The power transmission (PT) system is at the very heart of the power industry and which is vital to the development of a country. Delays in PT projects have a significant adverse effect on the economic development of a country and although billions of dollars are invested globally in PT projects, costly delays are common. Despite the critical nature of PT, the literature relating to the causes of delays is embryonic, with no theoretical or empirical studies yet conducted to establish the factors involved. This study presents a first step in rectifying this situation. A total of 74 published articles are reviewed that are most closely related to PT projects in order to identify their likely causes of delay. As a result, 82 potential causes of delay are identified and classified into nine major groups. The causes are then ranked in terms of their frequency of occurrence in the literature. Finally, conclusions are drawn concerning the extent to which this review and analysis may form a theoretical framework that can be tested empirically, as well as providing crucial information with recommendation to PT project stakeholders to achieve their key targets including the realisation of the benefits involved.

The volatile feed-in of distributed generation based on renewable energy sources as well as new and intelligent loads and storages require an appropriate consideration in the distribution grid planning process. With the conventional planning method being dependent on extreme scenarios, the consideration is very limited. Therefore, a new planning tool based on the concept of a multi-agent system is presented. In this system, every network user is represented by an agent, allowing not only the consideration of the volatile feed-in characteristics of renewable energy sources but also of the dependencies between the grid users and their environment. Within this contribution, a system overview is given and the agent design process demonstrated on the example of the storage agent, including negotiations. This multi-agent system generates time series for all relevant system variables, defining detailed input parameters in the distribution grid planning process. For the first time, this allows for a detailed determination of the conditions in the up to now rarely measured medium- and low-voltage grids. As a consequence, new assumptions for the planning process are derivable, permitting a demand- and future-oriented grid planning and avoiding over-dimensioning of the grids.

Scalable and computationally efficient model of voltage source converter (VSC) that accurately captures the dynamics is key to the modelling, analysis and control of VSC–high-voltage direct current system. In this study, a dynamic equivalent model of VSC including the dynamics of control system is obtained by using singular perturbation method for the first time. The reduced second-order model with simple form and good generality captures the steady-state and transient behaviours of original full model with a high degree of accuracy. This equivalent model retains the physical meaning of the variables, accommodates different control modes and significantly reduces the computational burden compared with the original full model. Singular perturbation method itself contains some systematic procedures to be able to improve the accuracy of the dynamic behaviour of the lower-order model. The ability of the dynamic equivalent model to accurately describe the original dynamics of the system has been verified with numerical simulations in normal operation and on fault case associated with MTDC grids.

Estimating phasors as quickly as possible while guaranteeing accuracy is important to ensure reliable fault detection and isolation in power systems. Window length is an important factor for phasor estimation. The conventional fixed window length cannot handle well the many and diverse fault voltage and current signals. By analysing the relationship between accuracy and window length of a phasor estimation using the matrix pencil method, a criterion is established to determine whether or not the estimated phasor is credible. Then, an adaptive algorithm to estimate the phasors using dynamic window length is proposed. Analytical and experimental investigations show that the proposed algorithm can accurately and timely estimate phasors and can enable reliable and quick relay operation.

This study presents a Lyapunov exponent (LE)-based framework for transient instability prediction and mitigation using wide area measurement systems data. For transient instability prediction, maximum LEs calculated using post-fault voltage magnitudes are used as input features to support vector machines to predict the transient stability status. To ensure that the proposed transient instability prediction approach does not rely on full network observability and is effective even if limited numbers of phasor measurement units (PMUs) are installed across large power grids, an optimal PMU placement from the transient stability point of view is also proposed. The robustness of the proposed instability prediction scheme is verified with respect to network topology change and measurement errors. For transient instability mitigation, an LE-based controlled islanding scheme is proposed. The proposed controlled islanding scheme determines the coherent generators, identifies proper load buses that should remain inside each group of coherent generators, specifies the boundary circuits and finally partitions the system into different islands while placing the coherent generators in the same island, maintaining connectivity inside islands and minimising the generation–load imbalance of islands.

