Medium Voltage Feeders Research Articles

Design and Evaluation of a Tidal In-Stream Generator Power Port

Oceanic currents and tidal streams are a predictable and vast source of energy. The astronomical nature of the underlying forces causing such streams, results in speed variations that change at certain time intervals. There are different methods for harnessing part of this vast and renewable source of energy; however, regardless of the method used, integrating a large-scale tidal in-stream energy converter into a conventional power system poses many challenges, in particular, in weaker networks. Injection of the captured stream power to a nonstiff network changes the magnitude of the voltage at different times of the day. The impact on the voltage magnitude is commonly most critical if tidal generators and consumers share the same medium voltage feeder, which is a case that seems inevitable especially when considering the electrically remote but energy-rich areas of estuaries, oceanfronts, and natural water channels. This investigation provides designing details of a hybrid power port solution that establishes an independent active and reactive power control, enabling it to regulate the point of common coupling voltage, while transferring variable amounts of captured stream power to a nonstiff grid. To verify the feasibility of the proposed scheme, an example system is designed and tested using a common tidal stream power profile. This investigation is a timely contribution to the emerging field of marine current power generation.

On optimal multistage electric power distribution networks expansion planning

The optimal expansion planning of electric power distribution network to meet system load growth and overcome to pseudo dynamic behavior of network parameters considering a large number of constraints is a hard satisfactory multiobjective optimization problem. This paper implements new developed Imperialist Competitive Algorithm (ICA) for the optimal expansion planning of distribution network. The topology of medium voltage (MV) distribution network as backbone of electric power distribution systems is designed by optimal sizing, siting and timing of medium voltage network components such as HV substation and MV feeders’ routes. A multistage expansion planning is proposed to consider dynamic behavior of the system parameters asset management and geographical constraints. In order to reach the global solution an efficient coding is developed for ICA parameters. The Greedy algorithm is used to solve the minimum spanning tree problem to construct a radial configuration of the mesh network. At each stage of the problem the results are fully illustrated either by figures or by tables. A sensitivity analysis is used to show the robustness of the results with respect to ICA parameters variation. The obtained results are compared with GA as well known heuristic optimization tool. The efficiency and capability of the methodology has been tested on an under developed relatively large-scale distribution network.

PV Units Accommodation Strategy In Baghdad M.V Distribution Feeder

Photovoltaic units have been adopted recently as embedded generators in distribution feeders; the accommodation of this green source of energy in medium voltage feeders is a challenging task due to complexity and extensive dimensionality of finding optimal site and size problems. The optimal selected site should reflect the best impacts over both network and consumer side. Genetic Algorithm is employed successfully in this work to find the optimal site and size of PV units in a practical 11kV feeder within Baghdad distribution network. Accommodating photovoltaic units in the optimal sites improve both service availability, quality and reduce network loss.

Comprehensive Distribution Network Fault Location Using the Distributed Parameter Model

A typical low- or medium-voltage distribution feeder consists of numerous branches as well as laterals and heterogenic conductor lines. The lack of measurement points and the presence of unbalanced loads make it more complicated for the construction of fault-location algorithms. In this paper, a brief and comprehensive review is presented which introduces and compares published papers in this area to date. In addition, the authors have devised a single-end fault-location algorithm using the distributed parameter model to overcome all of the aforementioned limitations in distribution feeders. The validity of the devised algorithm is studied within the PSCAD-EMTDC environment. This model provides more accurate results as the distributed nature of losses and capacitive effects are considered whereas in the available algorithms, these are ignored. A comparison which is made between the proposed method and two of the most complete available algorithms shows the superiority of our algorithm. Also, the proposed algorithm is able to locate various fault types in the network that has different phase laterals unbalanced loads and heterogeneity of the feeder line.

