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Islanding operation in a distribution network connected to Distributed Generations (DGs) has the advantage of being able to continuously supply power to the loads even when disconnected from the grid. However, there are technical issues that need to be solved in order to guarantee a successful islanding operation. The main challenge in the successful islanding operation is to ensure the stability of frequency and voltage of the distribution system. Commonly load shedding schemes are used as a mechanism to stabilize the magnitude of the frequency and the voltage by shedding some of the loads to ensure an adequate balance between generation and loads. This paper reviews recent load shedding schemes focusing on distribution system application. Their respective merits and demerits are presented. Moreover, this paper also highlights the application of Voltage Stability (VS) index for load shedding schemes. A brief overview of the DG with their respective advantages also presented at the beginning of this paper. [ABSTRACT FROM AUTHOR]

Distribution systems are continuously exposed to fault occurrences due to various reasons, such as lightning strike, failure of power system components due to aging of equipment and human errors. These phenomena affect the system reliability and results in expensive repairs, lost of productivity and power loss to customers. Since fault is unpredictable, a fast fault location and isolation is required to minimize the impact of fault in distribution systems. Therefore, many methods have been developed since the past to locate and detect faults in distribution systems with distributed generation. The methods can be divided into two categories, conventional and artificial intelligence techniques. Conventional techniques include travelling wave method and impedance based method while artificial intelligence techniques include Artificial Neural Network (ANN), Support Vector Machine (SVM), Fuzzy Logic, Genetic Algorithm (GA) and matching approach. However, fault location using intelligent methods are challenging since they require training data for processing and are time consuming. In this paper, most of the techniques that have been developed since the past and commonly used to locate and detect faults in distribution systems with distributed generation are reviewed. Research works in fault location area, the working principles, advantages and disadvantages of past works related to each fault location technique are highlighted in this paper. Hence, from this review, the opportunities in fault location research area in power distribution system can be explored further. [ABSTRACT FROM AUTHOR]

Preservation of the environment has become the main motivation to integrate more renewable energy sources (RESs) in electrical networks. However, several technical issues are prevalent at high level RES penetration. The most important technical issue is the difficulty in achieving the frequency stability of these new systems, as they contain less generation units that provide reserve power. Moreover, new power systems have small inertia constant due to the decoupling of the RESs from the AC grid using power converters. Therefore, the RESs in normal operation cannot participate with other conventional generation sources in frequency regulation. This paper reviews several inertia and frequency control techniques proposed for variable speed wind turbines and solar PV generators. Generally, the inertia and frequency regulation techniques were divided into two main groups. The first group includes the deloading technique, which allow the RESs to keep a certain amount of reserve power, while the second group includes inertia emulation, fast power reserve, and droop techniques, which is used to release the RESs reserve power at under frequency events. [ABSTRACT FROM AUTHOR]

The solar energy generation has grown significantly in the past years. The importance of PV penetration in power system as a major element of renewable energy source has seen it being widely used on a global scale. Despite its promising success, PV penetration presents various issues and its impact on the distribution system has to address for seamless integration in the power system. In this paper, a comprehensive overview on important issues affecting the distribution system as a result of PV penetration is presented. Pertinent issues such as voltage fluctuation, voltage rise, voltage balance, and harmonics and their effect on the system are discussed in details. The islanding issues, which are of critical importance to the stability and integrity of the system, are also thoroughly reviewed. Details on different islanding techniques – remote and local techniques and their advantage and disadvantages are shown. Therefore, this paper can provide useful information and serve as a reference for researchers and utility engineers on issues to be considered with regards to PV penetration. [ABSTRACT FROM AUTHOR]

This paper presents the second order load flow method (SOLFM) based on the constant Jacobian matrix, with flat initial guesses (1.0∠0°) in polar coordinates. The proposed SOLFM does not need to calculate the Jacobian and Hessian matrix separately; keeping the PV type buses. Accordingly, the solution sped up the proposed SOLFM to a level that is much faster than the classical Newton Raphson Load Flow Method (NRLFM). Moreover, the polar coordinate system can simplify the proposed method's load flow equation. The convergence characteristic of the proposed SOLFM is superior to the NRLFM due to the usage of the Hessian matrix. The validation of proposed SOLFM is proven by testing the Malaysian 664 bus system with respect to NRLFM and the Fast Decoupled Load Flow Method (FDLFM) in the context of computation time and convergence characteristic. [ABSTRACT FROM AUTHOR]

