, research conducted in this area is limited and the awareness on ferroresonance is relatively low among utility engineers. However, as the electrical system evolves, its complexity increases in line with the increasing risk of ferroresonance. As a result, this paper provides a consolidated review on the research conducted on ferroresonance to highlight its importance. This paper covers the fundamental inductor–capacitor pair for ferroresonance initiation and the modes of ferroresonance, followed by ferroresonance in capacitive voltage transformer (CVT), constituting its impact, initiation, and suppression techniques. The core focus in this paper is ferroresonance in CVT due to switching events, on which the documented literature is very scarce. © 2014 Institute of Electrical Engineers of Japan

The improvement of voltage sags pattern approach to locate a fault in distribution network

This paper describes an improvement of a faulted section identification method. The improvement has made the method not only able to identify a faulted section, but at the same time calculate fault distance from one-end of the faulted section. By having this new feature, the locating fault time can be further reduced. The method has been tested on an actual underground rural distribution network feeder with all type of fault. The results show that most faults can be located by the first attempt and with high accuracy of fault distance. Only few faulted sections found by the second attempt. Since the proposed method is using only voltage sag data, monitored at the primary substation, the method is considers economical to be implemented for a rural distribution network