Optimal integrated planning of MV–LV distribution systems using DPSO

A new technique for optimal planning of MV and LV segments of a distribution system is presented in this paper. The main goal is to find optimally distribution transformer and substation locations and ratings, as well as, the route and type of Medium Voltage (MV) and Low Voltage (LV) feeders. The proposed technique is applicable to both uniform and non-uniform load densities areas. In this method, the planning area is divided into regions with relatively uniform load density such as urban, semi-urban, sub-urban. Each of regions is divided into zones, called LV zone. Each LV zone is supplied by an MV/LV transformer. The dimensions of LV zones are found based on the average load of each region. The placement and rating of MV/LV transformers, the type and route of LV conductors in an LV zone all depend on its loads’ location and power. Regarding the placement and rating of MV/LV transformers in planning area and the space of regions, the dimensions of a zone which is supplied by a HV/MV transformer, called MV zone, is determined. Additionally, the location and rating of HV/MV transformers as well as the feeder's routes and types are calculated. Since the dimensions of an LV zone influence the associated length of MV feeder, the MV feeder cost needs to be included in the total cost associated with the LV zone. This requires the MV feeder type to be known to calculate the corresponding cost. However, the MV feeder type is determined as an output from MV zone planning. As a result, an iterative based method is proposed to consider this common element in computations to develop integrated planning of both LV and MV zones. It is observed that the iterative technique quickly converges to the same results as the exhaustive search method. Discrete particle swarm optimization (DPSO) method is employed for solving the planning problem. The results are compared with nonlinear programming, genetic algorithm and exhaustive search methods. It is observed that DPSO is as accurate as the exhaustive search method for integrated planning of MV–LV distribution systems while its computation time is significantly lower.

Optimal placement of switching equipment in reconfigurable distribution systems

This paper presents a comparative analysis of some measures that can improve the reliability of medium-voltage (MV) distribution feeder. Strictly speaking, the impact of certain types of switching equipment installed on the feeder and possibilities of backup supply from the adjacent feeders were analyzed. For each analyzed case, equations for the calculation of System Average Interruption Duration Index and energy not delivered to the customers are given. The effects of certain measures are calculated for one real MV-feeder for radial supply to customers and in cases of possible backup supply to the customers. Installation locations of certain types of switching equipment for the given concept of energy supply are determined according to the criterion of minimum value of System Average Interruption Duration Index and according to the criterion of minimum value of energy not delivered to the customers.

Voltage transient measurements in a distribution network correlated with data from lightning location system and from sequence of events recorders

Measurement units of high-frequency voltage transients have been specifically developed and installed at three different busses of an Italian medium voltage (MV) feeder, mainly composed by overhead lines and located in a rural region characterized by a high ground flash density (4flashes/km2/yr). Several of the recorded voltage transients in the period from March 2007 to August 2008 are correlated with specific events detected by the Italian lightning location system (LLS) CESI-SIRF and with sequence of protection operations recorded by the utility's data acquisition system. The paper presents the analysis of these correlated events. Moreover, the paper compares some voltage transient measurements with the computer simulation results obtained by a detailed LIOV–EMTP model of the MV feeder response to indirect lightning strokes. The aim of the paper is to provide elements useful to solve the problem of correlating line faults with lightning events.

ON OPTIMAL DESIGN AND EXPANSION OF ELECTRICAL POWER DISTRIBUTION SYSTEMS

Optimal planning of large-scale distribution networks is a multiobjective combinatorial optimization problem with many complexities. This paper proposes the application of improved genetic algorithm (GA) for the optimal design of large-scale distribution systems in order to provide optimal sizing and locating of the high voltage (HV) substations and medium voltage (MV) feeders routing, using their corresponding fixed and variable costs associated with operational and optimization constraints. The novel approach presented in the paper, solves hard satisfactory optimization problems with different constraints in large-scale distribution networks. This paper presents a new concept based on MST in graph theory and GA for optimal locating of the HV substations and MV feeders routing in a real-size distribution network. Minimum spanning tree solved with Prim's algorithm is employed to generate a set of feasible population. In the present article, to reduce computational burden and avoid huge search space leading to infeasible solutions, special coding method is generated for GA operators to solve optimal feeders routing. The proposed coding method guarantees the validity of the solution during the progress of the GA toward the global optimal solution. The developed GA-based software is tested in a real-size large-scale distribution system and the well-satisfactory results are presented.