Network reconfiguration is an effective approach to reduce the power losses in distribution system. Recent studies have shown that the reconfiguration problem considering load profiles can give a significant improvement on the distribution network performance. This work proposes a novel method to determine the optimal daily configuration based on variable photovoltaic (PV) generation output and the load profile data. A good combination and coordination between these two varying data may give the lowest power loss in the system. Gravitational Search Algorithm (GSA) is applied to determine the optimum tie switches positions for 33-Bus distribution system. GSA based proposed method is also compared with Evolutionary Programming (EP) to examine the effectiveness of GSA algorithm. Obtained results show that the proposed optimal daily configuration method is able to improve the distribution network performance in term of its power loss reduction, number of switching minimization and voltage profile improvement. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Accurate and fast islanding detection of distributed generation is highly important for its successful operation in distribution networks. Up to now, various islanding detection technique based on communication, passive, active and hybrid methods have been proposed. However, each technique suffers from certain demerits that cause inaccuracies in islanding detection. Computational intelligence based techniques, due to their robustness and flexibility in dealing with complex nonlinear systems, is an option that might solve this problem. This paper aims to provide a comprehensive review of computational intelligence based techniques applied for islanding detection of distributed generation. Moreover, the paper compares the accuracies of computational intelligence based techniques over existing techniques to provide a handful of information for industries and utility researchers to determine the best method for their respective system. [ABSTRACT FROM AUTHOR]

This paper presents the implementation of the Firefly Algorithm (FA) with an online wavelet filter on the automatic generation control (AGC) model for a three unequal area interconnected reheat thermal power system. The model includes time delay, dead zone, boiler, Generation Rate Constraint (GRC), and high frequency noise components. A novel filtering technique based on wavelet transform is introduced for the purpose of removing noise(s) from the ACE signal. The performance of the filter is measured by formulating a signal integrity index. The simulation results show that the FA is able to outperform the Particle Swarm Optimization (PSO) in obtaining the minimum objective function based on Integral of Time Weighted Squared Error (ITSE). The results also shows that the proposed online wavelet filter performs with a higher degree of efficiency compared to the conventional low pass filter when the practical model of the AGC is analyzed. Further investigation by varying the GRC and time delay parameter confirms the robustness of the FA tuned controller with the online wavelet filter. [ABSTRACT FROM AUTHOR]

Power system network is an interconnected web of crucial electrical elements and system monitoring. It is imperative in ensuring system integrity and stability. In regard to this, state estimation is commonly employed to obtain the best estimate of the power system condition based on limited number of measurements. The placement of meters at appropriate locations is crucial in determining the accuracy of the state estimation. Hence, this paper presents a new optimal meter placement strategy for state estimation. A new evolutionary strategy for discrete optimization problem is proposed so that the location of additional meter placement will improve the accuracy of state estimation. The minimization of sum covariance error of state estimation is selected as the objective function to be minimized. Simulation results on the IEEE 30-bus system clearly shows that the proposed approach is able to outperform the conventional heuristic method in determining the optimal meter placement, which enhances the state estimation accuracy. [ABSTRACT FROM AUTHOR]

This paper utilises concavity properties in the optimal multiplier load flow method (OMLFM) to find the most suitable low voltage solution (LVS) for the systems having multiple LVS at the maximum loading point. In the previous method, the calculation of the optimal multiplier is based on only one remaining low voltage solution at the vicinity of voltage collapse point. However, this does not provide the best convergence for multi-low voltage solutions at the maximum loading point. Therefore, in this paper, concavity properties of the cost function in OMLFM are presented as the indicator to find the most suitable optimal multiplier in order to determine the most suitable low voltage solutions at the maximum loading point. The proposed method uses polar coordinate system instead of the rectangular coordinate system, which simplifies the task further and by keeping PV type buses. The polar coordinate in this method is based on the second order load flow equation in order to reduce the calculation time. The proposed method has been validated by the results obtained from the tests on the IEEE 57, 118 and 300-bus systems for well-conditioned systems and at the maximum loading point. [ABSTRACT FROM AUTHOR]

Highlights: [•] Determine the boundary zone between solvable and unsolvable of load flow solutions. [•] Calculating the maximum loading point. [•] Calculating low voltage solutions at the maximum loading point. [•] Implementing all straight lines through two distinct state variables solutions. [Copyright &y& Elsevier]