This study proposes a new voltage stability index based on the voltage equation of transmission lines. The proposed index is obtained by using the characteristic that the sensitivity of voltage to power at the voltage collapse point tends to be infinite. Furthermore, the proposed index is also validated in the case of inverse power flow, and the condition of monotonicity is discussed. Simulation results in a single branch system, a 10-bus system and a regional power system verify the effectiveness of the proposed on-line voltage index. The simulation results also show that the proposed index is better than the on-line branch voltage stability index and is more promising for use in industry. The proposed index can be readily calculated from the measurements at the two terminals of the branch, which can be obtained with PMUs. Hence it is suitable for online applications. Finally, issues related to the practical application of the proposed index are discussed.

Loss-of-excitation (LOE) relays work under pre-defined operating characteristics. If an abnormal condition should arise, such operating characteristics might not be suitable for current system conditions. In this study, an adaptive real-time data-based analytical methodology is proposed for improving LOE protection performance. The core idea is to generate in real time an adaptive operating characteristic for the Mho relay, based on the well know Berdy's method. The adaptive Mho operating characteristic is derived through the proposed methodology using the generator capability curve. Validation is obtained through comparative simulation test cases using DigSilent Power Factory^® program. Test case results show that the proposed protection adaptive analytical methodology displays secure and effective high speed LOE detection, indicating potential for real-life applications.

Despite the advantages of distributed generations (DGs) in electrical networks, they make some unwanted changes in network short-circuit levels which make new security risks arise. This imposes several new scenarios on the network operation in the presence of DGs. In addition to the mentioned security concerns, reducing network loss is among the objectives constantly sought by system operators. Therefore, this study discusses both the reconfiguration of a distribution network for efficient operation and protection coordination in the form of a multi-objective optimisation problem. The aforementioned objectives include reducing losses and maintaining short-circuit levels under several utilisation scenarios of DGs. Thus, the optimal reconfiguration of the network is simultaneously considered along with the optimal planning of fault current limiters through a two-stage stochastic programming. A fuzzy system is utilised to solve the multi-objective problem and a fuzzy imperialism competitive algorithm is proposed to reach the global optimum. The proposed model is implemented on IEEE 69-bus and a real life 77-bus system. Simulation results confirm that implementing the proposed technique not only reduces power losses, but also maintains a short-circuit level of the network under probable utilisation scenarios which in turn the protection coordination of system is improved.

Voltage drifting islanding detection methods (IDMs) force the voltage at point of common coupling (PCC) to move outside the appropriate limits, so that under/over voltage protection disconnects distributed generation (DG) units. This kind of IDMs does not possess the advantage of keeping micro-grid energized after islanding occurrence. There are active IDMs without forcing the islanded micro-grid to lose its stable operation but they degrade the power quality because of perturbation injection. In this study, an active IDM is proposed which makes the second harmonic of PCC voltage drift suddenly after islanding occurrence and pass a predefined threshold value without affecting the fundamental component. When islanding is detected the method is deactivated and the voltage and frequency remain in expected limits in the conditions of power balance. Another advantage of the proposed method is that it decreases the second harmonic of PCC voltage in grid-connected mode and improves the power quality of system unlike other active IDMs. The UL 1741 test results show that the proposed method detects islanding occurrence in a multi-inverter system in <100 ms. Also, the correct performance of the proposed method has been shown for non-islanding conditions. The paper simulations are performed using PSCAD/EMTDC software.

Dynamics of vehicle-to-grid service to frequency regulation may suffer from the uncertainties arising from the spatial and temporal diversities of the large-scale plug-in vehicles (PEVs). Communication delays incurred both in the aggregation of the PEVs and in load frequency control (LFC) loop also degrade the dynamics and even destabilise the system. This study designs the LFC scheme considering those uncertainties. First, a dynamic model of individual PEV based on equivalent circuit and an aggregated model for PEVs group considering driving behaviours, battery characteristics, and delays are developed. Then, a state-space model with time delays and uncertainties is constructed to model the closed-loop LFC scheme with PEVs in primary control loop. After constructing the relationships among control gains, robust performances, and delays, a robust proportional–integral–derivative-type LFC scheme design method is developed by using linear matrix inequality and particle swarm optimisation algorithm. Case studies based on a three-area LFC system demonstrate that the PEVs contribute to the frequency regulation under different load disturbances and that the proposed LFC scheme successfully suppresses frequency fluctuations in the presence of delays and provides robustness against the uncertainties arising from the PEVs.