A Framework for Optimal Planning in Large Distribution Networks

Large scale distribution system planning is a relatively complex and reasonably difficult problem. This paper proposes the application of improved genetic algorithm (GA) for the optimal design of large scale distribution systems in order to provide optimal sizing and locating of the high and medium voltage (HV and MV) substations, as well as medium voltage (MV) feeders routing, using their corresponding fixed and variable costs associated with operational and optimization constraints. The novel approach presented in the paper solves hard satisfactory optimization problems with different constraints in large scale distribution networks. This paper presents a new concept based on loss characteristic matrix introduced for optimal locating of MV substations, followed by new methodology based on graph theory and GA for optimal locating of the HV substations and MV feeders routing in a real size distribution network. Minimum spanning tree algorithm is employed to generate set of feasible initial population. In the present article to reduce computational burden and avoid huge search space leading to infeasible solutions, special coding methods are generated for GA operators to solve optimal feeders routing. The proposed coding methods guarantee the validity of the solution during the progress of the genetic algorithm toward the global optimal solution. The developed GA-based software is tested in a real size large scale distribution system and the well satisfactory results are presented.

Influence of Fault Current Limiter on Allowable Interconnecting Time Period of Customer Power System with Synchronous Generator

Distributed generators will be disconnected from a grid with a short-circuit fault to protect the generator and load in the customer system. In order to keep an isolated operation of the generator after the disconnection of customer system from the utility system, the customer system must adjust the power balance between supply and demand. This paper has investigated an influence of a fault current limiter on a probability of isolated operation after the disconnection of customer system with a synchronous generator from a medium voltage feeder. An allowable interconnecting time period, which is a critical time period from the fault occurrence to the isolated operation, has been simulated. It was assumed that the fault current limiter was installed in an interconnecting line between customer system with the synchronous generator and power distribution system. It was found that a resistive type fault current limiter does not improve the allowable interconnecting time period since the consumption power of fault current limiter causes the generator to decelerate. However, it was shown that the allowable interconnecting time period increases owing to the application of inductive type fault current limiter. This is because the active power of load is nearly equal to the generator output.

Voltage control with on-load tap changers in medium voltage feeders in presence of distributed generation

This paper discusses voltage regulation on medium-voltage feeders with distributed generation (DG) using on-load tap changer (LTC) and line drop compensation (LDC). The analysis shows that LTC is robust against DG, whereas DG can affect the effectiveness of the voltage regulation provided by LDC. However, with proper coordination between DG and LDC, it is possible to ensure voltage regulation without unnecessarily restricting the integration of DG. It is shown that, while lowering the LTC setting can increase the DG integration limit, even higher increase can be obtained by activating the LDC feature, which is present in most LTCs, but often not used. LDC regulation is also compared with other alternatives such as using a DG unit with voltage control capability and installing a line voltage regulator.

Business opportunities and dynamic competition through distributed generation in primary electricity distribution networks

In this paper, for a real electricity distribution network, an assessment of business opportunities to invest in distributed generation (DG) is performed through a simulation based on a full representation of three medium voltage (12kV) feeders. The three feeders representation includes 1062 sections of conductors with 13 different sizes. The economic assessment focuses on both, the incentives of the incumbent distribution company and those of a new entrant. The technical and economic impact on losses, reliability and voltage regulation in the network area are verified. The DG solution analyzed determines a business opportunity for new investors where end users are also benefited. This work calls in the debate on the need to reformulate the current regulation model on electricity distribution, by defining clear rules to incorporate DG to the existing network, and to enable any agent to develop the proposed business. DG success depends on the location of adequate sites to strategically establish few DG units being a substitute to network expansion.

Approximate calculation of backup supply profitability in medium voltage power distribution planning

In medium voltage (MV) power distribution network planning, especially in rural network planning, we often consider the costs of constructing a backup supply line and the resulting cost reduction for energy not supplied. A fast and simple method for this purpose is now presented. Accurate and approximate expressions for calculating the energy not supplied by a MV feeder with respect to backup supply availability are derived. The optimal number and locations of switching devices on the feeder are determined by use of approximate expressions. The minimum overall costs that consists in the energy not supplied costs and the switching equipment costs, are also calculated.Comparison of the difference in optimal total costs between the situations with and without a backup supply to the connecting line costs in the concerned period serves as a decision-making criterion. The application of the method is shown in the case of 10 kV MV feeder.