SUMMARY This paper proposes a fault location estimation method for distribution networks considering errors from measurement devices. The method determines the fault location based on the voltage sag and current magnitudes. The fault location is based on faulted section and fault distance measured from one end of the bus. Faulted section is determines by matching the measured voltage and current with a pre-developed data. For multiple faulted sections, ranking analysis is employed to rank the most likely faulted section. Fault distance is calculated from one end of the identified faulted section. By determining the faulted sections, a fault in homogenous and non-homogenous networks can be located. The method has been tested using an actual Malaysian 11 kV distribution network. Different values of measurement errors have been applied, which includes positive and negative values. The test results showed the effectiveness of the method under various uncertainty of error from measurement devices. The proposed method can serve as an alternative technique for estimating fault location in distribution networks. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY The Step Size of the Newton Raphson Method (SSNRM) is based on the optimal multiplier that is used to determine the Multiple Load Flow Solutions (MLFS) for an ill-conditioned power system. However, the SSNRM is incapable of determining the desirable Low Voltage Solution (LVS) from the MLFS at the Maximum Loading Point (MLP), due to the fact that when the load demand increases, the LVSs moves closer to each other at the MLP. Commonly, the smallest optimal multiplier was used to calculate the LVS at the MLP under this condition. However, this paper proves the fact that using the smallest optimal multiplier to determine the most suitable LVS for the systems having multiple solutions at the MLP will not guarantee a favourable outcome. Therefore, this paper investigates the application of the properties of scalar quadratic equations (PSQE) that enhances the function of the SSNRM at the MLP. Thus, an indicator, based on PSQE, is introduced in this work, which amends the existing SSNRM for the purpose of finding the desirable LVS at the MLP. The closest optimal multiplier to the proposed indicator is selected in order to determine the desirable LVS from all possible solutions at the MLP. The proposed method has been tested on a three-bus and IEEE 30-bus systems at the MLP for verification purposes. Additionally, the continuation power flow method is also utilized in order to compare it to the proposed method for the IEEE 30-bus system at the MLP. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Highlights: [•] A multiobjective optimization using ABC algorithm for LFC is presented. [•] Weighted sum approach is used to optimize both settling time and maximum overshoot. [•] Simultaneous tuning of PID parameters for both control areas are performed. [•] Multiobjective system output is compared with single objective optimization. [•] Simulation results shows the efficiency and robustness of proposed control strategy. [Copyright &y& Elsevier]

Highlights: [•] The requirement of DG interconnection with existing power system is discussed. [•] Various islanding detection techniques are discussed with their merits and demerits. [•] New islanding detection strategy is proposed for multiple mini hydro type DGs. [•] The proposed strategy is based on dq/dt and load connecting strategy. [•] The effectiveness of strategy is verified on various other cases. [ABSTRACT FROM AUTHOR]

Highlights: [•] The power system blackout history of last two decades is presented. [•] Conventional load shedding techniques, their types and limitations are presented. [•] Applications of intelligent techniques in load shedding are presented. [•] Intelligent techniques include ANN, fuzzy logic, ANFIS, genetic algorithm and PSO. [•] The discussion and comparison between these techniques are provided. [Copyright &y& Elsevier]

Abstract: Implementations of mini hydro schemes with conventional hydraulic, electrical equipment''s and controllers have proven very expensive and uneconomical. Many developing countries that are in need of rural electrification have encountered economical problem when setting up these mini hydro schemes. To address this problem, alternative options and new designs of these equipment''s have been explored by many researchers around the world. The application of these new designs would reduce the overall cost of mini hydro development and would help in making it a cost effective technology. These new designs will also help developing countries to provide electricity to rural areas or remote regions where interconnection of transmission line from the electrical grid is uneconomical. The new designs can also be an enabling factor in boosting up electricity generation using a renewable energy source. This paper provides survey of all these alternative options and new designs in the controller, hydraulic turbine and generators that have been implemented in different countries of the world. [Copyright &y& Elsevier]

Abstract: Differential protection scheme is based on comparison of measured variables such as current and voltage at the two ends of a line via a communication channel such as pilot wire. This scheme is preferred and extensively used in distribution feeder protection system in Malaysia due to its fast operation. However pilot-wire differential scheme has its own drawbacks especially on the maintenance of the pilot-wire. Once the plot-wire is out of service, the feeder protection is jeopardised. One of the options to overcome such maintenance issue is to adopt directional relay as the feeder protection. This paper investigates a suitable relay connection and the maximum torque angle for the directional relay for 33kV underground network. In this study, a section of 33kV underground network in Kuala Lumpur (KL) city has been analysed. All faults types have been simulated at all possible location in the network. The obtained voltage and current were then used to determine the operation of directional overcurrent and earth-fault relay. The simulation results indicate that 30° relay connection with 0° maximum torque angle (30°/0°) is the most suitable setting to be applied for 33kV underground network in KL, as against the best general and most versatile setting, 45°/90°. [Copyright &y& Elsevier]