In the study the methodology for evaluation of the total harmonics additional electrical power and energy measurement error caused by usage of instrument transformers in the measuring system for transformation of distorted current/voltage is discussed. In order to avoid the need for accurate measure of phase angles of distorted current/voltage higher harmonics the percentage components of the composite error, caused by current/voltage transformer's phase displacements, may be calculated. Moreover, the factor to determine the impact of change of voltage and current transformers’ accuracy of distorted current/voltage transformation in relation to sinusoidal conditions on power and energy measurement error is proposed. Finally, it has been shown that current and voltage distortion does not necessarily mean an increase of measuring system additional measurement error of total active power caused by usage of inductive instrument transformers.

Transmission line galloping often causes structural and electrical failures, which is a serious threat to the security of transmission systems. Through analysing the influence factors of galloping, it reveals that weather conditions are the most significant excitation factors and conductors of any voltage level and region may gallop when the apt-galloping weather conditions are satisfied. This study proposes an early warning method for transmission line galloping based on support vector machine (SVM) and AdaBoost bi-level classifiers. First, a prediction model of apt-galloping weather conditions based on an SVM classifier is built through data mining of historical weather parameters in regions where galloping frequently occurred. When the forecast weather conditions of a particular region satisfy the apt-galloping weather conditions, the conductor type, cross-section and span of transmission line are further considered to realise early warning of galloping through an AdaBoost classifier. Finally, the historical galloping events of a power grid are adopted to verify the validity of the proposed methods. The test results indicate that both the accurate classification rate and accurate warning rate are above 90%, whereas the missed warning rate is below 10%. The models are suitable for early warning of transmission line galloping and can provide important decision support for operation staff of power grid.

Effects of low reactance to resistance ratio in distribution networks are widely studied but little work dealing with the tuning of voltage and reactive power regulators of small synchronous generators has been reported. This study endeavours the design of a proportional integral controller for the reactive power regulator to fulfil the characteristic index (CI) objectives, which are based on the step-response characteristics. Two small-signal models of the reactive power regulator have been developed from the well-known k-parameter model and they are validated. Apart from offline tuning of the regulator, these models can be used to assess system robustness and stability. In addition to the analytical approach, the same regulator is tuned optimally by means of multiple simulations. Proposed objective functions rely on the CIs tracked during the sequence of runs, whereas the traditional cost functions are formulated on the basis of the integral of an error. This difference makes them suitable for the cases where the entire step-response data series are unavailable. The performances of differently tuned regulators are compared considering a test system including a 100 kW Diesel Generator Set equipped with a brushless exciter.

Voltage source converters (VSCs) are highly vulnerable to DC fault current; thus, protection is one of the most important concerns associated with the implementation of multi-terminal VSC-based DC networks. This study proposes a protection strategy for medium voltage DC distribution systems. The strategy consists of a communication-assisted fault location method and a fault isolation scheme that provides an economic, fast and selective protection by means of using the minimum number of DC circuit breakers. This study also introduces a backup protection which is activated if communication network fails. The effectiveness of the proposed protection strategy is analysed through real-time simulation studies by use of the hardware-in-the-loop approach. Furthermore, the effects of fault isolation process on the connected loads are also investigated. The results show that the proposed strategy can effectively protect multi-terminal DC distribution networks and VSC stations against different types of faults.

A new partition-composition method for online detection of transient stability of interconnected power system with the data from wide area measurement system (WAMS) is proposed. It consists of two parts: partition and composition. In the partition step, interconnected grids are divided into several local areas according to their geographical locations or ownership. Each area is modelled as an adjoint power system (APS) to determine its own synchronism. In the composition step, transient stability of entire grid is evaluated by the APS model of entire system composed with several key parameters of local areas, which can be directly derived from local WAMS. The proposed method only uses WAMS data, hence it is independent from the offline data, such as network topology, device model and system parameters. Another outstanding feature of the proposed method is that only a few key parameters are required to be transferred from the local control centres to the global control centre. These features are helpful for the interconnected grid with different owners since exhaustive data are unnecessary for the global control centre. Case studies on the 10-generator New England system and one of 2007 operation cases of North China Power Grid validate its correctness and effectiveness.