Planning of optimal location and sizes of distribution transformers using integer programming

During planning of the development of medium voltage distribution networks, new distribution transformers medium/low voltage can be developed on more than one location and have more options of connecting to the network. On the other side, planning of development medium-voltage distribution network usually includes optimization of location and rates of substations as well as optimal locations and feeder shaping, while the problem of location optimization and rate of distribution transformers has not been treated in literature so far available. Problem is brought down to associating distribution transformers geographically in to the supply area, associating one supply area to one distribution transformer. The most frequent case is that in one part (observed) of a consumer group appears a need to build one distribution transformer station with a possibility of construction on more than one location. It is enough to apply separate calculations to all possible locations and by comparing to attain the best possible solution. General and rather rare case is when in observed part of a consumer group there is a need to develop more than one distribution transformer with possibility, in addition to be in more locations, that individual distribution transformer also to be installed in different size (for example, 630 kV A and/or 2×630 kV A). In that case (general) it is needed to approach with more complex selection way, i.e. with optimization. In this paper a solution has been proposed for optimization of location for a new distribution transformer by associating one consumer area to several distribution transformers that together supply the corresponding area. Optimization is being performed by appliance of network penalty factors and integer programming. Penalty factors are obtained by calculation of medium voltage network state, voltage drops and losses in every medium voltage feeder. The basic idea is to choose from the set of solutions the most qualitative one, from the view point of annual investment costs, voltage drops, load of feeders and substations. At the same time a problem of reinforcement of the existing distribution network is concerned. By observing of one area for more distribution transformers instead of one area for one distribution transformer, the exploitation level of medium voltage network is being raised, since it is being decided to build a one distribution transformer out of the given set, which leads to the least increase of power losses and voltage drops in relation to newly made investment costs. Thus obtained results can be used for more precious definition of locations and powers of distribution transformer, in solving short-term development planning problems after made development plans for distribution system in the way as it has been so far done. Test example shows that developed method can be also used as an additional tool in planning distribution networks development.

A new approach to digital current differential protection for low and medium voltage feeder circuits using a digital voice-frequency grade communications channel

A new approach to digital current differential protection is described which provides the capabilities of conventional pilot wire differential protection while using the limited data transfer capabilities of a digital data voice-frequency grade communications channel. This approach compares polyphase polarised current measurements taken at the feeder's terminals to detect faults and can trip in under two power system cycles. The algorithms decouple the measurements from the power system frequency and its waveform, and thereby have a high inherent tolerance to the complications introduced by communication channel delays and their fluctuations. For this project, the communications requirements have been limited to a full duplex 2400 bits/sec system suitable for operation over a voice-frequency grade channel.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An economical distribution system for high-density commercial and industrial loads

Central business districts (CBDs) of most major cities of the world are supplied by underground medium-voltage radial feeders or networks which are meshed at medium or low voltage. Radial feeders are the simplest and cheapest way of supplying these major commercial loads, but a feeder fault will affect every customer on that feeder. Mesh networks provide a much more reliable and flexible supply, but require large numbers of medium-voltage (MV) or low-voltage (LV) circuit breakers such as network protectors for ease of operation. Using the CBD of South East Queensland, Australia as an example the authors present a more economical network of distribution substations. By minimising the number of circuit breakers and adopting standardised modules leading to standard layout, circuitry and protection designs, it has been possible to significantly reduce the cost of distribution.

Survey of Power Systems Reclosing Practices in Pulp and Paper Mills

This paper gives the results of a survey conducted by the Power Distribution System Subcommittee of the Pulp and Paper Industry Committee of the IEEE Industry Applications Society. Its purpose was twofold, 1) to explore utility/mill relaying and electrical tie practices and, 2) to explore and devise safe and expeditious operation practices in reenergizing a circuit after a primary or medium voltage feeder breaker tripout has occurred.