Due to its effective contribution to resolve many problems and its positive impact on distribution systems, great attention has been paid to DG during the last decade. In this paper, an efficient approach based on a newly developed metaheuristic that is the Water Cycle Algorithm (WCA) is adopted for the Optimal Incorporation of Distributed Generation (OIDG) in radial distribution systems (RDSs) for real power loss reduction, voltage stability enhancement and voltage profile improvement. Various case studies containing up to two different objective functions are investigated. The methodology adopted in this paper is carried out on the standard 33-bus, 69-bus and 85-bus distribution test systems. Some interesting results are also discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a simultaneous network reconfiguration with DG sizing and tap changer adjustment to minimize power loss in a distribution system. Imperialist Competitive Algorithm is used to identify the best set combination of reconfiguration, DG size and tap changer. The performance of the proposed method has been tested on 33 bus distribution system at different load levels and different scenarios of DGs location. The test results indicated an improvement of power loss reduction as compared to existing method. Furthermore, the simultaneous approach is able to produce lowest power loss than any combination of two components simultaneously. At the same time, voltage also maintains within allowable limit. [ABSTRACT FROM AUTHOR]

Solid Oxide Fuel Cells (SOFCs) have become the promising energy source for stationary and portable applications. The design of SOFCs including its structure and its operation are an important part to be properly optimized in order to achieve the best performance. The topic on optimization of SOFC has gained tremendous attention recently in line with the growing applications of fuel cell. This paper involves a literature survey of the application of SOFC in particular the optimization strategies. The strategies are reviewed in detail based on five features, which are the decision variable, objective analysis, constraint, method and tools. The future trends of research related to the optimization for SOFC are also discussed to provide better insight for future research work in this area. [ABSTRACT FROM AUTHOR]

This paper presents a new centralized adaptive underfrequency load shedding controller that is integrated with a distribution state estimator to improve the frequency stability of islanded microgrids. While underfrequency load shedding is a well-established corrective emergency frequency-control action, it is not entirely suitable for use in microgrids with low inertia and a limited number of measurement devices. The novel centralized controller presented in this paper overcomes these challenges by incorporating a distribution state estimator to estimate the power consumption of the demand. In parallel to this, the actual active power imbalance in the microgrid is estimated by simultaneously monitoring the system frequency and its rate of change. The centralized controller uses these two variables to determine the correct amount of load to be shed. The performance of the proposed controller has been validated using computer simulations of the actual distribution network in Malaysia. These simulation results show the effectiveness of the proposed centralized controller for preventing power system instabilities, which might lead to cascading outages and even a complete blackout in microgrids that have been disconnected/islanded, from the main grid. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review on mathematical modeling methods of photovoltaic (PV) solar cell/module/array which can be used for power system dynamic modeling purpose. The intermittent and non-linear properties of PV solar cells necessitate accurate modeling of such elements for power system studies. Large scale integration of photovoltaic distributed generation (PVDG) systems into the smart power grid can adversely affect the stability of whole network if the solar plant is not designed properly. A model of solar cell which can predict the PV system output precisely would be helpful to improve reliability and stability of the intelligent utility network. For the smart grid applications which integrate the rapidly growing technologies together with renewable resources, the suitable dynamic model of PV plant is very essential at preliminary evaluation steps. In this paper, a new classification is presented on existing PV cell/module/array modeling methods. Modeling techniques are categorized in two main classes, namely, circuitry based methods and equation based methods. The former class encompasses two sub-classes i.e. embedded function blocks (EFBs) and piecewise linear circuit (PLC) techniques. The second class also consists of two sub-classes i.e. analytical and numerical techniques. The characteristics of each class and its sub-classes are also analyzed and compared to others. Comparison between the methods in both categories indicates that the former class is easy to implement in power system simulation software. The latter class can be exploited to estimate parameters of solar cell in collaboration with EFBs method and vice versa. The second class is more accurate than the first although its computational burden is further. It is envisaged that this paper can serve researchers and designers who work in the field of solar power plant dynamic modeling as useful source of information. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the potential oxidative damage of di-(2-ethylhexyl) phthalate (DEHP) in the rat testis and to further elucidate the potential modulatory effect of quercetin. DEHP was diluted in corn oil and given to rats by oral gavage at doses 0, 300, 600, and 900 mg/kg/day (groups I, III, IV, or V, respectively) for 15 consecutive days. Group VI was pretreated with quercetin (90 mg/kg), 24 h before starting the experiment and then treated with DEHP (900 mg/kg/day) for 15 consecutive days. Group II was treated with quercetin (90 mg/kg/day). The relative testes weight and sperm motility were significantly decreased by treatment with 900 mg/kg of DEHP. Both sperm count and daily sperm production were significantly decreased by DEHP treatment at doses of 600 and 900 mg/kg. Serum testosterone level and prostatic acid phosphatase (ACP) activity and testicular lactate dehydrogenase-X (LDH-X) activity were significantly decreased in animals treated with 900 mg/kg. Serum total ACP activity was significantly increased in animals treated with 600 and 900 mg/kg of DEHP. DEHP treatment induced oxidative stress and histopathological abnormality. These abnormalities were effectively normalized by pretreatment with quercetin except for LDH-X near normalcy. In conclusion, the findings of this study demonstrate that DEHP impairs testicular function at least, in part, by inducing oxidative stress and quercetin has a potent protective effect against DEHP-induced testicular toxicity in rats. [ABSTRACT FROM AUTHOR]