The coexistence of ac and dc subgrids is going to be inevitable in microgrids (MGs). This study introduces a virtual active power filter (APF) to improve the power quality of a grid connected hybrid ac/dc MG. In this approach, the dc subgrid and the IC are integrated to form a virtual APF. Thus, an enhanced control method for IC is proposed that improves the performance of hybrid ac/dc MG under non-linear load conditions considering power quality of both ac and dc subgrids. The proposed control ensures acceptable power quality for both inverter-based and rectifier-based power transfer between ac and dc subgrids. Furthermore, the IC provides stable dc bus voltage for the dc subgrid and exchange power between the ac and dc buses, properly. A hybrid ac/dc MG is simulated using PSCAD/EMTDC software and various set of simulation studies is presented to validate the effectiveness and advantages of the proposed control method. Furthermore, experimental results are provided to validate the mentioned properties. These features have not been previously discussed in the literature for virtual APF in hybrid ac/dc MGs, where existing APFs are mostly presented for unidirectional power flow applications such as distributed generators.

A limit preserving equivalent method of interconnected power systems is proposed. Based on the equivalent network keeping the consistency of power flows and sensitivities, the equivalent active power constraints are derived under the condition of retaining the consistency of transfer capabilities before and after equivalence. The transfer capabilities are obtained by an optimisation model in which various limits of original external network are included. Based on the limit preserving equivalent network, an equivalent optimal power flow (EOPF) model for interconnected power systems is presented, which can effectively maintain both sensitivity and limit information of the external network. The accuracy and effectiveness of the proposed equivalent method and EOPF model are demonstrated using the IEEE 39-bus system and an actual 661-bus system.

Affected by long-term crosswind, insulator surface will get coated with fan-shaped non-uniform pollution, which lowers insulator flashover voltage as previous study revealed. In this study, a further research in specific to HVDC line insulation is presented. Taking typical dc insulator as the sample, its dc flashover performance under fan-shaped non-uniform pollution was tested. Then the influence of that kind non-uniformity was investigated through analysing the pollution layer residual resistance, the flashover process and critical flashover voltage. Finally the relevant HVDC insulation selection was made. Research results indicate that: under fan-shaped non-uniform pollution, insulator flashover voltage ( U ₅₀) gets impaired, and is more obviously impaired by ratio J of windward to leeward side salt deposit density (SDD) than leeward side area proportion T ; under various T and J , there is still an exponential relationship between U ₅₀ and SDD; under fan-shaped non-uniform pollution the pollution layer residual resistance decreases, which theoretically promotes the arc propagation and flashover process, and thus finally lowers flashover voltage; for the transmission line in area with fan-shaped non-uniform pollution, adding insulator units to strengthen the withstand property are needed.

The occurrence of large-scale haze–fog weather in some developing countries brings a new threat to the safe operation of outdoor insulation. In order to study the effect of the haze–fog on the flashover performance of insulators and the flashover mechanism, kieselguhr, calcium sulphate (CaSO^­ ₄) and ammonium sulphate ((NH₄)₂SO₄) in different particle sizes were mixed with ultrasonic fog to simulate the haze–fog environment and quantitative ac flashover experiments on the standard suspension porcelain insulator were carried out. The test results indicate that the flashover voltage is related with the pollution degree, particle component, particle size and fog-water conductivity, and may decrease by more than 20% under haze–fog environment. The effect of salt aerosols on flashover voltage is determined by the solubility and larger than that of non-soluble mineral aerosols or organic carbon aerosols. The flashover voltage increases with the increase of the particle size, but decreases with the increase of fog-water conductivity. The flashover of insulator under haze–fog condition is a special kind of pollution flashover in essence.

This study discusses the design of robust automatic generation control (AGC) regulators based on the Ricatti-equation approach for a two-area system interconnected via a DC tie-line in parallel with an AC tie-line as an area interconnection between the control areas. The proposed robust AGC regulator designs require only the bounds of the system parameters and enable to ensure the overall asymptotic system stability for all admissible uncertainties. In this study, different models of state cost-weighting matrix ( Q ) are also developed. Various aspects of controllability and observability of the system states which directly or indirectly affect the system dynamics are identified and used in the design of robust AGC regulators. The results obtained with proposed regulator designs in the wake of 1% load disturbance in area-1 and these results are compared with those obtained with optimal AGC regulators to ensure the superiority of the designed AGC regulators. The system eigenvalues are also presented to check the system stability margins available with the implementation of AGC regulators.

