Active Electrical Distribution Network. Группа авторов

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      5 Contingency analysis

      6 Reverse power flow due to inappropriate allocation of distributed generators

      7 Reactive power management

      8 Voltage profile management

      9 Network restructuring

      10 Impacts of distributed generator insertion

      11 Grid security

      12 Stability of the system

These problems persist from a long way back in the system and continued effort towards reducing their impact on the performance of the system are showing effective results, but much more is still impeding implementation.

      3.3.1.1 Distribution Losses

      A distribution system offers a linkage between a high-voltage transmission system and low-voltage consumers where heat loss in an overall network is high due to the high current. Distribution system operators have a financial incentive to diminish losses in these networks. This incentive is evaluated as the difference of the evaluated unit price between real and standard losses. Thus, if the real losses are higher as compared to standard losses then the distribution system faces the economic loss and in the opposite situation it gains the profit. Ultimately, this is revealed as a well-researched area as all available methodologies differ from each other in terms of selection of a tool for loss minimization, problem formulation, or problem solution methods executed for obtaining the best solution. Plenty of published formulations and methodologies of loss reduction, like network reconfiguration, capacitor allocation, increased voltage in the distribution system, conduct or grading, distributed generator (DG) insertion, etc., are showcasing their efficacy in improving the performance of the system.

Among all the predefined problems, the most important issue in the distribution system is the unavoidable unintended performance of the distribution sector due to improper design criteria, which leads to high transmission and distribution (T&D) losses, including electricity theft and unrealistic tariffs to consumers. This aspect highlights the financial status of the distribution companies, which is extremely stressed and leads to inadequate investment by the electricity sector, both in generation and in distribution. It also hampers the contribution of private investors toward generation due to the problems projected about the capacity of the unviable distribution companies to pay for power [9]. The power and energy losses in distribution grids are mostly related to energy conversion into heat subjected to the circulation of proportional currents in the line conductors, which is described as the Joule effect [10]. The transmission of electric energy over long lengths are subjected to power losses. The major part of these energy losses derives from the Joule effect in transformers, power lines, and other components in the power system. The energy is lost as heat in the transmission lines. The investigations have revealed that the overall losses lie in the range between 8 and 15%; thus its evaluation and analysis play an important role in calculating the efficiency of the distribution system. Pricing and appropriate cost allocation defining the precise contribution of operators in a power network in the total costs are counted as the most important problem identified along with all other important issues of the restructuring of the power industry. Fair allocation of price among all the contributors in the system is a complicated but still essential part of operating criteria in the electric power market [11].

      3.3.1.2 Reliability of the System

The distribution system links the complicated structure of the transmission system to the individual customers. The existing power system is smart, twofold, active, interconnected, interdependent, load-sharing, and phased-mission systems [12]. Subsequently, to showcase all these features efficiently it has undergone many modifications in its structure, such as:

       Incorporation of new protection devices

       Inclusion of distributed generators in the systems

       Reactive power compensating devices

       Capacitor bank requirements

Inclusion of all such foreign structures may affect the reliability of the system. Reliability of a power system is commonly defined as a measure of the ability of the system to provide the product to the customers with a passable stream. It is considered to be one of the most important performance criteria of the power sector, which includes the planning, performance, and maintenance of electric power systems [13]. Reliability engineering is a subdiscipline of systems engineering that focuses on the ability of system components to function without failure. It enhances the system output by reducing the failure rate of the system. It describes the ability of a utility to function under defined criteria for a quantified period of time. Reliability and quality are the two faces of the coin so need to be paid due attention. It is a well-known fact that is commonly discussed that the probable cause of almost 90% of failures that occur in the distribution systems are due to reliability issues. Thus the first work was oriented to reliability indices, defined as objectives to attempt to improve performance measures in the electricity market. Overviewing all these concerns of updating the qualitative and quantitative output of the distribution system by considering the importance of new technologies, its effective and fruitful implementation, revealed that reliability aspects and energy sustainability are two principal issues of evolvement in any society [14].

      3.3.1.3 Contingency Analysis

Contingency analysis plays a crucial role for understanding the impacts of sudden line outages due to failures of equipment, transformers, transmission lines, etc. This is mainly reflected in the system due to overburdened parts of the network caused by an irrational power flow in the lines. Its analysis is essential to take the necessary action for maintaining the security and reliable functioning of the system. The offline as well as online execution to envisage the effect of a distinct possibility of getting contingency in the system lines is a monotonous task due to the huge sizes and complication of the network. It has been found that only selected contingencies may result in severe situations in the power system and these can be tackled through precise contingency analysis. The procedure implemented for investigating and evaluating these conditions of overcrowding of power lines is referred to as contingency analysis, which can be done by calculating performance indices for each contingency criterion [15]. The analysis of such situations provides the eminent output of digital computing technologies of managing the various performance criteria, such as Energy Management Systems, SCADA systems, etc. The focus of these systems is primarily to give the network operator information regarding statistics improvement, grid security status, reliability, contingency, etc. Technically this is achieved by conducting a power flow analysis as there is the possibility of single or many contingency scenarios in the network, including lines, transformers, and generators. A mathematical execution of a contingency analysis is a critical function because of its prodigious extent of an information-gathering process in the execution of a problem [16]. It is considered as the most significant process in distribution system planning and operation. It has mainly been found that a line outage may lead to overburdened branches, sudden system voltage variations resulting in huge losses to the system in terms of economy, efficiency, and execution of all-important performance parameters, so the contingency analysis is often used to calculate violations in the predefined norms of the distribution system [17].

      3.3.1.4 Reverse Power Flow Due to Inappropriate Allocation of Distributed Generators

Distributed generation (DG) is considered as an essential part in future distribution power systems. Grids are eventually being converted into smart grids with annexation of advanced and improved, technologically sound distributed generation (DG) sets, along with their СКАЧАТЬ