This paper presents an approach to solve the unit commitment problem using a newly developed Multi-agent Evolutionary Programming incorporating Priority List optimisation technique (MAEP-PL). The objective of this study is to search for generation scheduling such that the total operating cost can be minimised when subjected to a variety of constraints, while at the same time reducing its computational time. The proposed technique assimilates the concepts of Priority Listing (PL), Multi-agent System (MAS) and Evolutionary Programming (EP) as its basis. In the proposed technique, deterministic PL technique is applied to produce a population of initial solutions. The search process is refined using heuristic EP-based algorithm with multi-agent approach to produce the final solution. The developed technique is tested on ten generating units test system for a 24-h scheduling period, and the results are compared with the standard Evolutionary Programming (EP), Evolutionary Programming with Priority Listing (EP-PL) and Multi-agent Evolutionary Programming (MAEP) optimisation techniques. From the obtained results and the comparative studies, it was found that the proposed MAEP-PL optimisation technique is able to solve the unit commitment problem where the total daily generation cost is effectively minimised and the computation time is reduced as compared to other techniques. [ABSTRACT FROM AUTHOR]

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 attained. [ABSTRACT FROM PUBLISHER]

The total power losses in a distribution network are usually minimized through the adjustment of the output of a distributed generator (DG). In line with this objective, most researchers concentrate on the optimization technique in order to regulate the DG′s output and compute its optimal size. In this article, a novel Rank Evolutionary Particle Swarm Optimization (REPSO) method is introduced. By hybridizing the Evolutionary Programming (EP) in Particle Swarm Optimization (PSO) algorithm, it will allow the entire particles to move toward the optimal value faster than usual and reach the convergence value. Moreover, the local best ( P best ) and global best ( G best ) values are obtained in simplify manner in the REPSO algorithm. The performance of this new algorithm will be compared to 3 well-known PSO methods, which are Conventional Particle Swarm Optimization (CPSO), Inertia Weight Particle Swarm Optimization (IWPSO), and Iteration Particle Swarm Optimization (IPSO) on 10 mathematical benchmark functions, and solving the optimal DG output problem. From the results, the IWPSO, IPSO and REPSO methods gave the similar “best” value in all functions after being tested 50 times, except for Function 6. However, the REPSO algorithm provided the lowest SD value in all problems. In the power system analysis, the performance of REPSO is similar to IWPSO and IPSO, and better than CPSO, but the REPSO algorithm requires less numbers of iteration and computing time. It can be concluded that the REPSO is a superior method in solving low dimension analysis, either in numerical optimization problems, or DG sizing problems. [ABSTRACT FROM AUTHOR]

Repetition of partial discharge (PD) activities within a dielectric insulation of high voltage equipment may lead to dielectric breakdown, eventually resulting in failure of the whole equipment. Thus, PD measurement is essential in high voltage insulation system. Modeling of PD activity may increase an understanding of PD phenomenon. One of the parameters which can be determined from PD modeling is the statistical time lag. In this work, a physical model of PD using finite element analysis (FEA) method has been developed to determine the relationship of statistical time lag with different applied stresses; these include different applied voltage, frequency and temperature. The statistical time lag as a function of different applied stresses was determined through comparison between measurement and simulation results. The proposed experimental-modeling approach may increase an understanding on the physical explanation about the statistical time lag. [ABSTRACT FROM AUTHOR]

