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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]

Abstract: The implementation of condition based monitoring (CBM) involves variety of disciplines, such as failure analysis, on-line diagnostics, diagnostic data interpretation, management and communication, corrective actions and program maintenance. However, the most important tasks for a comprehensive CBM analysis are to identify the actual root cause that contributes to equipment failure and the selection of appropriate mitigation techniques to address the root cause of the failure. In this paper, CBM actual site data of a 33kV switchgear from an electrical utility company in Malaysia (from 2007 to 2010) were used to develop failure root causes database. The database was used to identify the possible root cause of a failure and to propose a failure mitigation plan for any CBM activity. The CBM data were obtained using ultrasound, thermoscanning and transient earth voltage (TEV) methods at different compartments of the switchgear, which yielded specific root causes of failure. In order to verify the effectiveness of the proposed method, the method was tested using actual site data obtained in 2011. Using the proposed method, the actual root cause of a failure can be identified quickly; hence the time and cost of repairs can be reduced. [Copyright &y& Elsevier]

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: 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]

Abstract: Power networks contain capacitances and inductances that can saturate, presenting opportunities for ferroresonance to occur. Most power equipment is designed through linear theory but ferromagnetic materials are highly non-linear and when they resonate, the non-linearity produces currents and voltages that are larger than usual. Ferroresonance is a complex, non-linear electrical phenomenon. It can cause dielectric and thermal problems through overvoltage, an intrinsic phenomenon present in all networks. A network dynamic response to lightning and switching will be energy storage and release. The transfer of energy will propagate an overvoltage through the network and damage substation equipment when lightning strikes near the substation. Application of conventional mathematics is inappropriate to ferroresonance study in which actual events are simulated. Lightning strikes that occurred near a substation and that led to explosion of CVTs have been reported, so this study investigates the effect of a lightning strike on a tower with a 132kV Capacitor Voltage Transformer (CVT). Alternative Transient Program (ATP) was used for the simulation which duplicated the lightning-strike effect that causes a CVT to explode. [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]

With the increasing capacity of distributed generation (DG) connected to the power grid, the future generation of photovoltaic (PV) systems are expected to provide a full range of voltage regulation during grid faults in order to enhance the low-voltage ride-through (LVRT) capability of a PV system. In such a condition, the DG should remain connected to the grid for reactive power support, thereby improving voltage profile. This paper aims to propose a control strategy of active and reactive power for a single-stage three-phase grid-connected PV system to enhance the LVRT. The dynamic behaviours of the system were investigated by considering various scenarios such as varying irradiance, local load disconnection, and short circuits, at different locations during the multi-DG operation. Results confirm that the grid-connected PV system is able to remain connected to the power grid during steady-state and transient-state conditions without violating the grid code requirements. The established dynamic behaviour analysis model of the proposed control for grid-connected PV systems can be used in planning an operational strategy for a practical system. [ABSTRACT FROM AUTHOR]

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. [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]

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]

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 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: [•] 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]

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]

Highlights: • A new algorithm is proposed for optimum DG placement and sizing.• I 2 R losses minimization and voltage stability maximization is considered in fitness function.• Bus voltage stability and line stability is considered in voltage stability maximization.• Multi-objective PSO is used to solve the problem.• Proposed method is compared with analytical and grid search algorithm. [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]

As the development of renewable distributed generations (DGs) is growing rapidly, the autonomous self-healing microgrid had emerged as an effective solution for integrating renewable DGs in the distribution networks. However, before the autonomous self-healing microgrid can be realized, one of the main issues that needs to be resolved is the ability to utilize the most cost-effective protection system—overcurrent relays—to achieve the goal. However, the overcurrent relay is insensitive to the limited fault current contributed by the inverter-based distributed generation (IBDG). Therefore, this paper will propose a novel inverter fault current control with a reactive current injection (RCI) that injects the correct fault current vector, albeit with a limited magnitude, for detection by the cost-effective directional overcurrent relay. This paper will also evaluate the performances of the different RCI controls in delivering an efficient self-healing microgrid protection based on a directional overcurrent relay. The proposed self-healing protection scheme is tested with both a simple distribution test network and also the IEEE 16 bus test system, considering random system parameters like variations in IBDG location, fault location, load capacity and load power factor. Moreover, the performance of the proposed inverter RCI control is also tested under changing weather conditions. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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]