Generation dispatch decision making integrated into a centralised wholesale electricity market has been always a challenging concern for transmission system operators. The reason lies mainly in the complex and highly-interconnected structure of the grid, escalated demand, and the crisis of the amount and price of energy. For the dispatch solutions to be highly reliable with an acceptable level of accuracy, several factors need to be taken into account, among which one can mention the valve-point effect, multiple fuel options, disjoint prohibited zones, up/down ramp rate requirements of units, as well as the spinning reserve constraints which, in turn, intensify the non-smoothness, non-convexity, non-linearity, and dynamic restriction of such combinatorial problems. This study proposes a new optimization toolset for the bi-objective multi-area economic dispatch problem to determine the transmission power flow and power output of units while satisfying system demand and security constraints at each area. The proposed architecture builds on an improved gradient-based Jaya algorithm to generate a feasible set of Pareto-optimal solutions corresponding to the operation cost and emission calculated through a new robust bi-objective gradient-based method. The projected algorithm is proved to be capable of finding the robust global or near-global Pareto solutions fast and accurate.

DC line fault is a major threat to the security of ultra high-voltage direct-current system due to complex terrain and terrible weather conditions over long distances. This study proposes a DC line backup protection method on the basis of transient measured impedance (TMI), which is defined as the ratio of transient voltage and transient current at both sides of DC line. The characteristics of TMIs are theoretically analysed for DC line faults and external faults, and these characteristics are used to construct a protection scheme. Since the TMIs only depend on the system structure, the proposed method is able to identify the faults correctly, unaffected by the fault resistance and DC line attenuation. A selection method for the faulted line is also proposed based on the ratio of transient component on the bipolar lines. Comparison with the transient-component-based protections and conventional protections demonstrates the promising performance of the proposed protection. Numerous simulations on PSCAD/EMTDC platform and the tests with field fault-recording data have validated the effectiveness of the proposed protection scheme.

This study introduces a demand-side distributed and secured energy commitment framework and operations for a power producer and supplier (PPS) in deregulated environment. Due to the diversity of geographical location as well as customers’ energy profile coupled with high number of customers, managing energy transactions and resulting energy exchanges are challenging for a PPS. The envisioned PPS maintains several aggregators (e.g. microgrids), named as sub service provider (SSP) that manage customers/subscribers under their domains. The SSPs act as agents that perform local energy matching (inside their domains) and distributed energy matching within SSPs to determine the energy commitment. The goal of the distributed energy matching is to reduce the involvement of external energy supplier (e.g. Utility) while providing a platform to demand side players to be a part of energy transaction. A distributed assignment problem is designed that requires minimum and aggregated information exchange (hence, secured) and solved by linear programming that provides the distributed matching decision. The communicative burden among SSPs due to the exchange of energy information is reduced by applying an adaptive coalition formation method. The simulations are conducted by implementing a synchronous distributed matching algorithm while showing the effectiveness of the proposed framework.

Microgrids (MGs) are presented as a cornerstone of smart grid, which can integrate renewable energy sources environmentally, friendly, and reliably. Hierarchical control strategies, i.e. primary droop control, second automatic generation control (AGC), and tertiary economic dispatch (ED), are widely used to control and optimise an MG. However, the gap between large time-scale ED and small time-scale AGC may decrease the economical efficiency of an MG. To address this problem, this study proposes a distributed economic AGC (EAGC) algorithm. The algorithm is fully distributed, as each distributed generator is assigned with an agent and the agents only require the local measurements and communication with its neighbours. Compared with centralised algorithms, the distributed control algorithm is easy to fulfil the plug-and-play requirements and reduces costs to modify the architecture of an MG. Furthermore, the proposed EAGC algorithm is suitable for all possible operation modes of an MG, i.e. islanded mode, grid-connected mode, and transition mode. To improve the robustness against agent loss or communication link fault, the topology of agents’ communication network is designed to satisfy the N − 1 rule. The effectiveness of the proposed algorithm is demonstrated through the simulation tests which involve plenty of case studies.

For compensating reactive power, shunt capacitors are often installed in electrical distribution networks. Consequently, in such systems, power loss reduces, voltage profile improves and feeder capacity releases. However, finding optimal size and location of capacitors in distribution networks is a complex combinatorial optimisation problem. In such problem, an objective function which is usually defined based on power losses and capacitor installation costs should be minimised subject to operational limitations. In this study, a newly developed metaheuristic technique, named crow search algorithm (CSA), is proposed for finding the optimal placement of the capacitors in a distribution network. CSA is a population-based technique inspired by the greedy behaviour of crows in finding better food sources. The main reasons of using CSA are its easy implementation, few parameters to adjust, fast convergence speed and high efficiency. In the case studies, simulated results indicate that the proposed CSA produces more accurate results than the other studied search methods.