The gravitational search algorithm (GSA) has been used in this research to optimize output of the multiple distributed generator (DG) units in autonomous distribution network. With the optimal operation of DGs, the voltage profile can be improved, thus reducing the power losses in the system. The performance of GSA is compared with an established paper, which uses the genetic algorithm (GA) in analysing similar problem. The results show that the GSA has superior performance in finding the optimal DG output compared to the GA technique, either in terms of power loss as well as the voltage profile. Furthermore, the consistency of the proposed GSA method is proven by the small standard deviation value obtained from 20 repetitions of the same analysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel power management algorithm is developed. [•] An effective power smoothing index is derived. [•] Application of battery storage in smoothing the power fluctuations is investigated. [•] An applicable battery sizing and designing algorithm is proposed. [•] An efficient battery current control algorithm is designed. [Copyright &y& Elsevier]

Energy saving in a distribution system through minimization of power losses is a crucial task for cost-effective operation. One of the most effective approaches in minimizing losses is through the application of distributed generation (DG). To achieve minimum losses, the correct size of DG could be determined using various optimization techniques. Different from other approaches, this paper presents an alternative method to minimize losses through optimal size of DG and optimal location of charging station (CS), which overall reduces the power losses of the network. This paper also investigates the impact of constant voltage (PV) or constant power (PQ) mode of DG to the overall power losses with the aim of choosing the best mode. The suitable DG operation modes and proper sequential placement between DG and CS does not only reduce the power losses, it has also opened new possibilities to add new additional loads in the system. The algorithm's performance shows promising results in minimizing power losses when tested using 33 bus radial distribution networks. [ABSTRACT FROM AUTHOR]

Highlights: [•] Optimal BSS placement reduces the impacts to distribution system performance. [•] The analytical method gave results similar to ABC for optimal BSS placement. [•] ABC gave faster solution in solving BSS sizing cases. [•] Simultaneous BSS and DG Sizing gave the lowest total DG capacity and power loss. [Copyright &y& Elsevier]

The Particle Swarm Optimization (PSO) Algorithm is a popular optimization method that is widely used in various applications, due to its simplicity and capability in obtaining optimal results. However, ordinary PSOsmay be trapped in the local optimal point, especially in high dimensional problems. To overcome this problem, an efficient Global Particle Swarm Optimization (GPSO) algorithm is proposed in this paper, based on a new updated strategy of the particle position. This is done through sharing information of particle position between the dimensions (variables) at any iteration. The strategy can enhance the exploration capability of the GPSO algorithm to determine the optimum global solution and avoid traps at the local optimum. The proposed GPSO algorithmis validated on a 12-benchmarkmathematical function and compared with three different types of PSO techniques. The performance of this algorithm is measured based on the solutions' quality, convergence characteristics, and their robustness after 50 trials. The simulation results showed that the new updated strategy in GPSO assists in realizing a better optimum solution with the smallest standard deviation value compared to other techniques. It can be concluded that the proposed GPSO method is a superior technique for solving high dimensional numerical function optimization problems. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a study on flashover patterns due to double tripping using EMTP software. The simulation was performed on a 132kV line double circuit for economic installation of transmission line arresters (TLAs). The simulation results were validated with the field data of 132kV transmission line in Malaysia. A vertically configured double circuit transmission line was modelled and the effects of tower footing resistance, lighting current values, power frequency voltage and the coupling effect of the phase conductors study were taken into account. A good agreement between the simulation and field data was obtained. A specific back flashover phase of the double circuit line can be determined by considering the effects that have been mentioned. Through determination of the tripping pattern, a suitable installation of line arresters and mitigation of line tripping due to back flashover can be achieved. [Copyright &y& Elsevier]

Abstract: This paper proposes a new algorithm for Distributed Generator (DG) placement and sizing for distribution systems based on a novel index. The index is developed considering stable node voltages referred as power stability index (PSI). A new analytical approach is adopted to visualize the impact of DG on system losses, voltage profile and voltage stability. The proposed algorithm is tested on 12-bus, modified 12-bus and 69-bus radial distribution networks. The test results are also compared and found to be in close agreement with the existing Golden Section Search (GSS) algorithm. [Copyright &y& Elsevier]

Abstract: Under-Frequency Load Shedding (UFLS) is a common technique to maintain power system stability by removing the overload in some part of the system. The existing UFLS schemes operate successfully in the interconnected grid system. A particular approach of UFLS scheme is required for an islanded system which is known to be not as strong as the grid. This paper presents a new approach of UFLS scheme for the implementation in an islanded distribution system. The scheme is based on a combination of adaptive and intelligent techniques. The disturbance magnitude for response based and event based is treated differently: (1) event based is based on the power imbalance and (2) response based is based on the swing equation which relies on the frequency and rate of change of frequency measurement. Dynamic simulation on an intentional islanding operation is performed on an existing Malaysian network interconnected with a mini hydro generation. The objective is to investigate the effectiveness of the proposed scheme. The simulation results demonstrate that the proposed scheme is capable of improving the frequency response of the islanded system. A significant finding is that the scheme can successfully reduce the effect of power deficiency following the grid connected to islanding operation transition. [Copyright &y& Elsevier]