Abstract: Electricity is always considered as an important ingredient for development of a country. Energy deficit affects the growth rate of the country and causes discomfort to the consumer. The power shortage in Karachi, the largest city and economical hub of Pakistan, is highly hampering the progress of the city. Presently the energy deficit in the city is around 328MW. This paper presents an analytical analysis of incorporation of small residential windmills to reduce the power shortage in Karachi. To estimate the wind energy potential in the city, four years wind data is collected from Pakistan Metrological Department (PMD) at various heights (10m, 30m, 50m, 75m and 100m). The statistical calculations on wind data using SPSS software show that the city has an enormous wind potential available. A case study is also carried to show the effect of incorporation of small residential wind mills in power system. The results shows 1678MWh of energy could be saved if 50% of residential consumers are equipped with small windmills. The paper also discusses the possible resistance in the introduction of small residential windmills in domestic sector. The potential benefits to the utility and consumers are also presented in this paper. [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]

• Proper charging coordination of electric vehicles is essential in achieving an efficient interconnection to the power system avoiding overloading effect. • Electric vehicles are capable of feeding power back to grid during high peak demands reducing the electricity cost and earning profit for consumer. • The incorporation of electric vehicles in the power grid improves the stability of the system as they can behave as energy consumer and energy providers during the low and high load periods respectively. • The optimized solution for battery energy management system is proposed by taking into account the battery degradation cost, which is modelled for real time analysis considering DOD at each time interval. With the growing concerns on the energy depletion and the reduction of CO 2 emission, electric vehicles (EVs) have gained popularity in transport sector due to clean and reliable energy source. However, the charging of EVs has imposed significant load in the electrical distribution system. The stability of power network is disturbed with uncoordinated charging. This work aims to investigate the optimal EV coordination with vehicle to grid (V2G) technology for the cost-benefit analysis. However, the cost of EV battery replacement due to degradation is of paramount concern for the EV users, which constitute the most important ingredient to ensure active participation in V2G energy exchanges. Therefore, battery degradation cost is formulated for real time analysis taking depth of discharge at each time interval. The firefly algorithm has been used to optimize the system cost. The performance of the proposed system is tested on modified 33 bus distribution system in the presence of renewable energy sources (RES). The impact of system cost and energy losses are analysed for different RES penetration, EV capacities and travelling distances. The simulation results show significant reduction in operating cost when RESs are integrated into distribution network. Moreover, V2G technology is beneficial for EV consumers with high penetration of RES. [ABSTRACT FROM AUTHOR]

The objective of this study is to propose a decision-tree-based peak shaving algorithm for islanded microgrid. The proposed algorithm helps an islanded microgrid to operate its generation units efficiently. Effectiveness of the proposed algorithm was tested with a BESS-based MATLAB/Simulink model of an actual microgrid under realistic load conditions which were recorded. To evaluate the performance, simulation case studies were conducted under various load conditions and results were compared with conventional techniques. Results showed that the proposed algorithm offers a simple and effective way of peak load shaving without heavy computational burdens often needed in other methods. The comparison analysis verified that the proposed algorithm can effectively mitigate the peak load demand regardless of the schedule of the generators, where conventional methods were limited. The financial benefit investigation shows that microgrid utility can enjoy substantial savings, while reducing of the peak demand of the microgrid. Thus, the islanded microgrid that include fuel-based generation can implement the proposed technique to reduce the consumption of fuel and increase the efficiency of fuel-based generation through peak load mitigation. • A novel peak shaving algorithm is presented for the islanded microgrid. • The proposed algorithm is tested for a real microgrid under various load conditions. • A comparative analysis is carried out with conventional peak shaving methods. • Results show the proposed algorithm successfully supplied peak shaving services. • The proposed algorithm shows a robust behavior under the realistic circumstance. [ABSTRACT FROM AUTHOR]