Utilities around the world are under increasing pressure to provide reliable and good quality power supply to their retail customers, and to reduce their operational costs. These concerns call for real time monitoring and control of the distribution system, which can be accomplished by deploying distribution automation (DA) systems, a key enabling technology for smart grids. This book provides a detailed description of all the major components of a DA system, including communication infrastructure and analysis tools. Topics covered include communication systems for distribution automation; load flow analysis; short circuit analysis; state estimation; feeder reconfiguration for loss reduction, service restoration, and load balancing; volt-var control; fault location; fault type identification; and economic analysis/cost benefit analysis. Concluding with an international case study (Enexis, one of the major Distribution System Operators in The Netherlands) showing how DA has been implemented in practice, this book is essential reading for researchers and advanced students working in power engineering and practitioners engaged in distribution automation, such as utility engineers, vendors, and consultant
Inspec keywords: fault location; power distribution economics; cost-benefit analysis; voltage control; load flow
Other keywords: volt-VAR control; short-circuit analysis; feeder reconfiguration; fault location; load flow analysis; power distribution automation; cost-benefit analysis; fault detection; economic analysis
Subjects: Power systems; General and management topics; General electrical engineering topics; Voltage control; Power transmission, distribution and supply; Control of electric power systems
In this chapter, we discussed various issues related to communication systems and techniques. These include different modulation techniques, multiplexing schemes, transmission media and existing communication networks. Communication plays a crucial role in distribution automation and hence, sufficient knowledge in communication theory is necessary for proper understanding of this topic. Hope that this chapter will serve as a starting foundation in communication networks, as necessary for understanding the distribution automation system.
In an automated distribution system, several tasks, such as network reconfiguration (for loss reduction, load balancing, service restoration), volt-var control, etc., are undertaken regularly to improve the performance of the system. Further, these tasks should be accomplished without violating any system constraints such as bus voltage magnitudes, line power flow limits, etc. These constraints are checked at each step of the algorithms (for accomplishing these tasks) through load flow analysis. Therefore, an efficient load flow analysis is an integral part of an effective distribution automation system. In this chapter, load flow analysis methods for balanced and unbalanced distribution system are discussed.
In this chapter, a method for the short-circuit analysis of radial and meshed distribution systems has been explained in details. The results obtained from the discussed method have also been compared with PSCAD simulation results to establish their accuracy. The values of the calculated short-circuit currents can be used for the selection of equipment ratings and protection coordination.
In this chapter, a statistical framework is introduced to assess the suitability of various state estimation methodologies for the purpose of distribution system state estimation. The existing algorithms adopted in the transmission system state estimation are re-evaluated for the distribution system. The performance of three-state estimation algorithms has been examined and discussed in standard 12-bus and 95-bus United Kingdom-Generic Distribution System network models.
Distribution networks are generally built as meshed networks, while they are operated radially. Their configurations may be varied with manual or automatic switching operations so that all of the loads are supplied and reduce power loss, increase system security, and enhance power quality. Reconfiguration also relieves the overloading of the network components. The change in network configuration is performed by opening sectionalizing (normally closed) and closing tie (normally open) switches of the network. These switching are performed in such a way that the radiality of the network is maintained and all of the loads are energized. Obviously, the greater the number of switches is, the greater the possibilities are for reconfiguration and the better the effects are. In recent years, considerable attention has been conducted for loss minimization in the area of network reconfiguration of distribution systems using heuristics as well as artificial intelligence techniques. In this chapter, the author has considered multiple objectives and reduction of real power loss is one of the objectives. Hence, the work formulates the network reconfiguration problem as a multiple objective problem subject to operational and electric constraints.
When a fault occurs in a feeder of a distribution system, usually the circuit breaker located at the substation end of the feeder operates to trip the faulty feeder. As a result, electricity supply to a large number of loads gets interrupted. Under this condition, the task of the system dispatch centre is to locate and isolate the fault and subsequently restore supply to as large an out-of-service area as possible by appropriate switching actions. Theoretically, all the lost loads should be re-connected to alternative feeders to restore supply to them. However, this operation often leads to infeasible operation of the distribution system in terms of low bus voltages and line overloads.
Automatic reconfiguration of a distribution low-voltage feeder by rearranging the load distribution such that the phase imbalance is always zero, or at the barest minimum achievable, but not more than the level allowed by regulation has been discussed in this chapter. The system is easily expandable to incorporate other distribution networks and feeder reconfigurations, including those through feeder bifurcation and the tie and sectionalizing switches controls. The formulation of the optimization problem has been presented and possible solution methods have also been discussed. A brief insight into the practical feasibility and economic considerations of the system concludes the presentation.
The main objective of the electrical distribution system is to provide reliable highquality power supply. Voltage is the key parameter defining the quality of electrical service. The majority of customers (small and medium size residential, commercial, and agricultural) do not have means to regulate voltages. The customer voltage is regulated by distribution utilities. The customer voltage changes during the day, staying within the limits defined by standards. An example of the typical 24-hour voltage at the customer service delivery point is shown.
This chapter discusses the challenges of distribution system fault location and presents possible algorithms to overcome some of the challenges. One type of fault location method assumes the fault type to be known and the other dispenses with fault type information. Fault location methods for a single fault and methods for simultaneous multiple faults are presented. When there are only limited measurements available, a portion or portions of the network may be unobservable in terms of fault location. More meters will be needed, and design of an optimal meter placement scheme is possible based on network topology and parameters. It is noted that a great deal of valuable literature on fault location has been published in the past. Interested readers are suggested to read more on this intriguing topic.
On the basis of the extraction of the amplitude-frequency and phase-frequency characteristics of signals using S transform, the faulty feeder selection method is discussed, which merges the voting results of several sampling points. A voting mechanism for faulty feeder selection is introduced, and the voting confidence is defined with the consideration of the phase angle shift caused by the module at certain frequency points. The phase of zero-sequence feeder current is obtained with S transform. The results of faulty feeder selection are presented in the form of the faulty feeder number and the faulty feeder identification confidence degree. The faulty feeder identification results and its confidence degrees are provided to related staffs, helping them gain an insight knowledge on the fault condition and the reliability of faulty feeder selection.
This chapter presents the methodology and results for the economic evaluation of an extensive DA project. The outage costs and benefits of the DA system are quantified by using standard mathematical expressions. An economic evaluation method based on value-based analysis and present worth analysis is performed to identify the most beneficial functions in the DA projects. Test results obtained in this chapter have indicated that the feeder automation (FA) is the most beneficial function to utilities. Therefore, the candidate feeders and number of switch for further FA extension is also conducted in this chapter. The results and expressions of this chapter can serve as the basis for the utilities' DA system implementation guideline. The results can also be used for cost-benefit analysis, return-of-investment, or possible performance measure of the DA systems.
This chapter will describe in detail the DA concept developed by Enexis, and will explain which steps have been taken. The main lessons learned will be presented. Afterwards the preparation of the large-scale roll-out and the impact of DA on the organisation of the DSO will be described. Finally the findings after automation of more than 1000 substations will be given.