Fault current studies are often required to determine the proper settings for the overcurrent relays. The conventional synchronous generators are known to exhibit high current magnitude during fault, which present an ideal scenario for fault isolation using the cost-effective overcurrent relays. On the other hand, the fault current magnitude from renewable based generation such as solar photovoltaic (PV) is intentionally limited due to the constraints in the power electronic components. Therefore, dispute pertaining to the feasibility of overcurrent relay in inverter based distributed generations (IBDG) applications arises. These disputes mainly arise due to the unavailability of firm understanding of the fault current characteristics from the IBDGs. The problem is further compounded with the availability of numerous possible fault current controls, where various fault current characteristics can be obtained from the IBDGs. In light of this problem, this paper aims to establish the various possible IBDG fault current characteristics, with special attention paid to compliance to the latest grid codes requirements such as low voltage ride through (LVRT) with reactive current injection (RCI). Five different types of RCI controls are analyzed as follows: variable active current control, constant active power control, constant reactive power control, constant active current control, and maximum current control. From the established fault current characteristics in this paper, the disputes pertaining to the feasibility of overcurrent relay for IBDG applications can be resolved and the suitable types of RCI control that allow satisfactory performance of overcurrent relays can be identified. [ABSTRACT FROM AUTHOR]

An ever-increasing demand of electricity and the advent of clean renewable energy along with the limitations of conventional sources of energy are the prime driving force for the planners to incorporate distributed generation in electric power systems at the distribution side. The main objective of the Optimal Integration of Distributed Generation (OIDG) in distribution systems is to optimize the operation and planning of such systems. In the last two decades, significant research efforts have been devoted to formulating and solving the OIDG problem in distribution systems. The main aim of this work is to present a review describing the majority of high quality research work pertaining to OIDG in distribution systems. [ABSTRACT FROM AUTHOR]

Dimensioning a current transformer (CT) is one of the most important tasks during the substation planning process. The installation of a correctly specified CT will ensure the integrity of the protection scheme. However, some parameters required for dimensioning a CT can be obtained only after the CT is installed in the substation. Because of the conflicting requirements, utility companies commonly adopt a simplified approach in compensating for the missing parameters. Two other methods for dimensioning CT under the given constraint during the planning stage have also been proposed by several authors. In view of the availability of the three methods of approximating CT specifications, this paper will conduct a comparative study to evaluate their accuracies. The approximated specifications of the CT during the planning stage are compared against those measured from a practical substation. Based on the findings from the comparative studies, the most reliable approach for CT dimensioning during the planning stage is proposed. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In the presence of void in cable insulation, repetition of partial discharge (PD) occurrences is one of the main sources of insulation degradation, which may lead to complete breakdown. Therefore, it is important to monitor the condition of cable insulation through PD measurement. Replicating PD measurement on a test object with the presence of a void within cable insulation may help a better understanding of PD characteristics within cable insulation to be achieved. Therefore, in this work, test samples of cable insulation geometry containing an artificial void were prepared in the laboratory for PD experiment. The PD measurements were done as a function of void size and applied voltage. A physical model of PD activities within an artificial void in cable insulation geometry was also designed using finite element analysis method. The model was developed by considering PD occurrences within non-uniform electric field distribution in the void and charge movement along the void surface. The model was applied for simulation of PDs within the void in cable insulation geometry to increase the understanding on PD physical phenomena. This includes the impact of distribution of void surface charge on the distribution of the electric field within the void through comparison with the captured measurement results. [ABSTRACT FROM PUBLISHER]

The occurrence of power swing had been reported to threaten the seamless operation of power system. Several cascaded outages and major blackouts in the world have been traced to mal-operation of distance relays due to power swing occurrences. As such, this paper will present a consolidated review on the power swing phenomenon, covering the causes of power swing, its impact to consumers and generators, as well as its detection and relay blocking schemes to prevent the mal-operation of distance relay. Given the wide arrays of power swing detection techniques and blocking schemes available up to date, particular attention is concentrated at the various power swing detection techniques on high voltage power system. In addition, the effect of modern renewable energy generations to the power swing characteristics is also presented in this paper. [ABSTRACT FROM AUTHOR]