To improve the computational efficiency of electromagnetic transient (EMT) simulation in power system, as well as avoid the numerical oscillation, the high order Radau method is proposed for EMT simulation in this study. For solving the differential equation in EMT simulation effectively, the high order Radau method uses its weighting coefficient matrix satisfying the important V -transformation feature to make the relevant high dimension linear algebraic equation decoupled into blocks in time domain, then forms the multi-stage block recursive method. Because of this technology, in every integration step, the variable value at each different internal point can be calculated simultaneously. On this basis, bigger integration step can be selected to improve the computational speed when carrying out EMT simulation since the high order Radau method is of high computational accuracy. Besides, because this method is both L-stable and B-stable, it can be free of numerical oscillation in EMT simulation effectively. Finally, the validity of this high order Radau method has been demonstrated compared with critical damping adjustment by implementing EMT simulation of transmission line.

In this study, an aging identification approach is proposed for capacitive voltage transformers (CVTs). Aging is an unavoidable phenomenon which emerges and spreads in equipment structure and mainly affects the insulation parts. The aging may affect transformer output in its primary stages. If it grows, it may cause serious damages to the equipment, substation and the staff. Accordingly, it is necessary to diagnose the aging of CVTs in its primary steps in order to implement the required maintenance and repair. The proposed aging identification method is an efficient method which collects data from different sources in digital substations to diagnose aging in CVT structures. Moreover, the possible external disturbances are also taken into account. A modified method is proposed based on the distance between the evidences. In addition, the algorithm is capable to identify the CVTs providing bad data arising from their aging.

In this study, the authors introduce a new solution to the alternating current optimal power flow problem based on successive linear approximation of power flow equations. The polar coordination of the power flow equations is used to take advantage of the quasi-linear P– θ relationship. A mathematical transformation for the crossing term of voltage magnitude is used, which guarantees the accuracy of the linear approximation when the quality of initial points regarding voltage magnitude is relatively low in the first few iterations. As a result, the accuracy of the proposed approximation becomes very high in very few iterations. Linearisation method for the quadratic apparent branch flow limits is provided. Methods to recover the AC feasibility from the obtained optimal power flow solution and correct possible constraint violations are introduced. The proposed method is tested in several IEEE and Polish benchmark systems. The difference in objective functions relative to MATPOWER benchmark results is generally <0.1% when the algorithm terminates.

Online impulse frequency response analysis (IFRA) method is proposed and developed as a new technique to detect the winding mechanical deformation of a running transformer. The preliminary application of IFRA has been realised by using the bushing capacitive coupling sensor (CCS). However, whether the installation of the sensor affects the normal operation of the transformer is still unknown. To study above problem, this study first establishes a simulation model for transformer bushing based on the finite-element method and discusses the influence of sensor installation on the electric field distribution of capacitive bushing. The simulation proves that the installation of the CCS has minimal effect on the safe operation of the bushing. Second, the bushing withstand voltage tests are conducted in a lab, which proves that the installation of CCS meet the requirement for safe operation of capacitive bushing. Finally, the CCSs are installed on running power facilities, and the long and safe running experience indicates that the bushing and related facilities are unaffected by CCSs. The simulation analysis, withstand voltage test, and field application verify that the installation of CCS would not threaten the safe operation of high-voltage bushing, laying the foundation for engineering application of IFRA.

Distributed generators (DGs) play an important role to reduce the real power loss and to improve the voltage stability of the power system. However, proper placement and sizing of DGs in the distribution network is a vital issue, as any improper location and size of DGs may increase the overall system loss. In this study, a novel chaotic symbiotic organisms search (CSOS) algorithm is proposed to find out the optimal location and sizes of real power DGs in a radial distribution system (RDS) considering constant load models. This DG siting and sizing problem is associated with real power loss minimisation and voltage stability improvement objectives. The effectiveness of the proposed algorithm is tested on benchmark test functions as well as on 33-, 69- and 118-bus RDS. The simulation results obtained by the proposed CSOS algorithm are compared with the results offered by the basic SOS and other nature inspired algorithms to establish the superiority of the proposed CSOS algorithm over the others in terms of quality of solution and convergence mobility.