Solar energy is one of the cleanest forms of energy sources and considered as a green source of energy. Solar energy benefit ranges from low carbon emission, no fossil fuel requirement, long term solar resources, less payback time and other. However like other power generation sources, solar energy has also some Safety, Health and Environmental (SHE) concerns. This paper presents the overview of solar energy technologies and addresses the SHE impact of solar energy technologies to the sustainability of human activities. This paper will also recommend the possible ways to reduce the effect of potential hazards of widespread use of solar energy technologies. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents detail assessment of the impact of renewable energy type distributed generation operation modes on the voltage stability indices. Most of renewable distributed energy sources are capable of operating in two modes, which are constant voltage and constant power modes. Different simulation results were obtained for voltage stability index (VSI), which serves as indicator of stability. Furthermore, this study has also considered charging station (CS) as a load, that is, gradually increased at the selected bus until the system attains instability state. The persistence of the instability can lead to voltage collapse, and VSI value can give an indication of the collapse as well. In this paper, the concept of active power voltage stability index (P-VSI) is introduced with the aim of predicting the voltage collapse as a result of incremental CS loading in the network. Based on the analysis conducted in radial networks with multiple distributed generation units, the P-VSI gave better indication for the voltage collapse much more than reactive power voltage stability index. The analysis was conducted on 33 bus distribution system. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The power loss is one of the constraints to achieve a more reliable and economic distribution system. The installation of distributed generation (DG) in the existing problem is one of the available solutions; however, the random use of DGs will actually worsen the problem. Moreover, the network reconfiguration is another approach for losses reduction. This method works by controlling the tie and sectionalizes switches to change the topology of the distribution network. Nevertheless, this process must maintain the system in radial network due to protection scheme. Hence, a suitable technique is needed to tackle the DG coordination (DG output and DG location) and network reconfiguration problems. This paper presents a new hybrid optimization technique based on Artificial Bee Colony and Artificial Immune System algorithm to determine the optimal DG coordination with network reconfiguration for multiple DG simultaneously. The effectiveness of the proposed method is demonstrated on a 33-bus distribution test system and validated with various test cases. The results prove that the approach to determine DG coordination with network reconfiguration simultaneously reduces the power losses by 95.10 % from the initial power losses. Furthermore, the proposed method gives a better percentage of minimum voltage increment and improvement of stability index, which is 9.14 % and 0.0428, respectively. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new approach for optimum simultaneous multi-DG (distributed generation) placement and sizing based on maximization of system loadability without violating the system constraints. DG penetration level, line limit and voltage magnitudes are considered as system constraints. HPSO (hybrid particle swarm optimization) algorithm is also proposed in this paper to find the optimum solution considering maximization of system loadability and the corresponding minimum power losses. The proposed method is tested on standard 16-bus, 33-bus and 69-bus radial distribution test systems. This paper will also compare the proposed method with existing Ettehadi method and present the effectiveness of the proposed method in terms of reduction in power system losses, maximization of system loadability and voltage quality improvement. [Copyright &y& Elsevier]

Abstract: Shunt capacitors are commonly used in distribution system for reactive power compensation. Different analytical, numerical programming, heuristic and artificial intelligent based techniques have been proposed in the literature for optimum shunt capacitor bank (SCB) placement. This paper will present a very detailed overview of optimum SCB placement techniques. Six different approaches of optimum SCB placement based on minimization of power losses, weakest voltage bus approach and maximization of system loadability will be applied on four different radial distribution test systems. The results will be compared on the basis of power loss reduction, voltage profile improvement, system loadability maximization and the line limit constraint. [Copyright &y& Elsevier]

Highlights: [•] A new approach to detect and locate high impedance fault is proposed. [•] Wavelet transforms and predetermined faulty database is used to locate the fault. [•] A simulation using PSCAD/EMTP was done to detect and locate high impedance fault. [•] A typical 11kV underground system in Malaysia was used in the simulation. [Copyright &y& Elsevier]

Highlights: [•] Study on directional over-current and earth-fault for biomass micro grid. [•] The delta side of the transformer cannot be cleared by earth-fault relay for single phase to earth fault. [•] Under voltage relay is adopted at the delta side of the transformer. [•] Simulation shows good coordination at all possible locations. [Copyright &y& Elsevier]

Highlights: [•] New algorithm is proposed for network reconfiguration using loadability index λ. [•] Continuation power flow is used to find the maximum loadability index λ max. [•] Simplified artificial bee colony algorithm is used to find the optimum solution. [•] Graph theory is used to maintain the radiality of the system. [•] The proposed algorithm has significantly improved the efficiency of system. [ABSTRACT FROM AUTHOR]